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https://oercommons.org/courseware/lesson/99163/overview	Precalculus Textbook (Openstax) Overview Open Textbooks for Rural Arizona participants are invited to remix this template to share their courses, textbooks, and other OER material on our Hub. Material Description Material Description Algebra and Trigonometry 2e provides a comprehensive exploration of mathematical principles and meets scope and sequence requirements for a typical introductory algebra and trigonometry course. The modular approach and the richness of content ensure that the book addresses the needs of a variety of courses. Algebra and Trigonometry 2e offers a wealth of examples with detailed, conceptual explanations, building a strong foundation in the material before asking students to apply what they’ve learned. The Algebra and Trigonometry 2e revision focused on improving relevance and representation as well as mathematical clarity and accuracy. Introductory narratives, examples, and problems were reviewed and revised using a diversity, equity, and inclusion framework. Many contexts, scenarios, and images have been changed to become even more relevant to students’ lives and interests. To maintain our commitment to accuracy and precision, examples, exercises, and solutions were reviewed by multiple faculty experts. All improvement suggestions and errata updates from the first edition were considered and unified across the different formats of the text. The first edition of Algebra and Trigonometry by OpenStax is available in web view here. Context for sharing: This textbook was adopted at Coconino Community College as the precalculus textbook. Material Attachment Abramson, J. (2021) Algebra and Trigonometry, Openstax.	oercommons	2025-03-18T00:35:13.086017	Textbook	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/99163/overview", "title": "Precalculus Textbook (Openstax)", "author": "Mathematics" }
https://oercommons.org/courseware/lesson/118394/overview	Nursing OER Nursing Open Educational Resources (OER) Overview Open resources covering essential nursing topics such as patient care principles, pharmacology, intravenous therapy, and cardiac arrest management.	oercommons	2025-03-18T00:35:13.103649	07/25/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/118394/overview", "title": "Nursing Open Educational Resources (OER)", "author": "Red Rocks CC" }
https://oercommons.org/courseware/lesson/116527/overview	Kindergarten Common Assessment Overview This resource can be used as a math common assessment for Kindergarten. This Kindergarten Common Assessment was created as a summative assessment for Math. It is inteded to be given during the third quarter of the year but can also be used as a resource to check for mastery of certain skills throughout the year.	oercommons	2025-03-18T00:35:13.119330	06/02/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/116527/overview", "title": "Kindergarten Common Assessment", "author": "Kayla Eller" }
https://oercommons.org/courseware/lesson/11765/overview	Pop Culture, Subculture, and Cultural Change Overview - Discuss the roles of both high culture and pop culture within society - Differentiate between subculture and counterculture - Explain the role of innovation, invention, and discovery in culture - Understand the role of cultural lag and globalization in cultural change It may seem obvious that there are a multitude of cultural differences between societies in the world. After all, we can easily see that people vary from one society to the next. It’s natural that a young woman from rural Kenya would have a very different view of the world from an elderly man in Mumbai—one of the most populated cities in the world. Additionally, each culture has its own internal variations. Sometimes the differences between cultures are not nearly as large as the differences inside cultures. High Culture and Popular Culture Do you prefer listening to opera or hip hop music? Do you like watching horse racing or NASCAR? Do you read books of poetry or celebrity magazines? In each pair, one type of entertainment is considered high-brow and the other low-brow. Sociologists use the term high culture to describe the pattern of cultural experiences and attitudes that exist in the highest class segments of a society. People often associate high culture with intellectualism, political power, and prestige. In America, high culture also tends to be associated with wealth. Events considered high culture can be expensive and formal—attending a ballet, seeing a play, or listening to a live symphony performance. The term popular culture refers to the pattern of cultural experiences and attitudes that exist in mainstream society. Popular culture events might include a parade, a baseball game, or the season finale of a television show. Rock and pop music—“pop” is short for “popular”—are part of popular culture. Popular culture is often expressed and spread via commercial media such as radio, television, movies, the music industry, publishers, and corporate-run websites. Unlike high culture, popular culture is known and accessible to most people. You can share a discussion of favorite football teams with a new coworker or comment onAmerican Idol when making small talk in line at the grocery store. But if you tried to launch into a deep discussion on the classical Greek playAntigone, few members of U.S. society today would be familiar with it. Although high culture may be viewed as superior to popular culture, the labels of high culture and popular culture vary over time and place. Shakespearean plays, considered pop culture when they were written, are now part of our society’s high culture. Five hundred years from now, will our descendants associate Breaking Bad with the cultural elite? Subculture and Counterculture A subculture is just what it sounds like—a smaller cultural group within a larger culture; people of a subculture are part of the larger culture but also share a specific identity within a smaller group. Thousands of subcultures exist within the United States. Ethnic and racial groups share the language, food, and customs of their heritage. Other subcultures are united by shared experiences. Biker culture revolves around a dedication to motorcycles. Some subcultures are formed by members who possess traits or preferences that differ from the majority of a society’s population. The body modification community embraces aesthetic additions to the human body, such as tattoos, piercings, and certain forms of plastic surgery. In the United States, adolescents often form subcultures to develop a shared youth identity. Alcoholics Anonymous offers support to those suffering from alcoholism. But even as members of a subculture band together, they still identify with and participate in the larger society. Sociologists distinguish subcultures from countercultures, which are a type of subculture that rejects some of the larger culture’s norms and values. In contrast to subcultures, which operate relatively smoothly within the larger society, countercultures might actively defy larger society by developing their own set of rules and norms to live by, sometimes even creating communities that operate outside of greater society. Cults, a word derived from culture, are also considered counterculture group. The group “Yearning for Zion” (YFZ) in Eldorado, Texas, existed outside the mainstream and the limelight, until its leader was accused of statutory rape and underage marriage. The sect’s formal norms clashed too severely to be tolerated by U.S. law, and in 2008, authorities raided the compound and removed more than two hundred women and children from the property. The Evolution of American Hipster Subculture Skinny jeans, chunky glasses, and T-shirts with vintage logos—the American hipster is a recognizable figure in the modern United States. Based predominately in metropolitan areas, sometimes clustered around hotspots such as the Williamsburg neighborhood in New York City, hipsters define themselves through a rejection of the mainstream. As a subculture, hipsters spurn many of the values and beliefs of U.S. culture and prefer vintage clothing to fashion and a bohemian lifestyle to one of wealth and power. While hipster culture may seem to be the new trend among young, middle-class youth, the history of the group stretches back to the early decades of the 1900s. Where did the hipster culture begin? In the early 1940s, jazz music was on the rise in the United States. Musicians were known as “hepcats” and had a smooth, relaxed quality that went against upright, mainstream life. Those who were “hep” or “hip” lived by the code of jazz, while those who were “square” lived according to society’s rules. The idea of a “hipster” was born. The hipster movement spread, and young people, drawn to the music and fashion, took on attitudes and language derived from the culture of jazz. Unlike the vernacular of the day, hipster slang was purposefully ambiguous. When hipsters said, “It’s cool, man,” they meant not that everything was good, but that it was the way it was. By the 1950s, the jazz culture was winding down and many traits of hepcat culture were becoming mainstream. A new subculture was on the rise. The “Beat Generation,” a title coined by writer Jack Kerouac, were anticonformist and antimaterialistic. They were writers who listened to jazz and embraced radical politics. They bummed around, hitchhiked the country, and lived in squalor. The lifestyle spread. College students, clutching copies of Kerouac’s On the Road, dressed in berets, black turtlenecks, and black-rimmed glasses. Women wore black leotards and grew their hair long. Herb Caen, a San Francisco journalist, used the suffix fromSputnik 1, the Russian satellite that orbited Earth in 1957, to dub the movement’s followers “Beatniks.” As the Beat Generation faded, a new, related movement began. It too focused on breaking social boundaries, but it also advocated freedom of expression, philosophy, and love. It took its name from the generations before; in fact, some theorists claim that Beats themselves coined the term to describe their children. Over time, the “little hipsters” of the 1970s became known simply as “hippies.” Today’s generation of hipsters rose out of the hippie movement in the same way that hippies rose from Beats and Beats from hepcats. Although contemporary hipsters may not seem to have much in common with 1940s hipsters, the emulation of nonconformity is still there. In 2010, sociologist Mark Greif set about investigating the hipster subculture of the United States and found that much of what tied the group members together was not based on fashion, musical taste, or even a specific point of contention with the mainstream. “All hipsters play at being the inventors or first adopters of novelties,” Greif wrote. “Pride comes from knowing, and deciding, what’s cool in advance of the rest of the world. Yet the habits of hatred and accusation are endemic to hipsters because they feel the weakness of everyone’s position—including their own” (Greif 2010). Much as the hepcats of the jazz era opposed common culture with carefully crafted appearances of coolness and relaxation, modern hipsters reject mainstream values with a purposeful apathy. Young people are often drawn to oppose mainstream conventions, even if in the same way that others do. Ironic, cool to the point of noncaring, and intellectual, hipsters continue to embody a subculture, while simultaneously impacting mainstream culture. Cultural Change As the hipster example illustrates, culture is always evolving. Moreover, new things are added to material culture every day, and they affect nonmaterial culture as well. Cultures change when something new (say, railroads or smartphones) opens up new ways of living and when new ideas enter a culture (say, as a result of travel or globalization). Innovation: Discovery and Invention An innovation refers to an object or concept’s initial appearance in society—it’s innovative because it is markedly new. There are two ways to come across an innovative object or idea: discover it or invent it.Discoveries make known previously unknown but existing aspects of reality. In 1610, when Galileo looked through his telescope and discovered Saturn, the planet was already there, but until then, no one had known about it. When Christopher Columbus encountered America, the land was, of course, already well known to its inhabitants. However, Columbus’s discovery was new knowledge for Europeans, and it opened the way to changes in European culture, as well as to the cultures of the discovered lands. For example, new foods such as potatoes and tomatoes transformed the European diet, and horses brought from Europe changed hunting practices of Native American tribes of the Great Plains. Inventions result when something new is formed from existing objects or concepts—when things are put together in an entirely new manner. In the late 1800s and early 1900s, electric appliances were invented at an astonishing pace. Cars, airplanes, vacuum cleaners, lamps, radios, telephones, and televisions were all new inventions. Inventions may shape a culture when people use them in place of older ways of carrying out activities and relating to others, or as a way to carry out new kinds of activities. Their adoption reflects (and may shape) cultural values, and their use may require new norms for new situations. Consider the introduction of modern communication technology, such as mobile phones and smartphones. As more and more people began carrying these devices, phone conversations no longer were restricted to homes, offices, and phone booths. People on trains, in restaurants, and in other public places became annoyed by listening to one-sided conversations. Norms were needed for cell phone use. Some people pushed for the idea that those who are out in the world should pay attention to their companions and surroundings. However, technology enabled a workaround: texting, which enables quiet communication and has surpassed phoning as the chief way to meet today’s highly valued ability to stay in touch anywhere, everywhere. When the pace of innovation increases, it can lead to generation gaps. Technological gadgets that catch on quickly with one generation are sometimes dismissed by a skeptical older generation. A culture’s objects and ideas can cause not just generational but cultural gaps. Material culture tends to diffuse more quickly than nonmaterial culture; technology can spread through society in a matter of months, but it can take generations for the ideas and beliefs of society to change. Sociologist William F. Ogburn coined the term culture lag to refer to this time that elapses between the introduction of a new item of material culture and its acceptance as part of nonmaterial culture (Ogburn 1957). Culture lag can also cause tangible problems. The infrastructure of the United States, built a hundred years ago or more, is having trouble supporting today’s more heavily populated and fast-paced life. Yet there is a lag in conceptualizing solutions to infrastructure problems. Rising fuel prices, increased air pollution, and traffic jams are all symptoms of culture lag. Although people are becoming aware of the consequences of overusing resources, the means to support changes takes time to achieve. Diffusion and Globalization The integration of world markets and technological advances of the last decades have allowed for greater exchange between cultures through the processes of globalization and diffusion. Beginning in the 1980s, Western governments began to deregulate social services while granting greater liberties to private businesses. As a result, world markets became dominated by multinational companies in the 1980s, a new state of affairs at that time. We have since come to refer to this integration of international trade and finance markets as globalization. Increased communications and air travel have further opened doors for international business relations, facilitating the flow not only of goods but also of information and people as well (Scheuerman 2014 (revised)). Today, many U.S. companies set up offices in other nations where the costs of resources and labor are cheaper. When a person in the United States calls to get information about banking, insurance, or computer services, the person taking that call may be working in another country. Alongside the process of globalization is diffusion, or the spread of material and nonmaterial culture. While globalization refers to the integration of markets, diffusion relates to a similar process in the integration of international cultures. Middle-class Americans can fly overseas and return with a new appreciation of Thai noodles or Italian gelato. Access to television and the Internet has brought the lifestyles and values portrayed in U.S. sitcoms into homes around the globe. Twitter feeds from public demonstrations in one nation have encouraged political protesters in other countries. When this kind of diffusion occurs, material objects and ideas from one culture are introduced into another. Summary Sociologists recognize high culture and popular culture within societies. Societies are also comprised of many subcultures—smaller groups that share an identity. Countercultures reject mainstream values and create their own cultural rules and norms. Through invention or discovery, cultures evolve via new ideas and new ways of thinking. In many modern cultures, the cornerstone of innovation is technology, the rapid growth of which can lead to cultural lag. Technology is also responsible for the spread of both material and nonmaterial culture that contributes to globalization. Section Quiz An example of high culture is ___________, whereas an example of popular culture would be ____________. - Dostoevsky style in film; “American Idol” winners - medical marijuana; film noir - country music; pop music - political theory; sociological theory Hint: A The Ku Klux Klan is an example of what part of culture? - Counterculture - Subculture - Multiculturalism - Afrocentricity Hint: A Modern-day hipsters are an example of: - ethnocentricity - counterculture - subculture - high culture Hint: C Your eighty-three-year-old grandmother has been using a computer for some time now. As a way to keep in touch, you frequently send emails of a few lines to let her know about your day. She calls after every email to respond point by point, but she has never emailed a response back. This can be viewed as an example of: - cultural lag - innovation - ethnocentricity - xenophobia Hint: A Some jobs today advertise in multinational markets and permit telecommuting in lieu of working from a primary location. This broadening of the job market and the way that jobs are performed can be attributed to: - cultural lag - innovation - discovery - globalization Hint: D The major difference between invention and discovery is: - Invention is based on technology, whereas discovery is usually based on culture - Discovery involves finding something that already exists, but invention puts things together in a new way - Invention refers to material culture, whereas discovery can be material or theoretic, like laws of physics - Invention is typically used to refer to international objects, whereas discovery refers to that which is local to one’s culture Hint: B That McDonald’s is found in almost every country around the world is an example of: - globalization - diffusion - culture lag - xenocentrism Hint: B Short Answer Identify several examples of popular culture and describe how they inform larger culture. How prevalent is the effect of these examples in your everyday life? Consider some of the specific issues or concerns of your generation. Are any ideas countercultural? What subcultures have emerged from your generation? How have the issues of your generation expressed themselves culturally? How has your generation made its mark on society’s collective culture? What are some examples of cultural lag that are present in your life? Do you think technology affects culture positively or negatively? Explain. Further Research The Beats were a counterculture that birthed an entire movement of art, music, and literature—much of which is still highly regarded and studied today. The man responsible for naming the generation was Jack Kerouac; however, the man responsible for introducing the world to that generation was John Clellon Holmes, a writer often lumped in with the group. In 1952 he penned an article for the New York Times Magazine titled, “This Is the Beat Generation.” Read that article and learn more about Clellon Holmes and the Beats:http://openstaxcollege.org/l/The-Beats Popular culture meets counterculture in this as Oprah Winfrey interacts with members of the Yearning for Zion cult. Read about it here: http://openstaxcollege.org/l/Oprah References Greif, Mark. 2010. “The Hipster in the Mirror.” New York Times, November 12. Retrieved February 10, 2012 (http://www.nytimes.com/2010/11/14/books/review/Greif-t.html?pagewanted=1). Ogburn, William F. 1957. “Cultural Lag as Theory.” Sociology & Social Research 41(3):167–174. Rogers, Everett M. 1962. Diffusion of Innovations. Glencoe: Free Press. Scheuerman, William. 2010. “Globalization.” The Stanford Encyclopedia of Philosophy, edited by E. N. Revised 2014. Zalta, Summer. Retrieved February 10, 2012 (http://plato.stanford.edu/archives/sum2010/entries/globalization/).	oercommons	2025-03-18T00:35:13.155125	Module	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11765/overview", "title": "Introduction to Sociology 2e, Culture, Pop Culture, Subculture, and Cultural Change", "author": null }
https://oercommons.org/courseware/lesson/66291/overview	Glossary Overview Glossary Glossary: The Court System of Texas arraignment: when a defendant is formally charged and made aware of their rights capital case: a criminal case in which the death penalty is a possible punishment civil law: a branch of law that deals with disputes, usually between private individuals over relationships, obligations, and responsibility complaint: the presentation of a grievance by the plaintiff in a civil case courts of appeal: the 14 intermediate-level appellate courts that hear appeals from district and county courts to determine whether the decisions of these lower courts followed legal principles and court procedures. criminal law: the branch of law that regulates the conduct of individuals, defines crimes, and specifies punishments for criminal acts. defendant: an individual, company, or institution sued or accused in a court of law district courts: the major trial courts in Texas, which usually have general jurisdiction over a broad range of civil and criminal cases due process: in the Texas criminal justice system, the state must ensure that every person is treated equally in legal matters felony: a serious criminal offense, punishable by a prison sentence or a fine; a capital felony is punishable by death or a life sentence hierarchical: In the Texas court system, cases start in local trial courts, then work their way up to appeals courts. justice of the peace courts: local trial courts with limited jurisdiction over small claims and very minor criminal misdemeanors juvenile courts: in Texas, a juvenile is defined as young as 10 years old, and a juvenile can be convicted as an adult as young as 14 years old. Juvenile courts preside in the District Courts misdemeanor: a minor criminal offense usually punishable by a small fine or short jail sentence municipal courts: local trial courts with limited jurisdiction over violations of city ordinances and very minor criminal misdemeanors plaintiff: the party who initiates a lawsuit (also known as an action) before a court in order to seek a legal remedy plea bargaining: occurs when the defendant and the prosecutor negotiate a deal to avoid having to go to trial precedent: in common law legal systems, a principle or rule established in a previous legal case that is either binding on or persuasive for a court or other tribunal when deciding subsequent cases with similar issues or facts. probate courts: handle wills and estates for deceased persons in Texas’ largest counties Texas Supreme Court: the highest civil court in Texas; consists of nine justices and has final state appellate authority over civil cases. Licenses and Attributions CC LICENSED CONTENT, ORIGINAL The Court System of Texas: Glossary. Authored by: Andrew Teas. License: CC BY: Attribution	oercommons	2025-03-18T00:35:13.179710	05/05/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66291/overview", "title": "Texas Government 2.0, The Court System of Texas, Glossary", "author": "Kris Seago" }
https://oercommons.org/courseware/lesson/58776/overview	Development and Inheritance Introduction Figure 28.1 Newborn A single fertilized egg develops over the span of nine months into an infant consisting of trillions of cells and capable of surviving outside the womb. (credit: “Seattleye”/flickr.com) CHAPTER OBJECTIVES After studying this chapter, you will be able to: - List and explain the steps involved in fertilization - Describe the major events in embryonic development - Describe the major events in fetal development - Discuss the adaptations of a woman’s body to pregnancy - Describe the physiologic adjustments that the newborn must make in the first hours of extrauterine life - Summarize the physiology of lactation - Classify and describe the different patterns of inheritance In approximately nine months, a single cell—a fertilized egg—develops into a fully formed infant consisting of trillions of cells with myriad specialized functions. The dramatic changes of fertilization, embryonic development, and fetal development are followed by remarkable adaptations of the newborn to life outside the womb. An offspring’s normal development depends upon the appropriate synthesis of structural and functional proteins. This, in turn, is governed by the genetic material inherited from the parental egg and sperm, as well as environmental factors. Fertilization - Describe the obstacles that sperm must overcome to reach an oocyte - Explain capacitation and its importance in fertilization - Summarize the events that occur as a sperm fertilizes an oocyte Fertilization occurs when a sperm and an oocyte (egg) combine and their nuclei fuse. Because each of these reproductive cells is a haploid cell containing half of the genetic material needed to form a human being, their combination forms a diploid cell. This new single cell, called a zygote, contains all of the genetic material needed to form a human—half from the mother and half from the father. Transit of Sperm Fertilization is a numbers game. During ejaculation, hundreds of millions of sperm (spermatozoa) are released into the vagina. Almost immediately, millions of these sperm are overcome by the acidity of the vagina (approximately pH 3.8), and millions more may be blocked from entering the uterus by thick cervical mucus. Of those that do enter, thousands are destroyed by phagocytic uterine leukocytes. Thus, the race into the uterine tubes, which is the most typical site for sperm to encounter the oocyte, is reduced to a few thousand contenders. Their journey—thought to be facilitated by uterine contractions—usually takes from 30 minutes to 2 hours. If the sperm do not encounter an oocyte immediately, they can survive in the uterine tubes for another 3–5 days. Thus, fertilization can still occur if intercourse takes place a few days before ovulation. In comparison, an oocyte can survive independently for only approximately 24 hours following ovulation. Intercourse more than a day after ovulation will therefore usually not result in fertilization. During the journey, fluids in the female reproductive tract prepare the sperm for fertilization through a process called capacitation, or priming. The fluids improve the motility of the spermatozoa. They also deplete cholesterol molecules embedded in the membrane of the head of the sperm, thinning the membrane in such a way that will help facilitate the release of the lysosomal (digestive) enzymes needed for the sperm to penetrate the oocyte’s exterior once contact is made. Sperm must undergo the process of capacitation in order to have the “capacity” to fertilize an oocyte. If they reach the oocyte before capacitation is complete, they will be unable to penetrate the oocyte’s thick outer layer of cells. Contact Between Sperm and Oocyte Upon ovulation, the oocyte released by the ovary is swept into—and along—the uterine tube. Fertilization must occur in the distal uterine tube because an unfertilized oocyte cannot survive the 72-hour journey to the uterus. As you will recall from your study of the oogenesis, this oocyte (specifically a secondary oocyte) is surrounded by two protective layers. The corona radiatais an outer layer of follicular (granulosa) cells that form around a developing oocyte in the ovary and remain with it upon ovulation. The underlying zona pellucida (pellucid = “transparent”) is a transparent, but thick, glycoprotein membrane that surrounds the cell’s plasma membrane. As it is swept along the distal uterine tube, the oocyte encounters the surviving capacitated sperm, which stream toward it in response to chemical attractants released by the cells of the corona radiata. To reach the oocyte itself, the sperm must penetrate the two protective layers. The sperm first burrow through the cells of the corona radiata. Then, upon contact with the zona pellucida, the sperm bind to receptors in the zona pellucida. This initiates a process called the acrosomal reaction in which the enzyme-filled “cap” of the sperm, called the acrosome, releases its stored digestive enzymes. These enzymes clear a path through the zona pellucida that allows sperm to reach the oocyte. Finally, a single sperm makes contact with sperm-binding receptors on the oocyte’s plasma membrane (Figure 28.2). The plasma membrane of that sperm then fuses with the oocyte’s plasma membrane, and the head and mid-piece of the “winning” sperm enter the oocyte interior. How do sperm penetrate the corona radiata? Some sperm undergo a spontaneous acrosomal reaction, which is an acrosomal reaction not triggered by contact with the zona pellucida. The digestive enzymes released by this reaction digest the extracellular matrix of the corona radiata. As you can see, the first sperm to reach the oocyte is never the one to fertilize it. Rather, hundreds of sperm cells must undergo the acrosomal reaction, each helping to degrade the corona radiata and zona pellucida until a path is created to allow one sperm to contact and fuse with the plasma membrane of the oocyte. If you consider the loss of millions of sperm between entry into the vagina and degradation of the zona pellucida, you can understand why a low sperm count can cause male infertility. Figure 28.2 Sperm and the Process of Fertilization Before fertilization, hundreds of capacitated sperm must break through the surrounding corona radiata and zona pellucida so that one can contact and fuse with the oocyte plasma membrane. When the first sperm fuses with the oocyte, the oocyte deploys two mechanisms to prevent polyspermy, which is penetration by more than one sperm. This is critical because if more than one sperm were to fertilize the oocyte, the resulting zygote would be a triploid organism with three sets of chromosomes. This is incompatible with life. The first mechanism is the fast block, which involves a near instantaneous change in sodium ion permeability upon binding of the first sperm, depolarizing the oocyte plasma membrane and preventing the fusion of additional sperm cells. The fast block sets in almost immediately and lasts for about a minute, during which time an influx of calcium ions following sperm penetration triggers the second mechanism, the slow block. In this process, referred to as the cortical reaction, cortical granules sitting immediately below the oocyte plasma membrane fuse with the membrane and release zonal inhibiting proteins and mucopolysaccharides into the space between the plasma membrane and the zona pellucida. Zonal inhibiting proteins cause the release of any other attached sperm and destroy the oocyte’s sperm receptors, thus preventing any more sperm from binding. The mucopolysaccharides then coat the nascent zygote in an impenetrable barrier that, together with hardened zona pellucida, is called a fertilization membrane. The Zygote Recall that at the point of fertilization, the oocyte has not yet completed meiosis; all secondary oocytes remain arrested in metaphase of meiosis II until fertilization. Only upon fertilization does the oocyte complete meiosis. The unneeded complement of genetic material that results is stored in a second polar body that is eventually ejected. At this moment, the oocyte has become an ovum, the female haploid gamete. The two haploid nuclei derived from the sperm and oocyte and contained within the egg are referred to as pronuclei. They decondense, expand, and replicate their DNA in preparation for mitosis. The pronuclei then migrate toward each other, their nuclear envelopes disintegrate, and the male- and female-derived genetic material intermingles. This step completes the process of fertilization and results in a single-celled diploid zygote with all the genetic instructions it needs to develop into a human. Most of the time, a woman releases a single egg during an ovulation cycle. However, in approximately 1 percent of ovulation cycles, two eggs are released and both are fertilized. Two zygotes form, implant, and develop, resulting in the birth of dizygotic (or fraternal) twins. Because dizygotic twins develop from two eggs fertilized by two sperm, they are no more identical than siblings born at different times. Much less commonly, a zygote can divide into two separate offspring during early development. This results in the birth of monozygotic (or identical) twins. Although the zygote can split as early as the two-cell stage, splitting occurs most commonly during the early blastocyst stage, with roughly 70–100 cells present. These two scenarios are distinct from each other, in that the twin embryos that separated at the two-cell stage will have individual placentas, whereas twin embryos that form from separation at the blastocyst stage will share a placenta and a chorionic cavity. EVERYDAY CONNECTION In Vitro Fertilization IVF, which stands for in vitro fertilization, is an assisted reproductive technology. In vitro, which in Latin translates to “in glass,” refers to a procedure that takes place outside of the body. There are many different indications for IVF. For example, a woman may produce normal eggs, but the eggs cannot reach the uterus because the uterine tubes are blocked or otherwise compromised. A man may have a low sperm count, low sperm motility, sperm with an unusually high percentage of morphological abnormalities, or sperm that are incapable of penetrating the zona pellucida of an egg. A typical IVF procedure begins with egg collection. A normal ovulation cycle produces only one oocyte, but the number can be boosted significantly (to 10–20 oocytes) by administering a short course of gonadotropins. The course begins with follicle-stimulating hormone (FSH) analogs, which support the development of multiple follicles, and ends with a luteinizing hormone (LH) analog that triggers ovulation. Right before the ova would be released from the ovary, they are harvested using ultrasound-guided oocyte retrieval. In this procedure, ultrasound allows a physician to visualize mature follicles. The ova are aspirated (sucked out) using a syringe. In parallel, sperm are obtained from the male partner or from a sperm bank. The sperm are prepared by washing to remove seminal fluid because seminal fluid contains a peptide, FPP (or, fertilization promoting peptide), that—in high concentrations—prevents capacitation of the sperm. The sperm sample is also concentrated, to increase the sperm count per milliliter. Next, the eggs and sperm are mixed in a petri dish. The ideal ratio is 75,000 sperm to one egg. If there are severe problems with the sperm—for example, the count is exceedingly low, or the sperm are completely nonmotile, or incapable of binding to or penetrating the zona pellucida—a sperm can be injected into an egg. This is called intracytoplasmic sperm injection (ICSI). The embryos are then incubated until they either reach the eight-cell stage or the blastocyst stage. In the United States, fertilized eggs are typically cultured to the blastocyst stage because this results in a higher pregnancy rate. Finally, the embryos are transferred to a woman’s uterus using a plastic catheter (tube). Figure 28.3 illustrates the steps involved in IVF. Figure 28.3 IVF In vitro fertilization involves egg collection from the ovaries, fertilization in a petri dish, and the transfer of embryos into the uterus. IVF is a relatively new and still evolving technology, and until recently it was necessary to transfer multiple embryos to achieve a good chance of a pregnancy. Today, however, transferred embryos are much more likely to implant successfully, so countries that regulate the IVF industry cap the number of embryos that can be transferred per cycle at two. This reduces the risk of multiple-birth pregnancies. The rate of success for IVF is correlated with a woman’s age. More than 40 percent of women under 35 succeed in giving birth following IVF, but the rate drops to a little over 10 percent in women over 40. INTERACTIVE LINK Go to this site to view resources covering various aspects of fertilization, including movies and animations showing sperm structure and motility, ovulation, and fertilization. Embryonic Development - By the end of this section, you will be able to: - Distinguish the stages of embryonic development that occur before implantation - Describe the process of implantation - List and describe four embryonic membranes - Explain gastrulation - Describe how the placenta is formed and identify its functions - Explain how an embryo transforms from a flat disc of cells into a three-dimensional shape resembling a human - Summarize the process of organogenesis Throughout this chapter, we will express embryonic and fetal ages in terms of weeks from fertilization, commonly called conception. The period of time required for full development of a fetus in utero is referred to as gestation (gestare = “to carry” or “to bear”). It can be subdivided into distinct gestational periods. The first 2 weeks of prenatal development are referred to as the pre-embryonic stage. A developing human is referred to as an embryo during weeks 3–8, and a fetus from the ninth week of gestation until birth. In this section, we’ll cover the pre-embryonic and embryonic stages of development, which are characterized by cell division, migration, and differentiation. By the end of the embryonic period, all of the organ systems are structured in rudimentary form, although the organs themselves are either nonfunctional or only semi-functional. Pre-implantation Embryonic Development Following fertilization, the zygote and its associated membranes, together referred to as the conceptus, continue to be projected toward the uterus by peristalsis and beating cilia. During its journey to the uterus, the zygote undergoes five or six rapid mitotic cell divisions. Although each cleavage results in more cells, it does not increase the total volume of the conceptus (Figure 28.4). Each daughter cell produced by cleavage is called a blastomere (blastos = “germ,” in the sense of a seed or sprout). Approximately 3 days after fertilization, a 16-cell conceptus reaches the uterus. The cells that had been loosely grouped are now compacted and look more like a solid mass. The name given to this structure is the morula (morula = “little mulberry”). Once inside the uterus, the conceptus floats freely for several more days. It continues to divide, creating a ball of approximately 100 cells, and consuming nutritive endometrial secretions called uterine milk while the uterine lining thickens. The ball of now tightly bound cells starts to secrete fluid and organize themselves around a fluid-filled cavity, the blastocoel. At this developmental stage, the conceptus is referred to as a blastocyst. Within this structure, a group of cells forms into an inner cell mass, which is fated to become the embryo. The cells that form the outer shell are called trophoblasts (trophe = “to feed” or “to nourish”). These cells will develop into the chorionic sac and the fetal portion of the placenta (the organ of nutrient, waste, and gas exchange between mother and the developing offspring). The inner mass of embryonic cells is totipotent during this stage, meaning that each cell has the potential to differentiate into any cell type in the human body. Totipotency lasts for only a few days before the cells’ fates are set as being the precursors to a specific lineage of cells. Figure 28.4 Pre-Embryonic Cleavages Pre-embryonic cleavages make use of the abundant cytoplasm of the conceptus as the cells rapidly divide without changing the total volume. As the blastocyst forms, the trophoblast excretes enzymes that begin to degrade the zona pellucida. In a process called “hatching,” the conceptus breaks free of the zona pellucida in preparation for implantation. INTERACTIVE LINK View this time-lapse movie of a conceptus starting at day 3. What is the first structure you see? At what point in the movie does the blastocoel first appear? What event occurs at the end of the movie? Implantation At the end of the first week, the blastocyst comes in contact with the uterine wall and adheres to it, embedding itself in the uterine lining via the trophoblast cells. Thus begins the process of implantation, which signals the end of the pre-embryonic stage of development (Figure 28.5). Implantation can be accompanied by minor bleeding. The blastocyst typically implants in the fundus of the uterus or on the posterior wall. However, if the endometrium is not fully developed and ready to receive the blastocyst, the blastocyst will detach and find a better spot. A significant percentage (50–75 percent) of blastocysts fail to implant; when this occurs, the blastocyst is shed with the endometrium during menses. The high rate of implantation failure is one reason why pregnancy typically requires several ovulation cycles to achieve. Figure 28.5 Pre-Embryonic Development Ovulation, fertilization, pre-embryonic development, and implantation occur at specific locations within the female reproductive system in a time span of approximately 1 week. When implantation succeeds and the blastocyst adheres to the endometrium, the superficial cells of the trophoblast fuse with each other, forming the syncytiotrophoblast, a multinucleated body that digests endometrial cells to firmly secure the blastocyst to the uterine wall. In response, the uterine mucosa rebuilds itself and envelops the blastocyst (Figure 28.6). The trophoblast secretes human chorionic gonadotropin (hCG), a hormone that directs the corpus luteum to survive, enlarge, and continue producing progesterone and estrogen to suppress menses. These functions of hCG are necessary for creating an environment suitable for the developing embryo. As a result of this increased production, hCG accumulates in the maternal bloodstream and is excreted in the urine. Implantation is complete by the middle of the second week. Just a few days after implantation, the trophoblast has secreted enough hCG for an at-home urine pregnancy test to give a positive result. Figure 28.6 Implantation During implantation, the trophoblast cells of the blastocyst adhere to the endometrium and digest endometrial cells until it is attached securely. Most of the time an embryo implants within the body of the uterus in a location that can support growth and development. However, in one to two percent of cases, the embryo implants either outside the uterus (an ectopic pregnancy) or in a region of uterus that can create complications for the pregnancy. If the embryo implants in the inferior portion of the uterus, the placenta can potentially grow over the opening of the cervix, a condition call placenta previa. DISORDERS OF THE... Development of the Embryo In the vast majority of ectopic pregnancies, the embryo does not complete its journey to the uterus and implants in the uterine tube, referred to as a tubal pregnancy. However, there are also ovarian ectopic pregnancies (in which the egg never left the ovary) and abdominal ectopic pregnancies (in which an egg was “lost” to the abdominal cavity during the transfer from ovary to uterine tube, or in which an embryo from a tubal pregnancy re-implanted in the abdomen). Once in the abdominal cavity, an embryo can implant into any well-vascularized structure—the rectouterine cavity (Douglas’ pouch), the mesentery of the intestines, and the greater omentum are some common sites. Tubal pregnancies can be caused by scar tissue within the tube following a sexually transmitted bacterial infection. The scar tissue impedes the progress of the embryo into the uterus—in some cases “snagging” the embryo and, in other cases, blocking the tube completely. Approximately one half of tubal pregnancies resolve spontaneously. Implantation in a uterine tube causes bleeding, which appears to stimulate smooth muscle contractions and expulsion of the embryo. In the remaining cases, medical or surgical intervention is necessary. If an ectopic pregnancy is detected early, the embryo’s development can be arrested by the administration of the cytotoxic drug methotrexate, which inhibits the metabolism of folic acid. If diagnosis is late and the uterine tube is already ruptured, surgical repair is essential. Even if the embryo has successfully found its way to the uterus, it does not always implant in an optimal location (the fundus or the posterior wall of the uterus). Placenta previa can result if an embryo implants close to the internal os of the uterus (the internal opening of the cervix). As the fetus grows, the placenta can partially or completely cover the opening of the cervix (Figure 28.7). Although it occurs in only 0.5 percent of pregnancies, placenta previa is the leading cause of antepartum hemorrhage (profuse vaginal bleeding after week 24 of pregnancy but prior to childbirth). Figure 28.7 Placenta Previa An embryo that implants too close to the opening of the cervix can lead to placenta previa, a condition in which the placenta partially or completely covers the cervix. Embryonic Membranes During the second week of development, with the embryo implanted in the uterus, cells within the blastocyst start to organize into layers. Some grow to form the extra-embryonic membranes needed to support and protect the growing embryo: the amnion, the yolk sac, the allantois, and the chorion. At the beginning of the second week, the cells of the inner cell mass form into a two-layered disc of embryonic cells, and a space—the amniotic cavity—opens up between it and the trophoblast (Figure 28.8). Cells from the upper layer of the disc (the epiblast) extend around the amniotic cavity, creating a membranous sac that forms into the amnion by the end of the second week. The amnion fills with amniotic fluid and eventually grows to surround the embryo. Early in development, amniotic fluid consists almost entirely of a filtrate of maternal plasma, but as the kidneys of the fetus begin to function at approximately the eighth week, they add urine to the volume of amniotic fluid. Floating within the amniotic fluid, the embryo—and later, the fetus—is protected from trauma and rapid temperature changes. It can move freely within the fluid and can prepare for swallowing and breathing out of the uterus. Figure 28.8 Development of the Embryonic Disc Formation of the embryonic disc leaves spaces on either side that develop into the amniotic cavity and the yolk sac. On the ventral side of the embryonic disc, opposite the amnion, cells in the lower layer of the embryonic disk (the hypoblast) extend into the blastocyst cavity and form a yolk sac. The yolk sac supplies some nutrients absorbed from the trophoblast and also provides primitive blood circulation to the developing embryo for the second and third week of development. When the placenta takes over nourishing the embryo at approximately week 4, the yolk sac has been greatly reduced in size and its main function is to serve as the source of blood cells and germ cells (cells that will give rise to gametes). During week 3, a finger-like outpocketing of the yolk sac develops into the allantois, a primitive excretory duct of the embryo that will become part of the urinary bladder. Together, the stalks of the yolk sac and allantois establish the outer structure of the umbilical cord. The last of the extra-embryonic membranes is the chorion, which is the one membrane that surrounds all others. The development of the chorion will be discussed in more detail shortly, as it relates to the growth and development of the placenta. Embryogenesis As the third week of development begins, the two-layered disc of cells becomes a three-layered disc through the process of gastrulation, during which the cells transition from totipotency to multipotency. The embryo, which takes the shape of an oval-shaped disc, forms an indentation called the primitive streak along the dorsal surface of the epiblast. A node at the caudal or “tail” end of the primitive streak emits growth factors that direct cells to multiply and migrate. Cells migrate toward and through the primitive streak and then move laterally to create two new layers of cells. The first layer is the endoderm, a sheet of cells that displaces the hypoblast and lies adjacent to the yolk sac. The second layer of cells fills in as the middle layer, or mesoderm. The cells of the epiblast that remain (not having migrated through the primitive streak) become the ectoderm(Figure 28.9). Figure 28.9 Germ Layers Formation of the three primary germ layers occurs during the first 2 weeks of development. The embryo at this stage is only a few millimeters in length. Each of these germ layers will develop into specific structures in the embryo. Whereas the ectoderm and endoderm form tightly connected epithelial sheets, the mesodermal cells are less organized and exist as a loosely connected cell community. The ectoderm gives rise to cell lineages that differentiate to become the central and peripheral nervous systems, sensory organs, epidermis, hair, and nails. Mesodermal cells ultimately become the skeleton, muscles, connective tissue, heart, blood vessels, and kidneys. The endoderm goes on to form the epithelial lining of the gastrointestinal tract, liver, and pancreas, as well as the lungs (Figure 28.10). Figure 28.10 Fates of Germ Layers in Embryo Following gastrulation of the embryo in the third week, embryonic cells of the ectoderm, mesoderm, and endoderm begin to migrate and differentiate into the cell lineages that will give rise to mature organs and organ systems in the infant. Development of the Placenta During the first several weeks of development, the cells of the endometrium—referred to as decidual cells—nourish the nascent embryo. During prenatal weeks 4–12, the developing placenta gradually takes over the role of feeding the embryo, and the decidual cells are no longer needed. The mature placenta is composed of tissues derived from the embryo, as well as maternal tissues of the endometrium. The placenta connects to the conceptus via the umbilical cord, which carries deoxygenated blood and wastes from the fetus through two umbilical arteries; nutrients and oxygen are carried from the mother to the fetus through the single umbilical vein. The umbilical cord is surrounded by the amnion, and the spaces within the cord around the blood vessels are filled with Wharton’s jelly, a mucous connective tissue. The maternal portion of the placenta develops from the deepest layer of the endometrium, the decidua basalis. To form the embryonic portion of the placenta, the syncytiotrophoblast and the underlying cells of the trophoblast (cytotrophoblast cells) begin to proliferate along with a layer of extraembryonic mesoderm cells. These form the chorionic membrane, which envelops the entire conceptus as the chorion. The chorionic membrane forms finger-like structures called chorionic villi that burrow into the endometrium like tree roots, making up the fetal portion of the placenta. The cytotrophoblast cells perforate the chorionic villi, burrow farther into the endometrium, and remodel maternal blood vessels to augment maternal blood flow surrounding the villi. Meanwhile, fetal mesenchymal cells derived from the mesoderm fill the villi and differentiate into blood vessels, including the three umbilical blood vessels that connect the embryo to the developing placenta (Figure 28.11). Figure 28.11 Cross-Section of the Placenta In the placenta, maternal and fetal blood components are conducted through the surface of the chorionic villi, but maternal and fetal bloodstreams never mix directly. The placenta develops throughout the embryonic period and during the first several weeks of the fetal period; placentation is complete by weeks 14–16. As a fully developed organ, the placenta provides nutrition and excretion, respiration, and endocrine function (Table 28.1 and Figure 28.12). It receives blood from the fetus through the umbilical arteries. Capillaries in the chorionic villi filter fetal wastes out of the blood and return clean, oxygenated blood to the fetus through the umbilical vein. Nutrients and oxygen are transferred from maternal blood surrounding the villi through the capillaries and into the fetal bloodstream. Some substances move across the placenta by simple diffusion. Oxygen, carbon dioxide, and any other lipid-soluble substances take this route. Other substances move across by facilitated diffusion. This includes water-soluble glucose. The fetus has a high demand for amino acids and iron, and those substances are moved across the placenta by active transport. Maternal and fetal blood does not commingle because blood cells cannot move across the placenta. This separation prevents the mother’s cytotoxic T cells from reaching and subsequently destroying the fetus, which bears “non-self” antigens. Further, it ensures the fetal red blood cells do not enter the mother’s circulation and trigger antibody development (if they carry “non-self” antigens)—at least until the final stages of pregnancy or birth. This is the reason that, even in the absence of preventive treatment, an Rh− mother doesn’t develop antibodies that could cause hemolytic disease in her first Rh+ fetus. Although blood cells are not exchanged, the chorionic villi provide ample surface area for the two-way exchange of substances between maternal and fetal blood. The rate of exchange increases throughout gestation as the villi become thinner and increasingly branched. The placenta is permeable to lipid-soluble fetotoxic substances: alcohol, nicotine, barbiturates, antibiotics, certain pathogens, and many other substances that can be dangerous or fatal to the developing embryo or fetus. For these reasons, pregnant women should avoid fetotoxic substances. Alcohol consumption by pregnant women, for example, can result in a range of abnormalities referred to as fetal alcohol spectrum disorders (FASD). These include organ and facial malformations, as well as cognitive and behavioral disorders. Functions of the Placenta \| Nutrition and digestion \| Respiration \| Endocrine function \| \|---\|---\|---\| \| \| \| Table 28.1 Figure 28.12 Placenta This post-expulsion placenta and umbilical cord (white) are viewed from the fetal side. Organogenesis Following gastrulation, rudiments of the central nervous system develop from the ectoderm in the process of neurulation(Figure 28.13). Specialized neuroectodermal tissues along the length of the embryo thicken into the neural plate. During the fourth week, tissues on either side of the plate fold upward into a neural fold. The two folds converge to form the neural tube. The tube lies atop a rod-shaped, mesoderm-derived notochord, which eventually becomes the nucleus pulposus of intervertebral discs. Block-like structures called somites form on either side of the tube, eventually differentiating into the axial skeleton, skeletal muscle, and dermis. During the fourth and fifth weeks, the anterior neural tube dilates and subdivides to form vesicles that will become the brain structures. Folate, one of the B vitamins, is important to the healthy development of the neural tube. A deficiency of maternal folate in the first weeks of pregnancy can result in neural tube defects, including spina bifida—a birth defect in which spinal tissue protrudes through the newborn’s vertebral column, which has failed to completely close. A more severe neural tube defect is anencephaly, a partial or complete absence of brain tissue. Figure 28.13 Neurulation The embryonic process of neurulation establishes the rudiments of the future central nervous system and skeleton. The embryo, which begins as a flat sheet of cells, begins to acquire a cylindrical shape through the process of embryonic folding (Figure 28.14). The embryo folds laterally and again at either end, forming a C-shape with distinct head and tail ends. The embryo envelops a portion of the yolk sac, which protrudes with the umbilical cord from what will become the abdomen. The folding essentially creates a tube, called the primitive gut, that is lined by the endoderm. The amniotic sac, which was sitting on top of the flat embryo, envelops the embryo as it folds. Figure 28.14 Embryonic Folding Embryonic folding converts a flat sheet of cells into a hollow, tube-like structure. Within the first 8 weeks of gestation, a developing embryo establishes the rudimentary structures of all of its organs and tissues from the ectoderm, mesoderm, and endoderm. This process is called organogenesis. Like the central nervous system, the heart also begins its development in the embryo as a tube-like structure, connected via capillaries to the chorionic villi. Cells of the primitive tube-shaped heart are capable of electrical conduction and contraction. The heart begins beating in the beginning of the fourth week, although it does not actually pump embryonic blood until a week later, when the oversized liver has begun producing red blood cells. (This is a temporary responsibility of the embryonic liver that the bone marrow will assume during fetal development.) During weeks 4–5, the eye pits form, limb buds become apparent, and the rudiments of the pulmonary system are formed. During the sixth week, uncontrolled fetal limb movements begin to occur. The gastrointestinal system develops too rapidly for the embryonic abdomen to accommodate it, and the intestines temporarily loop into the umbilical cord. Paddle-shaped hands and feet develop fingers and toes by the process of apoptosis (programmed cell death), which causes the tissues between the fingers to disintegrate. By week 7, the facial structure is more complex and includes nostrils, outer ears, and lenses (Figure 28.15). By the eighth week, the head is nearly as large as the rest of the embryo’s body, and all major brain structures are in place. The external genitalia are apparent, but at this point, male and female embryos are indistinguishable. Bone begins to replace cartilage in the embryonic skeleton through the process of ossification. By the end of the embryonic period, the embryo is approximately 3 cm (1.2 in) from crown to rump and weighs approximately 8 g (0.25 oz). Figure 28.15 Embryo at 7 Weeks An embryo at the end of 7 weeks of development is only 10 mm in length, but its developing eyes, limb buds, and tail are already visible. (This embryo was derived from an ectopic pregnancy.) (credit: Ed Uthman) INTERACTIVE LINK Use this interactive tool to view the process of embryogenesis from fertilization through pregnancy to birth. Can you identify when neurulation occurs in the embryo? Fetal Development - Differentiate between the embryonic period and the fetal period - Briefly describe the process of sexual differentiation - Describe the fetal circulatory system and explain the role of the shunts - Trace the development of a fetus from the end of the embryonic period to birth As you will recall, a developing human is called a fetus from the ninth week of gestation until birth. This 30-week period of development is marked by continued cell growth and differentiation, which fully develop the structures and functions of the immature organ systems formed during the embryonic period. The completion of fetal development results in a newborn who, although still immature in many ways, is capable of survival outside the womb. Sexual Differentiation Sexual differentiation does not begin until the fetal period, during weeks 9–12. Embryonic males and females, though genetically distinguishable, are morphologically identical (Figure 28.16). Bipotential gonads, or gonads that can develop into male or female sexual organs, are connected to a central cavity called the cloaca via Müllerian ducts and Wolffian ducts. (The cloaca is an extension of the primitive gut.) Several events lead to sexual differentiation during this period. During male fetal development, the bipotential gonads become the testes and associated epididymis. The Müllerian ducts degenerate. The Wolffian ducts become the vas deferens, and the cloaca becomes the urethra and rectum. During female fetal development, the bipotential gonads develop into ovaries. The Wolffian ducts degenerate. The Müllerian ducts become the uterine tubes and uterus, and the cloaca divides and develops into a vagina, a urethra, and a rectum. Figure 28.16 Sexual Differentiation Differentiation of the male and female reproductive systems does not occur until the fetal period of development. The Fetal Circulatory System During prenatal development, the fetal circulatory system is integrated with the placenta via the umbilical cord so that the fetus receives both oxygen and nutrients from the placenta. However, after childbirth, the umbilical cord is severed, and the newborn’s circulatory system must be reconfigured. When the heart first forms in the embryo, it exists as two parallel tubes derived from mesoderm and lined with endothelium, which then fuse together. As the embryo develops into a fetus, the tube-shaped heart folds and further differentiates into the four chambers present in a mature heart. Unlike a mature cardiovascular system, however, the fetal cardiovascular system also includes circulatory shortcuts, or shunts. A shunt is an anatomical (or sometimes surgical) diversion that allows blood flow to bypass immature organs such as the lungs and liver until childbirth. The placenta provides the fetus with necessary oxygen and nutrients via the umbilical vein. (Remember that veins carry blood toward the heart. In this case, the blood flowing to the fetal heart is oxygenated because it comes from the placenta. The respiratory system is immature and cannot yet oxygenate blood on its own.) From the umbilical vein, the oxygenated blood flows toward the inferior vena cava, all but bypassing the immature liver, via the ductus venosus shunt (Figure 28.17). The liver receives just a trickle of blood, which is all that it needs in its immature, semifunctional state. Blood flows from the inferior vena cava to the right atrium, mixing with fetal venous blood along the way. Although the fetal liver is semifunctional, the fetal lungs are nonfunctional. The fetal circulation therefore bypasses the lungs by shifting some of the blood through the foramen ovale, a shunt that directly connects the right and left atria and avoids the pulmonary trunk altogether. Most of the rest of the blood is pumped to the right ventricle, and from there, into the pulmonary trunk, which splits into pulmonary arteries. However, a shunt within the pulmonary artery, the ductus arteriosus, diverts a portion of this blood into the aorta. This ensures that only a small volume of oxygenated blood passes through the immature pulmonary circuit, which has only minor metabolic requirements. Blood vessels of uninflated lungs have high resistance to flow, a condition that encourages blood to flow to the aorta, which presents much lower resistance. The oxygenated blood moves through the foramen ovale into the left atrium, where it mixes with the now deoxygenated blood returning from the pulmonary circuit. This blood then moves into the left ventricle, where it is pumped into the aorta. Some of this blood moves through the coronary arteries into the myocardium, and some moves through the carotid arteries to the brain. The descending aorta carries partially oxygenated and partially deoxygenated blood into the lower regions of the body. It eventually passes into the umbilical arteries through branches of the internal iliac arteries. The deoxygenated blood collects waste as it circulates through the fetal body and returns to the umbilical cord. Thus, the two umbilical arteries carry blood low in oxygen and high in carbon dioxide and fetal wastes. This blood is filtered through the placenta, where wastes diffuse into the maternal circulation. Oxygen and nutrients from the mother diffuse into the placenta and from there into the fetal blood, and the process repeats. Figure 28.17 Fetal Circulatory System The fetal circulatory system includes three shunts to divert blood from undeveloped and partially functioning organs, as well as blood supply to and from the placenta. Other Organ Systems During weeks 9–12 of fetal development, the brain continues to expand, the body elongates, and ossification continues. Fetal movements are frequent during this period, but are jerky and not well-controlled. The bone marrow begins to take over the process of erythrocyte production—a task that the liver performed during the embryonic period. The liver now secretes bile. The fetus circulates amniotic fluid by swallowing it and producing urine. The eyes are well-developed by this stage, but the eyelids are fused shut. The fingers and toes begin to develop nails. By the end of week 12, the fetus measures approximately 9 cm (3.5 in) from crown to rump. Weeks 13–16 are marked by sensory organ development. The eyes move closer together; blinking motions begin, although the eyes remain sealed shut. The lips exhibit sucking motions. The ears move upward and lie flatter against the head. The scalp begins to grow hair. The excretory system is also developing: the kidneys are well-formed, and meconium, or fetal feces, begins to accumulate in the intestines. Meconium consists of ingested amniotic fluid, cellular debris, mucus, and bile. During approximately weeks 16–20, as the fetus grows and limb movements become more powerful, the mother may begin to feel quickening, or fetal movements. However, space restrictions limit these movements and typically force the growing fetus into the “fetal position,” with the arms crossed and the legs bent at the knees. Sebaceous glands coat the skin with a waxy, protective substance called vernix caseosa that protects and moisturizes the skin and may provide lubrication during childbirth. A silky hair called lanugo also covers the skin during weeks 17–20, but it is shed as the fetus continues to grow. Extremely premature infants sometimes exhibit residual lanugo. Developmental weeks 21–30 are characterized by rapid weight gain, which is important for maintaining a stable body temperature after birth. The bone marrow completely takes over erythrocyte synthesis, and the axons of the spinal cord begin to be myelinated, or coated in the electrically insulating glial cell sheaths that are necessary for efficient nervous system functioning. (The process of myelination is not completed until adolescence.) During this period, the fetus grows eyelashes. The eyelids are no longer fused and can be opened and closed. The lungs begin producing surfactant, a substance that reduces surface tension in the lungs and assists proper lung expansion after birth. Inadequate surfactant production in premature newborns may result in respiratory distress syndrome, and as a result, the newborn may require surfactant replacement therapy, supplemental oxygen, or maintenance in a continuous positive airway pressure (CPAP) chamber during their first days or weeks of life. In male fetuses, the testes descend into the scrotum near the end of this period. The fetus at 30 weeks measures 28 cm (11 in) from crown to rump and exhibits the approximate body proportions of a full-term newborn, but still is much leaner. INTERACTIVE LINK Visit this site for a summary of the stages of pregnancy, as experienced by the mother, and view the stages of development of the fetus throughout gestation. At what point in fetal development can a regular heartbeat be detected? The fetus continues to lay down subcutaneous fat from week 31 until birth. The added fat fills out the hypodermis, and the skin transitions from red and wrinkled to soft and pink. Lanugo is shed, and the nails grow to the tips of the fingers and toes. Immediately before birth, the average crown-to-rump length is 35.5–40.5 cm (14–16 in), and the fetus weighs approximately 2.5–4 kg (5.5–8.8 lbs). Once born, the newborn is no longer confined to the fetal position, so subsequent measurements are made from head-to-toe instead of from crown-to-rump. At birth, the average length is approximately 51 cm (20 in). DISORDERS OF THE... Developing Fetus Throughout the second half of gestation, the fetal intestines accumulate a tarry, greenish black meconium. The newborn’s first stools consist almost entirely of meconium; they later transition to seedy yellow stools or slightly formed tan stools as meconium is cleared and replaced with digested breast milk or formula, respectively. Unlike these later stools, meconium is sterile; it is devoid of bacteria because the fetus is in a sterile environment and has not consumed any breast milk or formula. Typically, an infant does not pass meconium until after birth. However, in 5–20 percent of births, the fetus has a bowel movement in utero, which can cause major complications in the newborn. The passage of meconium in the uterus signals fetal distress, particularly fetal hypoxia (i.e., oxygen deprivation). This may be caused by maternal drug abuse (especially tobacco or cocaine), maternal hypertension, depletion of amniotic fluid, long labor or difficult birth, or a defect in the placenta that prevents it from delivering adequate oxygen to the fetus. Meconium passage is typically a complication of full-term or post-term newborns because it is rarely passed before 34 weeks of gestation, when the gastrointestinal system has matured and is appropriately controlled by nervous system stimuli. Fetal distress can stimulate the vagus nerve to trigger gastrointestinal peristalsis and relaxation of the anal sphincter. Notably, fetal hypoxic stress also induces a gasping reflex, increasing the likelihood that meconium will be inhaled into the fetal lungs. Although meconium is a sterile substance, it interferes with the antibiotic properties of the amniotic fluid and makes the newborn and mother more vulnerable to bacterial infections at birth and during the perinatal period. Specifically, inflammation of the fetal membranes, inflammation of the uterine lining, or neonatal sepsis (infection in the newborn) may occur. Meconium also irritates delicate fetal skin and can cause a rash. The first sign that a fetus has passed meconium usually does not come until childbirth, when the amniotic sac ruptures. Normal amniotic fluid is clear and watery, but amniotic fluid in which meconium has been passed is stained greenish or yellowish. Antibiotics given to the mother may reduce the incidence of maternal bacterial infections, but it is critical that meconium is aspirated from the newborn before the first breath. Under these conditions, an obstetrician will extensively aspirate the infant’s airways as soon as the head is delivered, while the rest of the infant’s body is still inside the birth canal. Aspiration of meconium with the first breath can result in labored breathing, a barrel-shaped chest, or a low Apgar score. An obstetrician can identify meconium aspiration by listening to the lungs with a stethoscope for a coarse rattling sound. Blood gas tests and chest X-rays of the infant can confirm meconium aspiration. Inhaled meconium after birth could obstruct a newborn’s airways leading to alveolar collapse, interfere with surfactant function by stripping it from the lungs, or cause pulmonary inflammation or hypertension. Any of these complications will make the newborn much more vulnerable to pulmonary infection, including pneumonia. Maternal Changes During Pregnancy, Labor, and Birth - Explain how estrogen, progesterone, and hCG are involved in maintaining pregnancy - List the contributors to weight gain during pregnancy - Describe the major changes to the maternal digestive, circulatory, and integumentary systems during pregnancy - Summarize the events leading to labor - Identify and describe each of the three stages of childbirth A full-term pregnancy lasts approximately 270 days (approximately 38.5 weeks) from conception to birth. Because it is easier to remember the first day of the last menstrual period (LMP) than to estimate the date of conception, obstetricians set the due date as 284 days (approximately 40.5 weeks) from the LMP. This assumes that conception occurred on day 14 of the woman’s cycle, which is usually a good approximation. The 40 weeks of an average pregnancy are usually discussed in terms of three trimesters, each approximately 13 weeks. During the second and third trimesters, the pre-pregnancy uterus—about the size of a fist—grows dramatically to contain the fetus, causing a number of anatomical changes in the mother (Figure 28.18). Figure 28.18 Size of Uterus throughout Pregnancy The uterus grows throughout pregnancy to accommodate the fetus. Effects of Hormones Virtually all of the effects of pregnancy can be attributed in some way to the influence of hormones—particularly estrogens, progesterone, and hCG. During weeks 7–12 from the LMP, the pregnancy hormones are primarily generated by the corpus luteum. Progesterone secreted by the corpus luteum stimulates the production of decidual cells of the endometrium that nourish the blastocyst before placentation. As the placenta develops and the corpus luteum degenerates during weeks 12–17, the placenta gradually takes over as the endocrine organ of pregnancy. The placenta converts weak androgens secreted by the maternal and fetal adrenal glands to estrogens, which are necessary for pregnancy to progress. Estrogen levels climb throughout the pregnancy, increasing 30-fold by childbirth. Estrogens have the following actions: - They suppress FSH and LH production, effectively preventing ovulation. (This function is the biological basis of hormonal birth control pills.) - They induce the growth of fetal tissues and are necessary for the maturation of the fetal lungs and liver. - They promote fetal viability by regulating progesterone production and triggering fetal synthesis of cortisol, which helps with the maturation of the lungs, liver, and endocrine organs such as the thyroid gland and adrenal gland. - They stimulate maternal tissue growth, leading to uterine enlargement and mammary duct expansion and branching. Relaxin, another hormone secreted by the corpus luteum and then by the placenta, helps prepare the mother’s body for childbirth. It increases the elasticity of the symphysis pubis joint and pelvic ligaments, making room for the growing fetus and allowing expansion of the pelvic outlet for childbirth. Relaxin also helps dilate the cervix during labor. The placenta takes over the synthesis and secretion of progesterone throughout pregnancy as the corpus luteum degenerates. Like estrogen, progesterone suppresses FSH and LH. It also inhibits uterine contractions, protecting the fetus from preterm birth. This hormone decreases in late gestation, allowing uterine contractions to intensify and eventually progress to true labor. The placenta also produces hCG. In addition to promoting survival of the corpus luteum, hCG stimulates the male fetal gonads to secrete testosterone, which is essential for the development of the male reproductive system. The anterior pituitary enlarges and ramps up its hormone production during pregnancy, raising the levels of thyrotropin, prolactin, and adrenocorticotropic hormone (ACTH). Thyrotropin, in conjunction with placental hormones, increases the production of thyroid hormone, which raises the maternal metabolic rate. This can markedly augment a pregnant woman’s appetite and cause hot flashes. Prolactin stimulates enlargement of the mammary glands in preparation for milk production. ACTH stimulates maternal cortisol secretion, which contributes to fetal protein synthesis. In addition to the pituitary hormones, increased parathyroid levels mobilize calcium from maternal bones for fetal use. Weight Gain The second and third trimesters of pregnancy are associated with dramatic changes in maternal anatomy and physiology. The most obvious anatomical sign of pregnancy is the dramatic enlargement of the abdominal region, coupled with maternal weight gain. This weight results from the growing fetus as well as the enlarged uterus, amniotic fluid, and placenta. Additional breast tissue and dramatically increased blood volume also contribute to weight gain (Table 28.2). Surprisingly, fat storage accounts for only approximately 2.3 kg (5 lbs) in a normal pregnancy and serves as a reserve for the increased metabolic demand of breastfeeding. During the first trimester, the mother does not need to consume additional calories to maintain a healthy pregnancy. However, a weight gain of approximately 0.45 kg (1 lb) per month is common. During the second and third trimesters, the mother’s appetite increases, but it is only necessary for her to consume an additional 300 calories per day to support the growing fetus. Most women gain approximately 0.45 kg (1 lb) per week. Contributors to Weight Gain During Pregnancy \| Component \| Weight (kg) \| Weight (lb) \| \|---\|---\|---\| \| Fetus \| 3.2–3.6 \| 7–8 \| \| Placenta and fetal membranes \| 0.9–1.8 \| 2–4 \| \| Amniotic fluid \| 0.9–1.4 \| 2–3 \| \| Breast tissue \| 0.9–1.4 \| 2–3 \| \| Blood \| 1.4 \| 4 \| \| Fat \| 0.9–4.1 \| 3–9 \| \| Uterus \| 0.9–2.3 \| 2–5 \| \| Total \| 10–16.3 \| 22–36 \| Table 28.2 Changes in Organ Systems During Pregnancy As the woman’s body adapts to pregnancy, characteristic physiologic changes occur. These changes can sometimes prompt symptoms often referred to collectively as the common discomforts of pregnancy. Digestive and Urinary System Changes Nausea and vomiting, sometimes triggered by an increased sensitivity to odors, are common during the first few weeks to months of pregnancy. This phenomenon is often referred to as “morning sickness,” although the nausea may persist all day. The source of pregnancy nausea is thought to be the increased circulation of pregnancy-related hormones, specifically circulating estrogen, progesterone, and hCG. Decreased intestinal peristalsis may also contribute to nausea. By about week 12 of pregnancy, nausea typically subsides. A common gastrointestinal complaint during the later stages of pregnancy is gastric reflux, or heartburn, which results from the upward, constrictive pressure of the growing uterus on the stomach. The same decreased peristalsis that may contribute to nausea in early pregnancy is also thought to be responsible for pregnancy-related constipation as pregnancy progresses. The downward pressure of the uterus also compresses the urinary bladder, leading to frequent urination. The problem is exacerbated by increased urine production. In addition, the maternal urinary system processes both maternal and fetal wastes, further increasing the total volume of urine. Circulatory System Changes Blood volume increases substantially during pregnancy, so that by childbirth, it exceeds its preconception volume by 30 percent, or approximately 1–2 liters. The greater blood volume helps to manage the demands of fetal nourishment and fetal waste removal. In conjunction with increased blood volume, the pulse and blood pressure also rise moderately during pregnancy. As the fetus grows, the uterus compresses underlying pelvic blood vessels, hampering venous return from the legs and pelvic region. As a result, many pregnant women develop varicose veins or hemorrhoids. Respiratory System Changes During the second half of pregnancy, the respiratory minute volume (volume of gas inhaled or exhaled by the lungs per minute) increases by 50 percent to compensate for the oxygen demands of the fetus and the increased maternal metabolic rate. The growing uterus exerts upward pressure on the diaphragm, decreasing the volume of each inspiration and potentially causing shortness of breath, or dyspnea. During the last several weeks of pregnancy, the pelvis becomes more elastic, and the fetus descends lower in a process called lightening. This typically ameliorates dyspnea. The respiratory mucosa swell in response to increased blood flow during pregnancy, leading to nasal congestion and nose bleeds, particularly when the weather is cold and dry. Humidifier use and increased fluid intake are often recommended to counteract congestion. Integumentary System Changes The dermis stretches extensively to accommodate the growing uterus, breast tissue, and fat deposits on the thighs and hips. Torn connective tissue beneath the dermis can cause striae (stretch marks) on the abdomen, which appear as red or purple marks during pregnancy that fade to a silvery white color in the months after childbirth. An increase in melanocyte-stimulating hormone, in conjunction with estrogens, darkens the areolae and creates a line of pigment from the umbilicus to the pubis called the linea nigra (Figure 28.19). Melanin production during pregnancy may also darken or discolor skin on the face to create a chloasma, or “mask of pregnancy.” Figure 28.19 Linea Nigra The linea nigra, a dark medial line running from the umbilicus to the pubis, forms during pregnancy and persists for a few weeks following childbirth. The linea nigra shown here corresponds to a pregnancy that is 22 weeks along. Physiology of Labor Childbirth, or parturition, typically occurs within a week of a woman’s due date, unless the woman is pregnant with more than one fetus, which usually causes her to go into labor early. As a pregnancy progresses into its final weeks, several physiological changes occur in response to hormones that trigger labor. First, recall that progesterone inhibits uterine contractions throughout the first several months of pregnancy. As the pregnancy enters its seventh month, progesterone levels plateau and then drop. Estrogen levels, however, continue to rise in the maternal circulation (Figure 28.20). The increasing ratio of estrogen to progesterone makes the myometrium (the uterine smooth muscle) more sensitive to stimuli that promote contractions (because progesterone no longer inhibits them). Moreover, in the eighth month of pregnancy, fetal cortisol rises, which boosts estrogen secretion by the placenta and further overpowers the uterine-calming effects of progesterone. Some women may feel the result of the decreasing levels of progesterone in late pregnancy as weak and irregular peristaltic Braxton Hicks contractions, also called false labor. These contractions can often be relieved with rest or hydration. Figure 28.20 Hormones Initiating Labor A positive feedback loop of hormones works to initiate labor. A common sign that labor will be short is the so-called “bloody show.” During pregnancy, a plug of mucus accumulates in the cervical canal, blocking the entrance to the uterus. Approximately 1–2 days prior to the onset of true labor, this plug loosens and is expelled, along with a small amount of blood. Meanwhile, the posterior pituitary has been boosting its secretion of oxytocin, a hormone that stimulates the contractions of labor. At the same time, the myometrium increases its sensitivity to oxytocin by expressing more receptors for this hormone. As labor nears, oxytocin begins to stimulate stronger, more painful uterine contractions, which—in a positive feedback loop—stimulate the secretion of prostaglandins from fetal membranes. Like oxytocin, prostaglandins also enhance uterine contractile strength. The fetal pituitary also secretes oxytocin, which increases prostaglandins even further. Given the importance of oxytocin and prostaglandins to the initiation and maintenance of labor, it is not surprising that, when a pregnancy is not progressing to labor and needs to be induced, a pharmaceutical version of these compounds (called pitocin) is administered by intravenous drip. Finally, stretching of the myometrium and cervix by a full-term fetus in the vertex (head-down) position is regarded as a stimulant to uterine contractions. The sum of these changes initiates the regular contractions known as true labor, which become more powerful and more frequent with time. The pain of labor is attributed to myometrial hypoxia during uterine contractions. Stages of Childbirth The process of childbirth can be divided into three stages: cervical dilation, expulsion of the newborn, and afterbirth (Figure 28.21). Cervical Dilation For vaginal birth to occur, the cervix must dilate fully to 10 cm in diameter—wide enough to deliver the newborn’s head. The dilation stage is the longest stage of labor and typically takes 6–12 hours. However, it varies widely and may take minutes, hours, or days, depending in part on whether the mother has given birth before; in each subsequent labor, this stage tends to be shorter. Figure 28.21 Stages of Childbirth The stages of childbirth include Stage 1, early cervical dilation; Stage 2, full dilation and expulsion of the newborn; and Stage 3, delivery of the placenta and associated fetal membranes. (The position of the newborn’s shoulder is described relative to the mother.) True labor progresses in a positive feedback loop in which uterine contractions stretch the cervix, causing it to dilate and efface, or become thinner. Cervical stretching induces reflexive uterine contractions that dilate and efface the cervix further. In addition, cervical dilation boosts oxytocin secretion from the pituitary, which in turn triggers more powerful uterine contractions. When labor begins, uterine contractions may occur only every 3–30 minutes and last only 20–40 seconds; however, by the end of this stage, contractions may occur as frequently as every 1.5–2 minutes and last for a full minute. Each contraction sharply reduces oxygenated blood flow to the fetus. For this reason, it is critical that a period of relaxation occur after each contraction. Fetal distress, measured as a sustained decrease or increase in the fetal heart rate, can result from severe contractions that are too powerful or lengthy for oxygenated blood to be restored to the fetus. Such a situation can be cause for an emergency birth with vacuum, forceps, or surgically by Caesarian section. The amniotic membranes rupture before the onset of labor in about 12 percent of women; they typically rupture at the end of the dilation stage in response to excessive pressure from the fetal head entering the birth canal. Expulsion Stage The expulsion stage begins when the fetal head enters the birth canal and ends with birth of the newborn. It typically takes up to 2 hours, but it can last longer or be completed in minutes, depending in part on the orientation of the fetus. The vertex presentation known as the occiput anterior vertex is the most common presentation and is associated with the greatest ease of vaginal birth. The fetus faces the maternal spinal cord and the smallest part of the head (the posterior aspect called the occiput) exits the birth canal first. In fewer than 5 percent of births, the infant is oriented in the breech presentation, or buttocks down. In a complete breech, both legs are crossed and oriented downward. In a frank breech presentation, the legs are oriented upward. Before the 1960s, it was common for breech presentations to be delivered vaginally. Today, most breech births are accomplished by Caesarian section. Vaginal birth is associated with significant stretching of the vaginal canal, the cervix, and the perineum. Until recent decades, it was routine procedure for an obstetrician to numb the perineum and perform an episiotomy, an incision in the posterior vaginal wall and perineum. The perineum is now more commonly allowed to tear on its own during birth. Both an episiotomy and a perineal tear need to be sutured shortly after birth to ensure optimal healing. Although suturing the jagged edges of a perineal tear may be more difficult than suturing an episiotomy, tears heal more quickly, are less painful, and are associated with less damage to the muscles around the vagina and rectum. Upon birth of the newborn’s head, an obstetrician will aspirate mucus from the mouth and nose before the newborn’s first breath. Once the head is birthed, the rest of the body usually follows quickly. The umbilical cord is then double-clamped, and a cut is made between the clamps. This completes the second stage of childbirth. Afterbirth The delivery of the placenta and associated membranes, commonly referred to as the afterbirth, marks the final stage of childbirth. After expulsion of the newborn, the myometrium continues to contract. This movement shears the placenta from the back of the uterine wall. It is then easily delivered through the vagina. Continued uterine contractions then reduce blood loss from the site of the placenta. Delivery of the placenta marks the beginning of the postpartum period—the period of approximately 6 weeks immediately following childbirth during which the mother’s body gradually returns to a non-pregnant state. If the placenta does not birth spontaneously within approximately 30 minutes, it is considered retained, and the obstetrician may attempt manual removal. If this is not successful, surgery may be required. It is important that the obstetrician examines the expelled placenta and fetal membranes to ensure that they are intact. If fragments of the placenta remain in the uterus, they can cause postpartum hemorrhage. Uterine contractions continue for several hours after birth to return the uterus to its pre-pregnancy size in a process called involution, which also allows the mother’s abdominal organs to return to their pre-pregnancy locations. Breastfeeding facilitates this process. Although postpartum uterine contractions limit blood loss from the detachment of the placenta, the mother does experience a postpartum vaginal discharge called lochia. This is made up of uterine lining cells, erythrocytes, leukocytes, and other debris. Thick, dark, lochia rubra (red lochia) typically continues for 2–3 days, and is replaced by lochia serosa, a thinner, pinkish form that continues until about the tenth postpartum day. After this period, a scant, creamy, or watery discharge called lochia alba (white lochia) may continue for another 1–2 weeks. Adjustments of the Infant at Birth and Postnatal Stages - Discuss the importance of an infant’s first breath - Explain the closing of the cardiac shunts - Describe thermoregulation in the newborn - Summarize the importance of intestinal flora in the newborn From a fetal perspective, the process of birth is a crisis. In the womb, the fetus was snuggled in a soft, warm, dark, and quiet world. The placenta provided nutrition and oxygen continuously. Suddenly, the contractions of labor and vaginal childbirth forcibly squeeze the fetus through the birth canal, limiting oxygenated blood flow during contractions and shifting the skull bones to accommodate the small space. After birth, the newborn’s system must make drastic adjustments to a world that is colder, brighter, and louder, and where he or she will experience hunger and thirst. The neonatal period (neo- = “new”; -natal = “birth”) spans the first to the thirtieth day of life outside of the uterus. Respiratory Adjustments Although the fetus “practices” breathing by inhaling amniotic fluid in utero, there is no air in the uterus and thus no true opportunity to breathe. (There is also no need to breathe because the placenta supplies the fetus with all the oxygenated blood it needs.) During gestation, the partially collapsed lungs are filled with amniotic fluid and exhibit very little metabolic activity. Several factors stimulate newborns to take their first breath at birth. First, labor contractions temporarily constrict umbilical blood vessels, reducing oxygenated blood flow to the fetus and elevating carbon dioxide levels in the blood. High carbon dioxide levels cause acidosis and stimulate the respiratory center in the brain, triggering the newborn to take a breath. The first breath typically is taken within 10 seconds of birth, after mucus is aspirated from the infant’s mouth and nose. The first breaths inflate the lungs to nearly full capacity and dramatically decrease lung pressure and resistance to blood flow, causing a major circulatory reconfiguration. Pulmonary alveoli open, and alveolar capillaries fill with blood. Amniotic fluid in the lungs drains or is absorbed, and the lungs immediately take over the task of the placenta, exchanging carbon dioxide for oxygen by the process of respiration. Circulatory Adjustments The process of clamping and cutting the umbilical cord collapses the umbilical blood vessels. In the absence of medical assistance, this occlusion would occur naturally within 20 minutes of birth because the Wharton’s jelly within the umbilical cord would swell in response to the lower temperature outside of the mother’s body, and the blood vessels would constrict. Natural occlusion has occurred when the umbilical cord is no longer pulsating. For the most part, the collapsed vessels atrophy and become fibrotic remnants, existing in the mature circulatory system as ligaments of the abdominal wall and liver. The ductus venosus degenerates to become the ligamentum venosum beneath the liver. Only the proximal sections of the two umbilical arteries remain functional, taking on the role of supplying blood to the upper part of the bladder (Figure 28.22). Figure 28.22 Neonatal Circulatory System A newborn’s circulatory system reconfigures immediately after birth. The three fetal shunts have been closed permanently, facilitating blood flow to the liver and lungs. The newborn’s first breath is vital to initiate the transition from the fetal to the neonatal circulatory pattern. Inflation of the lungs decreases blood pressure throughout the pulmonary system, as well as in the right atrium and ventricle. In response to this pressure change, the flow of blood temporarily reverses direction through the foramen ovale, moving from the left to the right atrium, and blocking the shunt with two flaps of tissue. Within 1 year, the tissue flaps usually fuse over the shunt, turning the foramen ovale into the fossa ovalis. The ductus arteriosus constricts as a result of increased oxygen concentration, and becomes the ligamentum arteriosum. Closing of the ductus arteriosus ensures that all blood pumped to the pulmonary circuit will be oxygenated by the newly functional neonatal lungs. Thermoregulatory Adjustments The fetus floats in warm amniotic fluid that is maintained at a temperature of approximately 98.6°F with very little fluctuation. Birth exposes newborns to a cooler environment in which they have to regulate their own body temperature. Newborns have a higher ratio of surface area to volume than adults. This means that their body has less volume throughout which to produce heat, and more surface area from which to lose heat. As a result, newborns produce heat more slowly and lose it more quickly. Newborns also have immature musculature that limits their ability to generate heat by shivering. Moreover, their nervous systems are underdeveloped, so they cannot quickly constrict superficial blood vessels in response to cold. They also have little subcutaneous fat for insulation. All these factors make it harder for newborns to maintain their body temperature. Newborns, however, do have a special method for generating heat: nonshivering thermogenesis, which involves the breakdown of brown adipose tissue, or brown fat, which is distributed over the back, chest, and shoulders. Brown fat differs from the more familiar white fat in two ways: - It is highly vascularized. This allows for faster delivery of oxygen, which leads to faster cellular respiration. - It is packed with a special type of mitochondria that are able to engage in cellular respiration reactions that produce less ATP and more heat than standard cellular respiration reactions. The breakdown of brown fat occurs automatically upon exposure to cold, so it is an important heat regulator in newborns. During fetal development, the placenta secretes inhibitors that prevent metabolism of brown adipose fat and promote its accumulation in preparation for birth. Gastrointestinal and Urinary Adjustments In adults, the gastrointestinal tract harbors bacterial flora—trillions of bacteria that aid in digestion, produce vitamins, and protect from the invasion or replication of pathogens. In stark contrast, the fetal intestine is sterile. The first consumption of breast milk or formula floods the neonatal gastrointestinal tract with beneficial bacteria that begin to establish the bacterial flora. The fetal kidneys filter blood and produce urine, but the neonatal kidneys are still immature and inefficient at concentrating urine. Therefore, newborns produce very dilute urine, making it particularly important for infants to obtain sufficient fluids from breast milk or formula. HOMEOSTATIC IMBALANCES Homeostasis in the Newborn: Apgar Score In the minutes following birth, a newborn must undergo dramatic systemic changes to be able to survive outside the womb. An obstetrician, midwife, or nurse can estimate how well a newborn is doing by obtaining an Apgar score. The Apgar score was introduced in 1952 by the anesthesiologist Dr. Virginia Apgar as a method to assess the effects on the newborn of anesthesia given to the laboring mother. Healthcare providers now use it to assess the general wellbeing of the newborn, whether or not analgesics or anesthetics were used. Five criteria—skin color, heart rate, reflex, muscle tone, and respiration—are assessed, and each criterion is assigned a score of 0, 1, or 2. Scores are taken at 1 minute after birth and again at 5 minutes after birth. Each time that scores are taken, the five scores are added together. High scores (out of a possible 10) indicate the baby has made the transition from the womb well, whereas lower scores indicate that the baby may be in distress. The technique for determining an Apgar score is quick and easy, painless for the newborn, and does not require any instruments except for a stethoscope. A convenient way to remember the five scoring criteria is to apply the mnemonic APGAR, for “appearance” (skin color), “pulse” (heart rate), “grimace” (reflex), “activity” (muscle tone), and “respiration.” Of the five Apgar criteria, heart rate and respiration are the most critical. Poor scores for either of these measurements may indicate the need for immediate medical attention to resuscitate or stabilize the newborn. In general, any score lower than 7 at the 5-minute mark indicates that medical assistance may be needed. A total score below 5 indicates an emergency situation. Normally, a newborn will get an intermediate score of 1 for some of the Apgar criteria and will progress to a 2 by the 5-minute assessment. Scores of 8 or above are normal. Lactation - Describe the structure of the lactating breast - Summarize the process of lactation - Explain how the composition of breast milk changes during the first days of lactation and in the course of a single feeding Lactation is the process by which milk is synthesized and secreted from the mammary glands of the postpartum female breast in response to an infant sucking at the nipple. Breast milk provides ideal nutrition and passive immunity for the infant, encourages mild uterine contractions to return the uterus to its pre-pregnancy size (i.e., involution), and induces a substantial metabolic increase in the mother, consuming the fat reserves stored during pregnancy. Structure of the Lactating Breast Mammary glands are modified sweat glands. The non-pregnant and non-lactating female breast is composed primarily of adipose and collagenous tissue, with mammary glands making up a very minor proportion of breast volume. The mammary gland is composed of milk-transporting lactiferous ducts, which expand and branch extensively during pregnancy in response to estrogen, growth hormone, cortisol, and prolactin. Moreover, in response to progesterone, clusters of breast alveoli bud from the ducts and expand outward toward the chest wall. Breast alveoli are balloon-like structures lined with milk-secreting cuboidal cells, or lactocytes, that are surrounded by a net of contractile myoepithelial cells. Milk is secreted from the lactocytes, fills the alveoli, and is squeezed into the ducts. Clusters of alveoli that drain to a common duct are called lobules; the lactating female has 12–20 lobules organized radially around the nipple. Milk drains from lactiferous ducts into lactiferous sinuses that meet at 4 to 18 perforations in the nipple, called nipple pores. The small bumps of the areola (the darkened skin around the nipple) are called Montgomery glands. They secrete oil to cleanse the nipple opening and prevent chapping and cracking of the nipple during breastfeeding. The Process of Lactation The pituitary hormone prolactin is instrumental in the establishment and maintenance of breast milk supply. It also is important for the mobilization of maternal micronutrients for breast milk. Near the fifth week of pregnancy, the level of circulating prolactin begins to increase, eventually rising to approximately 10–20 times the pre-pregnancy concentration. We noted earlier that, during pregnancy, prolactin and other hormones prepare the breasts anatomically for the secretion of milk. The level of prolactin plateaus in late pregnancy, at a level high enough to initiate milk production. However, estrogen, progesterone, and other placental hormones inhibit prolactin-mediated milk synthesis during pregnancy. It is not until the placenta is expelled that this inhibition is lifted and milk production commences. After childbirth, the baseline prolactin level drops sharply, but it is restored for a 1-hour spike during each feeding to stimulate the production of milk for the next feeding. With each prolactin spike, estrogen and progesterone also increase slightly. When the infant suckles, sensory nerve fibers in the areola trigger a neuroendocrine reflex that results in milk secretion from lactocytes into the alveoli. The posterior pituitary releases oxytocin, which stimulates myoepithelial cells to squeeze milk from the alveoli so it can drain into the lactiferous ducts, collect in the lactiferous sinuses, and discharge through the nipple pores. It takes less than 1 minute from the time when an infant begins suckling (the latent period) until milk is secreted (the let-down). Figure 28.23 summarizes the positive feedback loop of the let-down reflex. Figure 28.23 Let-Down Reflex A positive feedback loop ensures continued milk production as long as the infant continues to breastfeed. The prolactin-mediated synthesis of milk changes with time. Frequent milk removal by breastfeeding (or pumping) will maintain high circulating prolactin levels for several months. However, even with continued breastfeeding, baseline prolactin will decrease over time to its pre-pregnancy level. In addition to prolactin and oxytocin, growth hormone, cortisol, parathyroid hormone, and insulin contribute to lactation, in part by facilitating the transport of maternal amino acids, fatty acids, glucose, and calcium to breast milk. Changes in the Composition of Breast Milk In the final weeks of pregnancy, the alveoli swell with colostrum, a thick, yellowish substance that is high in protein but contains less fat and glucose than mature breast milk (Table 28.3). Before childbirth, some women experience leakage of colostrum from the nipples. In contrast, mature breast milk does not leak during pregnancy and is not secreted until several days after childbirth. Compositions of Human Colostrum, Mature Breast Milk, and Cow’s Milk (g/L) \| Human colostrum \| Human breast milk \| Cow’s milk* \| \| \|---\|---\|---\|---\| \| Total protein \| 23 \| 11 \| 31 \| \| Immunoglobulins \| 19 \| 0.1 \| 1 \| \| Fat \| 30 \| 45 \| 38 \| \| Lactose \| 57 \| 71 \| 47 \| \| Calcium \| 0.5 \| 0.3 \| 1.4 \| \| Phosphorus \| 0.16 \| 0.14 \| 0.90 \| \| Sodium \| 0.50 \| 0.15 \| 0.41 \| Table 28.3 *Cow’s milk should never be given to an infant. Its composition is not suitable and its proteins are difficult for the infant to digest. Colostrum is secreted during the first 48–72 hours postpartum. Only a small volume of colostrum is produced—approximately 3 ounces in a 24-hour period—but it is sufficient for the newborn in the first few days of life. Colostrum is rich with immunoglobulins, which confer gastrointestinal, and also likely systemic, immunity as the newborn adjusts to a nonsterile environment. After about the third postpartum day, the mother secretes transitional milk that represents an intermediate between mature milk and colostrum. This is followed by mature milk from approximately postpartum day 10 (see Table 28.3). As you can see in the accompanying table, cow’s milk is not a substitute for breast milk. It contains less lactose, less fat, and more protein and minerals. Moreover, the proteins in cow’s milk are difficult for an infant’s immature digestive system to metabolize and absorb. The first few weeks of breastfeeding may involve leakage, soreness, and periods of milk engorgement as the relationship between milk supply and infant demand becomes established. Once this period is complete, the mother will produce approximately 1.5 liters of milk per day for a single infant, and more if she has twins or triplets. As the infant goes through growth spurts, the milk supply constantly adjusts to accommodate changes in demand. A woman can continue to lactate for years, but once breastfeeding is stopped for approximately 1 week, any remaining milk will be reabsorbed; in most cases, no more will be produced, even if suckling or pumping is resumed. Mature milk changes from the beginning to the end of a feeding. The early milk, called foremilk, is watery, translucent, and rich in lactose and protein. Its purpose is to quench the infant’s thirst. Hindmilk is delivered toward the end of a feeding. It is opaque, creamy, and rich in fat, and serves to satisfy the infant’s appetite. During the first days of a newborn’s life, it is important for meconium to be cleared from the intestines and for bilirubin to be kept low in the circulation. Recall that bilirubin, a product of erythrocyte breakdown, is processed by the liver and secreted in bile. It enters the gastrointestinal tract and exits the body in the stool. Breast milk has laxative properties that help expel meconium from the intestines and clear bilirubin through the excretion of bile. A high concentration of bilirubin in the blood causes jaundice. Some degree of jaundice is normal in newborns, but a high level of bilirubin—which is neurotoxic—can cause brain damage. Newborns, who do not yet have a fully functional blood–brain barrier, are highly vulnerable to the bilirubin circulating in the blood. Indeed, hyperbilirubinemia, a high level of circulating bilirubin, is the most common condition requiring medical attention in newborns. Newborns with hyperbilirubinemia are treated with phototherapy because UV light helps to break down the bilirubin quickly. Patterns of inheritance - Differentiate between genotype and phenotype - Describe how alleles determine a person’s traits - Summarize Mendel’s experiments and relate them to human genetics - Explain the inheritance of autosomal dominant and recessive and sex-linked genetic disorders We have discussed the events that lead to the development of a newborn. But what makes each newborn unique? The answer lies, of course, in the DNA in the sperm and oocyte that combined to produce that first diploid cell, the human zygote. From Genotype to Phenotype Each human body cell has a full complement of DNA stored in 23 pairs of chromosomes. Figure 28.24 shows the pairs in a systematic arrangement called a karyotype. Among these is one pair of chromosomes, called the sex chromosomes, that determines the sex of the individual (XX in females, XY in males). The remaining 22 chromosome pairs are called autosomal chromosomes. Each of these chromosomes carries hundreds or even thousands of genes, each of which codes for the assembly of a particular protein—that is, genes are “expressed” as proteins. An individual’s complete genetic makeup is referred to as his or her genotype. The characteristics that the genes express, whether they are physical, behavioral, or biochemical, are a person’s phenotype. You inherit one chromosome in each pair—a full complement of 23—from each parent. This occurs when the sperm and oocyte combine at the moment of your conception. Homologous chromosomes—those that make up a complementary pair—have genes for the same characteristics in the same location on the chromosome. Because one copy of a gene, an allele, is inherited from each parent, the alleles in these complementary pairs may vary. Take for example an allele that encodes for dimples. A child may inherit the allele encoding for dimples on the chromosome from the father and the allele that encodes for smooth skin (no dimples) on the chromosome from the mother. Figure 28.24 Chromosomal Complement of a Male Each pair of chromosomes contains hundreds to thousands of genes. The banding patterns are nearly identical for the two chromosomes within each pair, indicating the same organization of genes. As is visible in this karyotype, the only exception to this is the XY sex chromosome pair in males. (credit: National Human Genome Research Institute) Although a person can have two identical alleles for a single gene (a homozygous state), it is also possible for a person to have two different alleles (a heterozygous state). The two alleles can interact in several different ways. The expression of an allele can be dominant, for which the activity of this gene will mask the expression of a nondominant, or recessive, allele. Sometimes dominance is complete; at other times, it is incomplete. In some cases, both alleles are expressed at the same time in a form of expression known as codominance. In the simplest scenario, a single pair of genes will determine a single heritable characteristic. However, it is quite common for multiple genes to interact to confer a feature. For instance, eight or more genes—each with their own alleles—determine eye color in humans. Moreover, although any one person can only have two alleles corresponding to a given gene, more than two alleles commonly exist in a population. This phenomenon is called multiple alleles. For example, there are three different alleles that encode ABO blood type; these are designated IA, IB, and i. Over 100 years of theoretical and experimental genetics studies, and the more recent sequencing and annotation of the human genome, have helped scientists to develop a better understanding of how an individual’s genotype is expressed as their phenotype. This body of knowledge can help scientists and medical professionals to predict, or at least estimate, some of the features that an offspring will inherit by examining the genotypes or phenotypes of the parents. One important application of this knowledge is to identify an individual’s risk for certain heritable genetic disorders. However, most diseases have a multigenic pattern of inheritance and can also be affected by the environment, so examining the genotypes or phenotypes of a person’s parents will provide only limited information about the risk of inheriting a disease. Only for a handful of single-gene disorders can genetic testing allow clinicians to calculate the probability with which a child born to the two parents tested may inherit a specific disease. Mendel’s Theory of Inheritance Our contemporary understanding of genetics rests on the work of a nineteenth-century monk. Working in the mid-1800s, long before anyone knew about genes or chromosomes, Gregor Mendel discovered that garden peas transmit their physical characteristics to subsequent generations in a discrete and predictable fashion. When he mated, or crossed, two pure-breeding pea plants that differed by a certain characteristic, the first-generation offspring all looked like one of the parents. For instance, when he crossed tall and dwarf pure-breeding pea plants, all of the offspring were tall. Mendel called tallness dominantbecause it was expressed in offspring when it was present in a purebred parent. He called dwarfism recessive because it was masked in the offspring if one of the purebred parents possessed the dominant characteristic. Note that tallness and dwarfism are variations on the characteristic of height. Mendel called such a variation a trait. We now know that these traits are the expression of different alleles of the gene encoding height. Mendel performed thousands of crosses in pea plants with differing traits for a variety of characteristics. And he repeatedly came up with the same results—among the traits he studied, one was always dominant, and the other was always recessive. (Remember, however, that this dominant–recessive relationship between alleles is not always the case; some alleles are codominant, and sometimes dominance is incomplete.) Using his understanding of dominant and recessive traits, Mendel tested whether a recessive trait could be lost altogether in a pea lineage or whether it would resurface in a later generation. By crossing the second-generation offspring of purebred parents with each other, he showed that the latter was true: recessive traits reappeared in third-generation plants in a ratio of 3:1 (three offspring having the dominant trait and one having the recessive trait). Mendel then proposed that characteristics such as height were determined by heritable “factors” that were transmitted, one from each parent, and inherited in pairs by offspring. In the language of genetics, Mendel’s theory applied to humans says that if an individual receives two dominant alleles, one from each parent, the individual’s phenotype will express the dominant trait. If an individual receives two recessive alleles, then the recessive trait will be expressed in the phenotype. Individuals who have two identical alleles for a given gene, whether dominant or recessive, are said to be homozygous for that gene (homo- = “same”). Conversely, an individual who has one dominant allele and one recessive allele is said to be heterozygous for that gene (hetero- = “different” or “other”). In this case, the dominant trait will be expressed, and the individual will be phenotypically identical to an individual who possesses two dominant alleles for the trait. It is common practice in genetics to use capital and lowercase letters to represent dominant and recessive alleles. Using Mendel’s pea plants as an example, if a tall pea plant is homozygous, it will possess two tall alleles (TT). A dwarf pea plant must be homozygous because its dwarfism can only be expressed when two recessive alleles are present (tt). A heterozygous pea plant (Tt) would be tall and phenotypically indistinguishable from a tall homozygous pea plant because of the dominant tall allele. Mendel deduced that a 3:1 ratio of dominant to recessive would be produced by the random segregation of heritable factors (genes) when crossing two heterozygous pea plants. In other words, for any given gene, parents are equally likely to pass down either one of their alleles to their offspring in a haploid gamete, and the result will be expressed in a dominant–recessive pattern if both parents are heterozygous for the trait. Because of the random segregation of gametes, the laws of chance and probability come into play when predicting the likelihood of a given phenotype. Consider a cross between an individual with two dominant alleles for a trait (AA) and an individual with two recessive alleles for the same trait (aa). All of the parental gametes from the dominant individual would be A, and all of the parental gametes from the recessive individual would be a (Figure 28.25). All of the offspring of that second generation, inheriting one allele from each parent, would have the genotype Aa, and the probability of expressing the phenotype of the dominant allele would be 4 out of 4, or 100 percent. This seems simple enough, but the inheritance pattern gets interesting when the second-generation Aa individuals are crossed. In this generation, 50 percent of each parent’s gametes are A and the other 50 percent are a. By Mendel’s principle of random segregation, the possible combinations of gametes that the offspring can receive are AA, Aa, aA (which is the same as Aa), and aa. Because segregation and fertilization are random, each offspring has a 25 percent chance of receiving any of these combinations. Therefore, if an Aa × Aa cross were performed 1000 times, approximately 250 (25 percent) of the offspring would be AA; 500 (50 percent) would be Aa (that is, Aa plus aA); and 250 (25 percent) would be aa. The genotypic ratio for this inheritance pattern is 1:2:1. However, we have already established that AA and Aa (and aA) individuals all express the dominant trait (i.e., share the same phenotype), and can therefore be combined into one group. The result is Mendel’s third-generation phenotype ratio of 3:1. Figure 28.25 Random Segregation In the formation of gametes, it is equally likely that either one of a pair alleles from one parent will be passed on to the offspring. This figure follows the possible combinations of alleles through two generations following a first-generation cross of homozygous dominant and homozygous recessive parents. The recessive phenotype, which is masked in the second generation, has a 1 in 4, or 25 percent, chance of reappearing in the third generation. Mendel’s observation of pea plants also included many crosses that involved multiple traits, which prompted him to formulate the principle of independent assortment. The law states that the members of one pair of genes (alleles) from a parent will sort independently from other pairs of genes during the formation of gametes. Applied to pea plants, that means that the alleles associated with the different traits of the plant, such as color, height, or seed type, will sort independently of one another. This holds true except when two alleles happen to be located close to one other on the same chromosome. Independent assortment provides for a great degree of diversity in offspring. Mendelian genetics represent the fundamentals of inheritance, but there are two important qualifiers to consider when applying Mendel’s findings to inheritance studies in humans. First, as we’ve already noted, not all genes are inherited in a dominant–recessive pattern. Although all diploid individuals have two alleles for every gene, allele pairs may interact to create several types of inheritance patterns, including incomplete dominance and codominance. Secondly, Mendel performed his studies using thousands of pea plants. He was able to identify a 3:1 phenotypic ratio in second-generation offspring because his large sample size overcame the influence of variability resulting from chance. In contrast, no human couple has ever had thousands of children. If we know that a man and woman are both heterozygous for a recessive genetic disorder, we would predict that one in every four of their children would be affected by the disease. In real life, however, the influence of chance could change that ratio significantly. For example, if a man and a woman are both heterozygous for cystic fibrosis, a recessive genetic disorder that is expressed only when the individual has two defective alleles, we would expect one in four of their children to have cystic fibrosis. However, it is entirely possible for them to have seven children, none of whom is affected, or for them to have two children, both of whom are affected. For each individual child, the presence or absence of a single gene disorder depends on which alleles that child inherits from his or her parents. Autosomal Dominant Inheritance In the case of cystic fibrosis, the disorder is recessive to the normal phenotype. However, a genetic abnormality may be dominant to the normal phenotype. When the dominant allele is located on one of the 22 pairs of autosomes (non-sex chromosomes), we refer to its inheritance pattern as autosomal dominant. An example of an autosomal dominant disorder is neurofibromatosis type I, a disease that induces tumor formation within the nervous system that leads to skin and skeletal deformities. Consider a couple in which one parent is heterozygous for this disorder (and who therefore has neurofibromatosis), Nn, and one parent is homozygous for the normal gene, nn. The heterozygous parent would have a 50 percent chance of passing the dominant allele for this disorder to his or her offspring, and the homozygous parent would always pass the normal allele. Therefore, four possible offspring genotypes are equally likely to occur: Nn, Nn, nn, and nn. That is, every child of this couple would have a 50 percent chance of inheriting neurofibromatosis. This inheritance pattern is shown in Figure 28.26, in a form called a Punnett square, named after its creator, the British geneticist Reginald Punnett. Figure 28.26 Autosomal Dominant Inheritance Inheritance pattern of an autosomal dominant disorder, such as neurofibromatosis, is shown in a Punnett square. Other genetic diseases that are inherited in this pattern are achondroplastic dwarfism, Marfan syndrome, and Huntington’s disease. Because autosomal dominant disorders are expressed by the presence of just one gene, an individual with the disorder will know that he or she has at least one faulty gene. The expression of the disease may manifest later in life, after the childbearing years, which is the case in Huntington’s disease (discussed in more detail later in this section). Autosomal Recessive Inheritance When a genetic disorder is inherited in an autosomal recessive pattern, the disorder corresponds to the recessive phenotype. Heterozygous individuals will not display symptoms of this disorder, because their unaffected gene will compensate. Such an individual is called a carrier. Carriers for an autosomal recessive disorder may never know their genotype unless they have a child with the disorder. An example of an autosomal recessive disorder is cystic fibrosis (CF), which we introduced earlier. CF is characterized by the chronic accumulation of a thick, tenacious mucus in the lungs and digestive tract. Decades ago, children with CF rarely lived to adulthood. With advances in medical technology, the average lifespan in developed countries has increased into middle adulthood. CF is a relatively common disorder that occurs in approximately 1 in 2000 Caucasians. A child born to two CF carriers would have a 25 percent chance of inheriting the disease. This is the same 3:1 dominant:recessive ratio that Mendel observed in his pea plants would apply here. The pattern is shown in Figure 28.27, using a diagram that tracks the likely incidence of an autosomal recessive disorder on the basis of parental genotypes. On the other hand, a child born to a CF carrier and someone with two unaffected alleles would have a 0 percent probability of inheriting CF, but would have a 50 percent chance of being a carrier. Other examples of autosome recessive genetic illnesses include the blood disorder sickle-cell anemia, the fatal neurological disorder Tay–Sachs disease, and the metabolic disorder phenylketonuria. Figure 28.27 Autosomal Recessive Inheritance The inheritance pattern of an autosomal recessive disorder with two carrier parents reflects a 3:1 probability of expression among offspring. (credit: U.S. National Library of Medicine) X-linked Dominant or Recessive Inheritance An X-linked transmission pattern involves genes located on the X chromosome of the 23rd pair (Figure 28.28). Recall that a male has one X and one Y chromosome. When a father transmits a Y chromosome, the child is male, and when he transmits an X chromosome, the child is female. A mother can transmit only an X chromosome, as both her sex chromosomes are X chromosomes. When an abnormal allele for a gene that occurs on the X chromosome is dominant over the normal allele, the pattern is described as X-linked dominant. This is the case with vitamin D–resistant rickets: an affected father would pass the disease gene to all of his daughters, but none of his sons, because he donates only the Y chromosome to his sons (see Figure 28.28a). If it is the mother who is affected, all of her children—male or female—would have a 50 percent chance of inheriting the disorder because she can only pass an X chromosome on to her children (see Figure 28.28b). For an affected female, the inheritance pattern would be identical to that of an autosomal dominant inheritance pattern in which one parent is heterozygous and the other is homozygous for the normal gene. Figure 28.28 X-Linked Patterns of Inheritance A chart of X-linked dominant inheritance patterns differs depending on whether (a) the father or (b) the mother is affected with the disease. (credit: U.S. National Library of Medicine) X-linked recessive inheritance is much more common because females can be carriers of the disease yet still have a normal phenotype. Diseases transmitted by X-linked recessive inheritance include color blindness, the blood-clotting disorder hemophilia, and some forms of muscular dystrophy. For an example of X-linked recessive inheritance, consider parents in which the mother is an unaffected carrier and the father is normal. None of the daughters would have the disease because they receive a normal gene from their father. However, they have a 50 percent chance of receiving the disease gene from their mother and becoming a carrier. In contrast, 50 percent of the sons would be affected (Figure 28.29). With X-linked recessive diseases, males either have the disease or are genotypically normal—they cannot be carriers. Females, however, can be genotypically normal, a carrier who is phenotypically normal, or affected with the disease. A daughter can inherit the gene for an X-linked recessive illness when her mother is a carrier or affected, or her father is affected. The daughter will be affected by the disease only if she inherits an X-linked recessive gene from both parents. As you can imagine, X-linked recessive disorders affect many more males than females. For example, color blindness affects at least 1 in 20 males, but only about 1 in 400 females. Figure 28.29 X-Linked Recessive Inheritance Given two parents in which the father is normal and the mother is a carrier of an X-linked recessive disorder, a son would have a 50 percent probability of being affected with the disorder, whereas daughters would either be carriers or entirely unaffected. (credit: U.S. National Library of Medicine) Other Inheritance Patterns: Incomplete Dominance, Codominance, and Lethal Alleles Not all genetic disorders are inherited in a dominant–recessive pattern. In incomplete dominance, the offspring express a heterozygous phenotype that is intermediate between one parent’s homozygous dominant trait and the other parent’s homozygous recessive trait. An example of this can be seen in snapdragons when red-flowered plants and white-flowered plants are crossed to produce pink-flowered plants. In humans, incomplete dominance occurs with one of the genes for hair texture. When one parent passes a curly hair allele (the incompletely dominant allele) and the other parent passes a straight-hair allele, the effect on the offspring will be intermediate, resulting in hair that is wavy. Codominance is characterized by the equal, distinct, and simultaneous expression of both parents’ different alleles. This pattern differs from the intermediate, blended features seen in incomplete dominance. A classic example of codominance in humans is ABO blood type. People are blood type A if they have an allele for an enzyme that facilitates the production of surface antigen A on their erythrocytes. This allele is designated IA. In the same manner, people are blood type B if they express an enzyme for the production of surface antigen B. People who have alleles for both enzymes (IA and IB) produce both surface antigens A and B. As a result, they are blood type AB. Because the effect of both alleles (or enzymes) is observed, we say that the IA and IB alleles are codominant. There is also a third allele that determines blood type. This allele (i) produces a nonfunctional enzyme. People who have two i alleles do not produce either A or B surface antigens: they have type O blood. If a person has IA and i alleles, the person will have blood type A. Notice that it does not make any difference whether a person has two IA alleles or one IA and one i allele. In both cases, the person is blood type A. Because IA masks i, we say that IA is dominant to i. Table 28.4 summarizes the expression of blood type. Expression of Blood Types \| Blood type \| Genotype \| Pattern of inheritance \| \|---\|---\|---\| \| A \| IAIA or IAi \| IA is dominant to i \| \| B \| IBIB or IBi \| IB is dominant to i \| \| AB \| IAIB \| IA is co-dominant to IB \| \| O \| ii \| Two recessive alleles \| Table 28.4 Certain combinations of alleles can be lethal, meaning they prevent the individual from developing in utero, or cause a shortened life span. In recessive lethal inheritance patterns, a child who is born to two heterozygous (carrier) parents and who inherited the faulty allele from both would not survive. An example of this is Tay–Sachs, a fatal disorder of the nervous system. In this disorder, parents with one copy of the allele for the disorder are carriers. If they both transmit their abnormal allele, their offspring will develop the disease and will die in childhood, usually before age 5. Dominant lethal inheritance patterns are much more rare because neither heterozygotes nor homozygotes survive. Of course, dominant lethal alleles that arise naturally through mutation and cause miscarriages or stillbirths are never transmitted to subsequent generations. However, some dominant lethal alleles, such as the allele for Huntington’s disease, cause a shortened life span but may not be identified until after the person reaches reproductive age and has children. Huntington’s disease causes irreversible nerve cell degeneration and death in 100 percent of affected individuals, but it may not be expressed until the individual reaches middle age. In this way, dominant lethal alleles can be maintained in the human population. Individuals with a family history of Huntington’s disease are typically offered genetic counseling, which can help them decide whether or not they wish to be tested for the faulty gene. Mutations A mutation is a change in the sequence of DNA nucleotides that may or may not affect a person’s phenotype. Mutations can arise spontaneously from errors during DNA replication, or they can result from environmental insults such as radiation, certain viruses, or exposure to tobacco smoke or other toxic chemicals. Because genes encode for the assembly of proteins, a mutation in the nucleotide sequence of a gene can change amino acid sequence and, consequently, a protein’s structure and function. Spontaneous mutations occurring during meiosis are thought to account for many spontaneous abortions (miscarriages). Chromosomal Disorders Sometimes a genetic disease is not caused by a mutation in a gene, but by the presence of an incorrect number of chromosomes. For example, Down syndrome is caused by having three copies of chromosome 21. This is known as trisomy 21. The most common cause of trisomy 21 is chromosomal nondisjunction during meiosis. The frequency of nondisjunction events appears to increase with age, so the frequency of bearing a child with Down syndrome increases in women over 36. The age of the father matters less because nondisjunction is much less likely to occur in a sperm than in an egg. Whereas Down syndrome is caused by having three copies of a chromosome, Turner syndrome is caused by having just one copy of the X chromosome. This is known as monosomy. The affected child is always female. Women with Turner syndrome are sterile because their sexual organs do not mature. CAREER CONNECTION Genetic Counselor Given the intricate orchestration of gene expression, cell migration, and cell differentiation during prenatal development, it is amazing that the vast majority of newborns are healthy and free of major birth defects. When a woman over 35 is pregnant or intends to become pregnant, or her partner is over 55, or if there is a family history of a genetic disorder, she and her partner may want to speak to a genetic counselor to discuss the likelihood that their child may be affected by a genetic or chromosomal disorder. A genetic counselor can interpret a couple’s family history and estimate the risks to their future offspring. For many genetic diseases, a DNA test can determine whether a person is a carrier. For instance, carrier status for Fragile X, an X-linked disorder associated with mental retardation, or for cystic fibrosis can be determined with a simple blood draw to obtain DNA for testing. A genetic counselor can educate a couple about the implications of such a test and help them decide whether to undergo testing. For chromosomal disorders, the available testing options include a blood test, amniocentesis (in which amniotic fluid is tested), and chorionic villus sampling (in which tissue from the placenta is tested). Each of these has advantages and drawbacks. A genetic counselor can also help a couple cope with the news that either one or both partners is a carrier of a genetic illness, or that their unborn child has been diagnosed with a chromosomal disorder or other birth defect. To become a genetic counselor, one needs to complete a 4-year undergraduate program and then obtain a Master of Science in Genetic Counseling from an accredited university. Board certification is attained after passing examinations by the American Board of Genetic Counseling. Genetic counselors are essential professionals in many branches of medicine, but there is a particular demand for preconception and prenatal genetic counselors. INTERACTIVE LINK Visit the National Society of Genetic Counselors website for more information about genetic counselors. INTERACTIVE LINK Visit the American Board of Genetic Counselors, Inc., website for more information about genetic counselors. Key Terms - acrosomal reaction - release of digestive enzymes by sperm that enables them to burrow through the corona radiata and penetrate the zona pellucida of an oocyte prior to fertilization - acrosome - cap-like vesicle located at the anterior-most region of a sperm that is rich with lysosomal enzymes capable of digesting the protective layers surrounding the oocyte - afterbirth - third stage of childbirth in which the placenta and associated fetal membranes are expelled - allantois - finger-like outpocketing of yolk sac forms the primitive excretory duct of the embryo; precursor to the urinary bladder - allele - alternative forms of a gene that occupy a specific locus on a specific gene - amnion - transparent membranous sac that encloses the developing fetus and fills with amniotic fluid - amniotic cavity - cavity that opens up between the inner cell mass and the trophoblast; develops into amnion - autosomal chromosome - in humans, the 22 pairs of chromosomes that are not the sex chromosomes (XX or XY) - autosomal dominant - pattern of dominant inheritance that corresponds to a gene on one of the 22 autosomal chromosomes - autosomal recessive - pattern of recessive inheritance that corresponds to a gene on one of the 22 autosomal chromosomes - blastocoel - fluid-filled cavity of the blastocyst - blastocyst - term for the conceptus at the developmental stage that consists of about 100 cells shaped into an inner cell mass that is fated to become the embryo and an outer trophoblast that is fated to become the associated fetal membranes and placenta - blastomere - daughter cell of a cleavage - Braxton Hicks contractions - weak and irregular peristaltic contractions that can occur in the second and third trimesters; they do not indicate that childbirth is imminent - brown adipose tissue - highly vascularized fat tissue that is packed with mitochondria; these properties confer the ability to oxidize fatty acids to generate heat - capacitation - process that occurs in the female reproductive tract in which sperm are prepared for fertilization; leads to increased motility and changes in their outer membrane that improve their ability to release enzymes capable of digesting an oocyte’s outer layers - carrier - heterozygous individual who does not display symptoms of a recessive genetic disorder but can transmit the disorder to his or her offspring - chorion - membrane that develops from the syncytiotrophoblast, cytotrophoblast, and mesoderm; surrounds the embryo and forms the fetal portion of the placenta through the chorionic villi - chorionic membrane - precursor to the chorion; forms from extra-embryonic mesoderm cells - chorionic villi - projections of the chorionic membrane that burrow into the endometrium and develop into the placenta - cleavage - form of mitotic cell division in which the cell divides but the total volume remains unchanged; this process serves to produce smaller and smaller cells - codominance - pattern of inheritance that corresponds to the equal, distinct, and simultaneous expression of two different alleles - colostrum - thick, yellowish substance secreted from a mother’s breasts in the first postpartum days; rich in immunoglobulins - conceptus - pre-implantation stage of a fertilized egg and its associated membranes - corona radiata - in an oocyte, a layer of granulosa cells that surrounds the oocyte and that must be penetrated by sperm before fertilization can occur - cortical reaction - following fertilization, the release of cortical granules from the oocyte’s plasma membrane into the zona pellucida creating a fertilization membrane that prevents any further attachment or penetration of sperm; part of the slow block to polyspermy - dilation - first stage of childbirth, involving an increase in cervical diameter - dominant - describes a trait that is expressed both in homozygous and heterozygous form - dominant lethal - inheritance pattern in which individuals with one or two copies of a lethal allele do not survive in utero or have a shortened life span - ductus arteriosus - shunt in the pulmonary trunk that diverts oxygenated blood back to the aorta - ductus venosus - shunt that causes oxygenated blood to bypass the fetal liver on its way to the inferior vena cava - ectoderm - primary germ layer that develops into the central and peripheral nervous systems, sensory organs, epidermis, hair, and nails - ectopic pregnancy - implantation of an embryo outside of the uterus - embryo - developing human during weeks 3–8 - embryonic folding - process by which an embryo develops from a flat disc of cells to a three-dimensional shape resembling a cylinder - endoderm - primary germ layer that goes on to form the gastrointestinal tract, liver, pancreas, and lungs - epiblast - upper layer of cells of the embryonic disc that forms from the inner cell mass; gives rise to all three germ layers - episiotomy - incision made in the posterior vaginal wall and perineum that facilitates vaginal birth - expulsion - second stage of childbirth, during which the mother bears down with contractions; this stage ends in birth - fertilization - unification of genetic material from male and female haploid gametes - fertilization membrane - impenetrable barrier that coats a nascent zygote; part of the slow block to polyspermy - fetus - developing human during the time from the end of the embryonic period (week 9) to birth - foramen ovale - shunt that directly connects the right and left atria and helps divert oxygenated blood from the fetal pulmonary circuit - foremilk - watery, translucent breast milk that is secreted first during a feeding and is rich in lactose and protein; quenches the infant’s thirst - gastrulation - process of cell migration and differentiation into three primary germ layers following cleavage and implantation - genotype - complete genetic makeup of an individual - gestation - in human development, the period required for embryonic and fetal development in utero; pregnancy - heterozygous - having two different alleles for a given gene - hindmilk - opaque, creamy breast milk delivered toward the end of a feeding; rich in fat; satisfies the infant’s appetite - homozygous - having two identical alleles for a given gene - human chorionic gonadotropin (hCG) - hormone that directs the corpus luteum to survive, enlarge, and continue producing progesterone and estrogen to suppress menses and secure an environment suitable for the developing embryo - hypoblast - lower layer of cells of the embryonic disc that extend into the blastocoel to form the yolk sac - implantation - process by which a blastocyst embeds itself in the uterine endometrium - incomplete dominance - pattern of inheritance in which a heterozygous genotype expresses a phenotype intermediate between dominant and recessive phenotypes - inner cell mass - cluster of cells within the blastocyst that is fated to become the embryo - involution - postpartum shrinkage of the uterus back to its pre-pregnancy volume - karyotype - systematic arrangement of images of chromosomes into homologous pairs - lactation - process by which milk is synthesized and secreted from the mammary glands of the postpartum female breast in response to sucking at the nipple - lanugo - silk-like hairs that coat the fetus; shed later in fetal development - let-down reflex - release of milk from the alveoli triggered by infant suckling - lightening - descent of the fetus lower into the pelvis in late pregnancy; also called “dropping” - lochia - postpartum vaginal discharge that begins as blood and ends as a whitish discharge; the end of lochia signals that the site of placental attachment has healed - meconium - fetal wastes consisting of ingested amniotic fluid, cellular debris, mucus, and bile - mesoderm - primary germ layer that becomes the skeleton, muscles, connective tissue, heart, blood vessels, and kidneys - morula - tightly packed sphere of blastomeres that has reached the uterus but has not yet implanted itself - mutation - change in the nucleotide sequence of DNA - neural fold - elevated edge of the neural groove - neural plate - thickened layer of neuroepithelium that runs longitudinally along the dorsal surface of an embryo and gives rise to nervous system tissue - neural tube - precursor to structures of the central nervous system, formed by the invagination and separation of neuroepithelium - neurulation - embryonic process that establishes the central nervous system - nonshivering thermogenesis - process of breaking down brown adipose tissue to produce heat in the absence of a shivering response - notochord - rod-shaped, mesoderm-derived structure that provides support for growing fetus - organogenesis - development of the rudimentary structures of all of an embryo’s organs from the germ layers - parturition - childbirth - phenotype - physical or biochemical manifestation of the genotype; expression of the alleles - placenta - organ that forms during pregnancy to nourish the developing fetus; also regulates waste and gas exchange between mother and fetus - placenta previa - low placement of fetus within uterus causes placenta to partially or completely cover the opening of the cervix as it grows - placentation - formation of the placenta; complete by weeks 14–16 of pregnancy - polyspermy - penetration of an oocyte by more than one sperm - primitive streak - indentation along the dorsal surface of the epiblast through which cells migrate to form the endoderm and mesoderm during gastrulation - prolactin - pituitary hormone that establishes and maintains the supply of breast milk; also important for the mobilization of maternal micronutrients for breast milk - Punnett square - grid used to display all possible combinations of alleles transmitted by parents to offspring and predict the mathematical probability of offspring inheriting a given genotype - quickening - fetal movements that are strong enough to be felt by the mother - recessive - describes a trait that is only expressed in homozygous form and is masked in heterozygous form - recessive lethal - inheritance pattern in which individuals with two copies of a lethal allele do not survive in utero or have a shortened life span - sex chromosomes - pair of chromosomes involved in sex determination; in males, the XY chromosomes; in females, the XX chromosomes - shunt - circulatory shortcut that diverts the flow of blood from one region to another - somite - one of the paired, repeating blocks of tissue located on either side of the notochord in the early embryo - syncytiotrophoblast - superficial cells of the trophoblast that fuse to form a multinucleated body that digests endometrial cells to firmly secure the blastocyst to the uterine wall - trait - variation of an expressed characteristic - trimester - division of the duration of a pregnancy into three 3-month terms - trophoblast - fluid-filled shell of squamous cells destined to become the chorionic villi, placenta, and associated fetal membranes - true labor - regular contractions that immediately precede childbirth; they do not abate with hydration or rest, and they become more frequent and powerful with time - umbilical cord - connection between the developing conceptus and the placenta; carries deoxygenated blood and wastes from the fetus and returns nutrients and oxygen from the mother - vernix caseosa - waxy, cheese-like substance that protects the delicate fetal skin until birth - X-linked - pattern of inheritance in which an allele is carried on the X chromosome of the 23rd pair - X-linked dominant - pattern of dominant inheritance that corresponds to a gene on the X chromosome of the 23rd pair - X-linked recessive - pattern of recessive inheritance that corresponds to a gene on the X chromosome of the 23rd pair - yolk sac - membrane associated with primitive circulation to the developing embryo; source of the first blood cells and germ cells and contributes to the umbilical cord structure - zona pellucida - thick, gel-like glycoprotein membrane that coats the oocyte and must be penetrated by sperm before fertilization can occur - zygote - fertilized egg; a diploid cell resulting from the fertilization of haploid gametes from the male and female lines Chapter Review 28.1 Fertilization Hundreds of millions of sperm deposited in the vagina travel toward the oocyte, but only a few hundred actually reach it. The number of sperm that reach the oocyte is greatly reduced because of conditions within the female reproductive tract. Many sperm are overcome by the acidity of the vagina, others are blocked by mucus in the cervix, whereas others are attacked by phagocytic leukocytes in the uterus. Those sperm that do survive undergo a change in response to those conditions. They go through the process of capacitation, which improves their motility and alters the membrane surrounding the acrosome, the cap-like structure in the head of a sperm that contains the digestive enzymes needed for it to attach to and penetrate the oocyte. The oocyte that is released by ovulation is protected by a thick outer layer of granulosa cells known as the corona radiata and by the zona pellucida, a thick glycoprotein membrane that lies just outside the oocyte’s plasma membrane. When capacitated sperm make contact with the oocyte, they release the digestive enzymes in the acrosome (the acrosomal reaction) and are thus able to attach to the oocyte and burrow through to the oocyte’s zona pellucida. One of the sperm will then break through to the oocyte’s plasma membrane and release its haploid nucleus into the oocyte. The oocyte’s membrane structure changes in response (cortical reaction), preventing any further penetration by another sperm and forming a fertilization membrane. Fertilization is complete upon unification of the haploid nuclei of the two gametes, producing a diploid zygote. 28.2 Embryonic Development As the zygote travels toward the uterus, it undergoes numerous cleavages in which the number of cells doubles (blastomeres). Upon reaching the uterus, the conceptus has become a tightly packed sphere of cells called the morula, which then forms into a blastocyst consisting of an inner cell mass within a fluid-filled cavity surrounded by trophoblasts. The blastocyst implants in the uterine wall, the trophoblasts fuse to form a syncytiotrophoblast, and the conceptus is enveloped by the endometrium. Four embryonic membranes form to support the growing embryo: the amnion, the yolk sac, the allantois, and the chorion. The chorionic villi of the chorion extend into the endometrium to form the fetal portion of the placenta. The placenta supplies the growing embryo with oxygen and nutrients; it also removes carbon dioxide and other metabolic wastes. Following implantation, embryonic cells undergo gastrulation, in which they differentiate and separate into an embryonic disc and establish three primary germ layers (the endoderm, mesoderm, and ectoderm). Through the process of embryonic folding, the fetus begins to take shape. Neurulation starts the process of the development of structures of the central nervous system and organogenesis establishes the basic plan for all organ systems. 28.3 Fetal Development The fetal period lasts from the ninth week of development until birth. During this period, male and female gonads differentiate. The fetal circulatory system becomes much more specialized and efficient than its embryonic counterpart. It includes three shunts—the ductus venosus, the foramen ovale, and the ductus arteriosus—that enable it to bypass the semifunctional liver and pulmonary circuit until after childbirth. The brain continues to grow and its structures differentiate. Facial features develop, the body elongates, and the skeleton ossifies. In the womb, the developing fetus moves, blinks, practices sucking, and circulates amniotic fluid. The fetus grows from an embryo measuring approximately 3.3 cm (1.3 in) and weighing 7 g (0.25 oz) to an infant measuring approximately 51 cm (20 in) and weighing an average of approximately 3.4 kg (7.5 lbs). Embryonic organ structures that were primitive and nonfunctional develop to the point that the newborn can survive in the outside world. 28.4 Maternal Changes During Pregnancy, Labor, and Birth Hormones (especially estrogens, progesterone, and hCG) secreted by the corpus luteum and later by the placenta are responsible for most of the changes experienced during pregnancy. Estrogen maintains the pregnancy, promotes fetal viability, and stimulates tissue growth in the mother and developing fetus. Progesterone prevents new ovarian follicles from developing and suppresses uterine contractility. Pregnancy weight gain primarily occurs in the breasts and abdominal region. Nausea, heartburn, and frequent urination are common during pregnancy. Maternal blood volume increases by 30 percent during pregnancy and respiratory minute volume increases by 50 percent. The skin may develop stretch marks and melanin production may increase. Toward the late stages of pregnancy, a drop in progesterone and stretching forces from the fetus lead to increasing uterine irritability and prompt labor. Contractions serve to dilate the cervix and expel the newborn. Delivery of the placenta and associated fetal membranes follows. 28.5 Adjustments of the Infant at Birth and Postnatal Stages The first breath a newborn takes at birth inflates the lungs and dramatically alters the circulatory system, closing the three shunts that directed oxygenated blood away from the lungs and liver during fetal life. Clamping and cutting the umbilical cord collapses the three umbilical blood vessels. The proximal umbilical arteries remain a part of the circulatory system, whereas the distal umbilical arteries and the umbilical vein become fibrotic. The newborn keeps warm by breaking down brown adipose tissue in the process of nonshivering thermogenesis. The first consumption of breast milk or formula floods the newborn’s sterile gastrointestinal tract with beneficial bacteria that eventually establish themselves as the bacterial flora, which aid in digestion. 28.6 Lactation The lactating mother supplies all the hydration and nutrients that a growing infant needs for the first 4–6 months of life. During pregnancy, the body prepares for lactation by stimulating the growth and development of branching lactiferous ducts and alveoli lined with milk-secreting lactocytes, and by creating colostrum. These functions are attributable to the actions of several hormones, including prolactin. Following childbirth, suckling triggers oxytocin release, which stimulates myoepithelial cells to squeeze milk from alveoli. Breast milk then drains toward the nipple pores to be consumed by the infant. Colostrum, the milk produced in the first postpartum days, provides immunoglobulins that increase the newborn’s immune defenses. Colostrum, transitional milk, and mature breast milk are ideally suited to each stage of the newborn’s development, and breastfeeding helps the newborn’s digestive system expel meconium and clear bilirubin. Mature milk changes from the beginning to the end of a feeding. Foremilk quenches the infant’s thirst, whereas hindmilk satisfies the infant’s appetite. 28.7 Patterns of Inheritance There are two aspects to a person’s genetic makeup. Their genotype refers to the genetic makeup of the chromosomes found in all their cells and the alleles that are passed down from their parents. Their phenotype is the expression of that genotype, based on the interaction of the paired alleles, as well as how environmental conditions affect that expression. Working with pea plants, Mendel discovered that the factors that account for different traits in parents are discretely transmitted to offspring in pairs, one from each parent. He articulated the principles of random segregation and independent assortment to account for the inheritance patterns he observed. Mendel’s factors are genes, with differing variants being referred to as alleles and those alleles being dominant or recessive in expression. Each parent passes one allele for every gene on to offspring, and offspring are equally likely to inherit any combination of allele pairs. When Mendel crossed heterozygous individuals, he repeatedly found a 3:1 dominant–recessive ratio. He correctly postulated that the expression of the recessive trait was masked in heterozygotes but would resurface in their offspring in a predictable manner. Human genetics focuses on identifying different alleles and understanding how they express themselves. Medical researchers are especially interested in the identification of inheritance patterns for genetic disorders, which provides the means to estimate the risk that a given couple’s offspring will inherit a genetic disease or disorder. Patterns of inheritance in humans include autosomal dominance and recessiveness, X-linked dominance and recessiveness, incomplete dominance, codominance, and lethality. A change in the nucleotide sequence of DNA, which may or may not manifest in a phenotype, is called a mutation. Interactive Link Questions View this time-lapse movie of a conceptus starting at day 3. What is the first structure you see? At what point in the movie does the blastocoel first appear? What event occurs at the end of the movie? 2.Visit this site for a summary of the stages of pregnancy, as experienced by the mother, and view the stages of development of the fetus throughout gestation. At what point in fetal development can a regular heartbeat be detected? Review Questions Sperm and ova are similar in terms of ________. - size - quantity produced per year - chromosome number - flagellar motility Although the male ejaculate contains hundreds of millions of sperm, ________. - most do not reach the oocyte - most are destroyed by the alkaline environment of the uterus - it takes millions to penetrate the outer layers of the oocyte - most are destroyed by capacitation As sperm first reach the oocyte, they will contact the ________. - acrosome - corona radiata - sperm-binding receptors - zona pellucida Fusion of pronuclei occurs during ________. - spermatogenesis - ovulation - fertilization - capacitation Sperm must first complete ________ to enable the fertilization of an oocyte. - capacitation - the acrosomal reaction - the cortical reaction - the fast block Cleavage produces daughter cells called ________. - trophoblasts - blastocysts - morulae - blastomeres The conceptus, upon reaching the uterus, first ________. - implants - divides - disintegrates - hatches The inner cell mass of the blastocyst is destined to become the ________. - embryo - trophoblast - chorionic villi - placenta Which primary germ layer gave rise to the cells that eventually became the central nervous system? - endoderm - ectoderm - acrosome - mesoderm What would happen if the trophoblast did not secrete hCG upon implantation of the blastocyst? - The cells would not continue to divide. - The corpus luteum would continue to produce progesterone and estrogen. - Menses would flush the blastocyst out of the uterus. - The uterine mucosa would not envelop the blastocyst. During what process does the amnion envelop the embryo? - embryonic folding - gastrulation - implantation - organogenesis The placenta is formed from ________. - the embryo’s mesenchymal cells - the mother’s endometrium only - the mother’s endometrium and the embryo’s chorionic membrane - the mother’s endometrium and the embryo’s umbilical cord The foramen ovale causes the fetal circulatory system to bypass the ________. - liver - lungs - kidneys - gonads What happens to the urine excreted by the fetus when the kidneys begin to function? - The umbilical cord carries it to the placenta for removal. - The endometrium absorbs it. - It adds to the amniotic fluid. - It is turned into meconium. During weeks 9–12 of fetal development, ________. - bone marrow begins to assume erythrocyte production - meconium begins to accumulate in the intestines - surfactant production begins in the fetal lungs - the spinal cord begins to be myelinated Progesterone secreted by the placenta suppresses ________ to prevent maturation of ovarian follicles. - LH and estrogen - hCG and FSH - FSH and LH - estrogen and hCG Which of the following is a possible culprit of “morning sickness”? - increased minute respiration - decreased intestinal peristalsis - decreased aldosterone secretion - increased blood volume How does the decrease in progesterone at the last weeks of pregnancy help to bring on labor? - stimulating FSH production - decreasing the levels of estrogens - dilating the cervix - decreasing the inhibition of uterine contractility Which of these fetal presentations is the easiest for vaginal birth? - complete breech - vertex occiput anterior - frank breech - vertex occiput posterior Which of these shunts exists between the right and left atria? - foramen ovale - ductus venosus - ductus arteriosis - foramen venosus Why is brown fat important? - It is the newborn’s primary source of insulation. - It can be broken down to generate heat for thermoregulation. - It can be broken down for energy between feedings. - It can be converted to white fat. Constriction of umbilical blood vessels during vaginal birth ________. - causes respiratory alkalosis - inhibits the respiratory center in the brain - elevates carbon dioxide levels in the blood - both a and b Alveoli are connected to the lactiferous sinuses by ________. - lactocytes - lactiferous ducts - nipple pores - lobules How is colostrum most important to a newborn? - It helps boost the newborn’s immune system. - It provides much needed fat. - It satisfies the newborn’s thirst. - It satisfies the infant’s appetite. Mature breast milk ________. - has more sodium than cow’s milk - has more calcium than cow’s milk - has more protein than cow’s milk - has more fat than cow’s milk Marfan syndrome is inherited in an autosomal dominant pattern. Which of the following is true? - Female offspring are more likely to be carriers of the disease. - Male offspring are more likely to inherit the disease. - Male and female offspring have the same likelihood of inheriting the disease. - Female offspring are more likely to inherit the disease. In addition to codominance, the ABO blood group antigens are also an example of ________. - incomplete dominance - X-linked recessive inheritance - multiple alleles - recessive lethal inheritance Zoe has cystic fibrosis. Which of the following is the most likely explanation? - Zoe probably inherited one faulty allele from her father, who is a carrier, and one normal allele from her mother. - Zoe probably inherited one faulty allele from her mother, who must also have cystic fibrosis, and one normal allele from her father. - Zoe must have inherited faulty alleles from both parents, both of whom must also have cystic fibrosis. - Zoe must have inherited faulty alleles from both parents, both of whom are carriers. Critical Thinking Questions Darcy and Raul are having difficulty conceiving a child. Darcy ovulates every 28 days, and Raul’s sperm count is normal. If we could observe Raul’s sperm about an hour after ejaculation, however, we’d see that they appear to be moving only sluggishly. When Raul’s sperm eventually encounter Darcy’s oocyte, they appear to be incapable of generating an adequate acrosomal reaction. Which process has probably gone wrong? 32.Sherrise is a sexually active college student. On Saturday night, she has unprotected sex with her boyfriend. On Tuesday morning, she experiences the twinge of mid-cycle pain that she typically feels when she is ovulating. This makes Sherrise extremely anxious that she might soon learn she is pregnant. Is Sherrise’s concern valid? Why or why not? 33.Approximately 3 weeks after her last menstrual period, a sexually active woman experiences a brief episode of abdominopelvic cramping and minor bleeding. What might be the explanation? 34.The Food and Nutrition Board of the Institute of Medicine recommends that all women who might become pregnant consume at least 400 µg/day of folate from supplements or fortified foods. Why? 35.What is the physiological benefit of incorporating shunts into the fetal circulatory system? 36.Why would a premature infant require supplemental oxygen? 37.Devin is 35 weeks pregnant with her first child when she arrives at the birthing unit reporting that she believes she is in labor. She states that she has been experiencing diffuse, mild contractions for the past few hours. Examination reveals, however, that the plug of mucus blocking her cervix is intact and her cervix has not yet begun to dilate. She is advised to return home. Why? 38.Janine is 41 weeks pregnant with her first child when she arrives at the birthing unit reporting that she believes she has been in labor “for days” but that “it’s just not going anywhere.” During the clinical exam, she experiences a few mild contractions, each lasting about 15–20 seconds; however, her cervix is found to be only 2 cm dilated, and the amniotic sac is intact. Janine is admitted to the birthing unit and an IV infusion of pitocin is started. Why? 39.Describe how the newborn’s first breath alters the circulatory pattern. 40.Newborns are at much higher risk for dehydration than adults. Why? 41.Describe the transit of breast milk from lactocytes to nipple pores. 42.A woman who stopped breastfeeding suddenly is experiencing breast engorgement and leakage, just like she did in the first few weeks of breastfeeding. Why? 43.Explain why it was essential that Mendel perform his crosses using a large sample size? 44.How can a female carrier of an X-linked recessive disorder have a daughter who is affected?	oercommons	2025-03-18T00:35:13.307865	10/14/2019	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/58776/overview", "title": "Anatomy and Physiology, Human Development and the Continuity of Life, Development and Inheritance", "author": null }
https://oercommons.org/courseware/lesson/56365/overview	Bone Tissue and the Skeletal System Introduction Figure 6.1 Child Looking at Bones Bone is a living tissue. Unlike the bones of a fossil made inert by a process of mineralization, a child’s bones will continue to grow and develop while contributing to the support and function of other body systems. (credit: James Emery) CHAPTER OBJECTIVES After studying this chapter, you will be able to: - List and describe the functions of bones - Describe the classes of bones - Discuss the process of bone formation and development - Explain how bone repairs itself after a fracture - Discuss the effect of exercise, nutrition, and hormones on bone tissue - Describe how an imbalance of calcium can affect bone tissue Bones make good fossils. While the soft tissue of a once living organism will decay and fall away over time, bone tissue will, under the right conditions, undergo a process of mineralization, effectively turning the bone to stone. A well-preserved fossil skeleton can give us a good sense of the size and shape of an organism, just as your skeleton helps to define your size and shape. Unlike a fossil skeleton, however, your skeleton is a structure of living tissue that grows, repairs, and renews itself. The bones within it are dynamic and complex organs that serve a number of important functions, including some necessary to maintain homeostasis. The Functions of the Skeletal System - Define bone, cartilage, and the skeletal system - List and describe the functions of the skeletal system Bone, or osseous tissue, is a hard, dense connective tissue that forms most of the adult skeleton, the support structure of the body. In the areas of the skeleton where bones move (for example, the ribcage and joints), cartilage, a semi-rigid form of connective tissue, provides flexibility and smooth surfaces for movement. The skeletal system is the body system composed of bones and cartilage and performs the following critical functions for the human body: - supports the body - facilitates movement - protects internal organs - produces blood cells - stores and releases minerals and fat Support, Movement, and Protection The most apparent functions of the skeletal system are the gross functions—those visible by observation. Simply by looking at a person, you can see how the bones support, facilitate movement, and protect the human body. Just as the steel beams of a building provide a scaffold to support its weight, the bones and cartilage of your skeletal system compose the scaffold that supports the rest of your body. Without the skeletal system, you would be a limp mass of organs, muscle, and skin. Bones also facilitate movement by serving as points of attachment for your muscles. While some bones only serve as a support for the muscles, others also transmit the forces produced when your muscles contract. From a mechanical point of view, bones act as levers and joints serve as fulcrums (Figure 6.2). Unless a muscle spans a joint and contracts, a bone is not going to move. For information on the interaction of the skeletal and muscular systems, that is, the musculoskeletal system, seek additional content. Figure 6.2 Bones Support Movement Bones act as levers when muscles span a joint and contract. (credit: Benjamin J. DeLong) Bones also protect internal organs from injury by covering or surrounding them. For example, your ribs protect your lungs and heart, the bones of your vertebral column (spine) protect your spinal cord, and the bones of your cranium (skull) protect your brain (Figure 6.3). Figure 6.3 Bones Protect Brain The cranium completely surrounds and protects the brain from non-traumatic injury. CAREER CONNECTION Orthopedist An orthopedist is a doctor who specializes in diagnosing and treating disorders and injuries related to the musculoskeletal system. Some orthopedic problems can be treated with medications, exercises, braces, and other devices, but others may be best treated with surgery (Figure 6.4). Figure 6.4 Arm Brace An orthopedist will sometimes prescribe the use of a brace that reinforces the underlying bone structure it is being used to support. (credit: Juhan Sonin) While the origin of the word “orthopedics” (ortho- = “straight”; paed- = “child”), literally means “straightening of the child,” orthopedists can have patients who range from pediatric to geriatric. In recent years, orthopedists have even performed prenatal surgery to correct spina bifida, a congenital defect in which the neural canal in the spine of the fetus fails to close completely during embryologic development. Orthopedists commonly treat bone and joint injuries but they also treat other bone conditions including curvature of the spine. Lateral curvatures (scoliosis) can be severe enough to slip under the shoulder blade (scapula) forcing it up as a hump. Spinal curvatures can also be excessive dorsoventrally (kyphosis) causing a hunch back and thoracic compression. These curvatures often appear in preteens as the result of poor posture, abnormal growth, or indeterminate causes. Mostly, they are readily treated by orthopedists. As people age, accumulated spinal column injuries and diseases like osteoporosis can also lead to curvatures of the spine, hence the stooping you sometimes see in the elderly. Some orthopedists sub-specialize in sports medicine, which addresses both simple injuries, such as a sprained ankle, and complex injuries, such as a torn rotator cuff in the shoulder. Treatment can range from exercise to surgery. Mineral Storage, Energy Storage, and Hematopoiesis On a metabolic level, bone tissue performs several critical functions. For one, the bone matrix acts as a reservoir for a number of minerals important to the functioning of the body, especially calcium, and phosphorus. These minerals, incorporated into bone tissue, can be released back into the bloodstream to maintain levels needed to support physiological processes. Calcium ions, for example, are essential for muscle contractions and controlling the flow of other ions involved in the transmission of nerve impulses. Bone also serves as a site for fat storage and blood cell production. The softer connective tissue that fills the interior of most bone is referred to as bone marrow (Figure 6.5). There are two types of bone marrow: yellow marrow and red marrow. Yellow marrow contains adipose tissue; the triglycerides stored in the adipocytes of the tissue can serve as a source of energy. Red marrow is where hematopoiesis—the production of blood cells—takes place. Red blood cells, white blood cells, and platelets are all produced in the red marrow. Figure 6.5 Head of Femur Showing Red and Yellow Marrow The head of the femur contains both yellow and red marrow. Yellow marrow stores fat. Red marrow is responsible for hematopoiesis. (credit: modification of work by “stevenfruitsmaak”/Wikimedia Commons) Bone Classification - Classify bones according to their shapes - Describe the function of each category of bones The 206 bones that compose the adult skeleton are divided into five categories based on their shapes (Figure 6.6). Their shapes and their functions are related such that each categorical shape of bone has a distinct function. Figure 6.6 Classifications of Bones Bones are classified according to their shape. Long Bones A long bone is one that is cylindrical in shape, being longer than it is wide. Keep in mind, however, that the term describes the shape of a bone, not its size. Long bones are found in the arms (humerus, ulna, radius) and legs (femur, tibia, fibula), as well as in the fingers (metacarpals, phalanges) and toes (metatarsals, phalanges). Long bones function as levers; they move when muscles contract. Short Bones A short bone is one that is cube-like in shape, being approximately equal in length, width, and thickness. The only short bones in the human skeleton are in the carpals of the wrists and the tarsals of the ankles. Short bones provide stability and support as well as some limited motion. Flat Bones The term “flat bone” is somewhat of a misnomer because, although a flat bone is typically thin, it is also often curved. Examples include the cranial (skull) bones, the scapulae (shoulder blades), the sternum (breastbone), and the ribs. Flat bones serve as points of attachment for muscles and often protect internal organs. Irregular Bones An irregular bone is one that does not have any easily characterized shape and therefore does not fit any other classification. These bones tend to have more complex shapes, like the vertebrae that support the spinal cord and protect it from compressive forces. Many facial bones, particularly the ones containing sinuses, are classified as irregular bones. Sesamoid Bones A sesamoid bone is a small, round bone that, as the name suggests, is shaped like a sesame seed. These bones form in tendons (the sheaths of tissue that connect bones to muscles) where a great deal of pressure is generated in a joint. The sesamoid bones protect tendons by helping them overcome compressive forces. Sesamoid bones vary in number and placement from person to person but are typically found in tendons associated with the feet, hands, and knees. The patellae (singular = patella) are the only sesamoid bones found in common with every person. Table 6.1 reviews bone classifications with their associated features, functions, and examples. Bone Classifications \| Bone classification \| Features \| Function(s) \| Examples \| \|---\|---\|---\|---\| \| Long \| Cylinder-like shape, longer than it is wide \| Leverage \| Femur, tibia, fibula, metatarsals, humerus, ulna, radius, metacarpals, phalanges \| \| Short \| Cube-like shape, approximately equal in length, width, and thickness \| Provide stability, support, while allowing for some motion \| Carpals, tarsals \| \| Flat \| Thin and curved \| Points of attachment for muscles; protectors of internal organs \| Sternum, ribs, scapulae, cranial bones \| \| Irregular \| Complex shape \| Protect internal organs \| Vertebrae, facial bones \| \| Sesamoid \| Small and round; embedded in tendons \| Protect tendons from compressive forces \| Patellae \| Table 6.1 Bone Structure - Identify the anatomical features of a bone - Define and list examples of bone markings - Describe the histology of bone tissue - Compare and contrast compact and spongy bone - Identify the structures that compose compact and spongy bone - Describe how bones are nourished and innervated Bone tissue (osseous tissue) differs greatly from other tissues in the body. Bone is hard and many of its functions depend on that characteristic hardness. Later discussions in this chapter will show that bone is also dynamic in that its shape adjusts to accommodate stresses. This section will examine the gross anatomy of bone first and then move on to its histology. Gross Anatomy of Bone The structure of a long bone allows for the best visualization of all of the parts of a bone (Figure 6.7). A long bone has two parts: the diaphysis and the epiphysis. The diaphysis is the tubular shaft that runs between the proximal and distal ends of the bone. The hollow region in the diaphysis is called the medullary cavity, which is filled with yellow marrow. The walls of the diaphysis are composed of dense and hard compact bone. Figure 6.7 Anatomy of a Long Bone A typical long bone shows the gross anatomical characteristics of bone. The wider section at each end of the bone is called the epiphysis (plural = epiphyses), which is filled with spongy bone. Red marrow fills the spaces in the spongy bone. Each epiphysis meets the diaphysis at the metaphysis, the narrow area that contains the epiphyseal plate (growth plate), a layer of hyaline (transparent) cartilage in a growing bone. When the bone stops growing in early adulthood (approximately 18–21 years), the cartilage is replaced by osseous tissue and the epiphyseal plate becomes an epiphyseal line. The medullary cavity has a delicate membranous lining called the endosteum (end- = “inside”; oste- = “bone”), where bone growth, repair, and remodeling occur. The outer surface of the bone is covered with a fibrous membrane called the periosteum(peri- = “around” or “surrounding”). The periosteum contains blood vessels, nerves, and lymphatic vessels that nourish compact bone. Tendons and ligaments also attach to bones at the periosteum. The periosteum covers the entire outer surface except where the epiphyses meet other bones to form joints (Figure 6.8). In this region, the epiphyses are covered with articular cartilage, a thin layer of cartilage that reduces friction and acts as a shock absorber. Figure 6.8 Periosteum and Endosteum The periosteum forms the outer surface of bone, and the endosteum lines the medullary cavity. Flat bones, like those of the cranium, consist of a layer of diploë (spongy bone), lined on either side by a layer of compact bone (Figure 6.9). The two layers of compact bone and the interior spongy bone work together to protect the internal organs. If the outer layer of a cranial bone fractures, the brain is still protected by the intact inner layer. Figure 6.9 Anatomy of a Flat Bone This cross-section of a flat bone shows the spongy bone (diploë) lined on either side by a layer of compact bone. Bone Markings The surface features of bones vary considerably, depending on the function and location in the body. Table 6.2 describes the bone markings, which are illustrated in (Figure 6.10). There are three general classes of bone markings: (1) articulations, (2) projections, and (3) holes. As the name implies, an articulation is where two bone surfaces come together (articulus = “joint”). These surfaces tend to conform to one another, such as one being rounded and the other cupped, to facilitate the function of the articulation. A projection is an area of a bone that projects above the surface of the bone. These are the attachment points for tendons and ligaments. In general, their size and shape is an indication of the forces exerted through the attachment to the bone. A hole is an opening or groove in the bone that allows blood vessels and nerves to enter the bone. As with the other markings, their size and shape reflect the size of the vessels and nerves that penetrate the bone at these points. Bone Markings \| Marking \| Description \| Example \| \|---\|---\|---\| \| Articulations \| Where two bones meet \| Knee joint \| \| Head \| Prominent rounded surface \| Head of femur \| \| Facet \| Flat surface \| Vertebrae \| \| Condyle \| Rounded surface \| Occipital condyles \| \| Projections \| Raised markings \| Spinous process of the vertebrae \| \| Protuberance \| Protruding \| Chin \| \| Process \| Prominence feature \| Transverse process of vertebra \| \| Spine \| Sharp process \| Ischial spine \| \| Tubercle \| Small, rounded process \| Tubercle of humerus \| \| Tuberosity \| Rough surface \| Deltoid tuberosity \| \| Line \| Slight, elongated ridge \| Temporal lines of the parietal bones \| \| Crest \| Ridge \| Iliac crest \| \| Holes \| Holes and depressions \| Foramen (holes through which blood vessels can pass through) \| \| Fossa \| Elongated basin \| Mandibular fossa \| \| Fovea \| Small pit \| Fovea capitis on the head of the femur \| \| Sulcus \| Groove \| Sigmoid sulcus of the temporal bones \| \| Canal \| Passage in bone \| Auditory canal \| \| Fissure \| Slit through bone \| Auricular fissure \| \| Foramen \| Hole through bone \| Foramen magnum in the occipital bone \| \| Meatus \| Opening into canal \| External auditory meatus \| \| Sinus \| Air-filled space in bone \| Nasal sinus \| Table 6.2 Figure 6.10 Bone Features The surface features of bones depend on their function, location, attachment of ligaments and tendons, or the penetration of blood vessels and nerves. Bone Cells and Tissue Bone contains a relatively small number of cells entrenched in a matrix of collagen fibers that provide a surface for inorganic salt crystals to adhere. These salt crystals form when calcium phosphate and calcium carbonate combine to create hydroxyapatite, which incorporates other inorganic salts like magnesium hydroxide, fluoride, and sulfate as it crystallizes, or calcifies, on the collagen fibers. The hydroxyapatite crystals give bones their hardness and strength, while the collagen fibers give them flexibility so that they are not brittle. Although bone cells compose a small amount of the bone volume, they are crucial to the function of bones. Four types of cells are found within bone tissue: osteoblasts, osteocytes, osteogenic cells, and osteoclasts (Figure 6.11). Figure 6.11 Bone Cells Four types of cells are found within bone tissue. Osteogenic cells are undifferentiated and develop into osteoblasts. When osteoblasts get trapped within the calcified matrix, their structure and function changes, and they become osteocytes. Osteoclasts develop from monocytes and macrophages and differ in appearance from other bone cells. The osteoblast is the bone cell responsible for forming new bone and is found in the growing portions of bone, including the periosteum and endosteum. Osteoblasts, which do not divide, synthesize and secrete the collagen matrix and calcium salts. As the secreted matrix surrounding the osteoblast calcifies, the osteoblast become trapped within it; as a result, it changes in structure and becomes an osteocyte, the primary cell of mature bone and the most common type of bone cell. Each osteocyte is located in a space called a lacuna and is surrounded by bone tissue. Osteocytes maintain the mineral concentration of the matrix via the secretion of enzymes. Like osteoblasts, osteocytes lack mitotic activity. They can communicate with each other and receive nutrients via long cytoplasmic processes that extend through canaliculi (singular = canaliculus), channels within the bone matrix. If osteoblasts and osteocytes are incapable of mitosis, then how are they replenished when old ones die? The answer lies in the properties of a third category of bone cells—the osteogenic cell. These osteogenic cells are undifferentiated with high mitotic activity and they are the only bone cells that divide. Immature osteogenic cells are found in the deep layers of the periosteum and the marrow. They differentiate and develop into osteoblasts. The dynamic nature of bone means that new tissue is constantly formed, and old, injured, or unnecessary bone is dissolved for repair or for calcium release. The cell responsible for bone resorption, or breakdown, is the osteoclast. They are found on bone surfaces, are multinucleated, and originate from monocytes and macrophages, two types of white blood cells, not from osteogenic cells. Osteoclasts are continually breaking down old bone while osteoblasts are continually forming new bone. The ongoing balance between osteoblasts and osteoclasts is responsible for the constant but subtle reshaping of bone. Table 6.3reviews the bone cells, their functions, and locations. Bone Cells \| Cell type \| Function \| Location \| \|---\|---\|---\| \| Osteogenic cells \| Develop into osteoblasts \| Deep layers of the periosteum and the marrow \| \| Osteoblasts \| Bone formation \| Growing portions of bone, including periosteum and endosteum \| \| Osteocytes \| Maintain mineral concentration of matrix \| Entrapped in matrix \| \| Osteoclasts \| Bone resorption \| Bone surfaces and at sites of old, injured, or unneeded bone \| Table 6.3 Compact and Spongy Bone The differences between compact and spongy bone are best explored via their histology. Most bones contain compact and spongy osseous tissue, but their distribution and concentration vary based on the bone’s overall function. Compact bone is dense so that it can withstand compressive forces, while spongy (cancellous) bone has open spaces and supports shifts in weight distribution. Compact Bone Compact bone is the denser, stronger of the two types of bone tissue (Figure 6.12). It can be found under the periosteum and in the diaphyses of long bones, where it provides support and protection. Figure 6.12 Diagram of Compact Bone (a) This cross-sectional view of compact bone shows the basic structural unit, the osteon. (b) In this micrograph of the osteon, you can clearly see the concentric lamellae and central canals. LM × 40. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) The microscopic structural unit of compact bone is called an osteon, or Haversian system. Each osteon is composed of concentric rings of calcified matrix called lamellae (singular = lamella). Running down the center of each osteon is the central canal, or Haversian canal, which contains blood vessels, nerves, and lymphatic vessels. These vessels and nerves branch off at right angles through a perforating canal, also known as Volkmann’s canals, to extend to the periosteum and endosteum. The osteocytes are located inside spaces called lacunae (singular = lacuna), found at the borders of adjacent lamellae. As described earlier, canaliculi connect with the canaliculi of other lacunae and eventually with the central canal. This system allows nutrients to be transported to the osteocytes and wastes to be removed from them. Spongy (Cancellous) Bone Like compact bone, spongy bone, also known as cancellous bone, contains osteocytes housed in lacunae, but they are not arranged in concentric circles. Instead, the lacunae and osteocytes are found in a lattice-like network of matrix spikes called trabeculae (singular = trabecula) (Figure 6.13). The trabeculae may appear to be a random network, but each trabecula forms along lines of stress to provide strength to the bone. The spaces of the trabeculated network provide balance to the dense and heavy compact bone by making bones lighter so that muscles can move them more easily. In addition, the spaces in some spongy bones contain red marrow, protected by the trabeculae, where hematopoiesis occurs. Figure 6.13 Diagram of Spongy Bone Spongy bone is composed of trabeculae that contain the osteocytes. Red marrow fills the spaces in some bones. AGING AND THE... Skeletal System: Paget’s Disease Paget’s disease usually occurs in adults over age 40. It is a disorder of the bone remodeling process that begins with overactive osteoclasts. This means more bone is resorbed than is laid down. The osteoblasts try to compensate but the new bone they lay down is weak and brittle and therefore prone to fracture. While some people with Paget’s disease have no symptoms, others experience pain, bone fractures, and bone deformities (Figure 6.14). Bones of the pelvis, skull, spine, and legs are the most commonly affected. When occurring in the skull, Paget’s disease can cause headaches and hearing loss. Figure 6.14 Paget's Disease Normal leg bones are relatively straight, but those affected by Paget’s disease are porous and curved. What causes the osteoclasts to become overactive? The answer is still unknown, but hereditary factors seem to play a role. Some scientists believe Paget’s disease is due to an as-yet-unidentified virus. Paget’s disease is diagnosed via imaging studies and lab tests. X-rays may show bone deformities or areas of bone resorption. Bone scans are also useful. In these studies, a dye containing a radioactive ion is injected into the body. Areas of bone resorption have an affinity for the ion, so they will light up on the scan if the ions are absorbed. In addition, blood levels of an enzyme called alkaline phosphatase are typically elevated in people with Paget’s disease. Bisphosphonates, drugs that decrease the activity of osteoclasts, are often used in the treatment of Paget’s disease. However, in a small percentage of cases, bisphosphonates themselves have been linked to an increased risk of fractures because the old bone that is left after bisphosphonates are administered becomes worn out and brittle. Still, most doctors feel that the benefits of bisphosphonates more than outweigh the risk; the medical professional has to weigh the benefits and risks on a case-by-case basis. Bisphosphonate treatment can reduce the overall risk of deformities or fractures, which in turn reduces the risk of surgical repair and its associated risks and complications. Blood and Nerve Supply The spongy bone and medullary cavity receive nourishment from arteries that pass through the compact bone. The arteries enter through the nutrient foramen (plural = foramina), small openings in the diaphysis (Figure 6.15). The osteocytes in spongy bone are nourished by blood vessels of the periosteum that penetrate spongy bone and blood that circulates in the marrow cavities. As the blood passes through the marrow cavities, it is collected by veins, which then pass out of the bone through the foramina. In addition to the blood vessels, nerves follow the same paths into the bone where they tend to concentrate in the more metabolically active regions of the bone. The nerves sense pain, and it appears the nerves also play roles in regulating blood supplies and in bone growth, hence their concentrations in metabolically active sites of the bone. Figure 6.15 Diagram of Blood and Nerve Supply to Bone Blood vessels and nerves enter the bone through the nutrient foramen. INTERACTIVE LINK Watch this video to see the microscopic features of a bone. Bone Formation and Development - Explain the function of cartilage - List the steps of intramembranous ossification - List the steps of endochondral ossification - Explain the growth activity at the epiphyseal plate - Compare and contrast the processes of modeling and remodeling In the early stages of embryonic development, the embryo’s skeleton consists of fibrous membranes and hyaline cartilage. By the sixth or seventh week of embryonic life, the actual process of bone development, ossification (osteogenesis), begins. There are two osteogenic pathways—intramembranous ossification and endochondral ossification—but bone is the same regardless of the pathway that produces it. Cartilage Templates Bone is a replacement tissue; that is, it uses a model tissue on which to lay down its mineral matrix. For skeletal development, the most common template is cartilage. During fetal development, a framework is laid down that determines where bones will form. This framework is a flexible, semi-solid matrix produced by chondroblasts and consists of hyaluronic acid, chondroitin sulfate, collagen fibers, and water. As the matrix surrounds and isolates chondroblasts, they are called chondrocytes. Unlike most connective tissues, cartilage is avascular, meaning that it has no blood vessels supplying nutrients and removing metabolic wastes. All of these functions are carried on by diffusion through the matrix. This is why damaged cartilage does not repair itself as readily as most tissues do. Throughout fetal development and into childhood growth and development, bone forms on the cartilaginous matrix. By the time a fetus is born, most of the cartilage has been replaced with bone. Some additional cartilage will be replaced throughout childhood, and some cartilage remains in the adult skeleton. Intramembranous Ossification During intramembranous ossification, compact and spongy bone develops directly from sheets of mesenchymal (undifferentiated) connective tissue. The flat bones of the face, most of the cranial bones, and the clavicles (collarbones) are formed via intramembranous ossification. The process begins when mesenchymal cells in the embryonic skeleton gather together and begin to differentiate into specialized cells (Figure 6.16a). Some of these cells will differentiate into capillaries, while others will become osteogenic cells and then osteoblasts. Although they will ultimately be spread out by the formation of bone tissue, early osteoblasts appear in a cluster called an ossification center. The osteoblasts secrete osteoid, uncalcified matrix, which calcifies (hardens) within a few days as mineral salts are deposited on it, thereby entrapping the osteoblasts within. Once entrapped, the osteoblasts become osteocytes (Figure 6.16b). As osteoblasts transform into osteocytes, osteogenic cells in the surrounding connective tissue differentiate into new osteoblasts. Osteoid (unmineralized bone matrix) secreted around the capillaries results in a trabecular matrix, while osteoblasts on the surface of the spongy bone become the periosteum (Figure 6.16c). The periosteum then creates a protective layer of compact bone superficial to the trabecular bone. The trabecular bone crowds nearby blood vessels, which eventually condense into red marrow (Figure 6.16d). Figure 6.16 Intramembranous Ossification Intramembranous ossification follows four steps. (a) Mesenchymal cells group into clusters, and ossification centers form. (b) Secreted osteoid traps osteoblasts, which then become osteocytes. (c) Trabecular matrix and periosteum form. (d) Compact bone develops superficial to the trabecular bone, and crowded blood vessels condense into red marrow. Intramembranous ossification begins in utero during fetal development and continues on into adolescence. At birth, the skull and clavicles are not fully ossified nor are the sutures of the skull closed. This allows the skull and shoulders to deform during passage through the birth canal. The last bones to ossify via intramembranous ossification are the flat bones of the face, which reach their adult size at the end of the adolescent growth spurt. Endochondral Ossification In endochondral ossification, bone develops by replacing hyaline cartilage. Cartilage does not become bone. Instead, cartilage serves as a template to be completely replaced by new bone. Endochondral ossification takes much longer than intramembranous ossification. Bones at the base of the skull and long bones form via endochondral ossification. In a long bone, for example, at about 6 to 8 weeks after conception, some of the mesenchymal cells differentiate into chondrocytes (cartilage cells) that form the cartilaginous skeletal precursor of the bones (Figure 6.17a). Soon after, the perichondrium, a membrane that covers the cartilage, appears Figure 6.17b). Figure 6.17 Endochondral Ossification Endochondral ossification follows five steps. (a) Mesenchymal cells differentiate into chondrocytes. (b) The cartilage model of the future bony skeleton and the perichondrium form. (c) Capillaries penetrate cartilage. Perichondrium transforms into periosteum. Periosteal collar develops. Primary ossification center develops. (d) Cartilage and chondrocytes continue to grow at ends of the bone. (e) Secondary ossification centers develop. (f) Cartilage remains at epiphyseal (growth) plate and at joint surface as articular cartilage. As more matrix is produced, the chondrocytes in the center of the cartilaginous model grow in size. As the matrix calcifies, nutrients can no longer reach the chondrocytes. This results in their death and the disintegration of the surrounding cartilage. Blood vessels invade the resulting spaces, not only enlarging the cavities but also carrying osteogenic cells with them, many of which will become osteoblasts. These enlarging spaces eventually combine to become the medullary cavity. As the cartilage grows, capillaries penetrate it. This penetration initiates the transformation of the perichondrium into the bone-producing periosteum. Here, the osteoblasts form a periosteal collar of compact bone around the cartilage of the diaphysis. By the second or third month of fetal life, bone cell development and ossification ramps up and creates the primary ossification center, a region deep in the periosteal collar where ossification begins (Figure 6.17c). While these deep changes are occurring, chondrocytes and cartilage continue to grow at the ends of the bone (the future epiphyses), which increases the bone’s length at the same time bone is replacing cartilage in the diaphyses. By the time the fetal skeleton is fully formed, cartilage only remains at the joint surface as articular cartilage and between the diaphysis and epiphysis as the epiphyseal plate, the latter of which is responsible for the longitudinal growth of bones. After birth, this same sequence of events (matrix mineralization, death of chondrocytes, invasion of blood vessels from the periosteum, and seeding with osteogenic cells that become osteoblasts) occurs in the epiphyseal regions, and each of these centers of activity is referred to as a secondary ossification center (Figure 6.17e). How Bones Grow in Length The epiphyseal plate is the area of growth in a long bone. It is a layer of hyaline cartilage where ossification occurs in immature bones. On the epiphyseal side of the epiphyseal plate, cartilage is formed. On the diaphyseal side, cartilage is ossified, and the diaphysis grows in length. The epiphyseal plate is composed of four zones of cells and activity (Figure 6.18). The reserve zoneis the region closest to the epiphyseal end of the plate and contains small chondrocytes within the matrix. These chondrocytes do not participate in bone growth but secure the epiphyseal plate to the osseous tissue of the epiphysis. Figure 6.18 Longitudinal Bone Growth The epiphyseal plate is responsible for longitudinal bone growth. The proliferative zone is the next layer toward the diaphysis and contains stacks of slightly larger chondrocytes. It makes new chondrocytes (via mitosis) to replace those that die at the diaphyseal end of the plate. Chondrocytes in the next layer, the zone of maturation and hypertrophy, are older and larger than those in the proliferative zone. The more mature cells are situated closer to the diaphyseal end of the plate. The longitudinal growth of bone is a result of cellular division in the proliferative zone and the maturation of cells in the zone of maturation and hypertrophy. Most of the chondrocytes in the zone of calcified matrix, the zone closest to the diaphysis, are dead because the matrix around them has calcified. Capillaries and osteoblasts from the diaphysis penetrate this zone, and the osteoblasts secrete bone tissue on the remaining calcified cartilage. Thus, the zone of calcified matrix connects the epiphyseal plate to the diaphysis. A bone grows in length when osseous tissue is added to the diaphysis. Bones continue to grow in length until early adulthood. The rate of growth is controlled by hormones, which will be discussed later. When the chondrocytes in the epiphyseal plate cease their proliferation and bone replaces the cartilage, longitudinal growth stops. All that remains of the epiphyseal plate is the epiphyseal line (Figure 6.19). Figure 6.19 Progression from Epiphyseal Plate to Epiphyseal Line As a bone matures, the epiphyseal plate progresses to an epiphyseal line. (a) Epiphyseal plates are visible in a growing bone. (b) Epiphyseal lines are the remnants of epiphyseal plates in a mature bone. How Bones Grow in Diameter While bones are increasing in length, they are also increasing in diameter; growth in diameter can continue even after longitudinal growth ceases. This is called appositional growth. Osteoclasts resorb old bone that lines the medullary cavity, while osteoblasts, via intramembranous ossification, produce new bone tissue beneath the periosteum. The erosion of old bone along the medullary cavity and the deposition of new bone beneath the periosteum not only increase the diameter of the diaphysis but also increase the diameter of the medullary cavity. This process is called modeling. Bone Remodeling The process in which matrix is resorbed on one surface of a bone and deposited on another is known as bone modeling. Modeling primarily takes place during a bone’s growth. However, in adult life, bone undergoes remodeling, in which resorption of old or damaged bone takes place on the same surface where osteoblasts lay new bone to replace that which is resorbed. Injury, exercise, and other activities lead to remodeling. Those influences are discussed later in the chapter, but even without injury or exercise, about 5 to 10 percent of the skeleton is remodeled annually just by destroying old bone and renewing it with fresh bone. DISEASES OF THE... Skeletal System Osteogenesis imperfecta (OI) is a genetic disease in which bones do not form properly and therefore are fragile and break easily. It is also called brittle bone disease. The disease is present from birth and affects a person throughout life. The genetic mutation that causes OI affects the body’s production of collagen, one of the critical components of bone matrix. The severity of the disease can range from mild to severe. Those with the most severe forms of the disease sustain many more fractures than those with a mild form. Frequent and multiple fractures typically lead to bone deformities and short stature. Bowing of the long bones and curvature of the spine are also common in people afflicted with OI. Curvature of the spine makes breathing difficult because the lungs are compressed. Because collagen is such an important structural protein in many parts of the body, people with OI may also experience fragile skin, weak muscles, loose joints, easy bruising, frequent nosebleeds, brittle teeth, blue sclera, and hearing loss. There is no known cure for OI. Treatment focuses on helping the person retain as much independence as possible while minimizing fractures and maximizing mobility. Toward that end, safe exercises, like swimming, in which the body is less likely to experience collisions or compressive forces, are recommended. Braces to support legs, ankles, knees, and wrists are used as needed. Canes, walkers, or wheelchairs can also help compensate for weaknesses. When bones do break, casts, splints, or wraps are used. In some cases, metal rods may be surgically implanted into the long bones of the arms and legs. Research is currently being conducted on using bisphosphonates to treat OI. Smoking and being overweight are especially risky in people with OI, since smoking is known to weaken bones, and extra body weight puts additional stress on the bones. INTERACTIVE LINK Watch this video to see how a bone grows. Fractures: Bone Repair - Differentiate among the different types of fractures - Describe the steps involved in bone repair A fracture is a broken bone. It will heal whether or not a physician resets it in its anatomical position. If the bone is not reset correctly, the healing process will keep the bone in its deformed position. When a broken bone is manipulated and set into its natural position without surgery, the procedure is called a closed reduction. Open reduction requires surgery to expose the fracture and reset the bone. While some fractures can be minor, others are quite severe and result in grave complications. For example, a fractured diaphysis of the femur has the potential to release fat globules into the bloodstream. These can become lodged in the capillary beds of the lungs, leading to respiratory distress and if not treated quickly, death. Types of Fractures Fractures are classified by their complexity, location, and other features (Figure 6.20). Table 6.4 outlines common types of fractures. Some fractures may be described using more than one term because it may have the features of more than one type (e.g., an open transverse fracture). Figure 6.20 Types of Fractures Compare healthy bone with different types of fractures: (a) closed fracture, (b) open fracture, (c) transverse fracture, (d) spiral fracture, (e) comminuted fracture, (f) impacted fracture, (g) greenstick fracture, and (h) oblique fracture. Types of Fractures \| Type of fracture \| Description \| \|---\|---\| \| Transverse \| Occurs straight across the long axis of the bone \| \| Oblique \| Occurs at an angle that is not 90 degrees \| \| Spiral \| Bone segments are pulled apart as a result of a twisting motion \| \| Comminuted \| Several breaks result in many small pieces between two large segments \| \| Impacted \| One fragment is driven into the other, usually as a result of compression \| \| Greenstick \| A partial fracture in which only one side of the bone is broken \| \| Open (or compound) \| A fracture in which at least one end of the broken bone tears through the skin; carries a high risk of infection \| \| Closed (or simple) \| A fracture in which the skin remains intact \| Table 6.4 Bone Repair When a bone breaks, blood flows from any vessel torn by the fracture. These vessels could be in the periosteum, osteons, and/or medullary cavity. The blood begins to clot, and about six to eight hours after the fracture, the clotting blood has formed a fracture hematoma (Figure 6.21a). The disruption of blood flow to the bone results in the death of bone cells around the fracture. Figure 6.21 Stages in Fracture Repair The healing of a bone fracture follows a series of progressive steps: (a) A fracture hematoma forms. (b) Internal and external calli form. (c) Cartilage of the calli is replaced by trabecular bone. (d) Remodeling occurs. Within about 48 hours after the fracture, chondrocytes from the endosteum have created an internal callus (plural = calli) by secreting a fibrocartilaginous matrix between the two ends of the broken bone, while the periosteal chondrocytes and osteoblasts create an external callus of hyaline cartilage and bone, respectively, around the outside of the break (Figure 6.21b). This stabilizes the fracture. Over the next several weeks, osteoclasts resorb the dead bone; osteogenic cells become active, divide, and differentiate into osteoblasts. The cartilage in the calli is replaced by trabecular bone via endochondral ossification (Figure 6.21c). Eventually, the internal and external calli unite, compact bone replaces spongy bone at the outer margins of the fracture, and healing is complete. A slight swelling may remain on the outer surface of the bone, but quite often, that region undergoes remodeling (Figure 6.21d), and no external evidence of the fracture remains. INTERACTIVE LINK Visit this website to review different types of fractures and then take a short self-assessment quiz. Exercise, Nutrition, Hormones, and Bone Tissue - Describe the effect exercise has on bone tissue - List the nutrients that affect bone health - Discuss the role those nutrients play in bone health - Describe the effects of hormones on bone tissue All of the organ systems of your body are interdependent, and the skeletal system is no exception. The food you take in via your digestive system and the hormones secreted by your endocrine system affect your bones. Even using your muscles to engage in exercise has an impact on your bones. Exercise and Bone Tissue During long space missions, astronauts can lose approximately 1 to 2 percent of their bone mass per month. This loss of bone mass is thought to be caused by the lack of mechanical stress on astronauts’ bones due to the low gravitational forces in space. Lack of mechanical stress causes bones to lose mineral salts and collagen fibers, and thus strength. Similarly, mechanical stress stimulates the deposition of mineral salts and collagen fibers. The internal and external structure of a bone will change as stress increases or decreases so that the bone is an ideal size and weight for the amount of activity it endures. That is why people who exercise regularly have thicker bones than people who are more sedentary. It is also why a broken bone in a cast atrophies while its contralateral mate maintains its concentration of mineral salts and collagen fibers. The bones undergo remodeling as a result of forces (or lack of forces) placed on them. Numerous, controlled studies have demonstrated that people who exercise regularly have greater bone density than those who are more sedentary. Any type of exercise will stimulate the deposition of more bone tissue, but resistance training has a greater effect than cardiovascular activities. Resistance training is especially important to slow down the eventual bone loss due to aging and for preventing osteoporosis. Nutrition and Bone Tissue The vitamins and minerals contained in all of the food we consume are important for all of our organ systems. However, there are certain nutrients that affect bone health. Calcium and Vitamin D You already know that calcium is a critical component of bone, especially in the form of calcium phosphate and calcium carbonate. Since the body cannot make calcium, it must be obtained from the diet. However, calcium cannot be absorbed from the small intestine without vitamin D. Therefore, intake of vitamin D is also critical to bone health. In addition to vitamin D’s role in calcium absorption, it also plays a role, though not as clearly understood, in bone remodeling. Milk and other dairy foods are not the only sources of calcium. This important nutrient is also found in green leafy vegetables, broccoli, and intact salmon and canned sardines with their soft bones. Nuts, beans, seeds, and shellfish provide calcium in smaller quantities. Except for fatty fish like salmon and tuna, or fortified milk or cereal, vitamin D is not found naturally in many foods. The action of sunlight on the skin triggers the body to produce its own vitamin D (Figure 6.22), but many people, especially those of darker complexion and those living in northern latitudes where the sun’s rays are not as strong, are deficient in vitamin D. In cases of deficiency, a doctor can prescribe a vitamin D supplement. Figure 6.22 Synthesis of Vitamin D Sunlight is one source of vitamin D. Other Nutrients Vitamin K also supports bone mineralization and may have a synergistic role with vitamin D in the regulation of bone growth. Green leafy vegetables are a good source of vitamin K. The minerals magnesium and fluoride may also play a role in supporting bone health. While magnesium is only found in trace amounts in the human body, more than 60 percent of it is in the skeleton, suggesting it plays a role in the structure of bone. Fluoride can displace the hydroxyl group in bone’s hydroxyapatite crystals and form fluorapatite. Similar to its effect on dental enamel, fluorapatite helps stabilize and strengthen bone mineral. Fluoride can also enter spaces within hydroxyapatite crystals, thus increasing their density. Omega-3 fatty acids have long been known to reduce inflammation in various parts of the body. Inflammation can interfere with the function of osteoblasts, so consuming omega-3 fatty acids, in the diet or in supplements, may also help enhance production of new osseous tissue. Table 6.5 summarizes the role of nutrients in bone health. Nutrients and Bone Health \| Nutrient \| Role in bone health \| \|---\|---\| \| Calcium \| Needed to make calcium phosphate and calcium carbonate, which form the hydroxyapatite crystals that give bone its hardness \| \| Vitamin D \| Needed for calcium absorption \| \| Vitamin K \| Supports bone mineralization; may have synergistic effect with vitamin D \| \| Magnesium \| Structural component of bone \| \| Fluoride \| Structural component of bone \| \| Omega-3 fatty acids \| Reduces inflammation that may interfere with osteoblast function \| Table 6.5 Hormones and Bone Tissue The endocrine system produces and secretes hormones, many of which interact with the skeletal system. These hormones are involved in controlling bone growth, maintaining bone once it is formed, and remodeling it. Hormones That Influence Osteoblasts and/or Maintain the Matrix Several hormones are necessary for controlling bone growth and maintaining the bone matrix. The pituitary gland secretes growth hormone (GH), which, as its name implies, controls bone growth in several ways. It triggers chondrocyte proliferation in epiphyseal plates, resulting in the increasing length of long bones. GH also increases calcium retention, which enhances mineralization, and stimulates osteoblastic activity, which improves bone density. GH is not alone in stimulating bone growth and maintaining osseous tissue. Thyroxine, a hormone secreted by the thyroid gland promotes osteoblastic activity and the synthesis of bone matrix. During puberty, the sex hormones (estrogen in girls, testosterone in boys) also come into play. They too promote osteoblastic activity and production of bone matrix, and in addition, are responsible for the growth spurt that often occurs during adolescence. They also promote the conversion of the epiphyseal plate to the epiphyseal line (i.e., cartilage to its bony remnant), thus bringing an end to the longitudinal growth of bones. Additionally, calcitriol, the active form of vitamin D, is produced by the kidneys and stimulates the absorption of calcium and phosphate from the digestive tract. AGING AND THE... Skeletal System Osteoporosis is a disease characterized by a decrease in bone mass that occurs when the rate of bone resorption exceeds the rate of bone formation, a common occurrence as the body ages. Notice how this is different from Paget’s disease. In Paget’s disease, new bone is formed in an attempt to keep up with the resorption by the overactive osteoclasts, but that new bone is produced haphazardly. In fact, when a physician is evaluating a patient with thinning bone, he or she will test for osteoporosis and Paget’s disease (as well as other diseases). Osteoporosis does not have the elevated blood levels of alkaline phosphatase found in Paget’s disease. Figure 6.23 Graph Showing Relationship Between Age and Bone Mass Bone density peaks at about 30 years of age. Women lose bone mass more rapidly than men. While osteoporosis can involve any bone, it most commonly affects the proximal ends of the femur, vertebrae, and wrist. As a result of the loss of bone density, the osseous tissue may not provide adequate support for everyday functions, and something as simple as a sneeze can cause a vertebral fracture. When an elderly person falls and breaks a hip (really, the femur), it is very likely the femur that broke first, which resulted in the fall. Histologically, osteoporosis is characterized by a reduction in the thickness of compact bone and the number and size of trabeculae in cancellous bone. Figure 6.23 shows that women lose bone mass more quickly than men starting at about 50 years of age. This occurs because 50 is the approximate age at which women go through menopause. Not only do their menstrual periods lessen and eventually cease, but their ovaries reduce in size and then cease the production of estrogen, a hormone that promotes osteoblastic activity and production of bone matrix. Thus, osteoporosis is more common in women than in men, but men can develop it, too. Anyone with a family history of osteoporosis has a greater risk of developing the disease, so the best treatment is prevention, which should start with a childhood diet that includes adequate intake of calcium and vitamin D and a lifestyle that includes weight-bearing exercise. These actions, as discussed above, are important in building bone mass. Promoting proper nutrition and weight-bearing exercise early in life can maximize bone mass before the age of 30, thus reducing the risk of osteoporosis. For many elderly people, a hip fracture can be life threatening. The fracture itself may not be serious, but the immobility that comes during the healing process can lead to the formation of blood clots that can lodge in the capillaries of the lungs, resulting in respiratory failure; pneumonia due to the lack of poor air exchange that accompanies immobility; pressure sores (bed sores) that allow pathogens to enter the body and cause infections; and urinary tract infections from catheterization. Current treatments for managing osteoporosis include bisphosphonates (the same medications often used in Paget’s disease), calcitonin, and estrogen (for women only). Minimizing the risk of falls, for example, by removing tripping hazards, is also an important step in managing the potential outcomes from the disease. Hormones That Influence Osteoclasts Bone modeling and remodeling require osteoclasts to resorb unneeded, damaged, or old bone, and osteoblasts to lay down new bone. Two hormones that affect the osteoclasts are parathyroid hormone (PTH) and calcitonin. PTH stimulates osteoclast proliferation and activity. As a result, calcium is released from the bones into the circulation, thus increasing the calcium ion concentration in the blood. PTH also promotes the reabsorption of calcium by the kidney tubules, which can affect calcium homeostasis (see below). The small intestine is also affected by PTH, albeit indirectly. Because another function of PTH is to stimulate the synthesis of vitamin D, and because vitamin D promotes intestinal absorption of calcium, PTH indirectly increases calcium uptake by the small intestine. Calcitonin, a hormone secreted by the thyroid gland, has some effects that counteract those of PTH. Calcitonin inhibits osteoclast activity and stimulates calcium uptake by the bones, thus reducing the concentration of calcium ions in the blood. As evidenced by their opposing functions in maintaining calcium homeostasis, PTH and calcitonin are generally notsecreted at the same time. Table 6.6 summarizes the hormones that influence the skeletal system. Hormones That Affect the Skeletal System \| Hormone \| Role \| \|---\|---\| \| Growth hormone \| Increases length of long bones, enhances mineralization, and improves bone density \| \| Thyroxine \| Stimulates bone growth and promotes synthesis of bone matrix \| \| Sex hormones \| Promote osteoblastic activity and production of bone matrix; responsible for adolescent growth spurt; promote conversion of epiphyseal plate to epiphyseal line \| \| Calcitriol \| Stimulates absorption of calcium and phosphate from digestive tract \| \| Parathyroid hormone \| Stimulates osteoclast proliferation and resorption of bone by osteoclasts; promotes reabsorption of calcium by kidney tubules; indirectly increases calcium absorption by small intestine \| \| Calcitonin \| Inhibits osteoclast activity and stimulates calcium uptake by bones \| Table 6.6 Calcium Homeostasis: Interactions of the Skeletal System and Other Organ Systems - Describe the effect of too much or too little calcium on the body - Explain the process of calcium homeostasis Calcium is not only the most abundant mineral in bone, it is also the most abundant mineral in the human body. Calcium ions are needed not only for bone mineralization but for tooth health, regulation of the heart rate and strength of contraction, blood coagulation, contraction of smooth and skeletal muscle cells, and regulation of nerve impulse conduction. The normal level of calcium in the blood is about 10 mg/dL. When the body cannot maintain this level, a person will experience hypo- or hypercalcemia. Hypocalcemia, a condition characterized by abnormally low levels of calcium, can have an adverse effect on a number of different body systems including circulation, muscles, nerves, and bone. Without adequate calcium, blood has difficulty coagulating, the heart may skip beats or stop beating altogether, muscles may have difficulty contracting, nerves may have difficulty functioning, and bones may become brittle. The causes of hypocalcemia can range from hormonal imbalances to an improper diet. Treatments vary according to the cause, but prognoses are generally good. Conversely, in hypercalcemia, a condition characterized by abnormally high levels of calcium, the nervous system is underactive, which results in lethargy, sluggish reflexes, constipation and loss of appetite, confusion, and in severe cases, coma. Obviously, calcium homeostasis is critical. The skeletal, endocrine, and digestive systems play a role in this, but the kidneys do, too. These body systems work together to maintain a normal calcium level in the blood (Figure 6.24). Figure 6.24 Pathways in Calcium Homeostasis The body regulates calcium homeostasis with two pathways; one is signaled to turn on when blood calcium levels drop below normal and one is the pathway that is signaled to turn on when blood calcium levels are elevated. Calcium is a chemical element that cannot be produced by any biological processes. The only way it can enter the body is through the diet. The bones act as a storage site for calcium: The body deposits calcium in the bones when blood levels get too high, and it releases calcium when blood levels drop too low. This process is regulated by PTH, vitamin D, and calcitonin. Cells of the parathyroid gland have plasma membrane receptors for calcium. When calcium is not binding to these receptors, the cells release PTH, which stimulates osteoclast proliferation and resorption of bone by osteoclasts. This demineralization process releases calcium into the blood. PTH promotes reabsorption of calcium from the urine by the kidneys, so that the calcium returns to the blood. Finally, PTH stimulates the synthesis of vitamin D, which in turn, stimulates calcium absorption from any digested food in the small intestine. When all these processes return blood calcium levels to normal, there is enough calcium to bind with the receptors on the surface of the cells of the parathyroid glands, and this cycle of events is turned off (Figure 6.24). When blood levels of calcium get too high, the thyroid gland is stimulated to release calcitonin (Figure 6.24), which inhibits osteoclast activity and stimulates calcium uptake by the bones, but also decreases reabsorption of calcium by the kidneys. All of these actions lower blood levels of calcium. When blood calcium levels return to normal, the thyroid gland stops secreting calcitonin. Key Terms - articular cartilage - thin layer of cartilage covering an epiphysis; reduces friction and acts as a shock absorber - articulation - where two bone surfaces meet - bone - hard, dense connective tissue that forms the structural elements of the skeleton - canaliculi - (singular = canaliculus) channels within the bone matrix that house one of an osteocyte’s many cytoplasmic extensions that it uses to communicate and receive nutrients - cartilage - semi-rigid connective tissue found on the skeleton in areas where flexibility and smooth surfaces support movement - central canal - longitudinal channel in the center of each osteon; contains blood vessels, nerves, and lymphatic vessels; also known as the Haversian canal - closed reduction - manual manipulation of a broken bone to set it into its natural position without surgery - compact bone - dense osseous tissue that can withstand compressive forces - diaphysis - tubular shaft that runs between the proximal and distal ends of a long bone - diploë - layer of spongy bone, that is sandwiched between two the layers of compact bone found in flat bones - endochondral ossification - process in which bone forms by replacing hyaline cartilage - endosteum - delicate membranous lining of a bone’s medullary cavity - epiphyseal line - completely ossified remnant of the epiphyseal plate - epiphyseal plate - (also, growth plate) sheet of hyaline cartilage in the metaphysis of an immature bone; replaced by bone tissue as the organ grows in length - epiphysis - wide section at each end of a long bone; filled with spongy bone and red marrow - external callus - collar of hyaline cartilage and bone that forms around the outside of a fracture - flat bone - thin and curved bone; serves as a point of attachment for muscles and protects internal organs - fracture - broken bone - fracture hematoma - blood clot that forms at the site of a broken bone - hematopoiesis - production of blood cells, which occurs in the red marrow of the bones - hole - opening or depression in a bone - hypercalcemia - condition characterized by abnormally high levels of calcium - hypocalcemia - condition characterized by abnormally low levels of calcium - internal callus - fibrocartilaginous matrix, in the endosteal region, between the two ends of a broken bone - intramembranous ossification - process by which bone forms directly from mesenchymal tissue - irregular bone - bone of complex shape; protects internal organs from compressive forces - lacunae - (singular = lacuna) spaces in a bone that house an osteocyte - long bone - cylinder-shaped bone that is longer than it is wide; functions as a lever - medullary cavity - hollow region of the diaphysis; filled with yellow marrow - modeling - process, during bone growth, by which bone is resorbed on one surface of a bone and deposited on another - nutrient foramen - small opening in the middle of the external surface of the diaphysis, through which an artery enters the bone to provide nourishment - open reduction - surgical exposure of a bone to reset a fracture - orthopedist - doctor who specializes in diagnosing and treating musculoskeletal disorders and injuries - osseous tissue - bone tissue; a hard, dense connective tissue that forms the structural elements of the skeleton - ossification - (also, osteogenesis) bone formation - ossification center - cluster of osteoblasts found in the early stages of intramembranous ossification - osteoblast - cell responsible for forming new bone - osteoclast - cell responsible for resorbing bone - osteocyte - primary cell in mature bone; responsible for maintaining the matrix - osteogenic cell - undifferentiated cell with high mitotic activity; the only bone cells that divide; they differentiate and develop into osteoblasts - osteoid - uncalcified bone matrix secreted by osteoblasts - osteon - (also, Haversian system) basic structural unit of compact bone; made of concentric layers of calcified matrix - osteoporosis - disease characterized by a decrease in bone mass; occurs when the rate of bone resorption exceeds the rate of bone formation, a common occurrence as the body ages - perforating canal - (also, Volkmann’s canal) channel that branches off from the central canal and houses vessels and nerves that extend to the periosteum and endosteum - perichondrium - membrane that covers cartilage - periosteum - fibrous membrane covering the outer surface of bone and continuous with ligaments - primary ossification center - region, deep in the periosteal collar, where bone development starts during endochondral ossification - projection - bone markings where part of the surface sticks out above the rest of the surface, where tendons and ligaments attach - proliferative zone - region of the epiphyseal plate that makes new chondrocytes to replace those that die at the diaphyseal end of the plate and contributes to longitudinal growth of the epiphyseal plate - red marrow - connective tissue in the interior cavity of a bone where hematopoiesis takes place - remodeling - process by which osteoclasts resorb old or damaged bone at the same time as and on the same surface where osteoblasts form new bone to replace that which is resorbed - reserve zone - region of the epiphyseal plate that anchors the plate to the osseous tissue of the epiphysis - secondary ossification center - region of bone development in the epiphyses - sesamoid bone - small, round bone embedded in a tendon; protects the tendon from compressive forces - short bone - cube-shaped bone that is approximately equal in length, width, and thickness; provides limited motion - skeletal system - organ system composed of bones and cartilage that provides for movement, support, and protection - spongy bone - (also, cancellous bone) trabeculated osseous tissue that supports shifts in weight distribution - trabeculae - (singular = trabecula) spikes or sections of the lattice-like matrix in spongy bone - yellow marrow - connective tissue in the interior cavity of a bone where fat is stored - zone of calcified matrix - region of the epiphyseal plate closest to the diaphyseal end; functions to connect the epiphyseal plate to the diaphysis - zone of maturation and hypertrophy - region of the epiphyseal plate where chondrocytes from the proliferative zone grow and mature and contribute to the longitudinal growth of the epiphyseal plate Chapter Review 6.1 The Functions of the Skeletal System The major functions of the bones are body support, facilitation of movement, protection of internal organs, storage of minerals and fat, and hematopoiesis. Together, the muscular system and skeletal system are known as the musculoskeletal system. 6.2 Bone Classification Bones can be classified according to their shapes. Long bones, such as the femur, are longer than they are wide. Short bones, such as the carpals, are approximately equal in length, width, and thickness. Flat bones are thin, but are often curved, such as the ribs. Irregular bones such as those of the face have no characteristic shape. Sesamoid bones, such as the patellae, are small and round, and are located in tendons. 6.3 Bone Structure A hollow medullary cavity filled with yellow marrow runs the length of the diaphysis of a long bone. The walls of the diaphysis are compact bone. The epiphyses, which are wider sections at each end of a long bone, are filled with spongy bone and red marrow. The epiphyseal plate, a layer of hyaline cartilage, is replaced by osseous tissue as the organ grows in length. The medullary cavity has a delicate membranous lining called the endosteum. The outer surface of bone, except in regions covered with articular cartilage, is covered with a fibrous membrane called the periosteum. Flat bones consist of two layers of compact bone surrounding a layer of spongy bone. Bone markings depend on the function and location of bones. Articulations are places where two bones meet. Projections stick out from the surface of the bone and provide attachment points for tendons and ligaments. Holes are openings or depressions in the bones. Bone matrix consists of collagen fibers and organic ground substance, primarily hydroxyapatite formed from calcium salts. Osteogenic cells develop into osteoblasts. Osteoblasts are cells that make new bone. They become osteocytes, the cells of mature bone, when they get trapped in the matrix. Osteoclasts engage in bone resorption. Compact bone is dense and composed of osteons, while spongy bone is less dense and made up of trabeculae. Blood vessels and nerves enter the bone through the nutrient foramina to nourish and innervate bones. 6.4 Bone Formation and Development All bone formation is a replacement process. Embryos develop a cartilaginous skeleton and various membranes. During development, these are replaced by bone during the ossification process. In intramembranous ossification, bone develops directly from sheets of mesenchymal connective tissue. In endochondral ossification, bone develops by replacing hyaline cartilage. Activity in the epiphyseal plate enables bones to grow in length. Modeling allows bones to grow in diameter. Remodeling occurs as bone is resorbed and replaced by new bone. Osteogenesis imperfecta is a genetic disease in which collagen production is altered, resulting in fragile, brittle bones. 6.5 Fractures: Bone Repair Fractured bones may be repaired by closed reduction or open reduction. Fractures are classified by their complexity, location, and other features. Common types of fractures are transverse, oblique, spiral, comminuted, impacted, greenstick, open (or compound), and closed (or simple). Healing of fractures begins with the formation of a hematoma, followed by internal and external calli. Osteoclasts resorb dead bone, while osteoblasts create new bone that replaces the cartilage in the calli. The calli eventually unite, remodeling occurs, and healing is complete. 6.6 Exercise, Nutrition, Hormones, and Bone Tissue Mechanical stress stimulates the deposition of mineral salts and collagen fibers within bones. Calcium, the predominant mineral in bone, cannot be absorbed from the small intestine if vitamin D is lacking. Vitamin K supports bone mineralization and may have a synergistic role with vitamin D. Magnesium and fluoride, as structural elements, play a supporting role in bone health. Omega-3 fatty acids reduce inflammation and may promote production of new osseous tissue. Growth hormone increases the length of long bones, enhances mineralization, and improves bone density. Thyroxine stimulates bone growth and promotes the synthesis of bone matrix. The sex hormones (estrogen in women; testosterone in men) promote osteoblastic activity and the production of bone matrix, are responsible for the adolescent growth spurt, and promote closure of the epiphyseal plates. Osteoporosis is a disease characterized by decreased bone mass that is common in aging adults. Calcitriol stimulates the digestive tract to absorb calcium and phosphate. Parathyroid hormone (PTH) stimulates osteoclast proliferation and resorption of bone by osteoclasts. Vitamin D plays a synergistic role with PTH in stimulating the osteoclasts. Additional functions of PTH include promoting reabsorption of calcium by kidney tubules and indirectly increasing calcium absorption from the small intestine. Calcitonin inhibits osteoclast activity and stimulates calcium uptake by bones. 6.7 Calcium Homeostasis: Interactions of the Skeletal System and Other Organ Systems Calcium homeostasis, i.e., maintaining a blood calcium level of about 10 mg/dL, is critical for normal body functions. Hypocalcemia can result in problems with blood coagulation, muscle contraction, nerve functioning, and bone strength. Hypercalcemia can result in lethargy, sluggish reflexes, constipation and loss of appetite, confusion, and coma. Calcium homeostasis is controlled by PTH, vitamin D, and calcitonin and the interactions of the skeletal, endocrine, digestive, and urinary systems. Review Questions Which function of the skeletal system would be especially important if you were in a car accident? - storage of minerals - protection of internal organs - facilitation of movement - fat storage Bone tissue can be described as ________. - dead calcified tissue - cartilage - the skeletal system - dense, hard connective tissue Without red marrow, bones would not be able to ________. - store phosphate - store calcium - make blood cells - move like levers Yellow marrow has been identified as ________. - an area of fat storage - a point of attachment for muscles - the hard portion of bone - the cause of kyphosis Which of the following can be found in areas of movement? - hematopoiesis - cartilage - yellow marrow - red marrow The skeletal system is made of ________. - muscles and tendons - bones and cartilage - vitreous humor - minerals and fat Most of the bones of the arms and hands are long bones; however, the bones in the wrist are categorized as ________. - flat bones - short bones - sesamoid bones - irregular bones Sesamoid bones are found embedded in ________. - joints - muscles - ligaments - tendons Bones that surround the spinal cord are classified as ________ bones. - irregular - sesamoid - flat - short Which category of bone is among the most numerous in the skeleton? - long bone - sesamoid bone - short bone - flat bone Long bones enable body movement by acting as a ________. - counterweight - resistive force - lever - fulcrum Which of the following occurs in the spongy bone of the epiphysis? - bone growth - bone remodeling - hematopoiesis - shock absorption The diaphysis contains ________. - the metaphysis - fat stores - spongy bone - compact bone The fibrous membrane covering the outer surface of the bone is the ________. - periosteum - epiphysis - endosteum - diaphysis Which of the following are incapable of undergoing mitosis? - osteoblasts and osteoclasts - osteocytes and osteoclasts - osteoblasts and osteocytes - osteogenic cells and osteoclasts Which cells do not originate from osteogenic cells? - osteoblasts - osteoclasts - osteocytes - osteoprogenitor cells Which of the following are found in compact bone and cancellous bone? - Haversian systems - Haversian canals - lamellae - lacunae Which of the following are only found in cancellous bone? - canaliculi - Volkmann’s canals - trabeculae - calcium salts The area of a bone where the nutrient foramen passes forms what kind of bone marking? - a hole - a facet - a canal - a fissure Why is cartilage slow to heal? - because it eventually develops into bone - because it is semi-solid and flexible - because it does not have a blood supply - because endochondral ossification replaces all cartilage with bone Why are osteocytes spread out in bone tissue? - They develop from mesenchymal cells. - They are surrounded by osteoid. - They travel through the capillaries. - Formation of osteoid spreads out the osteoblasts that formed the ossification centers. In endochondral ossification, what happens to the chondrocytes? - They develop into osteocytes. - They die in the calcified matrix that surrounds them and form the medullary cavity. - They grow and form the periosteum. - They group together to form the primary ossification center. Which of the following bones is (are) formed by intramembranous ossification? - the metatarsals - the femur - the ribs - the flat bones of the cranium Bones grow in length due to activity in the ________. - epiphyseal plate - perichondrium - periosteum - medullary cavity Bones grow in diameter due to bone formation ________. - in the medullary cavity - beneath the periosteum - in the epiphyseal plate - within the metaphysis Which of the following represents the correct sequence of zones in the epiphyseal plate? - proliferation, reserved, maturation, calcification - maturation, proliferation, reserved, calcification - calcification, maturation, proliferation, reserved - calcification, reserved, proliferation, maturation A fracture can be both ________. - open and closed - open and transverse - transverse and greenstick - greenstick and comminuted How can a fractured diaphysis release fat globules into the bloodstream? - The bone pierces fat stores in the skin. - The yellow marrow in the diaphysis is exposed and damaged. - The injury triggers the body to release fat from healthy bones. - The red marrow in the fractured bone releases fat to heal the fracture. In a compound fracture, ________. - the break occurs at an angle to the bone - the broken bone does not tear the skin - one fragment of broken bone is compressed into the other - broken bone pierces the skin The internal and external calli are replaced by ________. - hyaline cartilage - trabecular bone - osteogenic cells - osteoclasts The first type of bone to form during fracture repair is ________ bone. - compact - lamellar - spongy - dense Wolff’s law, which describes the effect of mechanical forces in bone modeling/remodeling, would predict that ________ - a right-handed pitcher will have thicker bones in his right arm compared to his left. - a right-handed cyclist will have thicker bones in her right leg compared to her left. - a broken bone will heal thicker than it was before the fracture. - a bed-ridden patient will have thicker bones than an athlete. Calcium cannot be absorbed from the small intestine if ________ is lacking. - vitamin D - vitamin K - calcitonin - fluoride Which one of the following foods is best for bone health? - carrots - liver - leafy green vegetables - oranges Which of the following hormones are responsible for the adolescent growth spurt? - estrogen and testosterone - calcitonin and calcitriol - growth hormone and parathyroid hormone - thyroxine and progesterone With respect to their direct effects on osseous tissue, which pair of hormones has actions that oppose each other? - estrogen and testosterone - calcitonin and calcitriol - estrogen and progesterone - calcitonin and parathyroid hormone When calcium levels are too high or too low, which body system is primarily affected? - skeletal system - endocrine system - digestive system - nervous system All of the following play a role in calcium homeostasis except - thyroxine - calcitonin - parathyroid hormone - vitamin D Which of the following is most likely to be released when blood calcium levels are elevated? - thyroxine - calcitonin - parathyroid hormone - vitamin D Critical Thinking Questions The skeletal system is composed of bone and cartilage and has many functions. Choose three of these functions and discuss what features of the skeletal system allow it to accomplish these functions. 41.What are the structural and functional differences between a tarsal and a metatarsal? 42.What are the structural and functional differences between the femur and the patella? 43.If the articular cartilage at the end of one of your long bones were to degenerate, what symptoms do you think you would experience? Why? 44.In what ways is the structural makeup of compact and spongy bone well suited to their respective functions? 45.In what ways do intramembranous and endochondral ossification differ? 46.Considering how a long bone develops, what are the similarities and differences between a primary and a secondary ossification center? 47.What is the difference between closed reduction and open reduction? In what type of fracture would closed reduction most likely occur? In what type of fracture would open reduction most likely occur? 48.In terms of origin and composition, what are the differences between an internal callus and an external callus? 49.If you were a dietician who had a young female patient with a family history of osteoporosis, what foods would you suggest she include in her diet? Why? 50.During the early years of space exploration our astronauts, who had been floating in space, would return to earth showing significant bone loss dependent on how long they were in space. Discuss how this might happen and what could be done to alleviate this condition. 51.An individual with very low levels of vitamin D presents themselves to you complaining of seemingly fragile bones. Explain how these might be connected. 52.Describe the effects caused when the parathyroid gland fails to respond to calcium bound to its receptors.	oercommons	2025-03-18T00:35:13.420046	07/23/2019	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/56365/overview", "title": "Anatomy and Physiology, Support and Movement, Bone Tissue and the Skeletal System", "author": null }
https://oercommons.org/courseware/lesson/58772/overview	Metabolism and Nutrition Introduction Figure 24.1 Metabolism Metabolism is the sum of all energy-requiring and energy-consuming processes of the body. Many factors contribute to overall metabolism, including lean muscle mass, the amount and quality of food consumed, and the physical demands placed on the human body. (credit: "tableatny"/flickr.com) CHAPTER OBJECTIVES After studying this chapter, you will be able to: - Describe the processes involved in anabolic and catabolic reactions - List and describe the steps necessary for carbohydrate, lipid, and protein metabolism - Explain the processes that regulate glucose levels during the absorptive and postabsorptive states - Explain how metabolism is essential to maintaining body temperature (thermoregulation) - Summarize the importance of vitamins and minerals in the diet Eating is essential to life. Many of us look to eating as not only a necessity, but also a pleasure. You may have been told since childhood to start the day with a good breakfast to give you the energy to get through most of the day. You most likely have heard about the importance of a balanced diet, with plenty of fruits and vegetables. But what does this all mean to your body and the physiological processes it carries out each day? You need to absorb a range of nutrients so that your cells have the building blocks for metabolic processes that release the energy for the cells to carry out their daily jobs, to manufacture new proteins, cells, and body parts, and to recycle materials in the cell. This chapter will take you through some of the chemical reactions essential to life, the sum of which is referred to as metabolism. The focus of these discussions will be anabolic reactions and catabolic reactions. You will examine the various chemical reactions that are important to sustain life, including why you must have oxygen, how mitochondria transfer energy, and the importance of certain “metabolic” hormones and vitamins. Metabolism varies, depending on age, gender, activity level, fuel consumption, and lean body mass. Your own metabolic rate fluctuates throughout life. By modifying your diet and exercise regimen, you can increase both lean body mass and metabolic rate. Factors affecting metabolism also play important roles in controlling muscle mass. Aging is known to decrease the metabolic rate by as much as 5 percent per year. Additionally, because men tend have more lean muscle mass then women, their basal metabolic rate (metabolic rate at rest) is higher; therefore, men tend to burn more calories than women do. Lastly, an individual’s inherent metabolic rate is a function of the proteins and enzymes derived from their genetic background. Thus, your genes play a big role in your metabolism. Nonetheless, each person’s body engages in the same overall metabolic processes. Overview of Metabolic Reactions - Describe the process by which polymers are broken down into monomers - Describe the process by which monomers are combined into polymers - Discuss the role of ATP in metabolism - Explain oxidation-reduction reactions - Describe the hormones that regulate anabolic and catabolic reactions Metabolic processes are constantly taking place in the body. Metabolism is the sum of all of the chemical reactions that are involved in catabolism and anabolism. The reactions governing the breakdown of food to obtain energy are called catabolic reactions. Conversely, anabolic reactions use the energy produced by catabolic reactions to synthesize larger molecules from smaller ones, such as when the body forms proteins by stringing together amino acids. Both sets of reactions are critical to maintaining life. Because catabolic reactions produce energy and anabolic reactions use energy, ideally, energy usage would balance the energy produced. If the net energy change is positive (catabolic reactions release more energy than the anabolic reactions use), then the body stores the excess energy by building fat molecules for long-term storage. On the other hand, if the net energy change is negative (catabolic reactions release less energy than anabolic reactions use), the body uses stored energy to compensate for the deficiency of energy released by catabolism. Catabolic Reactions Catabolic reactions break down large organic molecules into smaller molecules, releasing the energy contained in the chemical bonds. These energy releases (conversions) are not 100 percent efficient. The amount of energy released is less than the total amount contained in the molecule. Approximately 40 percent of energy yielded from catabolic reactions is directly transferred to the high-energy molecule adenosine triphosphate (ATP). ATP, the energy currency of cells, can be used immediately to power molecular machines that support cell, tissue, and organ function. This includes building new tissue and repairing damaged tissue. ATP can also be stored to fulfill future energy demands. The remaining 60 percent of the energy released from catabolic reactions is given off as heat, which tissues and body fluids absorb. Structurally, ATP molecules consist of an adenine, a ribose, and three phosphate groups (Figure 24.2). The chemical bond between the second and third phosphate groups, termed a high-energy bond, represents the greatest source of energy in a cell. It is the first bond that catabolic enzymes break when cells require energy to do work. The products of this reaction are a molecule of adenosine diphosphate (ADP) and a lone phosphate group (Pi). ATP, ADP, and Pi are constantly being cycled through reactions that build ATP and store energy, and reactions that break down ATP and release energy. Figure 24.2 Structure of ATP Molecule Adenosine triphosphate (ATP) is the energy molecule of the cell. During catabolic reactions, ATP is created and energy is stored until needed during anabolic reactions. The energy from ATP drives all bodily functions, such as contracting muscles, maintaining the electrical potential of nerve cells, and absorbing food in the gastrointestinal tract. The metabolic reactions that produce ATP come from various sources (Figure 24.3). Figure 24.3 Sources of ATP During catabolic reactions, proteins are broken down into amino acids, lipids are broken down into fatty acids, and polysaccharides are broken down into monosaccharides. These building blocks are then used for the synthesis of molecules in anabolic reactions. Of the four major macromolecular groups (carbohydrates, lipids, proteins, and nucleic acids) that are processed by digestion, carbohydrates are considered the most common source of energy to fuel the body. They take the form of either complex carbohydrates, polysaccharides like starch and glycogen, or simple sugars (monosaccharides) like glucose and fructose. Sugar catabolism breaks polysaccharides down into their individual monosaccharides. Among the monosaccharides, glucose is the most common fuel for ATP production in cells, and as such, there are a number of endocrine control mechanisms to regulate glucose concentration in the bloodstream. Excess glucose is either stored as an energy reserve in the liver and skeletal muscles as the complex polymer glycogen, or it is converted into fat (triglyceride) in adipose cells (adipocytes). Among the lipids (fats), triglycerides are most often used for energy via a metabolic process called β-oxidation. About one-half of excess fat is stored in adipocytes that accumulate in the subcutaneous tissue under the skin, whereas the rest is stored in adipocytes in other tissues and organs. Proteins, which are polymers, can be broken down into their monomers, individual amino acids. Amino acids can be used as building blocks of new proteins or broken down further for the production of ATP. When one is chronically starving, this use of amino acids for energy production can lead to a wasting away of the body, as more and more proteins are broken down. Nucleic acids are present in most of the foods you eat. During digestion, nucleic acids including DNA and various RNAs are broken down into their constituent nucleotides. These nucleotides are readily absorbed and transported throughout the body to be used by individual cells during nucleic acid metabolism. Anabolic Reactions In contrast to catabolic reactions, anabolic reactions involve the joining of smaller molecules into larger ones. Anabolic reactions combine monosaccharides to form polysaccharides, fatty acids to form triglycerides, amino acids to form proteins, and nucleotides to form nucleic acids. These processes require energy in the form of ATP molecules generated by catabolic reactions. Anabolic reactions, also called biosynthesis reactions, create new molecules that form new cells and tissues, and revitalize organs. Hormonal Regulation of Metabolism Catabolic and anabolic hormones in the body help regulate metabolic processes. Catabolic hormones stimulate the breakdown of molecules and the production of energy. These include cortisol, glucagon, adrenaline/epinephrine, and cytokines. All of these hormones are mobilized at specific times to meet the needs of the body. Anabolic hormones are required for the synthesis of molecules and include growth hormone, insulin-like growth factor, insulin, testosterone, and estrogen. Table 24.1summarizes the function of each of the catabolic hormones and Table 24.2 summarizes the functions of the anabolic hormones. Catabolic Hormones \| Hormone \| Function \| \|---\|---\| \| Cortisol \| Released from the adrenal gland in response to stress; its main role is to increase blood glucose levels by gluconeogenesis (breaking down fats and proteins) \| \| Glucagon \| Released from alpha cells in the pancreas either when starving or when the body needs to generate additional energy; it stimulates the breakdown of glycogen in the liver to increase blood glucose levels; its effect is the opposite of insulin; glucagon and insulin are a part of a negative-feedback system that stabilizes blood glucose levels \| \| Adrenaline/epinephrine \| Released in response to the activation of the sympathetic nervous system; increases heart rate and heart contractility, constricts blood vessels, is a bronchodilator that opens (dilates) the bronchi of the lungs to increase air volume in the lungs, and stimulates gluconeogenesis \| Table 24.1 Anabolic Hormones \| Hormone \| Function \| \|---\|---\| \| Growth hormone (GH) \| Synthesized and released from the pituitary gland; stimulates the growth of cells, tissues, and bones \| \| Insulin-like growth factor (IGF) \| Stimulates the growth of muscle and bone while also inhibiting cell death (apoptosis) \| \| Insulin \| Produced by the beta cells of the pancreas; plays an essential role in carbohydrate and fat metabolism, controls blood glucose levels, and promotes the uptake of glucose into body cells; causes cells in muscle, adipose tissue, and liver to take up glucose from the blood and store it in the liver and muscle as glycogen; its effect is the opposite of glucagon; glucagon and insulin are a part of a negative-feedback system that stabilizes blood glucose levels \| \| Testosterone \| Produced by the testes in males and the ovaries in females; stimulates an increase in muscle mass and strength as well as the growth and strengthening of bone \| \| Estrogen \| Produced primarily by the ovaries, it is also produced by the liver and adrenal glands; its anabolic functions include increasing metabolism and fat deposition \| Table 24.2 DISORDERS OF THE... Metabolic Processes: Cushing Syndrome and Addison’s Disease As might be expected for a fundamental physiological process like metabolism, errors or malfunctions in metabolic processing lead to a pathophysiology or—if uncorrected—a disease state. Metabolic diseases are most commonly the result of malfunctioning proteins or enzymes that are critical to one or more metabolic pathways. Protein or enzyme malfunction can be the consequence of a genetic alteration or mutation. However, normally functioning proteins and enzymes can also have deleterious effects if their availability is not appropriately matched with metabolic need. For example, excessive production of the hormone cortisol (see Table 24.1) gives rise to Cushing syndrome. Clinically, Cushing syndrome is characterized by rapid weight gain, especially in the trunk and face region, depression, and anxiety. It is worth mentioning that tumors of the pituitary that produce adrenocorticotropic hormone (ACTH), which subsequently stimulates the adrenal cortex to release excessive cortisol, produce similar effects. This indirect mechanism of cortisol overproduction is referred to as Cushing disease. Patients with Cushing syndrome can exhibit high blood glucose levels and are at an increased risk of becoming obese. They also show slow growth, accumulation of fat between the shoulders, weak muscles, bone pain (because cortisol causes proteins to be broken down to make glucose via gluconeogenesis), and fatigue. Other symptoms include excessive sweating (hyperhidrosis), capillary dilation, and thinning of the skin, which can lead to easy bruising. The treatments for Cushing syndrome are all focused on reducing excessive cortisol levels. Depending on the cause of the excess, treatment may be as simple as discontinuing the use of cortisol ointments. In cases of tumors, surgery is often used to remove the offending tumor. Where surgery is inappropriate, radiation therapy can be used to reduce the size of a tumor or ablate portions of the adrenal cortex. Finally, medications are available that can help to regulate the amounts of cortisol. Insufficient cortisol production is equally problematic. Adrenal insufficiency, or Addison’s disease, is characterized by the reduced production of cortisol from the adrenal gland. It can result from malfunction of the adrenal glands—they do not produce enough cortisol—or it can be a consequence of decreased ACTH availability from the pituitary. Patients with Addison’s disease may have low blood pressure, paleness, extreme weakness, fatigue, slow or sluggish movements, lightheadedness, and salt cravings due to the loss of sodium and high blood potassium levels (hyperkalemia). Victims also may suffer from loss of appetite, chronic diarrhea, vomiting, mouth lesions, and patchy skin color. Diagnosis typically involves blood tests and imaging tests of the adrenal and pituitary glands. Treatment involves cortisol replacement therapy, which usually must be continued for life. Oxidation-Reduction Reactions The chemical reactions underlying metabolism involve the transfer of electrons from one compound to another by processes catalyzed by enzymes. The electrons in these reactions commonly come from hydrogen atoms, which consist of an electron and a proton. A molecule gives up a hydrogen atom, in the form of a hydrogen ion (H+) and an electron, breaking the molecule into smaller parts. The loss of an electron, or oxidation, releases a small amount of energy; both the electron and the energy are then passed to another molecule in the process of reduction, or the gaining of an electron. These two reactions always happen together in an oxidation-reduction reaction (also called a redox reaction)—when an electron is passed between molecules, the donor is oxidized and the recipient is reduced. Oxidation-reduction reactions often happen in a series, so that a molecule that is reduced is subsequently oxidized, passing on not only the electron it just received but also the energy it received. As the series of reactions progresses, energy accumulates that is used to combine Pi and ADP to form ATP, the high-energy molecule that the body uses for fuel. Oxidation-reduction reactions are catalyzed by enzymes that trigger the removal of hydrogen atoms. Coenzymes work with enzymes and accept hydrogen atoms. The two most common coenzymes of oxidation-reduction reactions are nicotinamide adenine dinucleotide (NAD) and flavin adenine dinucleotide (FAD). Their respective reduced coenzymes are NADH and FADH2, which are energy-containing molecules used to transfer energy during the creation of ATP. Carbohydrate Metabolism - Explain the processes of glycolysis - Describe the pathway of a pyruvate molecule through the Krebs cycle - Explain the transport of electrons through the electron transport chain - Describe the process of ATP production through oxidative phosphorylation - Summarize the process of gluconeogenesis Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen atoms. The family of carbohydrates includes both simple and complex sugars. Glucose and fructose are examples of simple sugars, and starch, glycogen, and cellulose are all examples of complex sugars. The complex sugars are also called polysaccharides and are made of multiple monosaccharide molecules. Polysaccharides serve as energy storage (e.g., starch and glycogen) and as structural components (e.g., chitin in insects and cellulose in plants). During digestion, carbohydrates are broken down into simple, soluble sugars that can be transported across the intestinal wall into the circulatory system to be transported throughout the body. Carbohydrate digestion begins in the mouth with the action of salivary amylase on starches and ends with monosaccharides being absorbed across the epithelium of the small intestine. Once the absorbed monosaccharides are transported to the tissues, the process of cellular respiration begins (Figure 24.4). This section will focus first on glycolysis, a process where the monosaccharide glucose is oxidized, releasing the energy stored in its bonds to produce ATP. Figure 24.4 Cellular Respiration Cellular respiration oxidizes glucose molecules through glycolysis, the Krebs cycle, and oxidative phosphorylation to produce ATP. Glycolysis Glucose is the body’s most readily available source of energy. After digestive processes break polysaccharides down into monosaccharides, including glucose, the monosaccharides are transported across the wall of the small intestine and into the circulatory system, which transports them to the liver. In the liver, hepatocytes either pass the glucose on through the circulatory system or store excess glucose as glycogen. Cells in the body take up the circulating glucose in response to insulin and, through a series of reactions called glycolysis, transfer some of the energy in glucose to ADP to form ATP (Figure 24.5). The last step in glycolysis produces the product pyruvate. Glycolysis begins with the phosphorylation of glucose by hexokinase to form glucose-6-phosphate. This step uses one ATP, which is the donor of the phosphate group. Under the action of phosphofructokinase, glucose-6-phosphate is converted into fructose-6-phosphate. At this point, a second ATP donates its phosphate group, forming fructose-1,6-bisphosphate. This six-carbon sugar is split to form two phosphorylated three-carbon molecules, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate, which are both converted into glyceraldehyde-3-phosphate. The glyceraldehyde-3-phosphate is further phosphorylated with groups donated by dihydrogen phosphate present in the cell to form the three-carbon molecule 1,3-bisphosphoglycerate. The energy of this reaction comes from the oxidation of (removal of electrons from) glyceraldehyde-3-phosphate. In a series of reactions leading to pyruvate, the two phosphate groups are then transferred to two ADPs to form two ATPs. Thus, glycolysis uses two ATPs but generates four ATPs, yielding a net gain of two ATPs and two molecules of pyruvate. In the presence of oxygen, pyruvate continues on to the Krebs cycle (also called the citric acid cycle or tricarboxylic acid cycle (TCA), where additional energy is extracted and passed on. Figure 24.5 Glycolysis Overview During the energy-consuming phase of glycolysis, two ATPs are consumed, transferring two phosphates to the glucose molecule. The glucose molecule then splits into two three-carbon compounds, each containing a phosphate. During the second phase, an additional phosphate is added to each of the three-carbon compounds. The energy for this endergonic reaction is provided by the removal (oxidation) of two electrons from each three-carbon compound. During the energy-releasing phase, the phosphates are removed from both three-carbon compounds and used to produce four ATP molecules. INTERACTIVE LINK Watch this video to learn about glycolysis. Glycolysis can be divided into two phases: energy consuming (also called chemical priming) and energy yielding. The first phase is the energy-consuming phase, so it requires two ATP molecules to start the reaction for each molecule of glucose. However, the end of the reaction produces four ATPs, resulting in a net gain of two ATP energy molecules. Glycolysis can be expressed as the following equation: Glucose + 2ATP + 2NAD+ + 4ADP + 2P𝑖 → 2 Pyruvate + 4ATP + 2NADH + 2H+Glucose + 2ATP + 2NAD+ + 4ADP + 2Pi → 2 Pyruvate + 4ATP + 2NADH + 2H+This equation states that glucose, in combination with ATP (the energy source), NAD+ (a coenzyme that serves as an electron acceptor), and inorganic phosphate, breaks down into two pyruvate molecules, generating four ATP molecules—for a net yield of two ATP—and two energy-containing NADH coenzymes. The NADH that is produced in this process will be used later to produce ATP in the mitochondria. Importantly, by the end of this process, one glucose molecule generates two pyruvate molecules, two high-energy ATP molecules, and two electron-carrying NADH molecules. The following discussions of glycolysis include the enzymes responsible for the reactions. When glucose enters a cell, the enzyme hexokinase (or glucokinase, in the liver) rapidly adds a phosphate to convert it into glucose-6-phosphate. A kinase is a type of enzyme that adds a phosphate molecule to a substrate (in this case, glucose, but it can be true of other molecules also). This conversion step requires one ATP and essentially traps the glucose in the cell, preventing it from passing back through the plasma membrane, thus allowing glycolysis to proceed. It also functions to maintain a concentration gradient with higher glucose levels in the blood than in the tissues. By establishing this concentration gradient, the glucose in the blood will be able to flow from an area of high concentration (the blood) into an area of low concentration (the tissues) to be either used or stored. Hexokinase is found in nearly every tissue in the body. Glucokinase, on the other hand, is expressed in tissues that are active when blood glucose levels are high, such as the liver. Hexokinase has a higher affinity for glucose than glucokinase and therefore is able to convert glucose at a faster rate than glucokinase. This is important when levels of glucose are very low in the body, as it allows glucose to travel preferentially to those tissues that require it more. In the next step of the first phase of glycolysis, the enzyme glucose-6-phosphate isomerase converts glucose-6-phosphate into fructose-6-phosphate. Like glucose, fructose is also a six carbon-containing sugar. The enzyme phosphofructokinase-1 then adds one more phosphate to convert fructose-6-phosphate into fructose-1-6-bisphosphate, another six-carbon sugar, using another ATP molecule. Aldolase then breaks down this fructose-1-6-bisphosphate into two three-carbon molecules, glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. The triosephosphate isomerase enzyme then converts dihydroxyacetone phosphate into a second glyceraldehyde-3-phosphate molecule. Therefore, by the end of this chemical-priming or energy-consuming phase, one glucose molecule is broken down into two glyceraldehyde-3-phosphate molecules. The second phase of glycolysis, the energy-yielding phase, creates the energy that is the product of glycolysis. Glyceraldehyde-3-phosphate dehydrogenase converts each three-carbon glyceraldehyde-3-phosphate produced during the energy-consuming phase into 1,3-bisphosphoglycerate. This reaction releases an electron that is then picked up by NAD+ to create an NADH molecule. NADH is a high-energy molecule, like ATP, but unlike ATP, it is not used as energy currency by the cell. Because there are two glyceraldehyde-3-phosphate molecules, two NADH molecules are synthesized during this step. Each 1,3-bisphosphoglycerate is subsequently dephosphorylated (i.e., a phosphate is removed) by phosphoglycerate kinase into 3-phosphoglycerate. Each phosphate released in this reaction can convert one molecule of ADP into one high-energy ATP molecule, resulting in a gain of two ATP molecules. The enzyme phosphoglycerate mutase then converts the 3-phosphoglycerate molecules into 2-phosphoglycerate. The enolase enzyme then acts upon the 2-phosphoglycerate molecules to convert them into phosphoenolpyruvate molecules. The last step of glycolysis involves the dephosphorylation of the two phosphoenolpyruvate molecules by pyruvate kinase to create two pyruvate molecules and two ATP molecules. In summary, one glucose molecule breaks down into two pyruvate molecules, and creates two net ATP molecules and two NADH molecules by glycolysis. Therefore, glycolysis generates energy for the cell and creates pyruvate molecules that can be processed further through the aerobic Krebs cycle (also called the citric acid cycle or tricarboxylic acid cycle); converted into lactic acid or alcohol (in yeast) by fermentation; or used later for the synthesis of glucose through gluconeogenesis. Anaerobic Respiration When oxygen is limited or absent, pyruvate enters an anaerobic pathway. In these reactions, pyruvate can be converted into lactic acid. In addition to generating an additional ATP, this pathway serves to keep the pyruvate concentration low so glycolysis continues, and it oxidizes NADH into the NAD+ needed by glycolysis. In this reaction, lactic acid replaces oxygen as the final electron acceptor. Anaerobic respiration occurs in most cells of the body when oxygen is limited or mitochondria are absent or nonfunctional. For example, because erythrocytes (red blood cells) lack mitochondria, they must produce their ATP from anaerobic respiration. This is an effective pathway of ATP production for short periods of time, ranging from seconds to a few minutes. The lactic acid produced diffuses into the plasma and is carried to the liver, where it is converted back into pyruvate or glucose via the Cori cycle. Similarly, when a person exercises, muscles use ATP faster than oxygen can be delivered to them. They depend on glycolysis and lactic acid production for rapid ATP production. Aerobic Respiration In the presence of oxygen, pyruvate can enter the Krebs cycle where additional energy is extracted as electrons are transferred from the pyruvate to the receptors NAD+, GDP, and FAD, with carbon dioxide being a “waste product” (Figure 24.6). The NADH and FADH2 pass electrons on to the electron transport chain, which uses the transferred energy to produce ATP. As the terminal step in the electron transport chain, oxygen is the terminal electron acceptor and creates water inside the mitochondria. Figure 24.6 Aerobic versus Anaerobic Respiration The process of anaerobic respiration converts glucose into two lactate molecules in the absence of oxygen or within erythrocytes that lack mitochondria. During aerobic respiration, glucose is oxidized into two pyruvate molecules. Krebs Cycle/Citric Acid Cycle/Tricarboxylic Acid Cycle The pyruvate molecules generated during glycolysis are transported across the mitochondrial membrane into the inner mitochondrial matrix, where they are metabolized by enzymes in a pathway called the Krebs cycle (Figure 24.7). The Krebs cycle is also commonly called the citric acid cycle or the tricarboxylic acid (TCA) cycle. During the Krebs cycle, high-energy molecules, including ATP, NADH, and FADH2, are created. NADH and FADH2 then pass electrons through the electron transport chain in the mitochondria to generate more ATP molecules. Figure 24.7 Krebs Cycle During the Krebs cycle, each pyruvate that is generated by glycolysis is converted into a two-carbon acetyl CoA molecule. The acetyl CoA is systematically processed through the cycle and produces high-energy NADH, FADH2, and ATP molecules. INTERACTIVE LINK Watch this animation to observe the Krebs cycle. The three-carbon pyruvate molecule generated during glycolysis moves from the cytoplasm into the mitochondrial matrix, where it is converted by the enzyme pyruvate dehydrogenase into a two-carbon acetyl coenzyme A (acetyl CoA) molecule. This reaction is an oxidative decarboxylation reaction. It converts the three-carbon pyruvate into a two-carbon acetyl CoA molecule, releasing carbon dioxide and transferring two electrons that combine with NAD+ to form NADH. Acetyl CoA enters the Krebs cycle by combining with a four-carbon molecule, oxaloacetate, to form the six-carbon molecule citrate, or citric acid, at the same time releasing the coenzyme A molecule. The six-carbon citrate molecule is systematically converted to a five-carbon molecule and then a four-carbon molecule, ending with oxaloacetate, the beginning of the cycle. Along the way, each citrate molecule will produce one ATP, one FADH2, and three NADH. The FADH2 and NADH will enter the oxidative phosphorylation system located in the inner mitochondrial membrane. In addition, the Krebs cycle supplies the starting materials to process and break down proteins and fats. To start the Krebs cycle, citrate synthase combines acetyl CoA and oxaloacetate to form a six-carbon citrate molecule; CoA is subsequently released and can combine with another pyruvate molecule to begin the cycle again. The aconitase enzyme converts citrate into isocitrate. In two successive steps of oxidative decarboxylation, two molecules of CO2 and two NADH molecules are produced when isocitrate dehydrogenase converts isocitrate into the five-carbon α-ketoglutarate, which is then catalyzed and converted into the four-carbon succinyl CoA by α-ketoglutarate dehydrogenase. The enzyme succinyl CoA dehydrogenase then converts succinyl CoA into succinate and forms the high-energy molecule GTP, which transfers its energy to ADP to produce ATP. Succinate dehydrogenase then converts succinate into fumarate, forming a molecule of FADH2. Fumarase then converts fumarate into malate, which malate dehydrogenase then converts back into oxaloacetate while reducing NAD+ to NADH. Oxaloacetate is then ready to combine with the next acetyl CoA to start the Krebs cycle again (see Figure 24.7). For each turn of the cycle, three NADH, one ATP (through GTP), and one FADH2 are created. Each carbon of pyruvate is converted into CO2, which is released as a byproduct of oxidative (aerobic) respiration. Oxidative Phosphorylation and the Electron Transport Chain The electron transport chain (ETC) uses the NADH and FADH2 produced by the Krebs cycle to generate ATP. Electrons from NADH and FADH2 are transferred through protein complexes embedded in the inner mitochondrial membrane by a series of enzymatic reactions. The electron transport chain consists of a series of four enzyme complexes (Complex I – Complex IV) and two coenzymes (ubiquinone and Cytochrome c), which act as electron carriers and proton pumps used to transfer H+ ions into the space between the inner and outer mitochondrial membranes (Figure 24.8). The ETC couples the transfer of electrons between a donor (like NADH) and an electron acceptor (like O2) with the transfer of protons (H+ ions) across the inner mitochondrial membrane, enabling the process of oxidative phosphorylation. In the presence of oxygen, energy is passed, stepwise, through the electron carriers to collect gradually the energy needed to attach a phosphate to ADP and produce ATP. The role of molecular oxygen, O2, is as the terminal electron acceptor for the ETC. This means that once the electrons have passed through the entire ETC, they must be passed to another, separate molecule. These electrons, O2, and H+ ions from the matrix combine to form new water molecules. This is the basis for your need to breathe in oxygen. Without oxygen, electron flow through the ETC ceases. Figure 24.8 Electron Transport Chain The electron transport chain is a series of electron carriers and ion pumps that are used to pump H+ ions out of the inner mitochondrial matrix. INTERACTIVE LINK Watch this video to learn about the electron transport chain. The electrons released from NADH and FADH2 are passed along the chain by each of the carriers, which are reduced when they receive the electron and oxidized when passing it on to the next carrier. Each of these reactions releases a small amount of energy, which is used to pump H+ ions across the inner membrane. The accumulation of these protons in the space between the membranes creates a proton gradient with respect to the mitochondrial matrix. Also embedded in the inner mitochondrial membrane is an amazing protein pore complex called ATP synthase. Effectively, it is a turbine that is powered by the flow of H+ ions across the inner membrane down a gradient and into the mitochondrial matrix. As the H+ ions traverse the complex, the shaft of the complex rotates. This rotation enables other portions of ATP synthase to encourage ADP and Pi to create ATP. In accounting for the total number of ATP produced per glucose molecule through aerobic respiration, it is important to remember the following points: - A net of two ATP are produced through glycolysis (four produced and two consumed during the energy-consuming stage). However, these two ATP are used for transporting the NADH produced during glycolysis from the cytoplasm into the mitochondria. Therefore, the net production of ATP during glycolysis is zero. - In all phases after glycolysis, the number of ATP, NADH, and FADH2 produced must be multiplied by two to reflect how each glucose molecule produces two pyruvate molecules. - In the ETC, about three ATP are produced for every oxidized NADH. However, only about two ATP are produced for every oxidized FADH2. The electrons from FADH2 produce less ATP, because they start at a lower point in the ETC (Complex II) compared to the electrons from NADH (Complex I) (see Figure 24.8). Therefore, for every glucose molecule that enters aerobic respiration, a net total of 36 ATPs are produced (Figure 24.9). Figure 24.9 Carbohydrate Metabolism Carbohydrate metabolism involves glycolysis, the Krebs cycle, and the electron transport chain. Gluconeogenesis Gluconeogenesis is the synthesis of new glucose molecules from pyruvate, lactate, glycerol, or the amino acids alanine or glutamine. This process takes place primarily in the liver during periods of low glucose, that is, under conditions of fasting, starvation, and low carbohydrate diets. So, the question can be raised as to why the body would create something it has just spent a fair amount of effort to break down? Certain key organs, including the brain, can use only glucose as an energy source; therefore, it is essential that the body maintain a minimum blood glucose concentration. When the blood glucose concentration falls below that certain point, new glucose is synthesized by the liver to raise the blood concentration to normal. Gluconeogenesis is not simply the reverse of glycolysis. There are some important differences (Figure 24.10). Pyruvate is a common starting material for gluconeogenesis. First, the pyruvate is converted into oxaloacetate. Oxaloacetate then serves as a substrate for the enzyme phosphoenolpyruvate carboxykinase (PEPCK), which transforms oxaloacetate into phosphoenolpyruvate (PEP). From this step, gluconeogenesis is nearly the reverse of glycolysis. PEP is converted back into 2-phosphoglycerate, which is converted into 3-phosphoglycerate. Then, 3-phosphoglycerate is converted into 1,3 bisphosphoglycerate and then into glyceraldehyde-3-phosphate. Two molecules of glyceraldehyde-3-phosphate then combine to form fructose-1-6-bisphosphate, which is converted into fructose 6-phosphate and then into glucose-6-phosphate. Finally, a series of reactions generates glucose itself. In gluconeogenesis (as compared to glycolysis), the enzyme hexokinase is replaced by glucose-6-phosphatase, and the enzyme phosphofructokinase-1 is replaced by fructose-1,6-bisphosphatase. This helps the cell to regulate glycolysis and gluconeogenesis independently of each other. As will be discussed as part of lipolysis, fats can be broken down into glycerol, which can be phosphorylated to form dihydroxyacetone phosphate or DHAP. DHAP can either enter the glycolytic pathway or be used by the liver as a substrate for gluconeogenesis. Figure 24.10 Gluconeogenesis Gluconeogenesis is the synthesis of glucose from pyruvate, lactate, glycerol, alanine, or glutamate. AGING AND THE... Body’s Metabolic Rate The human body’s metabolic rate decreases nearly 2 percent per decade after age 30. Changes in body composition, including reduced lean muscle mass, are mostly responsible for this decrease. The most dramatic loss of muscle mass, and consequential decline in metabolic rate, occurs between 50 and 70 years of age. Loss of muscle mass is the equivalent of reduced strength, which tends to inhibit seniors from engaging in sufficient physical activity. This results in a positive-feedback system where the reduced physical activity leads to even more muscle loss, further reducing metabolism. There are several things that can be done to help prevent general declines in metabolism and to fight back against the cyclic nature of these declines. These include eating breakfast, eating small meals frequently, consuming plenty of lean protein, drinking water to remain hydrated, exercising (including strength training), and getting enough sleep. These measures can help keep energy levels from dropping and curb the urge for increased calorie consumption from excessive snacking. While these strategies are not guaranteed to maintain metabolism, they do help prevent muscle loss and may increase energy levels. Some experts also suggest avoiding sugar, which can lead to excess fat storage. Spicy foods and green tea might also be beneficial. Because stress activates cortisol release, and cortisol slows metabolism, avoiding stress, or at least practicing relaxation techniques, can also help. Lipid Metabolism - Explain how energy can be derived from fat - Explain the purpose and process of ketogenesis - Describe the process of ketone body oxidation - Explain the purpose and the process of lipogenesis Fats (or triglycerides) within the body are ingested as food or synthesized by adipocytes or hepatocytes from carbohydrate precursors (Figure 24.11). Lipid metabolism entails the oxidation of fatty acids to either generate energy or synthesize new lipids from smaller constituent molecules. Lipid metabolism is associated with carbohydrate metabolism, as products of glucose (such as acetyl CoA) can be converted into lipids. Figure 24.11 Triglyceride Broken Down into a Monoglyceride A triglyceride molecule (a) breaks down into a monoglyceride (b). Lipid metabolism begins in the intestine where ingested triglycerides are broken down into smaller chain fatty acids and subsequently into monoglyceride molecules (see Figure 24.11b) by pancreatic lipases, enzymes that break down fats after they are emulsified by bile salts. When food reaches the small intestine in the form of chyme, a digestive hormone called cholecystokinin (CCK) is released by intestinal cells in the intestinal mucosa. CCK stimulates the release of pancreatic lipase from the pancreas and stimulates the contraction of the gallbladder to release stored bile salts into the intestine. CCK also travels to the brain, where it can act as a hunger suppressant. Together, the pancreatic lipases and bile salts break down triglycerides into free fatty acids. These fatty acids can be transported across the intestinal membrane. However, once they cross the membrane, they are recombined to again form triglyceride molecules. Within the intestinal cells, these triglycerides are packaged along with cholesterol molecules in phospholipid vesicles called chylomicrons (Figure 24.12). The chylomicrons enable fats and cholesterol to move within the aqueous environment of your lymphatic and circulatory systems. Chylomicrons leave the enterocytes by exocytosis and enter the lymphatic system via lacteals in the villi of the intestine. From the lymphatic system, the chylomicrons are transported to the circulatory system. Once in the circulation, they can either go to the liver or be stored in fat cells (adipocytes) that comprise adipose (fat) tissue found throughout the body. Figure 24.12 Chylomicrons Chylomicrons contain triglycerides, cholesterol molecules, and other apolipoproteins (protein molecules). They function to carry these water-insoluble molecules from the intestine, through the lymphatic system, and into the bloodstream, which carries the lipids to adipose tissue for storage. Lipolysis To obtain energy from fat, triglycerides must first be broken down by hydrolysis into their two principal components, fatty acids and glycerol. This process, called lipolysis, takes place in the cytoplasm. The resulting fatty acids are oxidized by β-oxidation into acetyl CoA, which is used by the Krebs cycle. The glycerol that is released from triglycerides after lipolysis directly enters the glycolysis pathway as DHAP. Because one triglyceride molecule yields three fatty acid molecules with as much as 16 or more carbons in each one, fat molecules yield more energy than carbohydrates and are an important source of energy for the human body. Triglycerides yield more than twice the energy per unit mass when compared to carbohydrates and proteins. Therefore, when glucose levels are low, triglycerides can be converted into acetyl CoA molecules and used to generate ATP through aerobic respiration. The breakdown of fatty acids, called fatty acid oxidation or beta (β)-oxidation, begins in the cytoplasm, where fatty acids are converted into fatty acyl CoA molecules. This fatty acyl CoA combines with carnitine to create a fatty acyl carnitine molecule, which helps to transport the fatty acid across the mitochondrial membrane. Once inside the mitochondrial matrix, the fatty acyl carnitine molecule is converted back into fatty acyl CoA and then into acetyl CoA (Figure 24.13). The newly formed acetyl CoA enters the Krebs cycle and is used to produce ATP in the same way as acetyl CoA derived from pyruvate. Figure 24.13 Breakdown of Fatty Acids During fatty acid oxidation, triglycerides can be broken down into acetyl CoA molecules and used for energy when glucose levels are low. Ketogenesis If excessive acetyl CoA is created from the oxidation of fatty acids and the Krebs cycle is overloaded and cannot handle it, the acetyl CoA is diverted to create ketone bodies. These ketone bodies can serve as a fuel source if glucose levels are too low in the body. Ketones serve as fuel in times of prolonged starvation or when patients suffer from uncontrolled diabetes and cannot utilize most of the circulating glucose. In both cases, fat stores are liberated to generate energy through the Krebs cycle and will generate ketone bodies when too much acetyl CoA accumulates. In this ketone synthesis reaction, excess acetyl CoA is converted into hydroxymethylglutaryl CoA (HMG CoA). HMG CoA is a precursor of cholesterol and is an intermediate that is subsequently converted into β-hydroxybutyrate, the primary ketone body in the blood (Figure 24.14). Figure 24.14 Ketogenesis Excess acetyl CoA is diverted from the Krebs cycle to the ketogenesis pathway. This reaction occurs in the mitochondria of liver cells. The result is the production of β-hydroxybutyrate, the primary ketone body found in the blood. Ketone Body Oxidation Organs that have classically been thought to be dependent solely on glucose, such as the brain, can actually use ketones as an alternative energy source. This keeps the brain functioning when glucose is limited. When ketones are produced faster than they can be used, they can be broken down into CO2 and acetone. The acetone is removed by exhalation. One symptom of ketogenesis is that the patient’s breath smells sweet like alcohol. This effect provides one way of telling if a diabetic is properly controlling the disease. The carbon dioxide produced can acidify the blood, leading to diabetic ketoacidosis, a dangerous condition in diabetics. Ketones oxidize to produce energy for the brain. beta (β)-hydroxybutyrate is oxidized to acetoacetate and NADH is released. An HS-CoA molecule is added to acetoacetate, forming acetoacetyl CoA. The carbon within the acetoacetyl CoA that is not bonded to the CoA then detaches, splitting the molecule in two. This carbon then attaches to another free HS-CoA, resulting in two acetyl CoA molecules. These two acetyl CoA molecules are then processed through the Krebs cycle to generate energy (Figure 24.15). Figure 24.15 Ketone Oxidation When glucose is limited, ketone bodies can be oxidized to produce acetyl CoA to be used in the Krebs cycle to generate energy. Lipogenesis When glucose levels are plentiful, the excess acetyl CoA generated by glycolysis can be converted into fatty acids, triglycerides, cholesterol, steroids, and bile salts. This process, called lipogenesis, creates lipids (fat) from the acetyl CoA and takes place in the cytoplasm of adipocytes (fat cells) and hepatocytes (liver cells). When you eat more glucose or carbohydrates than your body needs, your system uses acetyl CoA to turn the excess into fat. Although there are several metabolic sources of acetyl CoA, it is most commonly derived from glycolysis. Acetyl CoA availability is significant, because it initiates lipogenesis. Lipogenesis begins with acetyl CoA and advances by the subsequent addition of two carbon atoms from another acetyl CoA; this process is repeated until fatty acids are the appropriate length. Because this is a bond-creating anabolic process, ATP is consumed. However, the creation of triglycerides and lipids is an efficient way of storing the energy available in carbohydrates. Triglycerides and lipids, high-energy molecules, are stored in adipose tissue until they are needed. Although lipogenesis occurs in the cytoplasm, the necessary acetyl CoA is created in the mitochondria and cannot be transported across the mitochondrial membrane. To solve this problem, pyruvate is converted into both oxaloacetate and acetyl CoA. Two different enzymes are required for these conversions. Oxaloacetate forms via the action of pyruvate carboxylase, whereas the action of pyruvate dehydrogenase creates acetyl CoA. Oxaloacetate and acetyl CoA combine to form citrate, which can cross the mitochondrial membrane and enter the cytoplasm. In the cytoplasm, citrate is converted back into oxaloacetate and acetyl CoA. Oxaloacetate is converted into malate and then into pyruvate. Pyruvate crosses back across the mitochondrial membrane to wait for the next cycle of lipogenesis. The acetyl CoA is converted into malonyl CoA that is used to synthesize fatty acids. Figure 24.16 summarizes the pathways of lipid metabolism. Figure 24.16 Lipid Metabolism Lipids may follow one of several pathways during metabolism. Glycerol and fatty acids follow different pathways. Protein Metabolism - Describe how the body digests proteins - Explain how the urea cycle prevents toxic concentrations of nitrogen - Differentiate between glucogenic and ketogenic amino acids - Explain how protein can be used for energy Much of the body is made of protein, and these proteins take on a myriad of forms. They represent cell signaling receptors, signaling molecules, structural members, enzymes, intracellular trafficking components, extracellular matrix scaffolds, ion pumps, ion channels, oxygen and CO2 transporters (hemoglobin). That is not even the complete list! There is protein in bones (collagen), muscles, and tendons; the hemoglobin that transports oxygen; and enzymes that catalyze all biochemical reactions. Protein is also used for growth and repair. Amid all these necessary functions, proteins also hold the potential to serve as a metabolic fuel source. Proteins are not stored for later use, so excess proteins must be converted into glucose or triglycerides, and used to supply energy or build energy reserves. Although the body can synthesize proteins from amino acids, food is an important source of those amino acids, especially because humans cannot synthesize all of the 20 amino acids used to build proteins. The digestion of proteins begins in the stomach. When protein-rich foods enter the stomach, they are greeted by a mixture of the enzyme pepsin and hydrochloric acid (HCl; 0.5 percent). The latter produces an environmental pH of 1.5–3.5 that denatures proteins within food. Pepsin cuts proteins into smaller polypeptides and their constituent amino acids. When the food-gastric juice mixture (chyme) enters the small intestine, the pancreas releases sodium bicarbonate to neutralize the HCl. This helps to protect the lining of the intestine. The small intestine also releases digestive hormones, including secretin and CCK, which stimulate digestive processes to break down the proteins further. Secretin also stimulates the pancreas to release sodium bicarbonate. The pancreas releases most of the digestive enzymes, including the proteases trypsin, chymotrypsin, and elastase, which aid protein digestion. Together, all of these enzymes break complex proteins into smaller individual amino acids (Figure 24.17), which are then transported across the intestinal mucosa to be used to create new proteins, or to be converted into fats or acetyl CoA and used in the Krebs cycle. Figure 24.17 Digestive Enzymes and Hormones Enzymes in the stomach and small intestine break down proteins into amino acids. HCl in the stomach aids in proteolysis, and hormones secreted by intestinal cells direct the digestive processes. In order to avoid breaking down the proteins that make up the pancreas and small intestine, pancreatic enzymes are released as inactive proenzymes that are only activated in the small intestine. In the pancreas, vesicles store trypsin and chymotrypsin as trypsinogen and chymotrypsinogen. Once released into the small intestine, an enzyme found in the wall of the small intestine, called enterokinase, binds to trypsinogen and converts it into its active form, trypsin. Trypsin then binds to chymotrypsinogen to convert it into the active chymotrypsin. Trypsin and chymotrypsin break down large proteins into smaller peptides, a process called proteolysis. These smaller peptides are catabolized into their constituent amino acids, which are transported across the apical surface of the intestinal mucosa in a process that is mediated by sodium-amino acid transporters. These transporters bind sodium and then bind the amino acid to transport it across the membrane. At the basal surface of the mucosal cells, the sodium and amino acid are released. The sodium can be reused in the transporter, whereas the amino acids are transferred into the bloodstream to be transported to the liver and cells throughout the body for protein synthesis. Freely available amino acids are used to create proteins. If amino acids exist in excess, the body has no capacity or mechanism for their storage; thus, they are converted into glucose or ketones, or they are decomposed. Amino acid decomposition results in hydrocarbons and nitrogenous waste. However, high concentrations of nitrogen are toxic. The urea cycle processes nitrogen and facilitates its excretion from the body. Urea Cycle The urea cycle is a set of biochemical reactions that produces urea from ammonium ions in order to prevent a toxic level of ammonium in the body. It occurs primarily in the liver and, to a lesser extent, in the kidney. Prior to the urea cycle, ammonium ions are produced from the breakdown of amino acids. In these reactions, an amine group, or ammonium ion, from the amino acid is exchanged with a keto group on another molecule. This transamination event creates a molecule that is necessary for the Krebs cycle and an ammonium ion that enters into the urea cycle to be eliminated. In the urea cycle, ammonium is combined with CO2, resulting in urea and water. The urea is eliminated through the kidneys in the urine (Figure 24.18). Figure 24.18 Urea Cycle Nitrogen is transaminated, creating ammonia and intermediates of the Krebs cycle. Ammonia is processed in the urea cycle to produce urea that is eliminated through the kidneys. Amino acids can also be used as a source of energy, especially in times of starvation. Because the processing of amino acids results in the creation of metabolic intermediates, including pyruvate, acetyl CoA, acetoacyl CoA, oxaloacetate, and α-ketoglutarate, amino acids can serve as a source of energy production through the Krebs cycle (Figure 24.19). Figure 24.20summarizes the pathways of catabolism and anabolism for carbohydrates, lipids, and proteins. Figure 24.19 Energy from Amino Acids Amino acids can be broken down into precursors for glycolysis or the Krebs cycle. Amino acids (in bold) can enter the cycle through more than one pathway. Figure 24.20 Catabolic and Anabolic Pathways Nutrients follow a complex pathway from ingestion through anabolism and catabolism to energy production. DISORDERS OF THE... Metabolism: Pyruvate Dehydrogenase Complex Deficiency and Phenylketonuria Pyruvate dehydrogenase complex deficiency (PDCD) and phenylketonuria (PKU) are genetic disorders. Pyruvate dehydrogenase is the enzyme that converts pyruvate into acetyl CoA, the molecule necessary to begin the Krebs cycle to produce ATP. With low levels of the pyruvate dehydrogenase complex (PDC), the rate of cycling through the Krebs cycle is dramatically reduced. This results in a decrease in the total amount of energy that is produced by the cells of the body. PDC deficiency results in a neurodegenerative disease that ranges in severity, depending on the levels of the PDC enzyme. It may cause developmental defects, muscle spasms, and death. Treatments can include diet modification, vitamin supplementation, and gene therapy; however, damage to the central nervous system usually cannot be reversed. PKU affects about 1 in every 15,000 births in the United States. People afflicted with PKU lack sufficient activity of the enzyme phenylalanine hydroxylase and are therefore unable to break down phenylalanine into tyrosine adequately. Because of this, levels of phenylalanine rise to toxic levels in the body, which results in damage to the central nervous system and brain. Symptoms include delayed neurological development, hyperactivity, mental retardation, seizures, skin rash, tremors, and uncontrolled movements of the arms and legs. Pregnant women with PKU are at a high risk for exposing the fetus to too much phenylalanine, which can cross the placenta and affect fetal development. Babies exposed to excess phenylalanine in utero may present with heart defects, physical and/or mental retardation, and microcephaly. Every infant in the United States and Canada is tested at birth to determine whether PKU is present. The earlier a modified diet is begun, the less severe the symptoms will be. The person must closely follow a strict diet that is low in phenylalanine to avoid symptoms and damage. Phenylalanine is found in high concentrations in artificial sweeteners, including aspartame. Therefore, these sweeteners must be avoided. Some animal products and certain starches are also high in phenylalanine, and intake of these foods should be carefully monitored. Metabolic States of the Body - Describe what defines each of the three metabolic states - Describe the processes that occur during the absorptive state of metabolism - Describe the processes that occur during the postabsorptive state of metabolism - Explain how the body processes glucose when the body is starved of fuel You eat periodically throughout the day; however, your organs, especially the brain, need a continuous supply of glucose. How does the body meet this constant demand for energy? Your body processes the food you eat both to use immediately and, importantly, to store as energy for later demands. If there were no method in place to store excess energy, you would need to eat constantly in order to meet energy demands. Distinct mechanisms are in place to facilitate energy storage, and to make stored energy available during times of fasting and starvation. The Absorptive State The absorptive state, or the fed state, occurs after a meal when your body is digesting the food and absorbing the nutrients (anabolism exceeds catabolism). Digestion begins the moment you put food into your mouth, as the food is broken down into its constituent parts to be absorbed through the intestine. The digestion of carbohydrates begins in the mouth, whereas the digestion of proteins and fats begins in the stomach and small intestine. The constituent parts of these carbohydrates, fats, and proteins are transported across the intestinal wall and enter the bloodstream (sugars and amino acids) or the lymphatic system (fats). From the intestines, these systems transport them to the liver, adipose tissue, or muscle cells that will process and use, or store, the energy. Depending on the amounts and types of nutrients ingested, the absorptive state can linger for up to 4 hours. The ingestion of food and the rise of glucose concentrations in the bloodstream stimulate pancreatic beta cells to release insulin into the bloodstream, where it initiates the absorption of blood glucose by liver hepatocytes, and by adipose and muscle cells. Once inside these cells, glucose is immediately converted into glucose-6-phosphate. By doing this, a concentration gradient is established where glucose levels are higher in the blood than in the cells. This allows for glucose to continue moving from the blood to the cells where it is needed. Insulin also stimulates the storage of glucose as glycogen in the liver and muscle cells where it can be used for later energy needs of the body. Insulin also promotes the synthesis of protein in muscle. As you will see, muscle protein can be catabolized and used as fuel in times of starvation. If energy is exerted shortly after eating, the dietary fats and sugars that were just ingested will be processed and used immediately for energy. If not, the excess glucose is stored as glycogen in the liver and muscle cells, or as fat in adipose tissue; excess dietary fat is also stored as triglycerides in adipose tissues. Figure 24.21 summarizes the metabolic processes occurring in the body during the absorptive state. Figure 24.21 Absorptive State During the absorptive state, the body digests food and absorbs the nutrients. The Postabsorptive State The postabsorptive state, or the fasting state, occurs when the food has been digested, absorbed, and stored. You commonly fast overnight, but skipping meals during the day puts your body in the postabsorptive state as well. During this state, the body must rely initially on stored glycogen. Glucose levels in the blood begin to drop as it is absorbed and used by the cells. In response to the decrease in glucose, insulin levels also drop. Glycogen and triglyceride storage slows. However, due to the demands of the tissues and organs, blood glucose levels must be maintained in the normal range of 80–120 mg/dL. In response to a drop in blood glucose concentration, the hormone glucagon is released from the alpha cells of the pancreas. Glucagon acts upon the liver cells, where it inhibits the synthesis of glycogen and stimulates the breakdown of stored glycogen back into glucose. This glucose is released from the liver to be used by the peripheral tissues and the brain. As a result, blood glucose levels begin to rise. Gluconeogenesis will also begin in the liver to replace the glucose that has been used by the peripheral tissues. After ingestion of food, fats and proteins are processed as described previously; however, the glucose processing changes a bit. The peripheral tissues preferentially absorb glucose. The liver, which normally absorbs and processes glucose, will not do so after a prolonged fast. The gluconeogenesis that has been ongoing in the liver will continue after fasting to replace the glycogen stores that were depleted in the liver. After these stores have been replenished, excess glucose that is absorbed by the liver will be converted into triglycerides and fatty acids for long-term storage. Figure 24.22 summarizes the metabolic processes occurring in the body during the postabsorptive state. Figure 24.22 Postabsorptive State During the postabsorptive state, the body must rely on stored glycogen for energy. Starvation When the body is deprived of nourishment for an extended period of time, it goes into “survival mode.” The first priority for survival is to provide enough glucose or fuel for the brain. The second priority is the conservation of amino acids for proteins. Therefore, the body uses ketones to satisfy the energy needs of the brain and other glucose-dependent organs, and to maintain proteins in the cells (see Figure 24.2). Because glucose levels are very low during starvation, glycolysis will shut off in cells that can use alternative fuels. For example, muscles will switch from using glucose to fatty acids as fuel. As previously explained, fatty acids can be converted into acetyl CoA and processed through the Krebs cycle to make ATP. Pyruvate, lactate, and alanine from muscle cells are not converted into acetyl CoA and used in the Krebs cycle, but are exported to the liver to be used in the synthesis of glucose. As starvation continues, and more glucose is needed, glycerol from fatty acids can be liberated and used as a source for gluconeogenesis. After several days of starvation, ketone bodies become the major source of fuel for the heart and other organs. As starvation continues, fatty acids and triglyceride stores are used to create ketones for the body. This prevents the continued breakdown of proteins that serve as carbon sources for gluconeogenesis. Once these stores are fully depleted, proteins from muscles are released and broken down for glucose synthesis. Overall survival is dependent on the amount of fat and protein stored in the body. Energy and Heat Balance - Describe how the body regulates temperature - Explain the significance of the metabolic rate The body tightly regulates the body temperature through a process called thermoregulation, in which the body can maintain its temperature within certain boundaries, even when the surrounding temperature is very different. The core temperature of the body remains steady at around 36.5–37.5 °C (or 97.7–99.5 °F). In the process of ATP production by cells throughout the body, approximately 60 percent of the energy produced is in the form of heat used to maintain body temperature. Thermoregulation is an example of negative feedback. The hypothalamus in the brain is the master switch that works as a thermostat to regulate the body’s core temperature (Figure 24.23). If the temperature is too high, the hypothalamus can initiate several processes to lower it. These include increasing the circulation of the blood to the surface of the body to allow for the dissipation of heat through the skin and initiation of sweating to allow evaporation of water on the skin to cool its surface. Conversely, if the temperature falls below the set core temperature, the hypothalamus can initiate shivering to generate heat. The body uses more energy and generates more heat. In addition, thyroid hormone will stimulate more energy use and heat production by cells throughout the body. An environment is said to be thermoneutral when the body does not expend or release energy to maintain its core temperature. For a naked human, this is an ambient air temperature of around 84 °F. If the temperature is higher, for example, when wearing clothes, the body compensates with cooling mechanisms. The body loses heat through the mechanisms of heat exchange. Figure 24.23 Hypothalamus Controls Thermoregulation The hypothalamus controls thermoregulation. Mechanisms of Heat Exchange When the environment is not thermoneutral, the body uses four mechanisms of heat exchange to maintain homeostasis: conduction, convection, radiation, and evaporation. Each of these mechanisms relies on the property of heat to flow from a higher concentration to a lower concentration; therefore, each of the mechanisms of heat exchange varies in rate according to the temperature and conditions of the environment. Conduction is the transfer of heat by two objects that are in direct contact with one another. It occurs when the skin comes in contact with a cold or warm object. For example, when holding a glass of ice water, the heat from your skin will warm the glass and in turn melt the ice. Alternatively, on a cold day, you might warm up by wrapping your cold hands around a hot mug of coffee. Only about 3 percent of the body’s heat is lost through conduction. Convection is the transfer of heat to the air surrounding the skin. The warmed air rises away from the body and is replaced by cooler air that is subsequently heated. Convection can also occur in water. When the water temperature is lower than the body’s temperature, the body loses heat by warming the water closest to the skin, which moves away to be replaced by cooler water. The convection currents created by the temperature changes continue to draw heat away from the body more quickly than the body can replace it, resulting in hyperthermia. About 15 percent of the body’s heat is lost through convection. Radiation is the transfer of heat via infrared waves. This occurs between any two objects when their temperatures differ. A radiator can warm a room via radiant heat. On a sunny day, the radiation from the sun warms the skin. The same principle works from the body to the environment. About 60 percent of the heat lost by the body is lost through radiation. Evaporation is the transfer of heat by the evaporation of water. Because it takes a great deal of energy for a water molecule to change from a liquid to a gas, evaporating water (in the form of sweat) takes with it a great deal of energy from the skin. However, the rate at which evaporation occurs depends on relative humidity—more sweat evaporates in lower humidity environments. Sweating is the primary means of cooling the body during exercise, whereas at rest, about 20 percent of the heat lost by the body occurs through evaporation. Metabolic Rate The metabolic rate is the amount of energy consumed minus the amount of energy expended by the body. The basal metabolic rate (BMR) describes the amount of daily energy expended by humans at rest, in a neutrally temperate environment, while in the postabsorptive state. It measures how much energy the body needs for normal, basic, daily activity. About 70 percent of all daily energy expenditure comes from the basic functions of the organs in the body. Another 20 percent comes from physical activity, and the remaining 10 percent is necessary for body thermoregulation or temperature control. This rate will be higher if a person is more active or has more lean body mass. As you age, the BMR generally decreases as the percentage of less lean muscle mass decreases. Nutrition and Diet - Explain how different foods can affect metabolism - Describe a healthy diet, as recommended by the U.S. Department of Agriculture (USDA) - List reasons why vitamins and minerals are critical to a healthy diet The carbohydrates, lipids, and proteins in the foods you eat are used for energy to power molecular, cellular, and organ system activities. Importantly, the energy is stored primarily as fats. The quantity and quality of food that is ingested, digested, and absorbed affects the amount of fat that is stored as excess calories. Diet—both what you eat and how much you eat—has a dramatic impact on your health. Eating too much or too little food can lead to serious medical issues, including cardiovascular disease, cancer, anorexia, and diabetes, among others. Combine an unhealthy diet with unhealthy environmental conditions, such as smoking, and the potential medical complications increase significantly. Food and Metabolism The amount of energy that is needed or ingested per day is measured in calories. The nutritional Calorie (C) is the amount of heat it takes to raise 1 kg (1000 g) of water by 1 °C. This is different from the calorie (c) used in the physical sciences, which is the amount of heat it takes to raise 1 g of water by 1 °C. When we refer to "calorie," we are referring to the nutritional Calorie. On average, a person needs 1500 to 2000 calories per day to sustain (or carry out) daily activities. The total number of calories needed by one person is dependent on their body mass, age, height, gender, activity level, and the amount of exercise per day. If exercise is regular part of one’s day, more calories are required. As a rule, people underestimate the number of calories ingested and overestimate the amount they burn through exercise. This can lead to ingestion of too many calories per day. The accumulation of an extra 3500 calories adds one pound of weight. If an excess of 200 calories per day is ingested, one extra pound of body weight will be gained every 18 days. At that rate, an extra 20 pounds can be gained over the course of a year. Of course, this increase in calories could be offset by increased exercise. Running or jogging one mile burns almost 100 calories. The type of food ingested also affects the body’s metabolic rate. Processing of carbohydrates requires less energy than processing of proteins. In fact, the breakdown of carbohydrates requires the least amount of energy, whereas the processing of proteins demands the most energy. In general, the amount of calories ingested and the amount of calories burned determines the overall weight. To lose weight, the number of calories burned per day must exceed the number ingested. Calories are in almost everything you ingest, so when considering calorie intake, beverages must also be considered. To help provide guidelines regarding the types and quantities of food that should be eaten every day, the USDA has updated their food guidelines from MyPyramid to MyPlate. They have put the recommended elements of a healthy meal into the context of a place setting of food. MyPlate categorizes food into the standard six food groups: fruits, vegetables, grains, protein foods, dairy, and oils. The accompanying website gives clear recommendations regarding quantity and type of each food that you should consume each day, as well as identifying which foods belong in each category. The accompanying graphic (Figure 24.24) gives a clear visual with general recommendations for a healthy and balanced meal. The guidelines recommend to “Make half your plate fruits and vegetables.” The other half is grains and protein, with a slightly higher quantity of grains than protein. Dairy products are represented by a drink, but the quantity can be applied to other dairy products as well. Figure 24.24 MyPlate The U.S. Department of Agriculture developed food guidelines called MyPlate to help demonstrate how to maintain a healthy lifestyle. ChooseMyPlate.gov provides extensive online resources for planning a healthy diet and lifestyle, including offering weight management tips and recommendations for physical activity. It also includes the SuperTracker, a web-based application to help you analyze your own diet and physical activity. EVERYDAY CONNECTION Metabolism and Obesity Obesity in the United States is epidemic. The rate of obesity has been steadily rising since the 1980s. In the 1990s, most states reported that less than 10 percent of their populations was obese, and the state with the highest rate reported that only 15 percent of their population was considered obese. By 2010, the U.S. Centers for Disease Control and Prevention reported that nearly 36 percent of adults over 20 years old were obese and an additional 33 percent were overweight, leaving only about 30 percent of the population at a healthy weight. These studies find the highest levels of obesity are concentrated in the southern states. They also find the level of childhood obesity is rising. Obesity is defined by the body mass index (BMI), which is a measure of an individual’s weight-to-height ratio. The normal, or healthy, BMI range is between 18 and 24.9 kg/m2. Overweight is defined as a BMI of 25 to 29.9 kg/m2, and obesity is considered to be a BMI greater than 30 kg/m2. Obesity can arise from a number of factors, including overeating, poor diet, sedentary lifestyle, limited sleep, genetic factors, and even diseases or drugs. Severe obesity (morbid obesity) or long-term obesity can result in serious medical conditions, including coronary heart disease; type 2 diabetes; endometrial, breast, or colon cancer; hypertension (high blood pressure); dyslipidemia (high cholesterol or elevated triglycerides); stroke; liver disease; gall bladder disease; sleep apnea or respiratory diseases; osteoarthritis; and infertility. Research has shown that losing weight can help reduce or reverse the complications associated with these conditions. Vitamins Vitamins are organic compounds found in foods and are a necessary part of the biochemical reactions in the body. They are involved in a number of processes, including mineral and bone metabolism, and cell and tissue growth, and they act as cofactors for energy metabolism. The B vitamins play the largest role of any vitamins in metabolism (Table 24.3 and Table 24.4). You get most of your vitamins through your diet, although some can be formed from the precursors absorbed during digestion. For example, the body synthesizes vitamin A from the β-carotene in orange vegetables like carrots and sweet potatoes. Vitamins are either fat-soluble or water-soluble. Fat-soluble vitamins A, D, E, and K, are absorbed through the intestinal tract with lipids in chylomicrons. Vitamin D is also synthesized in the skin through exposure to sunlight. Because they are carried in lipids, fat-soluble vitamins can accumulate in the lipids stored in the body. If excess vitamins are retained in the lipid stores in the body, hypervitaminosis can result. Water-soluble vitamins, including the eight B vitamins and vitamin C, are absorbed with water in the gastrointestinal tract. These vitamins move easily through bodily fluids, which are water based, so they are not stored in the body. Excess water-soluble vitamins are excreted in the urine. Therefore, hypervitaminosis of water-soluble vitamins rarely occurs, except with an excess of vitamin supplements. Fat-soluble Vitamins \| Vitamin and alternative name \| Sources \| Recommended daily allowance \| Function \| Problems associated with deficiency \| \|---\|---\|---\|---\|---\| \| A retinal or β-carotene \| Yellow and orange fruits and vegetables, dark green leafy vegetables, eggs, milk, liver \| 700–900 µg \| Eye and bone development, immune function \| Night blindness, epithelial changes, immune system deficiency \| \| D cholecalciferol \| Dairy products, egg yolks; also synthesized in the skin from exposure to sunlight \| 5–15 µg \| Aids in calcium absorption, promoting bone growth \| Rickets, bone pain, muscle weakness, increased risk of death from cardiovascular disease, cognitive impairment, asthma in children, cancer \| \| E tocopherols \| Seeds, nuts, vegetable oils, avocados, wheat germ \| 15 mg \| Antioxidant \| Anemia \| \| K phylloquinone \| Dark green leafy vegetables, broccoli, Brussels sprouts, cabbage \| 90–120 µg \| Blood clotting, bone health \| Hemorrhagic disease of newborn in infants; uncommon in adults \| Table 24.3 Water-soluble Vitamins \| Vitamin and alternative name \| Sources \| Recommended daily allowance \| Function \| Problems associated with deficiency \| \|---\|---\|---\|---\|---\| \| B1 thiamine \| Whole grains, enriched bread and cereals, milk, meat \| 1.1–1.2 mg \| Carbohydrate metabolism \| Beriberi, Wernicke-Korsikoff syndrome \| \| B2 riboflavin \| Brewer’s yeast, almonds, milk, organ meats, legumes, enriched breads and cereals, broccoli, asparagus \| 1.1–1.3 mg \| Synthesis of FAD for metabolism, production of red blood cells \| Fatigue, slowed growth, digestive problems, light sensitivity, epithelial problems like cracks in the corners of the mouth \| \| B3 niacin \| Meat, fish, poultry, enriched breads and cereals, peanuts \| 14–16 mg \| Synthesis of NAD, nerve function, cholesterol production \| Cracked, scaly skin; dementia; diarrhea; also known as pellagra \| \| B5 pantothenic acid \| Meat, poultry, potatoes, oats, enriched breads and cereals, tomatoes \| 5 mg \| Synthesis of coenzyme A in fatty acid metabolism \| Rare: symptoms may include fatigue, insomnia, depression, irritability \| \| B6 pyridoxine \| Potatoes, bananas, beans, seeds, nuts, meat, poultry, fish, eggs, dark green leafy vegetables, soy, organ meats \| 1.3–1.5 mg \| Sodium and potassium balance, red blood cell synthesis, protein metabolism \| Confusion, irritability, depression, mouth and tongue sores \| \| B7 biotin \| Liver, fruits, meats \| 30 µg \| Cell growth, metabolism of fatty acids, production of blood cells \| Rare in developed countries; symptoms include dermatitis, hair loss, loss of muscular coordination \| \| B9 folic acid \| Liver, legumes, dark green leafy vegetables, enriched breads and cereals, citrus fruits \| 400 µg \| DNA/protein synthesis \| Poor growth, gingivitis, appetite loss, shortness of breath, gastrointestinal problems, mental deficits \| \| B12 cyanocobalamin \| Fish, meat, poultry, dairy products, eggs \| 2.4 µg \| Fatty acid oxidation, nerve cell function, red blood cell production \| Pernicious anemia, leading to nerve cell damage \| \| C ascorbic acid \| Citrus fruits, red berries, peppers, tomatoes, broccoli, dark green leafy vegetables \| 75–90 mg \| Necessary to produce collagen for formation of connective tissue and teeth, and for wound healing \| Dry hair, gingivitis, bleeding gums, dry and scaly skin, slow wound healing, easy bruising, compromised immunity; can lead to scurvy \| Table 24.4 Minerals Minerals in food are inorganic compounds that work with other nutrients to ensure the body functions properly. Minerals cannot be made in the body; they come from the diet. The amount of minerals in the body is small—only 4 percent of the total body mass—and most of that consists of the minerals that the body requires in moderate quantities: potassium, sodium, calcium, phosphorus, magnesium, and chloride. The most common minerals in the body are calcium and phosphorous, both of which are stored in the skeleton and necessary for the hardening of bones. Most minerals are ionized, and their ionic forms are used in physiological processes throughout the body. Sodium and chloride ions are electrolytes in the blood and extracellular tissues, and iron ions are critical to the formation of hemoglobin. There are additional trace minerals that are still important to the body’s functions, but their required quantities are much lower. Like vitamins, minerals can be consumed in toxic quantities (although it is rare). A healthy diet includes most of the minerals your body requires, so supplements and processed foods can add potentially toxic levels of minerals. Table 24.5 and Table 24.6provide a summary of minerals and their function in the body. Major Minerals \| Mineral \| Sources \| Recommended daily allowance \| Function \| Problems associated with deficiency \| \|---\|---\|---\|---\|---\| \| Potassium \| Meats, some fish, fruits, vegetables, legumes, dairy products \| 4700 mg \| Nerve and muscle function; acts as an electrolyte \| Hypokalemia: weakness, fatigue, muscle cramping, gastrointestinal problems, cardiac problems \| \| Sodium \| Table salt, milk, beets, celery, processed foods \| 2300 mg \| Blood pressure, blood volume, muscle and nerve function \| Rare \| \| Calcium \| Dairy products, dark green leafy vegetables, blackstrap molasses, nuts, brewer’s yeast, some fish \| 1000 mg \| Bone structure and health; nerve and muscle functions, especially cardiac function \| Slow growth, weak and brittle bones \| \| Phosphorous \| Meat, milk \| 700 mg \| Bone formation, metabolism, ATP production \| Rare \| \| Magnesium \| Whole grains, nuts, leafy green vegetables \| 310–420 mg \| Enzyme activation, production of energy, regulation of other nutrients \| Agitation, anxiety, sleep problems, nausea and vomiting, abnormal heart rhythms, low blood pressure, muscular problems \| \| Chloride \| Most foods, salt, vegetables, especially seaweed, tomatoes, lettuce, celery, olives \| 2300 mg \| Balance of body fluids, digestion \| Loss of appetite, muscle cramps \| Table 24.5 Trace Minerals \| Mineral \| Sources \| Recommended daily allowance \| Function \| Problems associated with deficiency \| \|---\|---\|---\|---\|---\| \| Iron \| Meat, poultry, fish, shellfish, legumes, nuts, seeds, whole grains, dark leafy green vegetables \| 8–18 mg \| Transport of oxygen in blood, production of ATP \| Anemia, weakness, fatigue \| \| Zinc \| Meat, fish, poultry, cheese, shellfish \| 8–11 mg \| Immunity, reproduction, growth, blood clotting, insulin and thyroid function \| Loss of appetite, poor growth, weight loss, skin problems, hair loss, vision problems, lack of taste or smell \| \| Copper \| Seafood, organ meats, nuts, legumes, chocolate, enriched breads and cereals, some fruits and vegetables \| 900 µg \| Red blood cell production, nerve and immune system function, collagen formation, acts as an antioxidant \| Anemia, low body temperature, bone fractures, low white blood cell concentration, irregular heartbeat, thyroid problems \| \| Iodine \| Fish, shellfish, garlic, lima beans, sesame seeds, soybeans, dark leafy green vegetables \| 150 µg \| Thyroid function \| Hypothyroidism: fatigue, weight gain, dry skin, temperature sensitivity \| \| Sulfur \| Eggs, meat, poultry, fish, legumes \| None \| Component of amino acids \| Protein deficiency \| \| Fluoride \| Fluoridated water \| 3–4 mg \| Maintenance of bone and tooth structure \| Increased cavities, weak bones and teeth \| \| Manganese \| Nuts, seeds, whole grains, legumes \| 1.8–2.3 mg \| Formation of connective tissue and bones, blood clotting, sex hormone development, metabolism, brain and nerve function \| Infertility, bone malformation, weakness, seizures \| \| Cobalt \| Fish, nuts, leafy green vegetables, whole grains \| None \| Component of B12 \| None \| \| Selenium \| Brewer’s yeast, wheat germ, liver, butter, fish, shellfish, whole grains \| 55 µg \| Antioxidant, thyroid function, immune system function \| Muscle pain \| \| Chromium \| Whole grains, lean meats, cheese, black pepper, thyme, brewer’s yeast \| 25–35 µg \| Insulin function \| High blood sugar, triglyceride, and cholesterol levels \| \| Molybdenum \| Legumes, whole grains, nuts \| 45 µg \| Cofactor for enzymes \| Rare \| Table 24.6 Key Terms - absorptive state - also called the fed state; the metabolic state occurring during the first few hours after ingesting food in which the body is digesting food and absorbing the nutrients - acetyl coenzyme A (acetyl CoA) - starting molecule of the Krebs cycle - anabolic hormones - hormones that stimulate the synthesis of new, larger molecules - anabolic reactions - reactions that build smaller molecules into larger molecules - ATP synthase - protein pore complex that creates ATP - basal metabolic rate (BMR) - amount of energy expended by the body at rest - beta (β)-hydroxybutyrate - primary ketone body produced in the body - beta (β)-oxidation - fatty acid oxidation - bile salts - salts that are released from the liver in response to lipid ingestion and surround the insoluble triglycerides to aid in their conversion to monoglycerides and free fatty acids - biosynthesis reactions - reactions that create new molecules, also called anabolic reactions - body mass index (BMI) - relative amount of body weight compared to the overall height; a BMI ranging from 18–24.9 is considered normal weight, 25–29.9 is considered overweight, and greater than 30 is considered obese - calorie - amount of heat it takes to raise 1 kg (1000 g) of water by 1 °C - catabolic hormones - hormones that stimulate the breakdown of larger molecules - catabolic reactions - reactions that break down larger molecules into their constituent parts - cellular respiration - production of ATP from glucose oxidation via glycolysis, the Krebs cycle, and oxidative phosphorylation - cholecystokinin (CCK) - hormone that stimulates the release of pancreatic lipase and the contraction of the gallbladder to release bile salts - chylomicrons - vesicles containing cholesterol and triglycerides that transport lipids out of the intestinal cells and into the lymphatic and circulatory systems - chymotrypsin - pancreatic enzyme that digests protein - chymotrypsinogen - proenzyme that is activated by trypsin into chymotrypsin - citric acid cycle - also called the Krebs cycle or the tricarboxylic acid cycle; converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules - conduction - transfer of heat through physical contact - convection - transfer of heat between the skin and air or water - elastase - pancreatic enzyme that digests protein - electron transport chain (ETC) - ATP production pathway in which electrons are passed through a series of oxidation-reduction reactions that forms water and produces a proton gradient - energy-consuming phase - first phase of glycolysis, in which two molecules of ATP are necessary to start the reaction - energy-yielding phase - second phase of glycolysis, during which energy is produced - enterokinase - enzyme located in the wall of the small intestine that activates trypsin - evaporation - transfer of heat that occurs when water changes from a liquid to a gas - FADH2 - high-energy molecule needed for glycolysis - fatty acid oxidation - breakdown of fatty acids into smaller chain fatty acids and acetyl CoA - flavin adenine dinucleotide (FAD) - coenzyme used to produce FADH2 - glucokinase - cellular enzyme, found in the liver, which converts glucose into glucose-6-phosphate upon uptake into the cell - gluconeogenesis - process of glucose synthesis from pyruvate or other molecules - glucose-6-phosphate - phosphorylated glucose produced in the first step of glycolysis - glycogen - form that glucose assumes when it is stored - glycolysis - series of metabolic reactions that breaks down glucose into pyruvate and produces ATP - hexokinase - cellular enzyme, found in most tissues, that converts glucose into glucose-6-phosphate upon uptake into the cell - hydroxymethylglutaryl CoA (HMG CoA) - molecule created in the first step of the creation of ketone bodies from acetyl CoA - inactive proenzymes - forms in which proteases are stored and released to prevent the inappropriate digestion of the native proteins of the stomach, pancreas, and small intestine - insulin - hormone secreted by the pancreas that stimulates the uptake of glucose into the cells - ketone bodies - alternative source of energy when glucose is limited, created when too much acetyl CoA is created during fatty acid oxidation - Krebs cycle - also called the citric acid cycle or the tricarboxylic acid cycle, converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules - lipogenesis - synthesis of lipids that occurs in the liver or adipose tissues - lipolysis - breakdown of triglycerides into glycerol and fatty acids - metabolic rate - amount of energy consumed minus the amount of energy expended by the body - metabolism - sum of all catabolic and anabolic reactions that take place in the body - minerals - inorganic compounds required by the body to ensure proper function of the body - monoglyceride molecules - lipid consisting of a single fatty acid chain attached to a glycerol backbone - monosaccharide - smallest, monomeric sugar molecule - NADH - high-energy molecule needed for glycolysis - nicotinamide adenine dinucleotide (NAD) - coenzyme used to produce NADH - oxidation - loss of an electron - oxidation-reduction reaction - (also, redox reaction) pair of reactions in which an electron is passed from one molecule to another, oxidizing one and reducing the other - oxidative phosphorylation - process that converts high-energy NADH and FADH2 into ATP - pancreatic lipases - enzymes released from the pancreas that digest lipids in the diet - pepsin - enzyme that begins to break down proteins in the stomach - polysaccharides - complex carbohydrates made up of many monosaccharides - postabsorptive state - also called the fasting state; the metabolic state occurring after digestion when food is no longer the body’s source of energy and it must rely on stored glycogen - proteolysis - process of breaking proteins into smaller peptides - pyruvate - three-carbon end product of glycolysis and starting material that is converted into acetyl CoA that enters the Krebs cycle - radiation - transfer of heat via infrared waves - reduction - gaining of an electron - salivary amylase - digestive enzyme that is found in the saliva and begins the digestion of carbohydrates in the mouth - secretin - hormone released in the small intestine to aid in digestion - sodium bicarbonate - anion released into the small intestine to neutralize the pH of the food from the stomach - terminal electron acceptor - oxygen, the recipient of the free hydrogen at the end of the electron transport chain - thermoneutral - external temperature at which the body does not expend any energy for thermoregulation, about 84 °F - thermoregulation - process of regulating the temperature of the body - transamination - transfer of an amine group from one molecule to another as a way to turn nitrogen waste into ammonia so that it can enter the urea cycle - tricarboxylic acid cycle (TCA) - also called the Krebs cycle or the citric acid cycle; converts pyruvate into CO2 and high-energy FADH2, NADH, and ATP molecules - triglycerides - lipids, or fats, consisting of three fatty acid chains attached to a glycerol backbone - trypsin - pancreatic enzyme that activates chymotrypsin and digests protein - trypsinogen - proenzyme form of trypsin - urea cycle - process that converts potentially toxic nitrogen waste into urea that can be eliminated through the kidneys - vitamins - organic compounds required by the body to perform biochemical reactions like metabolism and bone, cell, and tissue growth Chapter Review 24.1 Overview of Metabolic Reactions Metabolism is the sum of all catabolic (break down) and anabolic (synthesis) reactions in the body. The metabolic rate measures the amount of energy used to maintain life. An organism must ingest a sufficient amount of food to maintain its metabolic rate if the organism is to stay alive for very long. Catabolic reactions break down larger molecules, such as carbohydrates, lipids, and proteins from ingested food, into their constituent smaller parts. They also include the breakdown of ATP, which releases the energy needed for metabolic processes in all cells throughout the body. Anabolic reactions, or biosynthetic reactions, synthesize larger molecules from smaller constituent parts, using ATP as the energy source for these reactions. Anabolic reactions build bone, muscle mass, and new proteins, fats, and nucleic acids. Oxidation-reduction reactions transfer electrons across molecules by oxidizing one molecule and reducing another, and collecting the released energy to convert Pi and ADP into ATP. Errors in metabolism alter the processing of carbohydrates, lipids, proteins, and nucleic acids, and can result in a number of disease states. 24.2 Carbohydrate Metabolism Metabolic enzymes catalyze catabolic reactions that break down carbohydrates contained in food. The energy released is used to power the cells and systems that make up your body. Excess or unutilized energy is stored as fat or glycogen for later use. Carbohydrate metabolism begins in the mouth, where the enzyme salivary amylase begins to break down complex sugars into monosaccharides. These can then be transported across the intestinal membrane into the bloodstream and then to body tissues. In the cells, glucose, a six-carbon sugar, is processed through a sequence of reactions into smaller sugars, and the energy stored inside the molecule is released. The first step of carbohydrate catabolism is glycolysis, which produces pyruvate, NADH, and ATP. Under anaerobic conditions, the pyruvate can be converted into lactate to keep glycolysis working. Under aerobic conditions, pyruvate enters the Krebs cycle, also called the citric acid cycle or tricarboxylic acid cycle. In addition to ATP, the Krebs cycle produces high-energy FADH2 and NADH molecules, which provide electrons to the oxidative phosphorylation process that generates more high-energy ATP molecules. For each molecule of glucose that is processed in glycolysis, a net of 36 ATPs can be created by aerobic respiration. Under anaerobic conditions, ATP production is limited to those generated by glycolysis. While a total of four ATPs are produced by glycolysis, two are needed to begin glycolysis, so there is a net yield of two ATP molecules. In conditions of low glucose, such as fasting, starvation, or low carbohydrate diets, glucose can be synthesized from lactate, pyruvate, glycerol, alanine, or glutamate. This process, called gluconeogenesis, is almost the reverse of glycolysis and serves to create glucose molecules for glucose-dependent organs, such as the brain, when glucose levels fall below normal. 24.3 Lipid Metabolism Lipids are available to the body from three sources. They can be ingested in the diet, stored in the adipose tissue of the body, or synthesized in the liver. Fats ingested in the diet are digested in the small intestine. The triglycerides are broken down into monoglycerides and free fatty acids, then imported across the intestinal mucosa. Once across, the triglycerides are resynthesized and transported to the liver or adipose tissue. Fatty acids are oxidized through fatty acid or β-oxidation into two-carbon acetyl CoA molecules, which can then enter the Krebs cycle to generate ATP. If excess acetyl CoA is created and overloads the capacity of the Krebs cycle, the acetyl CoA can be used to synthesize ketone bodies. When glucose is limited, ketone bodies can be oxidized and used for fuel. Excess acetyl CoA generated from excess glucose or carbohydrate ingestion can be used for fatty acid synthesis or lipogenesis. Acetyl CoA is used to create lipids, triglycerides, steroid hormones, cholesterol, and bile salts. Lipolysis is the breakdown of triglycerides into glycerol and fatty acids, making them easier for the body to process. 24.4 Protein Metabolism Digestion of proteins begins in the stomach, where HCl and pepsin begin the process of breaking down proteins into their constituent amino acids. As the chyme enters the small intestine, it mixes with bicarbonate and digestive enzymes. The bicarbonate neutralizes the acidic HCl, and the digestive enzymes break down the proteins into smaller peptides and amino acids. Digestive hormones secretin and CCK are released from the small intestine to aid in digestive processes, and digestive proenzymes are released from the pancreas (trypsinogen and chymotrypsinogen). Enterokinase, an enzyme located in the wall of the small intestine, activates trypsin, which in turn activates chymotrypsin. These enzymes liberate the individual amino acids that are then transported via sodium-amino acid transporters across the intestinal wall into the cell. The amino acids are then transported into the bloodstream for dispersal to the liver and cells throughout the body to be used to create new proteins. When in excess, the amino acids are processed and stored as glucose or ketones. The nitrogen waste that is liberated in this process is converted to urea in the urea acid cycle and eliminated in the urine. In times of starvation, amino acids can be used as an energy source and processed through the Krebs cycle. 24.5 Metabolic States of the Body There are three main metabolic states of the body: absorptive (fed), postabsorptive (fasting), and starvation. During any given day, your metabolism switches between absorptive and postabsorptive states. Starvation states happen very rarely in generally well-nourished individuals. When the body is fed, glucose, fats, and proteins are absorbed across the intestinal membrane and enter the bloodstream and lymphatic system to be used immediately for fuel. Any excess is stored for later fasting stages. As blood glucose levels rise, the pancreas releases insulin to stimulate the uptake of glucose by hepatocytes in the liver, muscle cells/fibers, and adipocytes (fat cells), and to promote its conversion to glycogen. As the postabsorptive state begins, glucose levels drop, and there is a corresponding drop in insulin levels. Falling glucose levels trigger the pancreas to release glucagon to turn off glycogen synthesis in the liver and stimulate its breakdown into glucose. The glucose is released into the bloodstream to serve as a fuel source for cells throughout the body. If glycogen stores are depleted during fasting, alternative sources, including fatty acids and proteins, can be metabolized and used as fuel. When the body once again enters the absorptive state after fasting, fats and proteins are digested and used to replenish fat and protein stores, whereas glucose is processed and used first to replenish the glycogen stores in the peripheral tissues, then in the liver. If the fast is not broken and starvation begins to set in, during the initial days, glucose produced from gluconeogenesis is still used by the brain and organs. After a few days, however, ketone bodies are created from fats and serve as the preferential fuel source for the heart and other organs, so that the brain can still use glucose. Once these stores are depleted, proteins will be catabolized first from the organs with fast turnover, such as the intestinal lining. Muscle will be spared to prevent the wasting of muscle tissue; however, these proteins will be used if alternative stores are not available. 24.6 Energy and Heat Balance Some of the energy from the food that is ingested is used to maintain the core temperature of the body. Most of the energy derived from the food is released as heat. The core temperature is kept around 36.5–37.5 °C (97.7–99.5 °F). This is tightly regulated by the hypothalamus in the brain, which senses changes in the core temperature and operates like a thermostat to increase sweating or shivering, or inducing other mechanisms to return the temperature to its normal range. The body can also gain or lose heat through mechanisms of heat exchange. Conduction transfers heat from one object to another through physical contact. Convection transfers heat to air or water. Radiation transfers heat via infrared radiation. Evaporation transfers heat as water changes state from a liquid to a gas. 24.7 Nutrition and Diet Nutrition and diet affect your metabolism. More energy is required to break down fats and proteins than carbohydrates; however, all excess calories that are ingested will be stored as fat in the body. On average, a person requires 1500 to 2000 calories for normal daily activity, although routine exercise will increase that amount. If you ingest more than that, the remainder is stored for later use. Conversely, if you ingest less than that, the energy stores in your body will be depleted. Both the quantity and quality of the food you eat affect your metabolism and can affect your overall health. Eating too much or too little can result in serious medical conditions, including cardiovascular disease, cancer, and diabetes. Vitamins and minerals are essential parts of the diet. They are needed for the proper function of metabolic pathways in the body. Vitamins are not stored in the body, so they must be obtained from the diet or synthesized from precursors available in the diet. Minerals are also obtained from the diet, but they are also stored, primarily in skeletal tissues. Review Questions A monosaccharide is formed from a polysaccharide in what kind of reaction? - oxidation–reduction reaction - anabolic reaction - catabolic reaction - biosynthetic reaction If anabolic reactions exceed catabolic reactions, the result will be ________. - weight loss - weight gain - metabolic rate change - development of disease When NAD becomes NADH, the coenzyme has been ________. - reduced - oxidized - metabolized - hydrolyzed Anabolic reactions use energy by ________. - turning ADP into ATP - removing a phosphate group from ATP - producing heat - breaking down molecules into smaller parts Glycolysis results in the production of two ________ molecules from a single molecule of glucose. In the absence of ________, the end product of glycolysis is ________. - acetyl CoA, pyruvate, lactate - ATP, carbon, pyruvate - pyruvate, oxygen, lactate - pyruvate, carbon, acetyl CoA The Krebs cycle converts ________ through a cycle of reactions. In the process, ATP, ________, and ________ are produced. - acetyl CoA; FAD, NAD - acetyl CoA; FADH2; NADH - pyruvate; NAD; FADH2 - pyruvate; oxygen; oxaloacetate Which pathway produces the most ATP molecules? - lactic acid fermentation - the Krebs cycle - the electron transport chain - glycolysis Aerobic cellular respiration results in the production of these two products. - NADH and FADH2 - ATP and pyruvate - ATP and glucose - ATP and H2O When NAD+ becomes NADH, the coenzyme has been ________. - reduced - oxidized - metabolized - hydrolyzed Lipids in the diet can be ________. - broken down into energy for the body - stored as triglycerides for later use - converted into acetyl CoA - all of the above The gallbladder provides ________ that aid(s) in transport of lipids across the intestinal membrane. - lipases - cholesterol - proteins - bile salts Triglycerides are transported by chylomicrons because ________. - they cannot move easily in the blood stream because they are fat based, while the blood is water based - they are too small to move by themselves - the chylomicrons contain enzymes they need for anabolism - they cannot fit across the intestinal membrane Which molecule produces the most ATP? - carbohydrates - FADH2 - triglycerides - NADH Which molecules can enter the Krebs cycle? - chylomicrons - acetyl CoA - monoglycerides - ketone bodies Acetyl CoA can be converted to all of the following except ________. - ketone bodies - fatty acids - polysaccharides - triglycerides Digestion of proteins begins in the ________ where ________ and ________ mix with food to break down protein into ________. - stomach; amylase; HCl; amino acids - mouth; pepsin; HCl; fatty acids - stomach; lipase; HCl; amino acids - stomach; pepsin; HCl; amino acids Amino acids are needed to ________. - build new proteins - serve as fat stores - supply energy for the cell - create red blood cells If an amino acid is not used to create new proteins, it can be ________. - converted to acetyl CoA - converted to glucose or ketones - converted to nitrogen - stored to be used later During the absorptive state, glucose levels are ________, insulin levels are ________, and glucagon levels ________. - high; low; stay the same - low; low; stay the same - high; high; are high - high; high; are low Starvation sets in after 3 to 4 days without food. Which hormones change in response to low glucose levels? - glucagon and insulin - ketones and glucagon - insulin, glucose, and glucagon - insulin and ketones The postabsorptive state relies on stores of ________ in the ________. - insulin; pancreas - glucagon; pancreas - glycogen; liver - glucose; liver The body’s temperature is controlled by the ________. This temperature is always kept between ________. - pituitary; 36.5–37.5 °C - hypothalamus; 97.7–99.5 °F - hypothalamus; 36.5–37.5 °F - pituitary; 97.7–99.5 °F Fever increases the body temperature and can induce chills to help cool the temperature back down. What other mechanisms are in place to regulate the body temperature? - shivering - sweating - erection of the hairs on the arms and legs - all of the above The heat you feel on your chair when you stand up was transferred from your skin via ________. - conduction - convection - radiation - evaporation A crowded room warms up through the mechanism of ________. - conduction - convection - radiation - evaporation A deficiency in vitamin A can result in ________. - improper bone development - scurvy - improper eye development or sight - all of the above Rickets results in improper bone development in children that arises from the malabsorption of calcium and a deficiency in ________. - vitamin D - vitamin C - vitamin B12 - niacin Consuming which type of food will help the most with weight loss? - fats - vegetables - lean meats - fruits Which of the following is stored in the body? - thiamine - phosphorous - folic acid - vitamin C Critical Thinking Questions Describe how metabolism can be altered. 31.Describe how Addison’s disease can be treated. 32.Explain how glucose is metabolized to yield ATP. 33.Insulin is released when food is ingested and stimulates the uptake of glucose into the cell. Discuss the mechanism cells employ to create a concentration gradient to ensure continual uptake of glucose from the bloodstream. 34.Discuss how carbohydrates can be stored as fat. 35.If a diabetic’s breath smells like alcohol, what could this mean? 36.Amino acids are not stored in the body. Describe how excess amino acids are processed in the cell. 37.Release of trypsin and chymotrypsin in their active form can result in the digestion of the pancreas or small intestine itself. What mechanism does the body employ to prevent its self-destruction? 38.In type II diabetes, insulin is produced but is nonfunctional. These patients are described as “starving in a sea of plenty,” because their blood glucose levels are high, but none of the glucose is transported into the cells. Describe how this leads to malnutrition. 39.Ketone bodies are used as an alternative source of fuel during starvation. Describe how ketones are synthesized. 40.How does vasoconstriction help increase the core temperature of the body? 41.How can the ingestion of food increase the body temperature? 42.Weight loss and weight gain are complex processes. What are some of the main factors that influence weight gain in people? 43.Some low-fat or non-fat foods contain a large amount of sugar to replace the fat content of the food. Discuss how this leads to increased fat in the body (and weight gain) even though the item is non-fat.	oercommons	2025-03-18T00:35:13.534474	10/14/2019	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/58772/overview", "title": "Anatomy and Physiology, Energy, Maintenance, and Environmental Exchange, Metabolism and Nutrition", "author": null }
https://oercommons.org/courseware/lesson/88051/overview	Hitler's Prewar Territorial Gains Overview Hitler's Territorial Gains: 1935-1938 In 1935, two years after coming to power in Germany, Hitler began preparing Germany to seize territory in Europe. Against provisions of the Treaty of Versailles, he remilitarized Germany. The draft was reintroduced in Germany in the spring of 1935, and Hitler further expanded the German Navy and the German Air Force. Over the next three years, Hitler carried out a series of incremental conquests, testing the tolerance of Great Britain and France. Learning Objectives Explain the significance of Hitler's acquisition of European territories between 1935-1938 Evaluate the significance of the Allies' policy of appeasement Key Terms / Key Concepts annexation of Austria: the incorporation of Austria into Nazi Germany's Third Reich in March 1938. appeasement: a diplomatic policy of making political or material concessions to an enemy power in order to avoid conflict Munich Conference: in September 1938, an internationally-agreed upon settlement permitting Nazi Germany’s annexation of portions of Czechoslovakia along the country’s borders mainly inhabited by German speakers Rhineland: a strip of land along Germany's western border with France, Belgium, Holland that is rich in natural resources and industries Saarland: a small pocket of territory in present-day southwest territory rich in natural resources and industry Hitler's Prewar Conquests The Saarland and Rhineland By 1935, the German military had grown exponentially. Hitler turned his attention to western Germany. Under the provisions of the 1919 Treaty of Versailles, Germany had lost control of two of the most industralized, and resource-rich areas along their western border: the Saarland, and the Rhineland. Historically German territory rich in coal and iron deposits, as well as heavy industry, Hitler wanted to reclaim them. Under the 1919 Treaty of Versailles, Germany had lost much of its territory along its western border. The Saarland, a small territory in Germany's southwest, was carved away. It operated under the joint rule of the League of Nations but was primarily controlled by the French, who also controlled its resource and industrial production. In 1933, the Nazis began applying pressure to the people to rejoin Germany. Two years later, a referendum was held. To the shock of Western European nations, and the Germans alike, the people of the Saarland voted overwhelming to rejoin Germany. Thus, the Saarland was restored to Germany, becoming Hitler's first territorial acquisition. It would set the stage for his subsequent advances. In 1935, another development took place that would give Hitler the context he needed to reclaim his main target, the Rhineland. France and the Soviet Union signed a pact assuring one another mutual assistance if either were attacked by a foreign nation. This thinly-veiled action in effect said, "Germany, if you attack either of our nations, then you will have to fight both Russia and France." Hitler was outraged but used the treaty to his advantage. In the spring of 1936, under the pretext of protecting Germany from a French threat, Hitler sent troops to reoccupy Germany's Rhineland. This was undertaken in direct violation of the Treaty of Versailles, which demanded complete demilitarization of the region. But the act was bold and unexpected, and it caught the British and French surprised and unprepared. They watched and questioned the situation. Ultimately, neither nation did anything. Hitler, thus, secured his second territorial goal in only one year, and he had done so with no decisive response from the British and French. Their inaction bolstered his courage to proceed with further territorial expansion, and his goal of uniting all German peoples. The Annexation of Austria Like Germany, Austria suffered significantly during the Great Depression and endured its own political struggles. Austrians also created their own branch of the Nazis, and the Austrian Nazis became enormously popular and influential. Hitler, himself an Austrian by birth, dreamed of uniting Germany and Austria into one German state. The two countries shared languages, many cultural features, as well as economic ties. After a failed coup four years earlier, German and Austrian Nazis began working together to create one German state. Hitler and his cabinet applied political pressure on the sitting Austrian government. The Austrian government also faced with growing discontent internally. Ultimately, they refused to willingly capitulate to Hitler's pressure. On March 12, 1938, the Nazis invaded Austria. Overwhelmingly, they were welcomed by the Austrian people. Such fanfare followed the Nazi invasion that twenty-four later, Hitler formally annexed Austria into his German Reich (empire). For their parts, Britain and France continued to watch and consider the annexation of Austria. What should they do? How should they respond? Again, their sluggishness and inactivity would only encourage further expansion by Hitler and the Nazis. The Sudetenland Crisis The success of the annexation of Austria emboldened Hitler. He spoke loudly of its triumph, and of uniting German peoples. However, he also spoke of the need to reunite all German peoples under one enormous, German empire, his Third Reich. Once again, he set his eyes on a target. This time, it was the Sudetenland. The Sudetenland is the present-day Czech Republic, just south and east of Germany. In 1938, it was a part of Czechoslovakia--a multiethnic nation that was home to a large German minority population. It was also a region rich in natural resources such as coal, which would be essential to fueling a war, and industry. Under the pretext of uniting Germans, Hitler began a campaign to annex the Sudetenland. Germans who lived there, he argued, were mistreated by the dysfunctional Czechoslovakian government, and needed to return home. In May 1938, he verbally launched his campaign to attack Czechoslovakia and annex the Sudetenland. War seemed immienent. British and French fears about Hitler's growing power and territorial acquisitions prompted them to take action. In September 1938, the British and French leaders agreed to meet with Hitler in the German city, Munich, to negotiate with him about his Sudetenland demands. Fascist Italian leader, Benito Mussolini, also joined in the negotiations at the Munich Conference in late September 1938. Neither the Czechs, not the Soviet Union, were present at the conference. Instrumental in the negotiations was British Prime Minister, Neville Chamberlain. A confirmed pacifist, he believed that war with Germany must be avoided at all costs. During the negotiations, Chamberlain became the main voice for launching a policy of appeasement. Rather than confront Hitler militarily, Chamberlain argued successfully that the British and French should allow Hitler to occupy parts of the Sudetenland in exchange for peace in Europe. Moreover, the agreement was made that Germany would pursue no further territorial acquisitions. The four heads of state shook hands, and Chamberlain returned to England, and said of the conference, "We have achieved peace for our time." German soldiers occupied the Sudetenland in October 1938. The following spring, Hitler pushed beyond the boundaries of the Sudetenland given to him at the Munich Conference. In March 1939, German troops entered the capital city of the Sudetenland, Prague. Six months later, they would invade Poland and launch Europe into a Second World War. Attributions Images courtesy of Wikimedia Commons.	oercommons	2025-03-18T00:35:13.563309	Neil Greenwood	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/88051/overview", "title": "Statewide Dual Credit World History, The Catastrophe of the Modern Era: 1919-Present CE, Chapter 14: The World Afire: World War II, Hitler's Prewar Territorial Gains", "author": "Anna McCollum" }
https://oercommons.org/courseware/lesson/124578/overview	The Adventure of the Cheap Flat The Final Problem The Purloined Letter The Mystery Genre Overview A selection of public domain reading related to the origins and conventions of the mystery genre. Reading 1. Poe, E.A. "The Purloined Letter" 2. Doyle, A.C. "The Final Problem" 3. Christie, A. "The Adventure of the Cheap Flat." 4. Orwell, G. "The Decline of the English Murder."	oercommons	2025-03-18T00:35:13.582257	02/11/2025	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/124578/overview", "title": "The Mystery Genre", "author": "Wendy Stephens" }
https://oercommons.org/courseware/lesson/56380/overview	The Endocrine System Introduction Figure 17.1 A Child Catches a Falling Leaf Hormones of the endocrine system coordinate and control growth, metabolism, temperature regulation, the stress response, reproduction, and many other functions. (credit: “seenthroughmylense”/flickr.com) CHAPTER OBJECTIVES After studying this chapter, you will be able to: - Identify the contributions of the endocrine system to homeostasis - Discuss the chemical composition of hormones and the mechanisms of hormone action - Summarize the site of production, regulation, and effects of the hormones of the pituitary, thyroid, parathyroid, adrenal, and pineal glands - Discuss the hormonal regulation of the reproductive system - Explain the role of the pancreatic endocrine cells in the regulation of blood glucose - Identify the hormones released by the heart, kidneys, and other organs with secondary endocrine functions - Discuss several common diseases associated with endocrine system dysfunction - Discuss the embryonic development of, and the effects of aging on, the endocrine system You may never have thought of it this way, but when you send a text message to two friends to meet you at the dining hall at six, you’re sending digital signals that (you hope) will affect their behavior—even though they are some distance away. Similarly, certain cells send chemical signals to other cells in the body that influence their behavior. This long-distance intercellular communication, coordination, and control is critical for homeostasis, and it is the fundamental function of the endocrine system. An Overview of the Endocrine System - Distinguish the types of intercellular communication, their importance, mechanisms, and effects - Identify the major organs and tissues of the endocrine system and their location in the body Communication is a process in which a sender transmits signals to one or more receivers to control and coordinate actions. In the human body, two major organ systems participate in relatively “long distance” communication: the nervous system and the endocrine system. Together, these two systems are primarily responsible for maintaining homeostasis in the body. Neural and Endocrine Signaling The nervous system uses two types of intercellular communication—electrical and chemical signaling—either by the direct action of an electrical potential, or in the latter case, through the action of chemical neurotransmitters such as serotonin or norepinephrine. Neurotransmitters act locally and rapidly. When an electrical signal in the form of an action potential arrives at the synaptic terminal, they diffuse across the synaptic cleft (the gap between a sending neuron and a receiving neuron or muscle cell). Once the neurotransmitters interact (bind) with receptors on the receiving (post-synaptic) cell, the receptor stimulation is transduced into a response such as continued electrical signaling or modification of cellular response. The target cell responds within milliseconds of receiving the chemical “message”; this response then ceases very quickly once the neural signaling ends. In this way, neural communication enables body functions that involve quick, brief actions, such as movement, sensation, and cognition.In contrast, the endocrine system uses just one method of communication: chemical signaling. These signals are sent by the endocrine organs, which secrete chemicals—the hormone—into the extracellular fluid. Hormones are transported primarily via the bloodstream throughout the body, where they bind to receptors on target cells, inducing a characteristic response. As a result, endocrine signaling requires more time than neural signaling to prompt a response in target cells, though the precise amount of time varies with different hormones. For example, the hormones released when you are confronted with a dangerous or frightening situation, called the fight-or-flight response, occur by the release of adrenal hormones—epinephrine and norepinephrine—within seconds. In contrast, it may take up to 48 hours for target cells to respond to certain reproductive hormones. INTERACTIVE LINK Visit this link to watch an animation of the events that occur when a hormone binds to a cell membrane receptor. What is the secondary messenger made by adenylyl cyclase during the activation of liver cells by epinephrine? In addition, endocrine signaling is typically less specific than neural signaling. The same hormone may play a role in a variety of different physiological processes depending on the target cells involved. For example, the hormone oxytocin promotes uterine contractions in women in labor. It is also important in breastfeeding, and may be involved in the sexual response and in feelings of emotional attachment in both males and females. In general, the nervous system involves quick responses to rapid changes in the external environment, and the endocrine system is usually slower acting—taking care of the internal environment of the body, maintaining homeostasis, and controlling reproduction (Table 17.1). So how does the fight-or-flight response that was mentioned earlier happen so quickly if hormones are usually slower acting? It is because the two systems are connected. It is the fast action of the nervous system in response to the danger in the environment that stimulates the adrenal glands to secrete their hormones. As a result, the nervous system can cause rapid endocrine responses to keep up with sudden changes in both the external and internal environments when necessary. Endocrine and Nervous Systems \| Endocrine system \| Nervous system \| \| \|---\|---\|---\| \| Signaling mechanism(s) \| Chemical \| Chemical/electrical \| \| Primary chemical signal \| Hormones \| Neurotransmitters \| \| Distance traveled \| Long or short \| Always short \| \| Response time \| Fast or slow \| Always fast \| \| Environment targeted \| Internal \| Internal and external \| Table 17.1 Structures of the Endocrine System The endocrine system consists of cells, tissues, and organs that secrete hormones as a primary or secondary function. The endocrine gland is the major player in this system. The primary function of these ductless glands is to secrete their hormones directly into the surrounding fluid. The interstitial fluid and the blood vessels then transport the hormones throughout the body. The endocrine system includes the pituitary, thyroid, parathyroid, adrenal, and pineal glands (Figure 17.2). Some of these glands have both endocrine and non-endocrine functions. For example, the pancreas contains cells that function in digestion as well as cells that secrete the hormones insulin and glucagon, which regulate blood glucose levels. The hypothalamus, thymus, heart, kidneys, stomach, small intestine, liver, skin, female ovaries, and male testes are other organs that contain cells with endocrine function. Moreover, adipose tissue has long been known to produce hormones, and recent research has revealed that even bone tissue has endocrine functions. Figure 17.2 Endocrine System Endocrine glands and cells are located throughout the body and play an important role in homeostasis. The ductless endocrine glands are not to be confused with the body’s exocrine system, whose glands release their secretions through ducts. Examples of exocrine glands include the sebaceous and sweat glands of the skin. As just noted, the pancreas also has an exocrine function: most of its cells secrete pancreatic juice through the pancreatic and accessory ducts to the lumen of the small intestine. Other Types of Chemical Signaling In endocrine signaling, hormones secreted into the extracellular fluid diffuse into the blood or lymph, and can then travel great distances throughout the body. In contrast, autocrine signaling takes place within the same cell. An autocrine (auto- = “self”) is a chemical that elicits a response in the same cell that secreted it. Interleukin-1, or IL-1, is a signaling molecule that plays an important role in inflammatory response. The cells that secrete IL-1 have receptors on their cell surface that bind these molecules, resulting in autocrine signaling. Local intercellular communication is the province of the paracrine, also called a paracrine factor, which is a chemical that induces a response in neighboring cells. Although paracrines may enter the bloodstream, their concentration is generally too low to elicit a response from distant tissues. A familiar example to those with asthma is histamine, a paracrine that is released by immune cells in the bronchial tree. Histamine causes the smooth muscle cells of the bronchi to constrict, narrowing the airways. Another example is the neurotransmitters of the nervous system, which act only locally within the synaptic cleft. CAREER CONNECTION Endocrinologist Endocrinology is a specialty in the field of medicine that focuses on the treatment of endocrine system disorders. Endocrinologists—medical doctors who specialize in this field—are experts in treating diseases associated with hormonal systems, ranging from thyroid disease to diabetes mellitus. Endocrine surgeons treat endocrine disease through the removal, or resection, of the affected endocrine gland. Patients who are referred to endocrinologists may have signs and symptoms or blood test results that suggest excessive or impaired functioning of an endocrine gland or endocrine cells. The endocrinologist may order additional blood tests to determine whether the patient’s hormonal levels are abnormal, or they may stimulate or suppress the function of the suspect endocrine gland and then have blood taken for analysis. Treatment varies according to the diagnosis. Some endocrine disorders, such as type 2 diabetes, may respond to lifestyle changes such as modest weight loss, adoption of a healthy diet, and regular physical activity. Other disorders may require medication, such as hormone replacement, and routine monitoring by the endocrinologist. These include disorders of the pituitary gland that can affect growth and disorders of the thyroid gland that can result in a variety of metabolic problems. Some patients experience health problems as a result of the normal decline in hormones that can accompany aging. These patients can consult with an endocrinologist to weigh the risks and benefits of hormone replacement therapy intended to boost their natural levels of reproductive hormones. In addition to treating patients, endocrinologists may be involved in research to improve the understanding of endocrine system disorders and develop new treatments for these diseases. Hormones - Identify the three major classes of hormones on the basis of chemical structure - Compare and contrast intracellular and cell membrane hormone receptors - Describe signaling pathways that involve cAMP and IP3 - Identify several factors that influence a target cell’s response - Discuss the role of feedback loops and humoral, hormonal, and neural stimuli in hormone control Although a given hormone may travel throughout the body in the bloodstream, it will affect the activity only of its target cells; that is, cells with receptors for that particular hormone. Once the hormone binds to the receptor, a chain of events is initiated that leads to the target cell’s response. Hormones play a critical role in the regulation of physiological processes because of the target cell responses they regulate. These responses contribute to human reproduction, growth and development of body tissues, metabolism, fluid, and electrolyte balance, sleep, and many other body functions. The major hormones of the human body and their effects are identified in Table 17.2. Endocrine Glands and Their Major Hormones \| Endocrine gland \| Associated hormones \| Chemical class \| Effect \| \|---\|---\|---\|---\| \| Pituitary (anterior) \| Growth hormone (GH) \| Protein \| Promotes growth of body tissues \| \| Pituitary (anterior) \| Prolactin (PRL) \| Peptide \| Promotes milk production \| \| Pituitary (anterior) \| Thyroid-stimulating hormone (TSH) \| Glycoprotein \| Stimulates thyroid hormone release \| \| Pituitary (anterior) \| Adrenocorticotropic hormone (ACTH) \| Peptide \| Stimulates hormone release by adrenal cortex \| \| Pituitary (anterior) \| Follicle-stimulating hormone (FSH) \| Glycoprotein \| Stimulates gamete production \| \| Pituitary (anterior) \| Luteinizing hormone (LH) \| Glycoprotein \| Stimulates androgen production by gonads \| \| Pituitary (posterior) \| Antidiuretic hormone (ADH) \| Peptide \| Stimulates water reabsorption by kidneys \| \| Pituitary (posterior) \| Oxytocin \| Peptide \| Stimulates uterine contractions during childbirth \| \| Thyroid \| Thyroxine (T4), triiodothyronine (T3) \| Amine \| Stimulate basal metabolic rate \| \| Thyroid \| Calcitonin \| Peptide \| Reduces blood Ca2+ levels \| \| Parathyroid \| Parathyroid hormone (PTH) \| Peptide \| Increases blood Ca2+ levels \| \| Adrenal (cortex) \| Aldosterone \| Steroid \| Increases blood Na+ levels \| \| Adrenal (cortex) \| Cortisol, corticosterone, cortisone \| Steroid \| Increase blood glucose levels \| \| Adrenal (medulla) \| Epinephrine, norepinephrine \| Amine \| Stimulate fight-or-flight response \| \| Pineal \| Melatonin \| Amine \| Regulates sleep cycles \| \| Pancreas \| Insulin \| Protein \| Reduces blood glucose levels \| \| Pancreas \| Glucagon \| Protein \| Increases blood glucose levels \| \| Testes \| Testosterone \| Steroid \| Stimulates development of male secondary sex characteristics and sperm production \| \| Ovaries \| Estrogens and progesterone \| Steroid \| Stimulate development of female secondary sex characteristics and prepare the body for childbirth \| Table 17.2 Types of Hormones The hormones of the human body can be divided into two major groups on the basis of their chemical structure. Hormones derived from amino acids include amines, peptides, and proteins. Those derived from lipids include steroids (Figure 17.3). These chemical groups affect a hormone’s distribution, the type of receptors it binds to, and other aspects of its function. Figure 17.3 Amine, Peptide, Protein, and Steroid Hormone Structure Amine Hormones Hormones derived from the modification of amino acids are referred to as amine hormones. Typically, the original structure of the amino acid is modified such that a –COOH, or carboxyl, group is removed, whereas the −NH+3−NH3+ Amine hormones are synthesized from the amino acids tryptophan or tyrosine. An example of a hormone derived from tryptophan is melatonin, which is secreted by the pineal gland and helps regulate circadian rhythm. Tyrosine derivatives include the metabolism-regulating thyroid hormones, as well as the catecholamines, such as epinephrine, norepinephrine, and dopamine. Epinephrine and norepinephrine are secreted by the adrenal medulla and play a role in the fight-or-flight response, whereas dopamine is secreted by the hypothalamus and inhibits the release of certain anterior pituitary hormones. Peptide and Protein Hormones Whereas the amine hormones are derived from a single amino acid, peptide and protein hormones consist of multiple amino acids that link to form an amino acid chain. Peptide hormones consist of short chains of amino acids, whereas protein hormones are longer polypeptides. Both types are synthesized like other body proteins: DNA is transcribed into mRNA, which is translated into an amino acid chain. Examples of peptide hormones include antidiuretic hormone (ADH), a pituitary hormone important in fluid balance, and atrial-natriuretic peptide, which is produced by the heart and helps to decrease blood pressure. Some examples of protein hormones include growth hormone, which is produced by the pituitary gland, and follicle-stimulating hormone (FSH), which has an attached carbohydrate group and is thus classified as a glycoprotein. FSH helps stimulate the maturation of eggs in the ovaries and sperm in the testes. Steroid Hormones The primary hormones derived from lipids are steroids. Steroid hormones are derived from the lipid cholesterol. For example, the reproductive hormones testosterone and the estrogens—which are produced by the gonads (testes and ovaries)—are steroid hormones. The adrenal glands produce the steroid hormone aldosterone, which is involved in osmoregulation, and cortisol, which plays a role in metabolism. Like cholesterol, steroid hormones are not soluble in water (they are hydrophobic). Because blood is water-based, lipid-derived hormones must travel to their target cell bound to a transport protein. This more complex structure extends the half-life of steroid hormones much longer than that of hormones derived from amino acids. A hormone’s half-life is the time required for half the concentration of the hormone to be degraded. For example, the lipid-derived hormone cortisol has a half-life of approximately 60 to 90 minutes. In contrast, the amino acid–derived hormone epinephrine has a half-life of approximately one minute. Pathways of Hormone Action The message a hormone sends is received by a hormone receptor, a protein located either inside the cell or within the cell membrane. The receptor will process the message by initiating other signaling events or cellular mechanisms that result in the target cell’s response. Hormone receptors recognize molecules with specific shapes and side groups, and respond only to those hormones that are recognized. The same type of receptor may be located on cells in different body tissues, and trigger somewhat different responses. Thus, the response triggered by a hormone depends not only on the hormone, but also on the target cell. Once the target cell receives the hormone signal, it can respond in a variety of ways. The response may include the stimulation of protein synthesis, activation or deactivation of enzymes, alteration in the permeability of the cell membrane, altered rates of mitosis and cell growth, and stimulation of the secretion of products. Moreover, a single hormone may be capable of inducing different responses in a given cell. Pathways Involving Intracellular Hormone Receptors Intracellular hormone receptors are located inside the cell. Hormones that bind to this type of receptor must be able to cross the cell membrane. Steroid hormones are derived from cholesterol and therefore can readily diffuse through the lipid bilayer of the cell membrane to reach the intracellular receptor (Figure 17.4). Thyroid hormones, which contain benzene rings studded with iodine, are also lipid-soluble and can enter the cell. The location of steroid and thyroid hormone binding differs slightly: a steroid hormone may bind to its receptor within the cytosol or within the nucleus. In either case, this binding generates a hormone-receptor complex that moves toward the chromatin in the cell nucleus and binds to a particular segment of the cell’s DNA. In contrast, thyroid hormones bind to receptors already bound to DNA. For both steroid and thyroid hormones, binding of the hormone-receptor complex with DNA triggers transcription of a target gene to mRNA, which moves to the cytosol and directs protein synthesis by ribosomes. Figure 17.4 Binding of Lipid-Soluble Hormones A steroid hormone directly initiates the production of proteins within a target cell. Steroid hormones easily diffuse through the cell membrane. The hormone binds to its receptor in the cytosol, forming a receptor–hormone complex. The receptor–hormone complex then enters the nucleus and binds to the target gene on the DNA. Transcription of the gene creates a messenger RNA that is translated into the desired protein within the cytoplasm. Pathways Involving Cell Membrane Hormone Receptors Hydrophilic, or water-soluble, hormones are unable to diffuse through the lipid bilayer of the cell membrane and must therefore pass on their message to a receptor located at the surface of the cell. Except for thyroid hormones, which are lipid-soluble, all amino acid–derived hormones bind to cell membrane receptors that are located, at least in part, on the extracellular surface of the cell membrane. Therefore, they do not directly affect the transcription of target genes, but instead initiate a signaling cascade that is carried out by a molecule called a second messenger. In this case, the hormone is called a first messenger. The second messenger used by most hormones is cyclic adenosine monophosphate (cAMP). In the cAMP second messenger system, a water-soluble hormone binds to its receptor in the cell membrane (Step 1 in Figure 17.5). This receptor is associated with an intracellular component called a G protein, and binding of the hormone activates the G-protein component (Step 2). The activated G protein in turn activates an enzyme called adenylyl cyclase, also known as adenylate cyclase (Step 3), which converts adenosine triphosphate (ATP) to cAMP (Step 4). As the second messenger, cAMP activates a type of enzyme called a protein kinase that is present in the cytosol (Step 5). Activated protein kinases initiate a phosphorylation cascade, in which multiple protein kinases phosphorylate (add a phosphate group to) numerous and various cellular proteins, including other enzymes (Step 6). Figure 17.5 Binding of Water-Soluble Hormones Water-soluble hormones cannot diffuse through the cell membrane. These hormones must bind to a surface cell-membrane receptor. The receptor then initiates a cell-signaling pathway within the cell involving G proteins, adenylyl cyclase, the secondary messenger cyclic AMP (cAMP), and protein kinases. In the final step, these protein kinases phosphorylate proteins in the cytoplasm. This activates proteins in the cell that carry out the changes specified by the hormone. The phosphorylation of cellular proteins can trigger a wide variety of effects, from nutrient metabolism to the synthesis of different hormones and other products. The effects vary according to the type of target cell, the G proteins and kinases involved, and the phosphorylation of proteins. Examples of hormones that use cAMP as a second messenger include calcitonin, which is important for bone construction and regulating blood calcium levels; glucagon, which plays a role in blood glucose levels; and thyroid-stimulating hormone, which causes the release of T3 and T4 from the thyroid gland. Overall, the phosphorylation cascade significantly increases the efficiency, speed, and specificity of the hormonal response, as thousands of signaling events can be initiated simultaneously in response to a very low concentration of hormone in the bloodstream. However, the duration of the hormone signal is short, as cAMP is quickly deactivated by the enzyme phosphodiesterase (PDE), which is located in the cytosol. The action of PDE helps to ensure that a target cell’s response ceases quickly unless new hormones arrive at the cell membrane. Importantly, there are also G proteins that decrease the levels of cAMP in the cell in response to hormone binding. For example, when growth hormone–inhibiting hormone (GHIH), also known as somatostatin, binds to its receptors in the pituitary gland, the level of cAMP decreases, thereby inhibiting the secretion of human growth hormone. Not all water-soluble hormones initiate the cAMP second messenger system. One common alternative system uses calcium ions as a second messenger. In this system, G proteins activate the enzyme phospholipase C (PLC), which functions similarly to adenylyl cyclase. Once activated, PLC cleaves a membrane-bound phospholipid into two molecules: diacylglycerol (DAG) and inositol triphosphate (IP3). Like cAMP, DAG activates protein kinases that initiate a phosphorylation cascade. At the same time, IP3 causes calcium ions to be released from storage sites within the cytosol, such as from within the smooth endoplasmic reticulum. The calcium ions then act as second messengers in two ways: they can influence enzymatic and other cellular activities directly, or they can bind to calcium-binding proteins, the most common of which is calmodulin. Upon binding calcium, calmodulin is able to modulate protein kinase within the cell. Examples of hormones that use calcium ions as a second messenger system include angiotensin II, which helps regulate blood pressure through vasoconstriction, and growth hormone–releasing hormone (GHRH), which causes the pituitary gland to release growth hormones. Factors Affecting Target Cell Response You will recall that target cells must have receptors specific to a given hormone if that hormone is to trigger a response. But several other factors influence the target cell response. For example, the presence of a significant level of a hormone circulating in the bloodstream can cause its target cells to decrease their number of receptors for that hormone. This process is called downregulation, and it allows cells to become less reactive to the excessive hormone levels. When the level of a hormone is chronically reduced, target cells engage in upregulation to increase their number of receptors. This process allows cells to be more sensitive to the hormone that is present. Cells can also alter the sensitivity of the receptors themselves to various hormones. Two or more hormones can interact to affect the response of cells in a variety of ways. The three most common types of interaction are as follows: - The permissive effect, in which the presence of one hormone enables another hormone to act. For example, thyroid hormones have complex permissive relationships with certain reproductive hormones. A dietary deficiency of iodine, a component of thyroid hormones, can therefore affect reproductive system development and functioning. - The synergistic effect, in which two hormones with similar effects produce an amplified response. In some cases, two hormones are required for an adequate response. For example, two different reproductive hormones—FSH from the pituitary gland and estrogens from the ovaries—are required for the maturation of female ova (egg cells). - The antagonistic effect, in which two hormones have opposing effects. A familiar example is the effect of two pancreatic hormones, insulin and glucagon. Insulin increases the liver’s storage of glucose as glycogen, decreasing blood glucose, whereas glucagon stimulates the breakdown of glycogen stores, increasing blood glucose. Regulation of Hormone Secretion To prevent abnormal hormone levels and a potential disease state, hormone levels must be tightly controlled. The body maintains this control by balancing hormone production and degradation. Feedback loops govern the initiation and maintenance of most hormone secretion in response to various stimuli. Role of Feedback Loops The contribution of feedback loops to homeostasis will only be briefly reviewed here. Positive feedback loops are characterized by the release of additional hormone in response to an original hormone release. The release of oxytocin during childbirth is a positive feedback loop. The initial release of oxytocin begins to signal the uterine muscles to contract, which pushes the fetus toward the cervix, causing it to stretch. This, in turn, signals the pituitary gland to release more oxytocin, causing labor contractions to intensify. The release of oxytocin decreases after the birth of the child. The more common method of hormone regulation is the negative feedback loop. Negative feedback is characterized by the inhibition of further secretion of a hormone in response to adequate levels of that hormone. This allows blood levels of the hormone to be regulated within a narrow range. An example of a negative feedback loop is the release of glucocorticoid hormones from the adrenal glands, as directed by the hypothalamus and pituitary gland. As glucocorticoid concentrations in the blood rise, the hypothalamus and pituitary gland reduce their signaling to the adrenal glands to prevent additional glucocorticoid secretion (Figure 17.6). Figure 17.6 Negative Feedback Loop The release of adrenal glucocorticoids is stimulated by the release of hormones from the hypothalamus and pituitary gland. This signaling is inhibited when glucocorticoid levels become elevated by causing negative signals to the pituitary gland and hypothalamus. Role of Endocrine Gland Stimuli Reflexes triggered by both chemical and neural stimuli control endocrine activity. These reflexes may be simple, involving only one hormone response, or they may be more complex and involve many hormones, as is the case with the hypothalamic control of various anterior pituitary–controlled hormones. Humoral stimuli are changes in blood levels of non-hormone chemicals, such as nutrients or ions, which cause the release or inhibition of a hormone to, in turn, maintain homeostasis. For example, osmoreceptors in the hypothalamus detect changes in blood osmolarity (the concentration of solutes in the blood plasma). If blood osmolarity is too high, meaning that the blood is not dilute enough, osmoreceptors signal the hypothalamus to release ADH. The hormone causes the kidneys to reabsorb more water and reduce the volume of urine produced. This reabsorption causes a reduction of the osmolarity of the blood, diluting the blood to the appropriate level. The regulation of blood glucose is another example. High blood glucose levels cause the release of insulin from the pancreas, which increases glucose uptake by cells and liver storage of glucose as glycogen. An endocrine gland may also secrete a hormone in response to the presence of another hormone produced by a different endocrine gland. Such hormonal stimuli often involve the hypothalamus, which produces releasing and inhibiting hormones that control the secretion of a variety of pituitary hormones. In addition to these chemical signals, hormones can also be released in response to neural stimuli. A common example of neural stimuli is the activation of the fight-or-flight response by the sympathetic nervous system. When an individual perceives danger, sympathetic neurons signal the adrenal glands to secrete norepinephrine and epinephrine. The two hormones dilate blood vessels, increase the heart and respiratory rate, and suppress the digestive and immune systems. These responses boost the body’s transport of oxygen to the brain and muscles, thereby improving the body’s ability to fight or flee. EVERYDAY CONNECTION Bisphenol A and Endocrine Disruption You may have heard news reports about the effects of a chemical called bisphenol A (BPA) in various types of food packaging. BPA is used in the manufacturing of hard plastics and epoxy resins. Common food-related items that may contain BPA include the lining of aluminum cans, plastic food-storage containers, drinking cups, as well as baby bottles and “sippy” cups. Other uses of BPA include medical equipment, dental fillings, and the lining of water pipes. Research suggests that BPA is an endocrine disruptor, meaning that it negatively interferes with the endocrine system, particularly during the prenatal and postnatal development period. In particular, BPA mimics the hormonal effects of estrogens and has the opposite effect—that of androgens. The U.S. Food and Drug Administration (FDA) notes in their statement about BPA safety that although traditional toxicology studies have supported the safety of low levels of exposure to BPA, recent studies using novel approaches to test for subtle effects have led to some concern about the potential effects of BPA on the brain, behavior, and prostate gland in fetuses, infants, and young children. The FDA is currently facilitating decreased use of BPA in food-related materials. Many US companies have voluntarily removed BPA from baby bottles, “sippy” cups, and the linings of infant formula cans, and most plastic reusable water bottles sold today boast that they are “BPA free.” In contrast, both Canada and the European Union have completely banned the use of BPA in baby products. The potential harmful effects of BPA have been studied in both animal models and humans and include a large variety of health effects, such as developmental delay and disease. For example, prenatal exposure to BPA during the first trimester of human pregnancy may be associated with wheezing and aggressive behavior during childhood. Adults exposed to high levels of BPA may experience altered thyroid signaling and male sexual dysfunction. BPA exposure during the prenatal or postnatal period of development in animal models has been observed to cause neurological delays, changes in brain structure and function, sexual dysfunction, asthma, and increased risk for multiple cancers. In vitro studies have also shown that BPA exposure causes molecular changes that initiate the development of cancers of the breast, prostate, and brain. Although these studies have implicated BPA in numerous ill health effects, some experts caution that some of these studies may be flawed and that more research needs to be done. In the meantime, the FDA recommends that consumers take precautions to limit their exposure to BPA. In addition to purchasing foods in packaging free of BPA, consumers should avoid carrying or storing foods or liquids in bottles with the recycling code 3 or 7. Foods and liquids should not be microwave-heated in any form of plastic: use paper, glass, or ceramics instead. The Pituitary Gland and Hypothalamus - Explain the interrelationships of the anatomy and functions of the hypothalamus and the posterior and anterior lobes of the pituitary gland - Identify the two hormones released from the posterior pituitary, their target cells, and their principal actions - Identify the six hormones produced by the anterior lobe of the pituitary gland, their target cells, their principal actions, and their regulation by the hypothalamus The hypothalamus–pituitary complex can be thought of as the “command center” of the endocrine system. This complex secretes several hormones that directly produce responses in target tissues, as well as hormones that regulate the synthesis and secretion of hormones of other glands. In addition, the hypothalamus–pituitary complex coordinates the messages of the endocrine and nervous systems. In many cases, a stimulus received by the nervous system must pass through the hypothalamus–pituitary complex to be translated into hormones that can initiate a response. The hypothalamus is a structure of the diencephalon of the brain located anterior and inferior to the thalamus (Figure 17.7). It has both neural and endocrine functions, producing and secreting many hormones. In addition, the hypothalamus is anatomically and functionally related to the pituitary gland (or hypophysis), a bean-sized organ suspended from it by a stem called the infundibulum (or pituitary stalk). The pituitary gland is cradled within the sellaturcica of the sphenoid bone of the skull. It consists of two lobes that arise from distinct parts of embryonic tissue: the posterior pituitary (neurohypophysis) is neural tissue, whereas the anterior pituitary (also known as the adenohypophysis) is glandular tissue that develops from the primitive digestive tract. The hormones secreted by the posterior and anterior pituitary, and the intermediate zone between the lobes are summarized in Table 17.3. Figure 17.7 Hypothalamus–Pituitary Complex The hypothalamus region lies inferior and anterior to the thalamus. It connects to the pituitary gland by the stalk-like infundibulum. The pituitary gland consists of an anterior and posterior lobe, with each lobe secreting different hormones in response to signals from the hypothalamus. Pituitary Hormones \| Pituitary lobe \| Associated hormones \| Chemical class \| Effect \| \|---\|---\|---\|---\| \| Anterior \| Growth hormone (GH) \| Protein \| Promotes growth of body tissues \| \| Anterior \| Prolactin (PRL) \| Peptide \| Promotes milk production from mammary glands \| \| Anterior \| Thyroid-stimulating hormone (TSH) \| Glycoprotein \| Stimulates thyroid hormone release from thyroid \| \| Anterior \| Adrenocorticotropic hormone (ACTH) \| Peptide \| Stimulates hormone release by adrenal cortex \| \| Anterior \| Follicle-stimulating hormone (FSH) \| Glycoprotein \| Stimulates gamete production in gonads \| \| Anterior \| Luteinizing hormone (LH) \| Glycoprotein \| Stimulates androgen production by gonads \| \| Posterior \| Antidiuretic hormone (ADH) \| Peptide \| Stimulates water reabsorption by kidneys \| \| Posterior \| Oxytocin \| Peptide \| Stimulates uterine contractions during childbirth \| \| Intermediate zone \| Melanocyte-stimulating hormone \| Peptide \| Stimulates melanin formation in melanocytes \| Table 17.3 Posterior Pituitary The posterior pituitary is actually an extension of the neurons of the paraventricular and supraoptic nuclei of the hypothalamus. The cell bodies of these regions rest in the hypothalamus, but their axons descend as the hypothalamic–hypophyseal tract within the infundibulum, and end in axon terminals that comprise the posterior pituitary (Figure 17.8). Figure 17.8 Posterior Pituitary Neurosecretory cells in the hypothalamus release oxytocin (OT) or ADH into the posterior lobe of the pituitary gland. These hormones are stored or released into the blood via the capillary plexus. The posterior pituitary gland does not produce hormones, but rather stores and secretes hormones produced by the hypothalamus. The paraventricular nuclei produce the hormone oxytocin, whereas the supraoptic nuclei produce ADH. These hormones travel along the axons into storage sites in the axon terminals of the posterior pituitary. In response to signals from the same hypothalamic neurons, the hormones are released from the axon terminals into the bloodstream. Oxytocin When fetal development is complete, the peptide-derived hormone oxytocin (tocia- = “childbirth”) stimulates uterine contractions and dilation of the cervix. Throughout most of pregnancy, oxytocin hormone receptors are not expressed at high levels in the uterus. Toward the end of pregnancy, the synthesis of oxytocin receptors in the uterus increases, and the smooth muscle cells of the uterus become more sensitive to its effects. Oxytocin is continually released throughout childbirth through a positive feedback mechanism. As noted earlier, oxytocin prompts uterine contractions that push the fetal head toward the cervix. In response, cervical stretching stimulates additional oxytocin to be synthesized by the hypothalamus and released from the pituitary. This increases the intensity and effectiveness of uterine contractions and prompts additional dilation of the cervix. The feedback loop continues until birth. Although the mother’s high blood levels of oxytocin begin to decrease immediately following birth, oxytocin continues to play a role in maternal and newborn health. First, oxytocin is necessary for the milk ejection reflex (commonly referred to as “let-down”) in breastfeeding women. As the newborn begins suckling, sensory receptors in the nipples transmit signals to the hypothalamus. In response, oxytocin is secreted and released into the bloodstream. Within seconds, cells in the mother’s milk ducts contract, ejecting milk into the infant’s mouth. Secondly, in both males and females, oxytocin is thought to contribute to parent–newborn bonding, known as attachment. Oxytocin is also thought to be involved in feelings of love and closeness, as well as in the sexual response. Antidiuretic Hormone (ADH) The solute concentration of the blood, or blood osmolarity, may change in response to the consumption of certain foods and fluids, as well as in response to disease, injury, medications, or other factors. Blood osmolarity is constantly monitored by osmoreceptors—specialized cells within the hypothalamus that are particularly sensitive to the concentration of sodium ions and other solutes. In response to high blood osmolarity, which can occur during dehydration or following a very salty meal, the osmoreceptors signal the posterior pituitary to release antidiuretic hormone (ADH). The target cells of ADH are located in the tubular cells of the kidneys. Its effect is to increase epithelial permeability to water, allowing increased water reabsorption. The more water reabsorbed from the filtrate, the greater the amount of water that is returned to the blood and the less that is excreted in the urine. A greater concentration of water results in a reduced concentration of solutes. ADH is also known as vasopressin because, in very high concentrations, it causes constriction of blood vessels, which increases blood pressure by increasing peripheral resistance. The release of ADH is controlled by a negative feedback loop. As blood osmolarity decreases, the hypothalamic osmoreceptors sense the change and prompt a corresponding decrease in the secretion of ADH. As a result, less water is reabsorbed from the urine filtrate. Interestingly, drugs can affect the secretion of ADH. For example, alcohol consumption inhibits the release of ADH, resulting in increased urine production that can eventually lead to dehydration and a hangover. A disease called diabetes insipidus is characterized by chronic underproduction of ADH that causes chronic dehydration. Because little ADH is produced and secreted, not enough water is reabsorbed by the kidneys. Although patients feel thirsty, and increase their fluid consumption, this doesn’t effectively decrease the solute concentration in their blood because ADH levels are not high enough to trigger water reabsorption in the kidneys. Electrolyte imbalances can occur in severe cases of diabetes insipidus. Anterior Pituitary The anterior pituitary originates from the digestive tract in the embryo and migrates toward the brain during fetal development. There are three regions: the pars distalis is the most anterior, the pars intermedia is adjacent to the posterior pituitary, and the pars tuberalis is a slender “tube” that wraps the infundibulum. Recall that the posterior pituitary does not synthesize hormones, but merely stores them. In contrast, the anterior pituitary does manufacture hormones. However, the secretion of hormones from the anterior pituitary is regulated by two classes of hormones. These hormones—secreted by the hypothalamus—are the releasing hormones that stimulate the secretion of hormones from the anterior pituitary and the inhibiting hormones that inhibit secretion. Hypothalamic hormones are secreted by neurons, but enter the anterior pituitary through blood vessels (Figure 17.9). Within the infundibulum is a bridge of capillaries that connects the hypothalamus to the anterior pituitary. This network, called the hypophyseal portal system, allows hypothalamic hormones to be transported to the anterior pituitary without first entering the systemic circulation. The system originates from the superior hypophyseal artery, which branches off the carotid arteries and transports blood to the hypothalamus. The branches of the superior hypophyseal artery form the hypophyseal portal system (see Figure 17.9). Hypothalamic releasing and inhibiting hormones travel through a primary capillary plexus to the portal veins, which carry them into the anterior pituitary. Hormones produced by the anterior pituitary (in response to releasing hormones) enter a secondary capillary plexus, and from there drain into the circulation. Figure 17.9 Anterior Pituitary The anterior pituitary manufactures seven hormones. The hypothalamus produces separate hormones that stimulate or inhibit hormone production in the anterior pituitary. Hormones from the hypothalamus reach the anterior pituitary via the hypophyseal portal system. The anterior pituitary produces seven hormones. These are the growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), beta endorphin, and prolactin. Of the hormones of the anterior pituitary, TSH, ACTH, FSH, and LH are collectively referred to as tropic hormones (trope- = “turning”) because they turn on or off the function of other endocrine glands. Growth Hormone The endocrine system regulates the growth of the human body, protein synthesis, and cellular replication. A major hormone involved in this process is growth hormone (GH), also called somatotropin—a protein hormone produced and secreted by the anterior pituitary gland. Its primary function is anabolic; it promotes protein synthesis and tissue building through direct and indirect mechanisms (Figure 17.10). GH levels are controlled by the release of GHRH and GHIH (also known as somatostatin) from the hypothalamus. Figure 17.10 Hormonal Regulation of Growth Growth hormone (GH) directly accelerates the rate of protein synthesis in skeletal muscle and bones. Insulin-like growth factor 1 (IGF-1) is activated by growth hormone and indirectly supports the formation of new proteins in muscle cells and bone. A glucose-sparing effect occurs when GH stimulates lipolysis, or the breakdown of adipose tissue, releasing fatty acids into the blood. As a result, many tissues switch from glucose to fatty acids as their main energy source, which means that less glucose is taken up from the bloodstream. GH also initiates the diabetogenic effect in which GH stimulates the liver to break down glycogen to glucose, which is then deposited into the blood. The name “diabetogenic” is derived from the similarity in elevated blood glucose levels observed between individuals with untreated diabetes mellitus and individuals experiencing GH excess. Blood glucose levels rise as the result of a combination of glucose-sparing and diabetogenic effects. GH indirectly mediates growth and protein synthesis by triggering the liver and other tissues to produce a group of proteins called insulin-like growth factors (IGFs). These proteins enhance cellular proliferation and inhibit apoptosis, or programmed cell death. IGFs stimulate cells to increase their uptake of amino acids from the blood for protein synthesis. Skeletal muscle and cartilage cells are particularly sensitive to stimulation from IGFs. Dysfunction of the endocrine system’s control of growth can result in several disorders. For example, gigantism is a disorder in children that is caused by the secretion of abnormally large amounts of GH, resulting in excessive growth. A similar condition in adults is acromegaly, a disorder that results in the growth of bones in the face, hands, and feet in response to excessive levels of GH in individuals who have stopped growing. Abnormally low levels of GH in children can cause growth impairment—a disorder called pituitary dwarfism (also known as growth hormone deficiency). Thyroid-Stimulating Hormone The activity of the thyroid gland is regulated by thyroid-stimulating hormone (TSH), also called thyrotropin. TSH is released from the anterior pituitary in response to thyrotropin-releasing hormone (TRH) from the hypothalamus. As discussed shortly, it triggers the secretion of thyroid hormones by the thyroid gland. In a classic negative feedback loop, elevated levels of thyroid hormones in the bloodstream then trigger a drop in production of TRH and subsequently TSH. Adrenocorticotropic Hormone The adrenocorticotropic hormone (ACTH), also called corticotropin, stimulates the adrenal cortex (the more superficial “bark” of the adrenal glands) to secrete corticosteroid hormones such as cortisol. ACTH come from a precursor molecule known as pro-opiomelanotropin (POMC) which produces several biologically active molecules when cleaved, including ACTH, melanocyte-stimulating hormone, and the brain opioid peptides known as endorphins. The release of ACTH is regulated by the corticotropin-releasing hormone (CRH) from the hypothalamus in response to normal physiologic rhythms. A variety of stressors can also influence its release, and the role of ACTH in the stress response is discussed later in this chapter. Follicle-Stimulating Hormone and Luteinizing Hormone The endocrine glands secrete a variety of hormones that control the development and regulation of the reproductive system (these glands include the anterior pituitary, the adrenal cortex, and the gonads—the testes in males and the ovaries in females). Much of the development of the reproductive system occurs during puberty and is marked by the development of sex-specific characteristics in both male and female adolescents. Puberty is initiated by gonadotropin-releasing hormone (GnRH), a hormone produced and secreted by the hypothalamus. GnRH stimulates the anterior pituitary to secrete gonadotropins—hormones that regulate the function of the gonads. The levels of GnRH are regulated through a negative feedback loop; high levels of reproductive hormones inhibit the release of GnRH. Throughout life, gonadotropins regulate reproductive function and, in the case of women, the onset and cessation of reproductive capacity. The gonadotropins include two glycoprotein hormones: follicle-stimulating hormone (FSH) stimulates the production and maturation of sex cells, or gametes, including ova in women and sperm in men. FSH also promotes follicular growth; these follicles then release estrogens in the female ovaries. Luteinizing hormone (LH) triggers ovulation in women, as well as the production of estrogens and progesterone by the ovaries. LH stimulates production of testosterone by the male testes. Prolactin As its name implies, prolactin (PRL) promotes lactation (milk production) in women. During pregnancy, it contributes to development of the mammary glands, and after birth, it stimulates the mammary glands to produce breast milk. However, the effects of prolactin depend heavily upon the permissive effects of estrogens, progesterone, and other hormones. And as noted earlier, the let-down of milk occurs in response to stimulation from oxytocin. In a non-pregnant woman, prolactin secretion is inhibited by prolactin-inhibiting hormone (PIH), which is actually the neurotransmitter dopamine, and is released from neurons in the hypothalamus. Only during pregnancy do prolactin levels rise in response to prolactin-releasing hormone (PRH) from the hypothalamus. Intermediate Pituitary: Melanocyte-Stimulating Hormone The cells in the zone between the pituitary lobes secrete a hormone known as melanocyte-stimulating hormone (MSH) that is formed by cleavage of the pro-opiomelanocortin (POMC) precursor protein. Local production of MSH in the skin is responsible for melanin production in response to UV light exposure. The role of MSH made by the pituitary is more complicated. For instance, people with lighter skin generally have the same amount of MSH as people with darker skin. Nevertheless, this hormone is capable of darkening of the skin by inducing melanin production in the skin’s melanocytes. Women also show increased MSH production during pregnancy; in combination with estrogens, it can lead to darker skin pigmentation, especially the skin of the areolas and labia minora. Figure 17.11 is a summary of the pituitary hormones and their principal effects. Figure 17.11 Major Pituitary Hormones Major pituitary hormones and their target organs. INTERACTIVE LINK Visit this link to watch an animation showing the role of the hypothalamus and the pituitary gland. Which hormone is released by the pituitary to stimulate the thyroid gland? The Thyroid Gland - Describe the location and anatomy of the thyroid gland - Discuss the synthesis of triiodothyronine and thyroxine - Explain the role of thyroid hormones in the regulation of basal metabolism - Identify the hormone produced by the parafollicular cells of the thyroid A butterfly-shaped organ, the thyroid gland is located anterior to the trachea, just inferior to the larynx (Figure 17.12). The medial region, called the isthmus, is flanked by wing-shaped left and right lobes. Each of the thyroid lobes are embedded with parathyroid glands, primarily on their posterior surfaces. The tissue of the thyroid gland is composed mostly of thyroid follicles. The follicles are made up of a central cavity filled with a sticky fluid called colloid. Surrounded by a wall of epithelial follicle cells, the colloid is the center of thyroid hormone production, and that production is dependent on the hormones’ essential and unique component: iodine. Figure 17.12 Thyroid Gland The thyroid gland is located in the neck where it wraps around the trachea. (a) Anterior view of the thyroid gland. (b) Posterior view of the thyroid gland. (c) The glandular tissue is composed primarily of thyroid follicles. The larger parafollicular cells often appear within the matrix of follicle cells. LM × 1332. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Synthesis and Release of Thyroid Hormones Hormones are produced in the colloid when atoms of the mineral iodine attach to a glycoprotein, called thyroglobulin, that is secreted into the colloid by the follicle cells. The following steps outline the hormones’ assembly: - Binding of TSH to its receptors in the follicle cells of the thyroid gland causes the cells to actively transport iodide ions (I–) across their cell membrane, from the bloodstream into the cytosol. As a result, the concentration of iodide ions “trapped” in the follicular cells is many times higher than the concentration in the bloodstream. - Iodide ions then move to the lumen of the follicle cells that border the colloid. There, the ions undergo oxidation (their negatively charged electrons are removed). The oxidation of two iodide ions (2 I–) results in iodine (I2), which passes through the follicle cell membrane into the colloid. - In the colloid, peroxidase enzymes link the iodine to the tyrosine amino acids in thyroglobulin to produce two intermediaries: a tyrosine attached to one iodine and a tyrosine attached to two iodines. When one of each of these intermediaries is linked by covalent bonds, the resulting compound is triiodothyronine (T3), a thyroid hormone with three iodines. Much more commonly, two copies of the second intermediary bond, forming tetraiodothyronine, also known as thyroxine (T4), a thyroid hormone with four iodines. These hormones remain in the colloid center of the thyroid follicles until TSH stimulates endocytosis of colloid back into the follicle cells. There, lysosomal enzymes break apart the thyroglobulin colloid, releasing free T3 and T4, which diffuse across the follicle cell membrane and enter the bloodstream. In the bloodstream, less than one percent of the circulating T3 and T4 remains unbound. This free T3 and T4 can cross the lipid bilayer of cell membranes and be taken up by cells. The remaining 99 percent of circulating T3 and T4 is bound to specialized transport proteins called thyroxine-binding globulins (TBGs), to albumin, or to other plasma proteins. This “packaging” prevents their free diffusion into body cells. When blood levels of T3 and T4 begin to decline, bound T3 and T4 are released from these plasma proteins and readily cross the membrane of target cells. T3 is more potent than T4, and many cells convert T4 to T3through the removal of an iodine atom. Regulation of TH Synthesis The release of T3 and T4 from the thyroid gland is regulated by thyroid-stimulating hormone (TSH). As shown in Figure 17.13, low blood levels of T3 and T4 stimulate the release of thyrotropin-releasing hormone (TRH) from the hypothalamus, which triggers secretion of TSH from the anterior pituitary. In turn, TSH stimulates the thyroid gland to secrete T3 and T4. The levels of TRH, TSH, T3, and T4 are regulated by a negative feedback system in which increasing levels of T3 and T4 decrease the production and secretion of TSH. Figure 17.13 Classic Negative Feedback Loop A classic negative feedback loop controls the regulation of thyroid hormone levels. Functions of Thyroid Hormones The thyroid hormones, T3 and T4, are often referred to as metabolic hormones because their levels influence the body’s basal metabolic rate, the amount of energy used by the body at rest. When T3 and T4 bind to intracellular receptors located on the mitochondria, they cause an increase in nutrient breakdown and the use of oxygen to produce ATP. In addition, T3 and T4 initiate the transcription of genes involved in glucose oxidation. Although these mechanisms prompt cells to produce more ATP, the process is inefficient, and an abnormally increased level of heat is released as a byproduct of these reactions. This so-called calorigenic effect (calor- = “heat”) raises body temperature. Adequate levels of thyroid hormones are also required for protein synthesis and for fetal and childhood tissue development and growth. They are especially critical for normal development of the nervous system both in utero and in early childhood, and they continue to support neurological function in adults. As noted earlier, these thyroid hormones have a complex interrelationship with reproductive hormones, and deficiencies can influence libido, fertility, and other aspects of reproductive function. Finally, thyroid hormones increase the body’s sensitivity to catecholamines (epinephrine and norepinephrine) from the adrenal medulla by upregulation of receptors in the blood vessels. When levels of T3 and T4 hormones are excessive, this effect accelerates the heart rate, strengthens the heartbeat, and increases blood pressure. Because thyroid hormones regulate metabolism, heat production, protein synthesis, and many other body functions, thyroid disorders can have severe and widespread consequences. DISORDERS OF THE... Endocrine System: Iodine Deficiency, Hypothyroidism, and Hyperthyroidism As discussed above, dietary iodine is required for the synthesis of T3 and T4. But for much of the world’s population, foods do not provide adequate levels of this mineral, because the amount varies according to the level in the soil in which the food was grown, as well as the irrigation and fertilizers used. Marine fish and shrimp tend to have high levels because they concentrate iodine from seawater, but many people in landlocked regions lack access to seafood. Thus, the primary source of dietary iodine in many countries is iodized salt. Fortification of salt with iodine began in the United States in 1924, and international efforts to iodize salt in the world’s poorest nations continue today. Dietary iodine deficiency can result in the impaired ability to synthesize T3 and T4, leading to a variety of severe disorders. When T3 and T4 cannot be produced, TSH is secreted in increasing amounts. As a result of this hyperstimulation, thyroglobulin accumulates in the thyroid gland follicles, increasing their deposits of colloid. The accumulation of colloid increases the overall size of the thyroid gland, a condition called a goiter (Figure 17.14). A goiter is only a visible indication of the deficiency. Other iodine deficiency disorders include impaired growth and development, decreased fertility, and prenatal and infant death. Moreover, iodine deficiency is the primary cause of preventable mental retardation worldwide. Neonatal hypothyroidism (cretinism) is characterized by cognitive deficits, short stature, and sometimes deafness and muteness in children and adults born to mothers who were iodine-deficient during pregnancy. Figure 17.14 Goiter (credit: “Almazi”/Wikimedia Commons) In areas of the world with access to iodized salt, dietary deficiency is rare. Instead, inflammation of the thyroid gland is the more common cause of low blood levels of thyroid hormones. Called hypothyroidism, the condition is characterized by a low metabolic rate, weight gain, cold extremities, constipation, reduced libido, menstrual irregularities, and reduced mental activity. In contrast, hyperthyroidism—an abnormally elevated blood level of thyroid hormones—is often caused by a pituitary or thyroid tumor. In Graves’ disease, the hyperthyroid state results from an autoimmune reaction in which antibodies overstimulate the follicle cells of the thyroid gland. Hyperthyroidism can lead to an increased metabolic rate, excessive body heat and sweating, diarrhea, weight loss, tremors, and increased heart rate. The person’s eyes may bulge (called exophthalmos) as antibodies produce inflammation in the soft tissues of the orbits. The person may also develop a goiter. Calcitonin The thyroid gland also secretes a hormone called calcitonin that is produced by the parafollicular cells (also called C cells) that stud the tissue between distinct follicles. Calcitonin is released in response to a rise in blood calcium levels. It appears to have a function in decreasing blood calcium concentrations by: - Inhibiting the activity of osteoclasts, bone cells that release calcium into the circulation by degrading bone matrix - Increasing osteoblastic activity - Decreasing calcium absorption in the intestines - Increasing calcium loss in the urine However, these functions are usually not significant in maintaining calcium homeostasis, so the importance of calcitonin is not entirely understood. Pharmaceutical preparations of calcitonin are sometimes prescribed to reduce osteoclast activity in people with osteoporosis and to reduce the degradation of cartilage in people with osteoarthritis. The hormones secreted by thyroid are summarized in Table 17.4. Thyroid Hormones \| Associated hormones \| Chemical class \| Effect \| \|---\|---\|---\| \| Thyroxine (T4), triiodothyronine (T3) \| Amine \| Stimulate basal metabolic rate \| \| Calcitonin \| Peptide \| Reduces blood Ca2+ levels \| Table 17.4 Of course, calcium is critical for many other biological processes. It is a second messenger in many signaling pathways, and is essential for muscle contraction, nerve impulse transmission, and blood clotting. Given these roles, it is not surprising that blood calcium levels are tightly regulated by the endocrine system. The organs involved in the regulation are the parathyroid glands. The Parathyroid Glands - Describe the location and structure of the parathyroid glands - Describe the hormonal control of blood calcium levels - Discuss the physiological response of parathyroid dysfunction The parathyroid glands are tiny, round structures usually found embedded in the posterior surface of the thyroid gland (Figure 17.15). A thick connective tissue capsule separates the glands from the thyroid tissue. Most people have four parathyroid glands, but occasionally there are more in tissues of the neck or chest. The function of one type of parathyroid cells, the oxyphil cells, is not clear. The primary functional cells of the parathyroid glands are the chief cells. These epithelial cells produce and secrete the parathyroid hormone (PTH), the major hormone involved in the regulation of blood calcium levels. Figure 17.15 Parathyroid Glands The small parathyroid glands are embedded in the posterior surface of the thyroid gland. LM × 760. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK View the University of Michigan WebScope to explore the tissue sample in greater detail. The parathyroid glands produce and secrete PTH, a peptide hormone, in response to low blood calcium levels (Figure 17.16). PTH secretion causes the release of calcium from the bones by stimulating osteoclasts, which secrete enzymes that degrade bone and release calcium into the interstitial fluid. PTH also inhibits osteoblasts, the cells involved in bone deposition, thereby sparing blood calcium. PTH causes increased reabsorption of calcium (and magnesium) in the kidney tubules from the urine filtrate. In addition, PTH initiates the production of the steroid hormone calcitriol (also known as 1,25-dihydroxyvitamin D), which is the active form of vitamin D3, in the kidneys. Calcitriol then stimulates increased absorption of dietary calcium by the intestines. A negative feedback loop regulates the levels of PTH, with rising blood calcium levels inhibiting further release of PTH. Figure 17.16 Parathyroid Hormone in Maintaining Blood Calcium Homeostasis Parathyroid hormone increases blood calcium levels when they drop too low. Conversely, calcitonin, which is released from the thyroid gland, decreases blood calcium levels when they become too high. These two mechanisms constantly maintain blood calcium concentration at homeostasis. Abnormally high activity of the parathyroid gland can cause hyperparathyroidism, a disorder caused by an overproduction of PTH that results in excessive calcium reabsorption from bone. Hyperparathyroidism can significantly decrease bone density, leading to spontaneous fractures or deformities. As blood calcium levels rise, cell membrane permeability to sodium is decreased, and the responsiveness of the nervous system is reduced. At the same time, calcium deposits may collect in the body’s tissues and organs, impairing their functioning. In contrast, abnormally low blood calcium levels may be caused by parathyroid hormone deficiency, called hypoparathyroidism, which may develop following injury or surgery involving the thyroid gland. Low blood calcium increases membrane permeability to sodium, resulting in muscle twitching, cramping, spasms, or convulsions. Severe deficits can paralyze muscles, including those involved in breathing, and can be fatal. When blood calcium levels are high, calcitonin is produced and secreted by the parafollicular cells of the thyroid gland. As discussed earlier, calcitonin inhibits the activity of osteoclasts, reduces the absorption of dietary calcium in the intestine, and signals the kidneys to reabsorb less calcium, resulting in larger amounts of calcium excreted in the urine. The Adrenal Glands - Describe the location and structure of the adrenal glands - Identify the hormones produced by the adrenal cortex and adrenal medulla, and summarize their target cells and effects The adrenal glands are wedges of glandular and neuroendocrine tissue adhering to the top of the kidneys by a fibrous capsule (Figure 17.17). The adrenal glands have a rich blood supply and experience one of the highest rates of blood flow in the body. They are served by several arteries branching off the aorta, including the suprarenal and renal arteries. Blood flows to each adrenal gland at the adrenal cortex and then drains into the adrenal medulla. Adrenal hormones are released into the circulation via the left and right suprarenal veins. Figure 17.17 Adrenal Glands Both adrenal glands sit atop the kidneys and are composed of an outer cortex and an inner medulla, all surrounded by a connective tissue capsule. The cortex can be subdivided into additional zones, all of which produce different types of hormones. LM × 204. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK View the University of Michigan WebScope to explore the tissue sample in greater detail. The adrenal gland consists of an outer cortex of glandular tissue and an inner medulla of nervous tissue. The cortex itself is divided into three zones: the zona glomerulosa, the zona fasciculata, and the zona reticularis. Each region secretes its own set of hormones. The adrenal cortex, as a component of the hypothalamic-pituitary-adrenal (HPA) axis, secretes steroid hormones important for the regulation of the long-term stress response, blood pressure and blood volume, nutrient uptake and storage, fluid and electrolyte balance, and inflammation. The HPA axis involves the stimulation of hormone release of adrenocorticotropic hormone (ACTH) from the pituitary by the hypothalamus. ACTH then stimulates the adrenal cortex to produce the hormone cortisol. This pathway will be discussed in more detail below. The adrenal medulla is neuroendocrine tissue composed of postganglionic sympathetic nervous system (SNS) neurons. It is really an extension of the autonomic nervous system, which regulates homeostasis in the body. The sympathomedullary (SAM) pathway involves the stimulation of the medulla by impulses from the hypothalamus via neurons from the thoracic spinal cord. The medulla is stimulated to secrete the amine hormones epinephrine and norepinephrine. One of the major functions of the adrenal gland is to respond to stress. Stress can be either physical or psychological or both. Physical stresses include exposing the body to injury, walking outside in cold and wet conditions without a coat on, or malnutrition. Psychological stresses include the perception of a physical threat, a fight with a loved one, or just a bad day at school. The body responds in different ways to short-term stress and long-term stress following a pattern known as the general adaptation syndrome (GAS). Stage one of GAS is called the alarm reaction. This is short-term stress, the fight-or-flight response, mediated by the hormones epinephrine and norepinephrine from the adrenal medulla via the SAM pathway. Their function is to prepare the body for extreme physical exertion. Once this stress is relieved, the body quickly returns to normal. The section on the adrenal medulla covers this response in more detail. If the stress is not soon relieved, the body adapts to the stress in the second stage called the stage of resistance. If a person is starving for example, the body may send signals to the gastrointestinal tract to maximize the absorption of nutrients from food. If the stress continues for a longer term however, the body responds with symptoms quite different than the fight-or-flight response. During the stage of exhaustion, individuals may begin to suffer depression, the suppression of their immune response, severe fatigue, or even a fatal heart attack. These symptoms are mediated by the hormones of the adrenal cortex, especially cortisol, released as a result of signals from the HPA axis. Adrenal hormones also have several non–stress-related functions, including the increase of blood sodium and glucose levels, which will be described in detail below. Adrenal Cortex The adrenal cortex consists of multiple layers of lipid-storing cells that occur in three structurally distinct regions. Each of these regions produces different hormones. INTERACTIVE LINK Visit this link to view an animation describing the location and function of the adrenal glands. Which hormone produced by the adrenal glands is responsible for the mobilization of energy stores? Hormones of the Zona Glomerulosa The most superficial region of the adrenal cortex is the zona glomerulosa, which produces a group of hormones collectively referred to as mineralocorticoids because of their effect on body minerals, especially sodium and potassium. These hormones are essential for fluid and electrolyte balance. Aldosterone is the major mineralocorticoid. It is important in the regulation of the concentration of sodium and potassium ions in urine, sweat, and saliva. For example, it is released in response to elevated blood K+, low blood Na+, low blood pressure, or low blood volume. In response, aldosterone increases the excretion of K+ and the retention of Na+, which in turn increases blood volume and blood pressure. Its secretion is prompted when CRH from the hypothalamus triggers ACTH release from the anterior pituitary. Aldosterone is also a key component of the renin-angiotensin-aldosterone system (RAAS) in which specialized cells of the kidneys secrete the enzyme renin in response to low blood volume or low blood pressure. Renin then catalyzes the conversion of the blood protein angiotensinogen, produced by the liver, to the hormone angiotensin I. Angiotensin I is converted in the lungs to angiotensin II by angiotensin-converting enzyme (ACE). Angiotensin II has three major functions: - Initiating vasoconstriction of the arterioles, decreasing blood flow - Stimulating kidney tubules to reabsorb NaCl and water, increasing blood volume - Signaling the adrenal cortex to secrete aldosterone, the effects of which further contribute to fluid retention, restoring blood pressure and blood volume For individuals with hypertension, or high blood pressure, drugs are available that block the production of angiotensin II. These drugs, known as ACE inhibitors, block the ACE enzyme from converting angiotensin I to angiotensin II, thus mitigating the latter’s ability to increase blood pressure. Hormones of the Zona Fasciculata The intermediate region of the adrenal cortex is the zona fasciculata, named as such because the cells form small fascicles (bundles) separated by tiny blood vessels. The cells of the zona fasciculata produce hormones called glucocorticoids because of their role in glucose metabolism. The most important of these is cortisol, some of which the liver converts to cortisone. A glucocorticoid produced in much smaller amounts is corticosterone. In response to long-term stressors, the hypothalamus secretes CRH, which in turn triggers the release of ACTH by the anterior pituitary. ACTH triggers the release of the glucocorticoids. Their overall effect is to inhibit tissue building while stimulating the breakdown of stored nutrients to maintain adequate fuel supplies. In conditions of long-term stress, for example, cortisol promotes the catabolism of glycogen to glucose, the catabolism of stored triglycerides into fatty acids and glycerol, and the catabolism of muscle proteins into amino acids. These raw materials can then be used to synthesize additional glucose and ketones for use as body fuels. The hippocampus, which is part of the temporal lobe of the cerebral cortices and important in memory formation, is highly sensitive to stress levels because of its many glucocorticoid receptors. You are probably familiar with prescription and over-the-counter medications containing glucocorticoids, such as cortisone injections into inflamed joints, prednisone tablets and steroid-based inhalers used to manage severe asthma, and hydrocortisone creams applied to relieve itchy skin rashes. These drugs reflect another role of cortisol—the downregulation of the immune system, which inhibits the inflammatory response. Hormones of the Zona Reticularis The deepest region of the adrenal cortex is the zona reticularis, which produces small amounts of a class of steroid sex hormones called androgens. During puberty and most of adulthood, androgens are produced in the gonads. The androgens produced in the zona reticularis supplement the gonadal androgens. They are produced in response to ACTH from the anterior pituitary and are converted in the tissues to testosterone or estrogens. In adult women, they may contribute to the sex drive, but their function in adult men is not well understood. In post-menopausal women, as the functions of the ovaries decline, the main source of estrogens becomes the androgens produced by the zona reticularis. Adrenal Medulla As noted earlier, the adrenal cortex releases glucocorticoids in response to long-term stress such as severe illness. In contrast, the adrenal medulla releases its hormones in response to acute, short-term stress mediated by the sympathetic nervous system (SNS). The medullary tissue is composed of unique postganglionic SNS neurons called chromaffin cells, which are large and irregularly shaped, and produce the neurotransmitters epinephrine (also called adrenaline) and norepinephrine (or noradrenaline). Epinephrine is produced in greater quantities—approximately a 4 to 1 ratio with norepinephrine—and is the more powerful hormone. Because the chromaffin cells release epinephrine and norepinephrine into the systemic circulation, where they travel widely and exert effects on distant cells, they are considered hormones. Derived from the amino acid tyrosine, they are chemically classified as catecholamines. The secretion of medullary epinephrine and norepinephrine is controlled by a neural pathway that originates from the hypothalamus in response to danger or stress (the SAM pathway). Both epinephrine and norepinephrine signal the liver and skeletal muscle cells to convert glycogen into glucose, resulting in increased blood glucose levels. These hormones increase the heart rate, pulse, and blood pressure to prepare the body to fight the perceived threat or flee from it. In addition, the pathway dilates the airways, raising blood oxygen levels. It also prompts vasodilation, further increasing the oxygenation of important organs such as the lungs, brain, heart, and skeletal muscle. At the same time, it triggers vasoconstriction to blood vessels serving less essential organs such as the gastrointestinal tract, kidneys, and skin, and downregulates some components of the immune system. Other effects include a dry mouth, loss of appetite, pupil dilation, and a loss of peripheral vision. The major hormones of the adrenal glands are summarized in Table 17.5. Hormones of the Adrenal Glands \| Adrenal gland \| Associated hormones \| Chemical class \| Effect \| \|---\|---\|---\|---\| \| Adrenal cortex \| Aldosterone \| Steroid \| Increases blood Na+ levels \| \| Adrenal cortex \| Cortisol, corticosterone, cortisone \| Steroid \| Increase blood glucose levels \| \| Adrenal medulla \| Epinephrine, norepinephrine \| Amine \| Stimulate fight-or-flight response \| Table 17.5 Disorders Involving the Adrenal Glands Several disorders are caused by the dysregulation of the hormones produced by the adrenal glands. For example, Cushing’s disease is a disorder characterized by high blood glucose levels and the accumulation of lipid deposits on the face and neck. It is caused by hypersecretion of cortisol. The most common source of Cushing’s disease is a pituitary tumor that secretes cortisol or ACTH in abnormally high amounts. Other common signs of Cushing’s disease include the development of a moon-shaped face, a buffalo hump on the back of the neck, rapid weight gain, and hair loss. Chronically elevated glucose levels are also associated with an elevated risk of developing type 2 diabetes. In addition to hyperglycemia, chronically elevated glucocorticoids compromise immunity, resistance to infection, and memory, and can result in rapid weight gain and hair loss. In contrast, the hyposecretion of corticosteroids can result in Addison’s disease, a rare disorder that causes low blood glucose levels and low blood sodium levels. The signs and symptoms of Addison’s disease are vague and are typical of other disorders as well, making diagnosis difficult. They may include general weakness, abdominal pain, weight loss, nausea, vomiting, sweating, and cravings for salty food. The Pineal Gland - Describe the location and structure of the pineal gland - Discuss the function of melatonin Recall that the hypothalamus, part of the diencephalon of the brain, sits inferior and somewhat anterior to the thalamus. Inferior but somewhat posterior to the thalamus is the pineal gland, a tiny endocrine gland whose functions are not entirely clear. The pinealocyte cells that make up the pineal gland are known to produce and secrete the amine hormone melatonin, which is derived from serotonin. The secretion of melatonin varies according to the level of light received from the environment. When photons of light stimulate the retinas of the eyes, a nerve impulse is sent to a region of the hypothalamus called the suprachiasmatic nucleus (SCN), which is important in regulating biological rhythms. From the SCN, the nerve signal is carried to the spinal cord and eventually to the pineal gland, where the production of melatonin is inhibited. As a result, blood levels of melatonin fall, promoting wakefulness. In contrast, as light levels decline—such as during the evening—melatonin production increases, boosting blood levels and causing drowsiness. INTERACTIVE LINK Visit this link to view an animation describing the function of the hormone melatonin. What should you avoid doing in the middle of your sleep cycle that would lower melatonin? The secretion of melatonin may influence the body’s circadian rhythms, the dark-light fluctuations that affect not only sleepiness and wakefulness, but also appetite and body temperature. Interestingly, children have higher melatonin levels than adults, which may prevent the release of gonadotropins from the anterior pituitary, thereby inhibiting the onset of puberty. Finally, an antioxidant role of melatonin is the subject of current research. Jet lag occurs when a person travels across several time zones and feels sleepy during the day or wakeful at night. Traveling across multiple time zones significantly disturbs the light-dark cycle regulated by melatonin. It can take up to several days for melatonin synthesis to adjust to the light-dark patterns in the new environment, resulting in jet lag. Some air travelers take melatonin supplements to induce sleep. Gonadal and Placental Hormones - Identify the most important hormones produced by the testes and ovaries - Name the hormones produced by the placenta and state their functions This section briefly discusses the hormonal role of the gonads—the male testes and female ovaries—which produce the sex cells (sperm and ova) and secrete the gonadal hormones. The roles of the gonadotropins released from the anterior pituitary (FSH and LH) were discussed earlier. The primary hormone produced by the male testes is testosterone, a steroid hormone important in the development of the male reproductive system, the maturation of sperm cells, and the development of male secondary sex characteristics such as a deepened voice, body hair, and increased muscle mass. Interestingly, testosterone is also produced in the female ovaries, but at a much reduced level. In addition, the testes produce the peptide hormone inhibin, which inhibits the secretion of FSH from the anterior pituitary gland. FSH stimulates spermatogenesis. The primary hormones produced by the ovaries are estrogens, which include estradiol, estriol, and estrone. Estrogens play an important role in a larger number of physiological processes, including the development of the female reproductive system, regulation of the menstrual cycle, the development of female secondary sex characteristics such as increased adipose tissue and the development of breast tissue, and the maintenance of pregnancy. Another significant ovarian hormone is progesterone, which contributes to regulation of the menstrual cycle and is important in preparing the body for pregnancy as well as maintaining pregnancy. In addition, the granulosa cells of the ovarian follicles produce inhibin, which—as in males—inhibits the secretion of FSH.During the initial stages of pregnancy, an organ called the placenta develops within the uterus. The placenta supplies oxygen and nutrients to the fetus, excretes waste products, and produces and secretes estrogens and progesterone. The placenta produces human chorionic gonadotropin (hCG) as well. The hCG hormone promotes progesterone synthesis and reduces the mother’s immune function to protect the fetus from immune rejection. It also secretes human placental lactogen (hPL), which plays a role in preparing the breasts for lactation, and relaxin, which is thought to help soften and widen the pubic symphysis in preparation for childbirth. The hormones controlling reproduction are summarized in Table 17.6. Reproductive Hormones \| Gonad \| Associated hormones \| Chemical class \| Effect \| \|---\|---\|---\|---\| \| Testes \| Testosterone \| Steroid \| Stimulates development of male secondary sex characteristics and sperm production \| \| Testes \| Inhibin \| Protein \| Inhibits FSH release from pituitary \| \| Ovaries \| Estrogens and progesterone \| Steroid \| Stimulate development of female secondary sex characteristics and prepare the body for childbirth \| \| Placenta \| Human chorionic gonadotropin \| Protein \| Promotes progesterone synthesis during pregnancy and inhibits immune response against fetus \| Table 17.6 EVERYDAY CONNECTION Anabolic Steroids The endocrine system can be exploited for illegal or unethical purposes. A prominent example of this is the use of steroid drugs by professional athletes. Commonly used for performance enhancement, anabolic steroids are synthetic versions of the male sex hormone, testosterone. By boosting natural levels of this hormone, athletes experience increased muscle mass. Synthetic versions of human growth hormone are also used to build muscle mass. The use of performance-enhancing drugs is banned by all major collegiate and professional sports organizations in the United States because they impart an unfair advantage to athletes who take them. In addition, the drugs can cause significant and dangerous side effects. For example, anabolic steroid use can increase cholesterol levels, raise blood pressure, and damage the liver. Altered testosterone levels (both too low or too high) have been implicated in causing structural damage to the heart, and increasing the risk for cardiac arrhythmias, heart attacks, congestive heart failure, and sudden death. Paradoxically, steroids can have a feminizing effect in males, including shriveled testicles and enlarged breast tissue. In females, their use can cause masculinizing effects such as an enlarged clitoris and growth of facial hair. In both sexes, their use can promote increased aggression (commonly known as “roid-rage”), depression, sleep disturbances, severe acne, and infertility. The Endocrine Pancreas - Describe the location and structure of the pancreas, and the morphology and function of the pancreatic islets - Compare and contrast the functions of insulin and glucagon The pancreas is a long, slender organ, most of which is located posterior to the bottom half of the stomach (Figure 17.18). Although it is primarily an exocrine gland, secreting a variety of digestive enzymes, the pancreas has an endocrine function. Its pancreatic islets—clusters of cells formerly known as the islets of Langerhans—secrete the hormones glucagon, insulin, somatostatin, and pancreatic polypeptide (PP). Figure 17.18 Pancreas The pancreatic exocrine function involves the acinar cells secreting digestive enzymes that are transported into the small intestine by the pancreatic duct. Its endocrine function involves the secretion of insulin (produced by beta cells) and glucagon (produced by alpha cells) within the pancreatic islets. These two hormones regulate the rate of glucose metabolism in the body. The micrograph reveals pancreatic islets. LM × 760. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK View the University of Michigan WebScope to explore the tissue sample in greater detail. Cells and Secretions of the Pancreatic Islets The pancreatic islets each contain four varieties of cells: - The alpha cell produces the hormone glucagon and makes up approximately 20 percent of each islet. Glucagon plays an important role in blood glucose regulation; low blood glucose levels stimulate its release. - The beta cell produces the hormone insulin and makes up approximately 75 percent of each islet. Elevated blood glucose levels stimulate the release of insulin. - The delta cell accounts for four percent of the islet cells and secretes the peptide hormone somatostatin. Recall that somatostatin is also released by the hypothalamus (as GHIH), and the stomach and intestines also secrete it. An inhibiting hormone, pancreatic somatostatin inhibits the release of both glucagon and insulin. - The PP cell accounts for about one percent of islet cells and secretes the pancreatic polypeptide hormone. It is thought to play a role in appetite, as well as in the regulation of pancreatic exocrine and endocrine secretions. Pancreatic polypeptide released following a meal may reduce further food consumption; however, it is also released in response to fasting. Regulation of Blood Glucose Levels by Insulin and Glucagon Glucose is required for cellular respiration and is the preferred fuel for all body cells. The body derives glucose from the breakdown of the carbohydrate-containing foods and drinks we consume. Glucose not immediately taken up by cells for fuel can be stored by the liver and muscles as glycogen, or converted to triglycerides and stored in the adipose tissue. Hormones regulate both the storage and the utilization of glucose as required. Receptors located in the pancreas sense blood glucose levels, and subsequently the pancreatic cells secrete glucagon or insulin to maintain normal levels. Glucagon Receptors in the pancreas can sense the decline in blood glucose levels, such as during periods of fasting or during prolonged labor or exercise (Figure 17.19). In response, the alpha cells of the pancreas secrete the hormone glucagon, which has several effects: - It stimulates the liver to convert its stores of glycogen back into glucose. This response is known as glycogenolysis. The glucose is then released into the circulation for use by body cells. - It stimulates the liver to take up amino acids from the blood and convert them into glucose. This response is known as gluconeogenesis. - It stimulates lipolysis, the breakdown of stored triglycerides into free fatty acids and glycerol. Some of the free glycerol released into the bloodstream travels to the liver, which converts it into glucose. This is also a form of gluconeogenesis. Taken together, these actions increase blood glucose levels. The activity of glucagon is regulated through a negative feedback mechanism; rising blood glucose levels inhibit further glucagon production and secretion. Figure 17.19 Homeostatic Regulation of Blood Glucose Levels Blood glucose concentration is tightly maintained between 70 mg/dL and 110 mg/dL. If blood glucose concentration rises above this range, insulin is released, which stimulates body cells to remove glucose from the blood. If blood glucose concentration drops below this range, glucagon is released, which stimulates body cells to release glucose into the blood. Insulin The primary function of insulin is to facilitate the uptake of glucose into body cells. Red blood cells, as well as cells of the brain, liver, kidneys, and the lining of the small intestine, do not have insulin receptors on their cell membranes and do not require insulin for glucose uptake. Although all other body cells do require insulin if they are to take glucose from the bloodstream, skeletal muscle cells and adipose cells are the primary targets of insulin. The presence of food in the intestine triggers the release of gastrointestinal tract hormones such as glucose-dependent insulinotropic peptide (previously known as gastric inhibitory peptide). This is in turn the initial trigger for insulin production and secretion by the beta cells of the pancreas. Once nutrient absorption occurs, the resulting surge in blood glucose levels further stimulates insulin secretion. Precisely how insulin facilitates glucose uptake is not entirely clear. However, insulin appears to activate a tyrosine kinase receptor, triggering the phosphorylation of many substrates within the cell. These multiple biochemical reactions converge to support the movement of intracellular vesicles containing facilitative glucose transporters to the cell membrane. In the absence of insulin, these transport proteins are normally recycled slowly between the cell membrane and cell interior. Insulin triggers the rapid movement of a pool of glucose transporter vesicles to the cell membrane, where they fuse and expose the glucose transporters to the extracellular fluid. The transporters then move glucose by facilitated diffusion into the cell interior. INTERACTIVE LINK Visit this link to view an animation describing the location and function of the pancreas. What goes wrong in the function of insulin in type 2 diabetes? Insulin also reduces blood glucose levels by stimulating glycolysis, the metabolism of glucose for generation of ATP. Moreover, it stimulates the liver to convert excess glucose into glycogen for storage, and it inhibits enzymes involved in glycogenolysis and gluconeogenesis. Finally, insulin promotes triglyceride and protein synthesis. The secretion of insulin is regulated through a negative feedback mechanism. As blood glucose levels decrease, further insulin release is inhibited. The pancreatic hormones are summarized in Table 17.7. Hormones of the Pancreas \| Associated hormones \| Chemical class \| Effect \| \|---\|---\|---\| \| Insulin (beta cells) \| Protein \| Reduces blood glucose levels \| \| Glucagon (alpha cells) \| Protein \| Increases blood glucose levels \| \| Somatostatin (delta cells) \| Protein \| Inhibits insulin and glucagon release \| \| Pancreatic polypeptide (PP cells) \| Protein \| Role in appetite \| Table 17.7 DISORDERS OF THE... Endocrine System: Diabetes Mellitus Dysfunction of insulin production and secretion, as well as the target cells’ responsiveness to insulin, can lead to a condition called diabetes mellitus. An increasingly common disease, diabetes mellitus has been diagnosed in more than 18 million adults in the United States, and more than 200,000 children. It is estimated that up to 7 million more adults have the condition but have not been diagnosed. In addition, approximately 79 million people in the US are estimated to have pre-diabetes, a condition in which blood glucose levels are abnormally high, but not yet high enough to be classified as diabetes. There are two main forms of diabetes mellitus. Type 1 diabetes is an autoimmune disease affecting the beta cells of the pancreas. Certain genes are recognized to increase susceptibility. The beta cells of people with type 1 diabetes do not produce insulin; thus, synthetic insulin must be administered by injection or infusion. This form of diabetes accounts for less than five percent of all diabetes cases. Type 2 diabetes accounts for approximately 95 percent of all cases. It is acquired, and lifestyle factors such as poor diet, inactivity, and the presence of pre-diabetes greatly increase a person’s risk. About 80 to 90 percent of people with type 2 diabetes are overweight or obese. In type 2 diabetes, cells become resistant to the effects of insulin. In response, the pancreas increases its insulin secretion, but over time, the beta cells become exhausted. In many cases, type 2 diabetes can be reversed by moderate weight loss, regular physical activity, and consumption of a healthy diet; however, if blood glucose levels cannot be controlled, the diabetic will eventually require insulin. Two of the early manifestations of diabetes are excessive urination and excessive thirst. They demonstrate how the out-of-control levels of glucose in the blood affect kidney function. The kidneys are responsible for filtering glucose from the blood. Excessive blood glucose draws water into the urine, and as a result the person eliminates an abnormally large quantity of sweet urine. The use of body water to dilute the urine leaves the body dehydrated, and so the person is unusually and continually thirsty. The person may also experience persistent hunger because the body cells are unable to access the glucose in the bloodstream. Over time, persistently high levels of glucose in the blood injure tissues throughout the body, especially those of the blood vessels and nerves. Inflammation and injury of the lining of arteries lead to atherosclerosis and an increased risk of heart attack and stroke. Damage to the microscopic blood vessels of the kidney impairs kidney function and can lead to kidney failure. Damage to blood vessels that serve the eyes can lead to blindness. Blood vessel damage also reduces circulation to the limbs, whereas nerve damage leads to a loss of sensation, called neuropathy, particularly in the hands and feet. Together, these changes increase the risk of injury, infection, and tissue death (necrosis), contributing to a high rate of toe, foot, and lower leg amputations in people with diabetes. Uncontrolled diabetes can also lead to a dangerous form of metabolic acidosis called ketoacidosis. Deprived of glucose, cells increasingly rely on fat stores for fuel. However, in a glucose-deficient state, the liver is forced to use an alternative lipid metabolism pathway that results in the increased production of ketone bodies (or ketones), which are acidic. The build-up of ketones in the blood causes ketoacidosis, which—if left untreated—may lead to a life-threatening “diabetic coma.” Together, these complications make diabetes the seventh leading cause of death in the United States. Diabetes is diagnosed when lab tests reveal that blood glucose levels are higher than normal, a condition called hyperglycemia. The treatment of diabetes depends on the type, the severity of the condition, and the ability of the patient to make lifestyle changes. As noted earlier, moderate weight loss, regular physical activity, and consumption of a healthful diet can reduce blood glucose levels. Some patients with type 2 diabetes may be unable to control their disease with these lifestyle changes, and will require medication. Historically, the first-line treatment of type 2 diabetes was insulin. Research advances have resulted in alternative options, including medications that enhance pancreatic function. INTERACTIVE LINK Visit this link to view an animation describing the role of insulin and the pancreas in diabetes. Organs with Secondary Endocrine Functions - Identify the organs with a secondary endocrine function, the hormone they produce, and its effects In your study of anatomy and physiology, you have already encountered a few of the many organs of the body that have secondary endocrine functions. Here, you will learn about the hormone-producing activities of the heart, gastrointestinal tract, kidneys, skeleton, adipose tissue, skin, and thymus. Heart When the body experiences an increase in blood volume or pressure, the cells of the heart’s atrial wall stretch. In response, specialized cells in the wall of the atria produce and secrete the peptide hormone atrial natriuretic peptide (ANP). ANP signals the kidneys to reduce sodium reabsorption, thereby decreasing the amount of water reabsorbed from the urine filtrate and reducing blood volume. Other actions of ANP include the inhibition of renin secretion, thus inhibition of the renin-angiotensin-aldosterone system (RAAS) and vasodilation. Therefore, ANP aids in decreasing blood pressure, blood volume, and blood sodium levels. Gastrointestinal Tract The endocrine cells of the GI tract are located in the mucosa of the stomach and small intestine. Some of these hormones are secreted in response to eating a meal and aid in digestion. An example of a hormone secreted by the stomach cells is gastrin, a peptide hormone secreted in response to stomach distention that stimulates the release of hydrochloric acid. Secretin is a peptide hormone secreted by the small intestine as acidic chyme (partially digested food and fluid) moves from the stomach. It stimulates the release of bicarbonate from the pancreas, which buffers the acidic chyme, and inhibits the further secretion of hydrochloric acid by the stomach. Cholecystokinin (CCK) is another peptide hormone released from the small intestine. It promotes the secretion of pancreatic enzymes and the release of bile from the gallbladder, both of which facilitate digestion. Other hormones produced by the intestinal cells aid in glucose metabolism, such as by stimulating the pancreatic beta cells to secrete insulin, reducing glucagon secretion from the alpha cells, or enhancing cellular sensitivity to insulin. Kidneys The kidneys participate in several complex endocrine pathways and produce certain hormones. A decline in blood flow to the kidneys stimulates them to release the enzyme renin, triggering the renin-angiotensin-aldosterone (RAAS) system, and stimulating the reabsorption of sodium and water. The reabsorption increases blood flow and blood pressure. The kidneys also play a role in regulating blood calcium levels through the production of calcitriol from vitamin D3, which is released in response to the secretion of parathyroid hormone (PTH). In addition, the kidneys produce the hormone erythropoietin (EPO) in response to low oxygen levels. EPO stimulates the production of red blood cells (erythrocytes) in the bone marrow, thereby increasing oxygen delivery to tissues. You may have heard of EPO as a performance-enhancing drug (in a synthetic form). Skeleton Although bone has long been recognized as a target for hormones, only recently have researchers recognized that the skeleton itself produces at least two hormones. Fibroblast growth factor 23 (FGF23) is produced by bone cells in response to increased blood levels of vitamin D3 or phosphate. It triggers the kidneys to inhibit the formation of calcitriol from vitamin D3 and to increase phosphorus excretion. Osteocalcin, produced by osteoblasts, stimulates the pancreatic beta cells to increase insulin production. It also acts on peripheral tissues to increase their sensitivity to insulin and their utilization of glucose. Adipose Tissue Adipose tissue produces and secretes several hormones involved in lipid metabolism and storage. One important example is leptin, a protein manufactured by adipose cells that circulates in amounts directly proportional to levels of body fat. Leptin is released in response to food consumption and acts by binding to brain neurons involved in energy intake and expenditure. Binding of leptin produces a feeling of satiety after a meal, thereby reducing appetite. It also appears that the binding of leptin to brain receptors triggers the sympathetic nervous system to regulate bone metabolism, increasing deposition of cortical bone. Adiponectin—another hormone synthesized by adipose cells—appears to reduce cellular insulin resistance and to protect blood vessels from inflammation and atherosclerosis. Its levels are lower in people who are obese, and rise following weight loss. Skin The skin functions as an endocrine organ in the production of the inactive form of vitamin D3, cholecalciferol. When cholesterol present in the epidermis is exposed to ultraviolet radiation, it is converted to cholecalciferol, which then enters the blood. In the liver, cholecalciferol is converted to an intermediate that travels to the kidneys and is further converted to calcitriol, the active form of vitamin D3. Vitamin D is important in a variety of physiological processes, including intestinal calcium absorption and immune system function. In some studies, low levels of vitamin D have been associated with increased risks of cancer, severe asthma, and multiple sclerosis. Vitamin D deficiency in children causes rickets, and in adults, osteomalacia—both of which are characterized by bone deterioration. Thymus The thymus is an organ of the immune system that is larger and more active during infancy and early childhood, and begins to atrophy as we age. Its endocrine function is the production of a group of hormones called thymosins that contribute to the development and differentiation of T lymphocytes, which are immune cells. Although the role of thymosins is not yet well understood, it is clear that they contribute to the immune response. Thymosins have been found in tissues other than the thymus and have a wide variety of functions, so the thymosins cannot be strictly categorized as thymic hormones. Liver The liver is responsible for secreting at least four important hormones or hormone precursors: insulin-like growth factor (somatomedin), angiotensinogen, thrombopoetin, and hepcidin. Insulin-like growth factor-1 is the immediate stimulus for growth in the body, especially of the bones. Angiotensinogen is the precursor to angiotensin, mentioned earlier, which increases blood pressure. Thrombopoetin stimulates the production of the blood’s platelets. Hepcidins block the release of iron from cells in the body, helping to regulate iron homeostasis in our body fluids. The major hormones of these other organs are summarized in Table 17.8. Organs with Secondary Endocrine Functions and Their Major Hormones \| Organ \| Major hormones \| Effects \| \|---\|---\|---\| \| Heart \| Atrial natriuretic peptide (ANP) \| Reduces blood volume, blood pressure, and Na+concentration \| \| Gastrointestinal tract \| Gastrin, secretin, and cholecystokinin \| Aid digestion of food and buffering of stomach acids \| \| Gastrointestinal tract \| Glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide 1 (GLP-1) \| Stimulate beta cells of the pancreas to release insulin \| \| Kidneys \| Renin \| Stimulates release of aldosterone \| \| Kidneys \| Calcitriol \| Aids in the absorption of Ca2+ \| \| Kidneys \| Erythropoietin \| Triggers the formation of red blood cells in the bone marrow \| \| Skeleton \| FGF23 \| Inhibits production of calcitriol and increases phosphate excretion \| \| Skeleton \| Osteocalcin \| Increases insulin production \| \| Adipose tissue \| Leptin \| Promotes satiety signals in the brain \| \| Adipose tissue \| Adiponectin \| Reduces insulin resistance \| \| Skin \| Cholecalciferol \| Modified to form vitamin D \| \| Thymus (and other organs) \| Thymosins \| Among other things, aids in the development of T lymphocytes of the immune system \| \| Liver \| Insulin-like growth factor-1 \| Stimulates bodily growth \| \| Liver \| Angiotensinogen \| Raises blood pressure \| \| Liver \| Thrombopoetin \| Causes increase in platelets \| \| Liver \| Hepcidin \| Blocks release of iron into body fluids \| Table 17.8 Development and Aging of the Endocrine System - Describe the embryonic origins of the endocrine system - Discuss the effects of aging on the endocrine system The endocrine system arises from all three embryonic germ layers. The endocrine glands that produce the steroid hormones, such as the gonads and adrenal cortex, arise from the mesoderm. In contrast, endocrine glands that arise from the endoderm and ectoderm produce the amine, peptide, and protein hormones. The pituitary gland arises from two distinct areas of the ectoderm: the anterior pituitary gland arises from the oral ectoderm, whereas the posterior pituitary gland arises from the neural ectoderm at the base of the hypothalamus. The pineal gland also arises from the ectoderm. The two structures of the adrenal glands arise from two different germ layers: the adrenal cortex from the mesoderm and the adrenal medulla from ectoderm neural cells. The endoderm gives rise to the thyroid and parathyroid glands, as well as the pancreas and the thymus. As the body ages, changes occur that affect the endocrine system, sometimes altering the production, secretion, and catabolism of hormones. For example, the structure of the anterior pituitary gland changes as vascularization decreases and the connective tissue content increases with increasing age. This restructuring affects the gland’s hormone production. For example, the amount of human growth hormone that is produced declines with age, resulting in the reduced muscle mass commonly observed in the elderly. The adrenal glands also undergo changes as the body ages; as fibrous tissue increases, the production of cortisol and aldosterone decreases. Interestingly, the production and secretion of epinephrine and norepinephrine remain normal throughout the aging process. A well-known example of the aging process affecting an endocrine gland is menopause and the decline of ovarian function. With increasing age, the ovaries decrease in both size and weight and become progressively less sensitive to gonadotropins. This gradually causes a decrease in estrogen and progesterone levels, leading to menopause and the inability to reproduce. Low levels of estrogens and progesterone are also associated with some disease states, such as osteoporosis, atherosclerosis, and hyperlipidemia, or abnormal blood lipid levels. Testosterone levels also decline with age, a condition called andropause (or viropause); however, this decline is much less dramatic than the decline of estrogens in women, and much more gradual, rarely affecting sperm production until very old age. Although this means that males maintain their ability to father children for decades longer than females, the quantity, quality, and motility of their sperm is often reduced. As the body ages, the thyroid gland produces less of the thyroid hormones, causing a gradual decrease in the basal metabolic rate. The lower metabolic rate reduces the production of body heat and increases levels of body fat. Parathyroid hormones, on the other hand, increase with age. This may be because of reduced dietary calcium levels, causing a compensatory increase in parathyroid hormone. However, increased parathyroid hormone levels combined with decreased levels of calcitonin (and estrogens in women) can lead to osteoporosis as PTH stimulates demineralization of bones to increase blood calcium levels. Notice that osteoporosis is common in both elderly males and females. Increasing age also affects glucose metabolism, as blood glucose levels spike more rapidly and take longer to return to normal in the elderly. In addition, increasing glucose intolerance may occur because of a gradual decline in cellular insulin sensitivity. Almost 27 percent of Americans aged 65 and older have diabetes. Key Terms - acromegaly - disorder in adults caused when abnormally high levels of GH trigger growth of bones in the face, hands, and feet - adenylyl cyclase - membrane-bound enzyme that converts ATP to cyclic AMP, creating cAMP, as a result of G-protein activation - adrenal cortex - outer region of the adrenal glands consisting of multiple layers of epithelial cells and capillary networks that produces mineralocorticoids and glucocorticoids - adrenal glands - endocrine glands located at the top of each kidney that are important for the regulation of the stress response, blood pressure and blood volume, water homeostasis, and electrolyte levels - adrenal medulla - inner layer of the adrenal glands that plays an important role in the stress response by producing epinephrine and norepinephrine - adrenocorticotropic hormone (ACTH) - anterior pituitary hormone that stimulates the adrenal cortex to secrete corticosteroid hormones (also called corticotropin) - alarm reaction - the short-term stress, or the fight-or-flight response, of stage one of the general adaptation syndrome mediated by the hormones epinephrine and norepinephrine - aldosterone - hormone produced and secreted by the adrenal cortex that stimulates sodium and fluid retention and increases blood volume and blood pressure - alpha cell - pancreatic islet cell type that produces the hormone glucagon - angiotensin-converting enzyme - the enzyme that converts angiotensin I to angiotensin II - antidiuretic hormone (ADH) - hypothalamic hormone that is stored by the posterior pituitary and that signals the kidneys to reabsorb water - atrial natriuretic peptide (ANP) - peptide hormone produced by the walls of the atria in response to high blood pressure, blood volume, or blood sodium that reduces the reabsorption of sodium and water in the kidneys and promotes vasodilation - autocrine - chemical signal that elicits a response in the same cell that secreted it - beta cell - pancreatic islet cell type that produces the hormone insulin - calcitonin - peptide hormone produced and secreted by the parafollicular cells (C cells) of the thyroid gland that functions to decrease blood calcium levels - chromaffin - neuroendocrine cells of the adrenal medulla - colloid - viscous fluid in the central cavity of thyroid follicles, containing the glycoprotein thyroglobulin - cortisol - glucocorticoid important in gluconeogenesis, the catabolism of glycogen, and downregulation of the immune system - cyclic adenosine monophosphate (cAMP) - second messenger that, in response to adenylyl cyclase activation, triggers a phosphorylation cascade - delta cell - minor cell type in the pancreas that secretes the hormone somatostatin - diabetes mellitus - condition caused by destruction or dysfunction of the beta cells of the pancreas or cellular resistance to insulin that results in abnormally high blood glucose levels - diacylglycerol (DAG) - molecule that, like cAMP, activates protein kinases, thereby initiating a phosphorylation cascade - downregulation - decrease in the number of hormone receptors, typically in response to chronically excessive levels of a hormone - endocrine gland - tissue or organ that secretes hormones into the blood and lymph without ducts such that they may be transported to organs distant from the site of secretion - endocrine system - cells, tissues, and organs that secrete hormones as a primary or secondary function and play an integral role in normal bodily processes - epinephrine - primary and most potent catecholamine hormone secreted by the adrenal medulla in response to short-term stress; also called adrenaline - erythropoietin (EPO) - protein hormone secreted in response to low oxygen levels that triggers the bone marrow to produce red blood cells - estrogens - class of predominantly female sex hormones important for the development and growth of the female reproductive tract, secondary sex characteristics, the female reproductive cycle, and the maintenance of pregnancy - exocrine system - cells, tissues, and organs that secrete substances directly to target tissues via glandular ducts - first messenger - hormone that binds to a cell membrane hormone receptor and triggers activation of a second messenger system - follicle-stimulating hormone (FSH) - anterior pituitary hormone that stimulates the production and maturation of sex cells - G protein - protein associated with a cell membrane hormone receptor that initiates the next step in a second messenger system upon activation by hormone–receptor binding - general adaptation syndrome (GAS) - the human body’s three-stage response pattern to short- and long-term stress - gigantism - disorder in children caused when abnormally high levels of GH prompt excessive growth - glucagon - pancreatic hormone that stimulates the catabolism of glycogen to glucose, thereby increasing blood glucose levels - glucocorticoids - hormones produced by the zona fasciculata of the adrenal cortex that influence glucose metabolism - goiter - enlargement of the thyroid gland either as a result of iodine deficiency or hyperthyroidism - gonadotropins - hormones that regulate the function of the gonads - growth hormone (GH) - anterior pituitary hormone that promotes tissue building and influences nutrient metabolism (also called somatotropin) - hormone - secretion of an endocrine organ that travels via the bloodstream or lymphatics to induce a response in target cells or tissues in another part of the body - hormone receptor - protein within a cell or on the cell membrane that binds a hormone, initiating the target cell response - hyperglycemia - abnormally high blood glucose levels - hyperparathyroidism - disorder caused by overproduction of PTH that results in abnormally elevated blood calcium - hyperthyroidism - clinically abnormal, elevated level of thyroid hormone in the blood; characterized by an increased metabolic rate, excess body heat, sweating, diarrhea, weight loss, and increased heart rate - hypoparathyroidism - disorder caused by underproduction of PTH that results in abnormally low blood calcium - hypophyseal portal system - network of blood vessels that enables hypothalamic hormones to travel into the anterior lobe of the pituitary without entering the systemic circulation - hypothalamus - region of the diencephalon inferior to the thalamus that functions in neural and endocrine signaling - hypothyroidism - clinically abnormal, low level of thyroid hormone in the blood; characterized by low metabolic rate, weight gain, cold extremities, constipation, and reduced mental activity - infundibulum - stalk containing vasculature and neural tissue that connects the pituitary gland to the hypothalamus (also called the pituitary stalk) - inhibin - hormone secreted by the male and female gonads that inhibits FSH production by the anterior pituitary - inositol triphosphate (IP3) - molecule that initiates the release of calcium ions from intracellular stores - insulin - pancreatic hormone that enhances the cellular uptake and utilization of glucose, thereby decreasing blood glucose levels - insulin-like growth factors (IGF) - protein that enhances cellular proliferation, inhibits apoptosis, and stimulates the cellular uptake of amino acids for protein synthesis - leptin - protein hormone secreted by adipose tissues in response to food consumption that promotes satiety - luteinizing hormone (LH) - anterior pituitary hormone that triggers ovulation and the production of ovarian hormones in females, and the production of testosterone in males - melatonin - amino acid–derived hormone that is secreted in response to low light and causes drowsiness - mineralocorticoids - hormones produced by the zona glomerulosa cells of the adrenal cortex that influence fluid and electrolyte balance - neonatal hypothyroidism - condition characterized by cognitive deficits, short stature, and other signs and symptoms in people born to women who were iodine-deficient during pregnancy - norepinephrine - secondary catecholamine hormone secreted by the adrenal medulla in response to short-term stress; also called noradrenaline - osmoreceptor - hypothalamic sensory receptor that is stimulated by changes in solute concentration (osmotic pressure) in the blood - oxytocin - hypothalamic hormone stored in the posterior pituitary gland and important in stimulating uterine contractions in labor, milk ejection during breastfeeding, and feelings of attachment (also produced in males) - pancreas - organ with both exocrine and endocrine functions located posterior to the stomach that is important for digestion and the regulation of blood glucose - pancreatic islets - specialized clusters of pancreatic cells that have endocrine functions; also called islets of Langerhans - paracrine - chemical signal that elicits a response in neighboring cells; also called paracrine factor - parathyroid glands - small, round glands embedded in the posterior thyroid gland that produce parathyroid hormone (PTH) - parathyroid hormone (PTH) - peptide hormone produced and secreted by the parathyroid glands in response to low blood calcium levels - phosphodiesterase (PDE) - cytosolic enzyme that deactivates and degrades cAMP - phosphorylation cascade - signaling event in which multiple protein kinases phosphorylate the next protein substrate by transferring a phosphate group from ATP to the protein - pineal gland - endocrine gland that secretes melatonin, which is important in regulating the sleep-wake cycle - pinealocyte - cell of the pineal gland that produces and secretes the hormone melatonin - pituitary dwarfism - disorder in children caused when abnormally low levels of GH result in growth retardation - pituitary gland - bean-sized organ suspended from the hypothalamus that produces, stores, and secretes hormones in response to hypothalamic stimulation (also called hypophysis) - PP cell - minor cell type in the pancreas that secretes the hormone pancreatic polypeptide - progesterone - predominantly female sex hormone important in regulating the female reproductive cycle and the maintenance of pregnancy - prolactin (PRL) - anterior pituitary hormone that promotes development of the mammary glands and the production of breast milk - protein kinase - enzyme that initiates a phosphorylation cascade upon activation - second messenger - molecule that initiates a signaling cascade in response to hormone binding on a cell membrane receptor and activation of a G protein - stage of exhaustion - stage three of the general adaptation syndrome; the body’s long-term response to stress mediated by the hormones of the adrenal cortex - stage of resistance - stage two of the general adaptation syndrome; the body’s continued response to stress after stage one diminishes - testosterone - steroid hormone secreted by the male testes and important in the maturation of sperm cells, growth and development of the male reproductive system, and the development of male secondary sex characteristics - thymosins - hormones produced and secreted by the thymus that play an important role in the development and differentiation of T cells - thymus - organ that is involved in the development and maturation of T-cells and is particularly active during infancy and childhood - thyroid gland - large endocrine gland responsible for the synthesis of thyroid hormones - thyroid-stimulating hormone (TSH) - anterior pituitary hormone that triggers secretion of thyroid hormones by the thyroid gland (also called thyrotropin) - thyroxine - (also, tetraiodothyronine, T4) amino acid–derived thyroid hormone that is more abundant but less potent than T3 and often converted to T3 by target cells - triiodothyronine - (also, T3) amino acid–derived thyroid hormone that is less abundant but more potent than T4 - upregulation - increase in the number of hormone receptors, typically in response to chronically reduced levels of a hormone - zona fasciculata - intermediate region of the adrenal cortex that produce hormones called glucocorticoids - zona glomerulosa - most superficial region of the adrenal cortex, which produces the hormones collectively referred to as mineralocorticoids - zona reticularis - deepest region of the adrenal cortex, which produces the steroid sex hormones called androgens Chapter Review 17.1 An Overview of the Endocrine System The endocrine system consists of cells, tissues, and organs that secrete hormones critical to homeostasis. The body coordinates its functions through two major types of communication: neural and endocrine. Neural communication includes both electrical and chemical signaling between neurons and target cells. Endocrine communication involves chemical signaling via the release of hormones into the extracellular fluid. From there, hormones diffuse into the bloodstream and may travel to distant body regions, where they elicit a response in target cells. Endocrine glands are ductless glands that secrete hormones. Many organs of the body with other primary functions—such as the heart, stomach, and kidneys—also have hormone-secreting cells. 17.2 Hormones Hormones are derived from amino acids or lipids. Amine hormones originate from the amino acids tryptophan or tyrosine. Larger amino acid hormones include peptides and protein hormones. Steroid hormones are derived from cholesterol. Steroid hormones and thyroid hormone are lipid soluble. All other amino acid–derived hormones are water soluble. Hydrophobic hormones are able to diffuse through the membrane and interact with an intracellular receptor. In contrast, hydrophilic hormones must interact with cell membrane receptors. These are typically associated with a G protein, which becomes activated when the hormone binds the receptor. This initiates a signaling cascade that involves a second messenger, such as cyclic adenosine monophosphate (cAMP). Second messenger systems greatly amplify the hormone signal, creating a broader, more efficient, and faster response. Hormones are released upon stimulation that is of either chemical or neural origin. Regulation of hormone release is primarily achieved through negative feedback. Various stimuli may cause the release of hormones, but there are three major types. Humoral stimuli are changes in ion or nutrient levels in the blood. Hormonal stimuli are changes in hormone levels that initiate or inhibit the secretion of another hormone. Finally, a neural stimulus occurs when a nerve impulse prompts the secretion or inhibition of a hormone. 17.3 The Pituitary Gland and Hypothalamus The hypothalamus–pituitary complex is located in the diencephalon of the brain. The hypothalamus and the pituitary gland are connected by a structure called the infundibulum, which contains vasculature and nerve axons. The pituitary gland is divided into two distinct structures with different embryonic origins. The posterior lobe houses the axon terminals of hypothalamic neurons. It stores and releases into the bloodstream two hypothalamic hormones: oxytocin and antidiuretic hormone (ADH). The anterior lobe is connected to the hypothalamus by vasculature in the infundibulum and produces and secretes six hormones. Their secretion is regulated, however, by releasing and inhibiting hormones from the hypothalamus. The six anterior pituitary hormones are: growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL). 17.4 The Thyroid Gland The thyroid gland is a butterfly-shaped organ located in the neck anterior to the trachea. Its hormones regulate basal metabolism, oxygen use, nutrient metabolism, the production of ATP, and calcium homeostasis. They also contribute to protein synthesis and the normal growth and development of body tissues, including maturation of the nervous system, and they increase the body’s sensitivity to catecholamines. The thyroid hormones triiodothyronine (T3) and thyroxine (T4) are produced and secreted by the thyroid gland in response to thyroid-stimulating hormone (TSH) from the anterior pituitary. Synthesis of the amino acid–derived T3 and T4 hormones requires iodine. Insufficient amounts of iodine in the diet can lead to goiter, cretinism, and many other disorders. 17.5 The Parathyroid Glands Calcium is required for a variety of important physiologic processes, including neuromuscular functioning; thus, blood calcium levels are closely regulated. The parathyroid glands are small structures located on the posterior thyroid gland that produce parathyroid hormone (PTH), which regulates blood calcium levels. Low blood calcium levels cause the production and secretion of PTH. In contrast, elevated blood calcium levels inhibit secretion of PTH and trigger secretion of the thyroid hormone calcitonin. Underproduction of PTH can result in hypoparathyroidism. In contrast, overproduction of PTH can result in hyperparathyroidism. 17.6 The Adrenal Glands The adrenal glands, located superior to each kidney, consist of two regions: the adrenal cortex and adrenal medulla. The adrenal cortex—the outer layer of the gland—produces mineralocorticoids, glucocorticoids, and androgens. The adrenal medulla at the core of the gland produces epinephrine and norepinephrine. The adrenal glands mediate a short-term stress response and a long-term stress response. A perceived threat results in the secretion of epinephrine and norepinephrine from the adrenal medulla, which mediate the fight-or-flight response. The long-term stress response is mediated by the secretion of CRH from the hypothalamus, which triggers ACTH, which in turn stimulates the secretion of corticosteroids from the adrenal cortex. The mineralocorticoids, chiefly aldosterone, cause sodium and fluid retention, which increases blood volume and blood pressure. 17.7 The Pineal Gland The pineal gland is an endocrine structure of the diencephalon of the brain, and is located inferior and posterior to the thalamus. It is made up of pinealocytes. These cells produce and secrete the hormone melatonin in response to low light levels. High blood levels of melatonin induce drowsiness. Jet lag, caused by traveling across several time zones, occurs because melatonin synthesis takes several days to readjust to the light-dark patterns in the new environment. 17.8 Gonadal and Placental Hormones The male and female reproductive system is regulated by follicle-stimulating hormone (FSH) and luteinizing hormone (LH) produced by the anterior lobe of the pituitary gland in response to gonadotropin-releasing hormone (GnRH) from the hypothalamus. In males, FSH stimulates sperm maturation, which is inhibited by the hormone inhibin. The steroid hormone testosterone, a type of androgen, is released in response to LH and is responsible for the maturation and maintenance of the male reproductive system, as well as the development of male secondary sex characteristics. In females, FSH promotes egg maturation and LH signals the secretion of the female sex hormones, the estrogens and progesterone. Both of these hormones are important in the development and maintenance of the female reproductive system, as well as maintaining pregnancy. The placenta develops during early pregnancy, and secretes several hormones important for maintaining the pregnancy. 17.9 The Endocrine Pancreas The pancreas has both exocrine and endocrine functions. The pancreatic islet cell types include alpha cells, which produce glucagon; beta cells, which produce insulin; delta cells, which produce somatostatin; and PP cells, which produce pancreatic polypeptide. Insulin and glucagon are involved in the regulation of glucose metabolism. Insulin is produced by the beta cells in response to high blood glucose levels. It enhances glucose uptake and utilization by target cells, as well as the storage of excess glucose for later use. Dysfunction of the production of insulin or target cell resistance to the effects of insulin causes diabetes mellitus, a disorder characterized by high blood glucose levels. The hormone glucagon is produced and secreted by the alpha cells of the pancreas in response to low blood glucose levels. Glucagon stimulates mechanisms that increase blood glucose levels, such as the catabolism of glycogen into glucose. 17.10 Organs with Secondary Endocrine Functions Some organs have a secondary endocrine function. For example, the walls of the atria of the heart produce the hormone atrial natriuretic peptide (ANP), the gastrointestinal tract produces the hormones gastrin, secretin, and cholecystokinin, which aid in digestion, and the kidneys produce erythropoietin (EPO), which stimulates the formation of red blood cells. Even bone, adipose tissue, and the skin have secondary endocrine functions. 17.11 Development and Aging of the Endocrine System The endocrine system originates from all three germ layers of the embryo, including the endoderm, ectoderm, and mesoderm. In general, different hormone classes arise from distinct germ layers. Aging affects the endocrine glands, potentially affecting hormone production and secretion, and can cause disease. The production of hormones, such as human growth hormone, cortisol, aldosterone, sex hormones, and the thyroid hormones, decreases with age. Interactive Link Questions Visit this link to watch an animation of the events that occur when a hormone binds to a cell membrane receptor. What is the secondary messenger made by adenylyl cyclase during the activation of liver cells by epinephrine? 2.Visit this link to watch an animation showing the role of the hypothalamus and the pituitary gland. Which hormone is released by the pituitary to stimulate the thyroid gland? 3.Visit this link to view an animation describing the location and function of the adrenal glands. Which hormone produced by the adrenal glands is responsible for mobilization of energy stores? 4.Visit this link to view an animation describing the function of the hormone melatonin. What should you avoid doing in the middle of your sleep cycle that would lower melatonin? 5.Visit this link to view an animation describing the location and function of the pancreas. What goes wrong in the function of insulin in type 2 diabetes? Review Questions Endocrine glands ________. - secrete hormones that travel through a duct to the target organs - release neurotransmitters into the synaptic cleft - secrete chemical messengers that travel in the bloodstream - include sebaceous glands and sweat glands Chemical signaling that affects neighboring cells is called ________. - autocrine - paracrine - endocrine - neuron A newly developed pesticide has been observed to bind to an intracellular hormone receptor. If ingested, residue from this pesticide could disrupt levels of ________. - melatonin - thyroid hormone - growth hormone - insulin A small molecule binds to a G protein, preventing its activation. What direct effect will this have on signaling that involves cAMP? - The hormone will not be able to bind to the hormone receptor. - Adenylyl cyclase will not be activated. - Excessive quantities of cAMP will be produced. - The phosphorylation cascade will be initiated. A student is in a car accident, and although not hurt, immediately experiences pupil dilation, increased heart rate, and rapid breathing. What type of endocrine system stimulus did the student receive? - humoral - hormonal - neural - positive feedback The hypothalamus is functionally and anatomically connected to the posterior pituitary lobe by a bridge of ________. - blood vessels - nerve axons - cartilage - bone Which of the following is an anterior pituitary hormone? - ADH - oxytocin - TSH - cortisol How many hormones are produced by the posterior pituitary? - 0 - 1 - 2 - 6 Which of the following hormones contributes to the regulation of the body’s fluid and electrolyte balance? - adrenocorticotropic hormone - antidiuretic hormone - luteinizing hormone - all of the above Which of the following statements about the thyroid gland is true? - It is located anterior to the trachea and inferior to the larynx. - The parathyroid glands are embedded within it. - It manufactures three hormones. - all of the above The secretion of thyroid hormones is controlled by ________. - TSH from the hypothalamus - TSH from the anterior pituitary - thyroxine from the anterior pituitary - thyroglobulin from the thyroid’s parafollicular cells The development of a goiter indicates that ________. - the anterior pituitary is abnormally enlarged - there is hypertrophy of the thyroid’s follicle cells - there is an excessive accumulation of colloid in the thyroid follicles - the anterior pituitary is secreting excessive growth hormone Iodide ions cross from the bloodstream into follicle cells via ________. - simple diffusion - facilitated diffusion - active transport - osmosis When blood calcium levels are low, PTH stimulates ________. - urinary excretion of calcium by the kidneys - a reduction in calcium absorption from the intestines - the activity of osteoblasts - the activity of osteoclasts Which of the following can result from hyperparathyroidism? - increased bone deposition - fractures - convulsions - all of the above The adrenal glands are attached superiorly to which organ? - thyroid - liver - kidneys - hypothalamus What secretory cell type is found in the adrenal medulla? - chromaffin cells - neuroglial cells - follicle cells - oxyphil cells Cushing’s disease is a disorder caused by ________. - abnormally low levels of cortisol - abnormally high levels of cortisol - abnormally low levels of aldosterone - abnormally high levels of aldosterone Which of the following responses s not part of the fight-or-flight response? - pupil dilation - increased oxygen supply to the lungs - suppressed digestion - reduced mental activity What cells secrete melatonin? - melanocytes - pinealocytes - suprachiasmatic nucleus cells - retinal cells The production of melatonin is inhibited by ________. - declining levels of light - exposure to bright light - the secretion of serotonin - the activity of pinealocytes The gonads produce what class of hormones? - amine hormones - peptide hormones - steroid hormones - catecholamines The production of FSH by the anterior pituitary is reduced by which hormone? - estrogens - progesterone - relaxin - inhibin The function of the placental hormone human placental lactogen (hPL) is to ________. - prepare the breasts for lactation - nourish the placenta - regulate the menstrual cycle - all of the above If an autoimmune disorder targets the alpha cells, production of which hormone would be directly affected? - somatostatin - pancreatic polypeptide - insulin - glucagon Which of the following statements about insulin is true? - Insulin acts as a transport protein, carrying glucose across the cell membrane. - Insulin facilitates the movement of intracellular glucose transporters to the cell membrane. - Insulin stimulates the breakdown of stored glycogen into glucose. - Insulin stimulates the kidneys to reabsorb glucose into the bloodstream. The walls of the atria produce which hormone? - cholecystokinin - atrial natriuretic peptide - renin - calcitriol The end result of the RAAS is to ________. - reduce blood volume - increase blood glucose - reduce blood pressure - increase blood pressure Athletes may take synthetic EPO to boost their ________. - blood calcium levels - secretion of growth hormone - blood oxygen levels - muscle mass Hormones produced by the thymus play a role in the ________. - development of T cells - preparation of the body for childbirth - regulation of appetite - release of hydrochloric acid in the stomach The anterior pituitary gland develops from which embryonic germ layer? - oral ectoderm - neural ectoderm - mesoderm - endoderm In the elderly, decreased thyroid function causes ________. - increased tolerance for cold - decreased basal metabolic rate - decreased body fat - osteoporosis Critical Thinking Questions Describe several main differences in the communication methods used by the endocrine system and the nervous system. 39.Compare and contrast endocrine and exocrine glands. 40.True or false: Neurotransmitters are a special class of paracrines. Explain your answer. 41.Compare and contrast the signaling events involved with the second messengers cAMP and IP3. 42.Describe the mechanism of hormone response resulting from the binding of a hormone with an intracellular receptor. 43.Compare and contrast the anatomical relationship of the anterior and posterior lobes of the pituitary gland to the hypothalamus. 44.Name the target tissues for prolactin. 45.Explain why maternal iodine deficiency might lead to neurological impairment in the fetus. 46.Define hyperthyroidism and explain why one of its symptoms is weight loss. 47.Describe the role of negative feedback in the function of the parathyroid gland. 48.Explain why someone with a parathyroid gland tumor might develop kidney stones. 49.What are the three regions of the adrenal cortex and what hormones do they produce? 50.If innervation to the adrenal medulla were disrupted, what would be the physiological outcome? 51.Compare and contrast the short-term and long-term stress response. 52.Seasonal affective disorder (SAD) is a mood disorder characterized by, among other symptoms, increased appetite, sluggishness, and increased sleepiness. It occurs most commonly during the winter months, especially in regions with long winter nights. Propose a role for melatonin in SAD and a possible non-drug therapy. 53.Retinitis pigmentosa (RP) is a disease that causes deterioration of the retinas of the eyes. Describe the impact RP would have on melatonin levels. 54.Compare and contrast the role of estrogens and progesterone. 55.Describe the role of placental secretion of relaxin in preparation for childbirth. 56.What would be the physiological consequence of a disease that destroyed the beta cells of the pancreas? 57.Why is foot care extremely important for people with diabetes mellitus? 58.Summarize the role of GI tract hormones following a meal. 59.Compare and contrast the thymus gland in infancy and adulthood. 60.Distinguish between the effects of menopause and andropause on fertility.	oercommons	2025-03-18T00:35:13.719026	07/23/2019	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/56380/overview", "title": "Anatomy and Physiology, Regulation, Integration, and Control, The Endocrine System", "author": null }
https://oercommons.org/courseware/lesson/72074/overview	Chapter 3 Reading Guide Overview This reading guide is intended to be used with the Open Stax Anatomy and Physiology textbook Open Stax Anatomy and Physiology Chapter 3 Reading Guide Human Anatomy and Physiology Chapter 3: The Cellular Level of Organization 3.1: The Cell Membrane Chapter 3: The Cellular Level of Organization Structure and Composition of the Cell Membrane - ______________ – boundary of the cell. - Made up of phospholipid molecules organized into a bilayer. - The presence of cholesterol contributes to the membrane's fluidity. - Various embedded proteins have a wide range of functions. - Structure of a phospholipid molecule - Phosphate head is ___________, attracted to water molecules, dissolves freely in water - Two fatty acid tails attached to the head are ______________, water-fearing, repel water molecules, will not dissolve in water. - __________________________ having both a hydrophilic and hydrophobic region. - Soap has amphipathic properties to remove oil and grease stains. - Cell membrane consists of two adjacent layers of phospholipids arranged into a ________________________. - The cell membrane separates ICF (__________________) from ECF (______________________) the fluid outside of the cell membrane. IF (________________) is extracellular fluid outside of blood vessels. Membrane Proteins - ____________________ – a membrane protein embedded in the cell membrane. - _________ – binds specific molecules (ligands) outside of the cell that induces a chemical reaction inside of the cell. - _________ - a specific molecule that binds to and activates a specific receptor - _________ – a protein with carbohydrate molecules attached, which extend into the extracellular matrix. Function in cell recognition, identify as self, immune responses. - _______________ – a coating around the cell made up of glycoproteins and glycolipids attached to the outside of the cell membrane - _____________ – any integral protein that selective allows specific materials to pass into or out of the cell - ____________________ – attached to either the inside or outside surface of the cell membrane. Perform various functions, see text. Cell Membrane Transport across the Cell Membrane - __________________ – the cell membrane regulates molecular traffic going inside and outside the cell. - Passive vs Active Transport - ________________ – The spontaneous movement of substances without the expenditure of cellular energy. - _______________ – requires cellular energy usually in the form of ATP. Passive Transport - ___________________________ – the difference in concentration of a substance across a space. - Molecules (or ions) will spread out from a region of high concentration to where they are less concentrated. Move down the concentration gradient. - _______________ – the movement of particles down the concentration gradient. - ____________________ – the diffusion process that is used for those substances that cannot cross the membrane due to size, charge, and polarity. - ______________ – the diffusion of water across a semipermeable membrane. - Movement of water inside or outside of cells is influenced by the concentration of solutes outside or inside of the cell. - Water always diffuses from an area with fewer solutes towards an area of more solutes, thus diffusing down its concentration gradient. - _________ – two solutions with equal concentration of solutes - When a cell and its extracellular environment is isotonic, the concentration of water molecules is equal both inside and outside the cell. - ____________ – an imbalance of solutes outside the cell relative to inside. When the concentration of solutes is greater outside than inside osmosis occurs and water will leave the cell. - ________________ – when the concentration of solutes is less outside than inside, osmosis occurs, and water will enter the cell. Active Transport - Requires ATP and specific protein carriers to move substances against its concentration gradient. - _______________________ or Na+/K+ ATPase, transports sodium out of the cell while moving potassium into the cell. - This pump maintains an electrical gradient across cell membranes - ____________________ – the difference in charge across a space. - Bulk flow – active transport mechanisms that do not involve membrane carriers - _______________ – cellular ingestion by enveloping the material in a portion of its cell membrane. Forms a membranous sac called a ____________. - _____________ – cellular eating, like Pac Man, white blood cells ingesting bacteria or viruses. - ________________ – cellular drinking of fluid with dissolved substances through vesicles. - __________________________ - endocytosis by a portion of membrane that contains receptors that are specific for a certain substance. - ___________ – cellular exporting material by vesicular transport. See text for details. 3.2: The Cytoplasm and Cellular Organelles Chapter 3: The Cellular Level of Organization - Basics of Cellular Structure - _________ – semi fluid substance within the cell provides the fluid medium necessary for biochemical reactions to occur - ___________ – most are membrane bounded, bodies inside the cell each performing a given function - __________ – The cytosol and organelles together. - ________ – the cell’s central organelle, which contains most of the cell’s DNA. - Example of a typical human cell figure Organelles of the Endomembrane System - ____________________ – a system of channels that begins outside of the nuclear envelope, provides passages through the cell that function in transport, synthesizing and storage of materials. - ___________ – its outer surface is covered with ____________ (the site of protein synthesis, synthesis, and modification of proteins - __________ – not covered with ribosomes, production of membranes, breaking down toxins. - _______________ – sorting, modifying and transportation of cellular products - ___________ – contain digestive enzymes - Breakdown and digest unneeded cellular components. - ________________ – the process of a cell digesting its own structures - _______________ – cellular self-destruct mechanism Organelles for Energy Production and Detoxification - _________________ - Carry out important energy transformation reactions that result in the production of ATP. - Mitochondrion Structure - Double membranes an outer lipid bilayer with an additional inner lipid bilayer. - ____________– finger-like folds of the inner membrane with a great deal of surface area. - ________________________ - A single membrane bound structure that contains enzymes for lipid metabolism and chemical detoxification - Critical to the neutralization of free radical species - Minimize the harm due to oxidative stress. The Cytoskeleton - _______________ – helps the cells to maintain their structural integrity. - Composed of fibrous proteins - Other functions - Provide structural support to cells - Cell motility - Cell reproduction - Transportation of substances within the cell. - Positioning of cellular organelles (cytoplasmic streaming) - The cytoskeleton is composed of three different kinds of protein-based filaments - _______________ - Thickest of the three - Composed of tubulin (a protein) - Maintain cell shape and structure, resist compression of the cell - Help position organelles inside the cell - Make up cilia and flagella - ____________ are found on the surface of cells, move like oars on a boat, move materials pass them - ________________ are longer than cilia and specialized for cell locomotion, function much like a boat propeller. - Set the path for chromosome movement during cell division - Make up _______________which assist in moving chromosomes during cell division. - _______________ – the thinnest type of cytoskeletal filaments formed of actin (a protein that forms chains). - Carry out muscle contraction along with the protein myosin - ______________________ – intermediate in thickness between microfilaments and microtubules - Made up of long fibrous protein subunits much like a rope. - Maintain cell shape and structure, resist tension. - Anchor organelles together and link cells together via cell to cell junctions 3.3: The Nucleus and DNA Replication Chapter 3: The Cellular Level of Organization - ______________________ - The largest and most prominent cellular organelle. - Considered the control center of the cell. - Contains all the genetic instructions for manufacturing proteins and replicating the cell’s DNA content. - Organization of the Nucleus and its DNA - __________________ – two adjacent lipid bilayers that surround the contents of the nucleus - _______________ – small passageways in the nuclear envelope for the passage of molecules - _______________ – A region inside the nucleus that manufactures ribosomal RNA (rRNA) needed for the construction of ribosomal sub-units. - _______________ – thin threads composed of DNA and histone proteins - DNA winds around sets of histone proteins forming ________________________ which resemble beads on a string. - A molecule of DNA is made up of multiple nucleosomes. - _______________ – the condensed form of chromatin. Chromosomes form during cell division. - Humans have an estimated 22,000 genes on 46 chromosomes. DNA Replication - Characteristics of DNA - Two strands of nucleotides that are complementary, hydrogen bond to one another, and resembles a long-twisted ladder (DNA double helix). - Each side rail of the DNA molecule is composed of alternating sugar and phosphate groups that form a backbone. - Nitrogen containing bases are positioned on one side of the strands of nucleotides, meeting in the middle for complementary base pairing. - A – T - C – G - The sequence of bases determines the genetic code. - 3’ – AGTGCCT – 5’ - 5’ – TCACGGA – 3’ - _____________________ – a process by which DNA is copied prior to cell division. - _______________________ – each new DNA molecule has one parent strand and one daughter strand. - Stages of DNA Replication - Stage 1: Initiation - Two complementary strands are separated by the enzyme __________________. - Stage 2: Elongation - _______________________ – brings in the correct bases to complement the template strand to synthesize a new strand base by base. - Stage 3: Termination - Once replication stops, the two new identical DNA molecules are complete. 3.4: Protein Synthesis Chapter 3: The Cellular Level of Organization - DNA is the blueprint for cell structure and physiology. - _____________ – the entire complement of a cell's DNA. - __________________ – the complete complement of a cell’s proteins. - ________________ – a DNA sequence that provides the instructions to build a specific protein. - _________________________ – the process by which the instructions in a gene are translated into a final gene product. - Gene interpretation steps - _______________ – a section of DNA bases in a row that codes for a specific amino acid - A single gene is composed of multiple triplets in a unique sequence. From DNA to RNA: Transcription - Occurs in the nucleus of cells - DNA sequence for a single gene is copied into an intermediate messenger - __________________ (mRNA) - A single stranded nucleic acid that carries the copy of the genetic code from the nucleus to the cytoplasm. - Comparison of DNA and RNA - Double stranded vs single stranded - Deoxyribose sugar vs ribose sugar (Ribose contains an additional oxygen atom) - The base thymine is replaced by uracil - ______________ is the synthesis of a strand of mRNA that is complementary to the gene transcribed. - DNA triplets are transcribed into ________, which are three base sequences of mRNA that directly encode amino acids - Stages of Transcription - Stage 1: _____________ - Transcription begins at the beginning of the gene, at a sequence called the __________________. - Stage 2: _________________ - ______________________ unwinds the DNA segment - Then it aligns the correct base with its complementary base on the coding strand of DNA. - RNA polymerase adds new nucleotides to the growing strand of mRNA - Stage 3: _____________________ - The polymerase reaches the end of the gene - One of three specific codons (UAA, UAG, or UGA) codes a stop signal. - Enzymes are triggered to terminate transcription and release the mRNA transcript. - mRNA modifications - Occur in the nucleus after transcription but before translation in the cytoplasm. - There are long regions that do not code for amino acids (________________). They must be removed before translation can take place. - ________________ is the name of the process that removes introns and join ________________ (coding regions) together. - A ___________________ is a structure that attaches to the pre mRNA and cuts out introns and joins the exons together into a single continuous RNA molecule. From RNA to Protein: Translation - ______________________ is the process of synthesizing a chain of amino acids called a _______________________. - Occurs at the ribosomes - Ribosomes are made of __________________ (rRNA) and proteins. - Exist as two subunits (large and small) which come together for translation to occur. - Also require a third type of RNA called ________________ (tRNA). - tRNA reads the mRNA codons to insert amino acids in the correct place. - _______________ is a sequence of 3 bases on tRNA that is complementary to the mRNA codon. - Steps of translation - _______________ – ribosome binds to mRNA transcript - _______________ – Recognition of codon with anticodon, amino acids are joined by peptide bonds. - ____________________ – occurs when a stop codon is reached. The polypeptide is released, and mRNA detaches from the ribosome. 3.5: Cell Growth and Division Chapter 3: The Cellular Level of Organization - Introduction to cell growth and division: important concepts - _______________ – general term for body cells. - ______________ – sperm and egg cells, and their progenitors. - _________________________ – two copies of a single chromosome found in each somatic cell. - ________________ – in humans it is having 23 homologous pairs or 46 chromosomes. - _______________– having only one of a type of chromosome, in humans that is 23, which is the number of chromosomes found in an egg or a sperm cell. - ___________________ – the sequence of events in the life of a cell from its creation until it divides itself. The Cell Cycle - Consists of Interphase and Mitosis - _______________ – the period in which the cell is not dividing. - ___________ – division of the nucleus - Usually accompanied by __________________ or division of the cytoplasm. - Mitosis and cytokinesis results in two distinctive cells. - Interphase - Divided into 3 separate periods - _______________ – first gap phase, the cell grows and carry's out normal functions - _______________ – the cell replicates its DNA - ________________ – second gap phase, the cell continues to grow and prepare for mitosis. - ______________ – a resting phase of the cell cycle, cells that have stopped dividing The Structure of Chromosomes - Prior to cell division - Each cell contains two copies of each chromosome. - Each copy is referred to as a ______________ and is attached to the other copy. - The ________________ is the structure that attaches one sister chromatid to another. Mitosis and Cytokinesis - ___________ – the first phase of mitosis - Chromatin condenses into chromosomes - Each chromosome consists of two sister chromatids joined at the centromere. - The nucleolus disappears along with the nuclear envelope. - ________________ – consists of a single pair of centrioles together. - The centrioles begin to move apart - ___________________ begins to form between the two centrioles - Spindle microtubules attach to the centromeres of the sister chromatids, to a protein structure on the centromere that is called the ___________________. - ___________________– the second stage of mitosis - The sister chromatids line up along an imaginary plane in the middle of the cell, named the _________________________. - The spindle microtubules are poised to pull the sister chromatids apart to bring one from each pole to each side of the cell. - ________________ – the third stage of mitosis - The sister chromatids are pulled apart, forming individual chromosomes - Each daughter chromosome moves to opposite sides of the cell. - Each end of the cell receives one partner from each pair of sister chromatids. - ___________________ – the final stage of mitosis - Formation of daughter nuclei, nucleoli appear, mitotic spindle breaks down - Cytokinesis occurs, cell is splitting in half around each daughter nucleus. - ____________________ – a contractile band of microfilaments squeezes the two cells apart. Cell Cycle Control - An elaborate system of regulation which involves molecules inside the cell as well as external stimuli. - This system provides stop and advance signals for the progression of the cell cycle. - Mechanisms of Cell Cycle Control - A __________________ is a point in the cell cycle at which a signal moves the cycle forward or stops it. - Different molecules provide the signals to stop or go forward at each checkpoint. - ____________ – is one of the primary classes of cell cycle control molecules. - _____________________________ (CDK) – interact with cyclins to determine progression past cell checkpoints. 3.6: Cellular Differentiation Chapter 3: The Cellular Level of Organization - Stem Cells - _____________ – an unspecialized cell that can divide without limit as needed, and differentiate into specialized cells - Categories of Stem Cells - ________________ – the first embryonic cells that arise from division of the zygote. - These cells can become any of the cells needed for an organism to grow and develop. - _______________ – a stem cell that has the potential to differentiate into any cell type, but cannot support full development of an organism - ________________ – has the potential to differentiate into different types of cells within a given cell lineage. - ________________ – a more specialized stem cell that is limited to becoming one of a few cell types - _____________- can only form cells of its own specific cell type. Differentiation - Each type of cell only reads the portions of DNA that are relevant to its cell type. - _________________________ – a class of proteins that can either promote or inhibit transcription of genes.	oercommons	2025-03-18T00:35:13.789625	09/04/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/72074/overview", "title": "Chapter 3 Reading Guide", "author": "Bryon Spicci" }
https://oercommons.org/courseware/lesson/77050/overview	OpenStax Anatomy & Physiology Chapter 1 Identification Images Overview Identification Images for Lab Exercises and Quizzes. Chapter 1 Identification Images Laboratory Images for Identificatoin Practice/Quizzing.	oercommons	2025-03-18T00:35:13.807787	Homework/Assignment	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/77050/overview", "title": "OpenStax Anatomy & Physiology Chapter 1 Identification Images", "author": "Assessment" }
https://oercommons.org/courseware/lesson/58764/overview	The Cardiovascular System: Blood Overview The Cardiovascular System: Blood Introduction Figure 18.1 Blood Cells A single drop of blood contains millions of red blood cells, white blood cells, and platelets. One of each type is shown here, isolated from a scanning electron micrograph. CHAPTER OBJECTIVES After studying this chapter, you will be able to: - Identify the primary functions of blood, its fluid and cellular components, and its physical characteristics - Identify the most important proteins and other solutes present in blood plasma - Describe the formation of the formed element components of blood - Discuss the structure and function of red blood cells and hemoglobin - Classify and characterize white blood cells - Describe the structure of platelets and explain the process of hemostasis - Explain the significance of AB and Rh blood groups in blood transfusions - Discuss a variety of blood disorders Single-celled organisms do not need blood. They obtain nutrients directly from and excrete wastes directly into their environment. The human organism cannot do that. Our large, complex bodies need blood to deliver nutrients to and remove wastes from our trillions of cells. The heart pumps blood throughout the body in a network of blood vessels. Together, these three components—blood, heart, and vessels—makes up the cardiovascular system. This chapter focuses on the medium of transport: blood. An Overview of Blood - Identify the primary functions of blood in transportation, defense, and maintenance of homeostasis - Name the fluid component of blood and the three major types of formed elements, and identify their relative proportions in a blood sample - Discuss the unique physical characteristics of blood - Identify the composition of blood plasma, including its most important solutes and plasma proteins Recall that blood is a connective tissue. Like all connective tissues, it is made up of cellular elements and an extracellular matrix. The cellular elements—referred to as the formed elements—include red blood cells (RBCs), white blood cells (WBCs), and cell fragments called platelets. The extracellular matrix, called plasma, makes blood unique among connective tissues because it is fluid. This fluid, which is mostly water, perpetually suspends the formed elements and enables them to circulate throughout the body within the cardiovascular system. Functions of Blood The primary function of blood is to deliver oxygen and nutrients to and remove wastes from body cells, but that is only the beginning of the story. The specific functions of blood also include defense, distribution of heat, and maintenance of homeostasis. Transportation Nutrients from the foods you eat are absorbed in the digestive tract. Most of these travel in the bloodstream directly to the liver, where they are processed and released back into the bloodstream for delivery to body cells. Oxygen from the air you breathe diffuses into the blood, which moves from the lungs to the heart, which then pumps it out to the rest of the body. Moreover, endocrine glands scattered throughout the body release their products, called hormones, into the bloodstream, which carries them to distant target cells. Blood also picks up cellular wastes and byproducts, and transports them to various organs for removal. For instance, blood moves carbon dioxide to the lungs for exhalation from the body, and various waste products are transported to the kidneys and liver for excretion from the body in the form of urine or bile. Defense Many types of WBCs protect the body from external threats, such as disease-causing bacteria that have entered the bloodstream in a wound. Other WBCs seek out and destroy internal threats, such as cells with mutated DNA that could multiply to become cancerous, or body cells infected with viruses. When damage to the vessels results in bleeding, blood platelets and certain proteins dissolved in the plasma, the fluid portion of the blood, interact to block the ruptured areas of the blood vessels involved. This protects the body from further blood loss. Maintenance of Homeostasis Recall that body temperature is regulated via a classic negative-feedback loop. If you were exercising on a warm day, your rising core body temperature would trigger several homeostatic mechanisms, including increased transport of blood from your core to your body periphery, which is typically cooler. As blood passes through the vessels of the skin, heat would be dissipated to the environment, and the blood returning to your body core would be cooler. In contrast, on a cold day, blood is diverted away from the skin to maintain a warmer body core. In extreme cases, this may result in frostbite. Blood also helps to maintain the chemical balance of the body. Proteins and other compounds in blood act as buffers, which thereby help to regulate the pH of body tissues. Blood also helps to regulate the water content of body cells. Composition of Blood You have probably had blood drawn from a superficial vein in your arm, which was then sent to a lab for analysis. Some of the most common blood tests—for instance, those measuring lipid or glucose levels in plasma—determine which substances are present within blood and in what quantities. Other blood tests check for the composition of the blood itself, including the quantities and types of formed elements. One such test, called a hematocrit, measures the percentage of RBCs, clinically known as erythrocytes, in a blood sample. It is performed by spinning the blood sample in a specialized centrifuge, a process that causes the heavier elements suspended within the blood sample to separate from the lightweight, liquid plasma (Figure 18.2). Because the heaviest elements in blood are the erythrocytes, these settle at the very bottom of the hematocrit tube. Located above the erythrocytes is a pale, thin layer composed of the remaining formed elements of blood. These are the WBCs, clinically known as leukocytes, and the platelets, cell fragments also called thrombocytes. This layer is referred to as the buffy coat because of its color; it normally constitutes less than 1 percent of a blood sample. Above the buffy coat is the blood plasma, normally a pale, straw-colored fluid, which constitutes the remainder of the sample. The volume of erythrocytes after centrifugation is also commonly referred to as packed cell volume (PCV). In normal blood, about 45 percent of a sample is erythrocytes. The hematocrit of any one sample can vary significantly, however, about 36–50 percent, according to gender and other factors. Normal hematocrit values for females range from 37 to 47, with a mean value of 41; for males, hematocrit ranges from 42 to 52, with a mean of 47. The percentage of other formed elements, the WBCs and platelets, is extremely small so it is not normally considered with the hematocrit. So the mean plasma percentage is the percent of blood that is not erythrocytes: for females, it is approximately 59 (or 100 minus 41), and for males, it is approximately 53 (or 100 minus 47). Figure 18.2 Composition of Blood The cellular elements of blood include a vast number of erythrocytes and comparatively fewer leukocytes and platelets. Plasma is the fluid in which the formed elements are suspended. A sample of blood spun in a centrifuge reveals that plasma is the lightest component. It floats at the top of the tube separated from the heaviest elements, the erythrocytes, by a buffy coat of leukocytes and platelets. Hematocrit is the percentage of the total sample that is comprised of erythrocytes. Depressed and elevated hematocrit levels are shown for comparison. Characteristics of Blood When you think about blood, the first characteristic that probably comes to mind is its color. Blood that has just taken up oxygen in the lungs is bright red, and blood that has released oxygen in the tissues is a more dusky red. This is because hemoglobin is a pigment that changes color, depending upon the degree of oxygen saturation. Blood is viscous and somewhat sticky to the touch. It has a viscosity approximately five times greater than water. Viscosity is a measure of a fluid’s thickness or resistance to flow, and is influenced by the presence of the plasma proteins and formed elements within the blood. The viscosity of blood has a dramatic impact on blood pressure and flow. Consider the difference in flow between water and honey. The more viscous honey would demonstrate a greater resistance to flow than the less viscous water. The same principle applies to blood. The normal temperature of blood is slightly higher than normal body temperature—about 38 °C (or 100.4 °F), compared to 37 °C (or 98.6 °F) for an internal body temperature reading, although daily variations of 0.5 °C are normal. Although the surface of blood vessels is relatively smooth, as blood flows through them, it experiences some friction and resistance, especially as vessels age and lose their elasticity, thereby producing heat. This accounts for its slightly higher temperature. The pH of blood averages about 7.4; however, it can range from 7.35 to 7.45 in a healthy person. Blood is therefore somewhat more basic (alkaline) on a chemical scale than pure water, which has a pH of 7.0. Blood contains numerous buffers that actually help to regulate pH. Blood constitutes approximately 8 percent of adult body weight. Adult males typically average about 5 to 6 liters of blood. Females average 4–5 liters. Blood Plasma Like other fluids in the body, plasma is composed primarily of water: In fact, it is about 92 percent water. Dissolved or suspended within this water is a mixture of substances, most of which are proteins. There are literally hundreds of substances dissolved or suspended in the plasma, although many of them are found only in very small quantities. INTERACTIVE LINK Visit this site for a list of normal levels established for many of the substances found in a sample of blood. Serum, one of the specimen types included, refers to a sample of plasma after clotting factors have been removed. What types of measurements are given for levels of glucose in the blood? Plasma Proteins About 7 percent of the volume of plasma—nearly all that is not water—is made of proteins. These include several plasma proteins (proteins that are unique to the plasma), plus a much smaller number of regulatory proteins, including enzymes and some hormones. The major components of plasma are summarized in Figure 18.3. The three major groups of plasma proteins are as follows: - Albumin is the most abundant of the plasma proteins. Manufactured by the liver, albumin molecules serve as binding proteins—transport vehicles for fatty acids and steroid hormones. Recall that lipids are hydrophobic; however, their binding to albumin enables their transport in the watery plasma. Albumin is also the most significant contributor to the osmotic pressure of blood; that is, its presence holds water inside the blood vessels and draws water from the tissues, across blood vessel walls, and into the bloodstream. This in turn helps to maintain both blood volume and blood pressure. Albumin normally accounts for approximately 54 percent of the total plasma protein content, in clinical levels of 3.5–5.0 g/dL blood. - The second most common plasma proteins are the globulins. A heterogeneous group, there are three main subgroups known as alpha, beta, and gamma globulins. The alpha and beta globulins transport iron, lipids, and the fat-soluble vitamins A, D, E, and K to the cells; like albumin, they also contribute to osmotic pressure. The gamma globulins are proteins involved in immunity and are better known as an antibodies or immunoglobulins. Although other plasma proteins are produced by the liver, immunoglobulins are produced by specialized leukocytes known as plasma cells. (Seek additional content for more information about immunoglobulins.) Globulins make up approximately 38 percent of the total plasma protein volume, in clinical levels of 1.0–1.5 g/dL blood. - The least abundant plasma protein is fibrinogen. Like albumin and the alpha and beta globulins, fibrinogen is produced by the liver. It is essential for blood clotting, a process described later in this chapter. Fibrinogen accounts for about 7 percent of the total plasma protein volume, in clinical levels of 0.2–0.45 g/dL blood. Other Plasma Solutes In addition to proteins, plasma contains a wide variety of other substances. These include various electrolytes, such as sodium, potassium, and calcium ions; dissolved gases, such as oxygen, carbon dioxide, and nitrogen; various organic nutrients, such as vitamins, lipids, glucose, and amino acids; and metabolic wastes. All of these nonprotein solutes combined contribute approximately 1 percent to the total volume of plasma. Figure 18.3 Major Blood Components CAREER CONNECTION Phlebotomy and Medical Lab Technology Phlebotomists are professionals trained to draw blood (phleb- = “a blood vessel”; -tomy = “to cut”). When more than a few drops of blood are required, phlebotomists perform a venipuncture, typically of a surface vein in the arm. They perform a capillary stick on a finger, an earlobe, or the heel of an infant when only a small quantity of blood is required. An arterial stick is collected from an artery and used to analyze blood gases. After collection, the blood may be analyzed by medical laboratories or perhaps used for transfusions, donations, or research. While many allied health professionals practice phlebotomy, the American Society of Phlebotomy Technicians issues certificates to individuals passing a national examination, and some large labs and hospitals hire individuals expressly for their skill in phlebotomy. Medical or clinical laboratories employ a variety of individuals in technical positions: - Medical technologists (MT), also known as clinical laboratory technologists (CLT), typically hold a bachelor’s degree and certification from an accredited training program. They perform a wide variety of tests on various body fluids, including blood. The information they provide is essential to the primary care providers in determining a diagnosis and in monitoring the course of a disease and response to treatment. - Medical laboratory technicians (MLT) typically have an associate’s degree but may perform duties similar to those of an MT. - Medical laboratory assistants (MLA) spend the majority of their time processing samples and carrying out routine assignments within the lab. Clinical training is required, but a degree may not be essential to obtaining a position. Production of the Formed Elements - Trace the generation of the formed elements of blood from bone marrow stem cells - Discuss the role of hemopoietic growth factors in promoting the production of the formed elements The lifespan of the formed elements is very brief. Although one type of leukocyte called memory cells can survive for years, most erythrocytes, leukocytes, and platelets normally live only a few hours to a few weeks. Thus, the body must form new blood cells and platelets quickly and continuously. When you donate a unit of blood during a blood drive (approximately 475 mL, or about 1 pint), your body typically replaces the donated plasma within 24 hours, but it takes about 4 to 6 weeks to replace the blood cells. This restricts the frequency with which donors can contribute their blood. The process by which this replacement occurs is called hemopoiesis, or hematopoiesis (from the Greek root haima- = “blood”; -poiesis = “production”). Sites of Hemopoiesis Prior to birth, hemopoiesis occurs in a number of tissues, beginning with the yolk sac of the developing embryo, and continuing in the fetal liver, spleen, lymphatic tissue, and eventually the red bone marrow. Following birth, most hemopoiesis occurs in the red marrow, a connective tissue within the spaces of spongy (cancellous) bone tissue. In children, hemopoiesis can occur in the medullary cavity of long bones; in adults, the process is largely restricted to the cranial and pelvic bones, the vertebrae, the sternum, and the proximal epiphyses of the femur and humerus. Throughout adulthood, the liver and spleen maintain their ability to generate the formed elements. This process is referred to as extramedullary hemopoiesis (meaning hemopoiesis outside the medullary cavity of adult bones). When a disease such as bone cancer destroys the bone marrow, causing hemopoiesis to fail, extramedullary hemopoiesis may be initiated. Differentiation of Formed Elements from Stem Cells All formed elements arise from stem cells of the red bone marrow. Recall that stem cells undergo mitosis plus cytokinesis (cellular division) to give rise to new daughter cells: One of these remains a stem cell and the other differentiates into one of any number of diverse cell types. Stem cells may be viewed as occupying a hierarchal system, with some loss of the ability to diversify at each step. The totipotent stem cell is the zygote, or fertilized egg. The totipotent (toti- = “all”) stem cell gives rise to all cells of the human body. The next level is the pluripotent stem cell, which gives rise to multiple types of cells of the body and some of the supporting fetal membranes. Beneath this level, the mesenchymal cell is a stem cell that develops only into types of connective tissue, including fibrous connective tissue, bone, cartilage, and blood, but not epithelium, muscle, and nervous tissue. One step lower on the hierarchy of stem cells is the hemopoietic stem cell, or hemocytoblast. All of the formed elements of blood originate from this specific type of cell. Hemopoiesis begins when the hemopoietic stem cell is exposed to appropriate chemical stimuli collectively called hemopoietic growth factors, which prompt it to divide and differentiate. One daughter cell remains a hemopoietic stem cell, allowing hemopoiesis to continue. The other daughter cell becomes either of two types of more specialized stem cells (Figure 18.4): - Lymphoid stem cells give rise to a class of leukocytes known as lymphocytes, which include the various T cells, B cells, and natural killer (NK) cells, all of which function in immunity. However, hemopoiesis of lymphocytes progresses somewhat differently from the process for the other formed elements. In brief, lymphoid stem cells quickly migrate from the bone marrow to lymphatic tissues, including the lymph nodes, spleen, and thymus, where their production and differentiation continues. B cells are so named since they mature in the bone marrow, while T cells mature in the thymus. - Myeloid stem cells give rise to all the other formed elements, including the erythrocytes; megakaryocytes that produce platelets; and a myeloblast lineage that gives rise to monocytes and three forms of granular leukocytes: neutrophils, eosinophils, and basophils. Figure 18.4 Hematopoietic System of Bone Marrow Hemopoiesis is the proliferation and differentiation of the formed elements of blood. Lymphoid and myeloid stem cells do not immediately divide and differentiate into mature formed elements. As you can see in Figure 18.4, there are several intermediate stages of precursor cells (literally, forerunner cells), many of which can be recognized by their names, which have the suffix -blast. For instance, megakaryoblasts are the precursors of megakaryocytes, and proerythroblasts become reticulocytes, which eject their nucleus and most other organelles before maturing into erythrocytes. Hemopoietic Growth Factors Development from stem cells to precursor cells to mature cells is again initiated by hemopoietic growth factors. These include the following: - Erythropoietin (EPO) is a glycoprotein hormone secreted by the interstitial fibroblast cells of the kidneys in response to low oxygen levels. It prompts the production of erythrocytes. Some athletes use synthetic EPO as a performance-enhancing drug (called blood doping) to increase RBC counts and subsequently increase oxygen delivery to tissues throughout the body. EPO is a banned substance in most organized sports, but it is also used medically in the treatment of certain anemia, specifically those triggered by certain types of cancer, and other disorders in which increased erythrocyte counts and oxygen levels are desirable. - Thrombopoietin, another glycoprotein hormone, is produced by the liver and kidneys. It triggers the development of megakaryocytes into platelets. - Cytokines are glycoproteins secreted by a wide variety of cells, including red bone marrow, leukocytes, macrophages, fibroblasts, and endothelial cells. They act locally as autocrine or paracrine factors, stimulating the proliferation of progenitor cells and helping to stimulate both nonspecific and specific resistance to disease. There are two major subtypes of cytokines known as colony-stimulating factors and interleukins. - Colony-stimulating factors (CSFs) are glycoproteins that act locally, as autocrine or paracrine factors. Some trigger the differentiation of myeloblasts into granular leukocytes, namely, neutrophils, eosinophils, and basophils. These are referred to as granulocyte CSFs. A different CSF induces the production of monocytes, called monocyte CSFs. Both granulocytes and monocytes are stimulated by GM-CSF; granulocytes, monocytes, platelets, and erythrocytes are stimulated by multi-CSF. Synthetic forms of these hormones are often administered to patients with various forms of cancer who are receiving chemotherapy to revive their WBC counts. - Interleukins are another class of cytokine signaling molecules important in hemopoiesis. They were initially thought to be secreted uniquely by leukocytes and to communicate only with other leukocytes, and were named accordingly, but are now known to be produced by a variety of cells including bone marrow and endothelium. Researchers now suspect that interleukins may play other roles in body functioning, including differentiation and maturation of cells, producing immunity and inflammation. To date, more than a dozen interleukins have been identified, with others likely to follow. They are generally numbered IL-1, IL-2, IL-3, etc. EVERYDAY CONNECTION Blood Doping In its original intent, the term blood doping was used to describe the practice of injecting by transfusion supplemental RBCs into an individual, typically to enhance performance in a sport. Additional RBCs would deliver more oxygen to the tissues, providing extra aerobic capacity, clinically referred to as VO2 max. The source of the cells was either from the recipient (autologous) or from a donor with compatible blood (homologous). This practice was aided by the well-developed techniques of harvesting, concentrating, and freezing of the RBCs that could be later thawed and injected, yet still retain their functionality. These practices are considered illegal in virtually all sports and run the risk of infection, significantly increasing the viscosity of the blood and the potential for transmission of blood-borne pathogens if the blood was collected from another individual. With the development of synthetic EPO in the 1980s, it became possible to provide additional RBCs by artificially stimulating RBC production in the bone marrow. Originally developed to treat patients suffering from anemia, renal failure, or cancer treatment, large quantities of EPO can be generated by recombinant DNA technology. Synthetic EPO is injected under the skin and can increase hematocrit for many weeks. It may also induce polycythemia and raise hematocrit to 70 or greater. This increased viscosity raises the resistance of the blood and forces the heart to pump more powerfully; in extreme cases, it has resulted in death. Other drugs such as cobalt II chloride have been shown to increase natural EPO gene expression. Blood doping has become problematic in many sports, especially cycling. Lance Armstrong, winner of seven Tour de France and many other cycling titles, was stripped of his victories and admitted to blood doping in 2013. INTERACTIVE LINK Watch this video to see doctors discuss the dangers of blood doping in sports. What are the some potential side effects of blood doping? Bone Marrow Sampling and Transplants Sometimes, a healthcare provider will order a bone marrow biopsy, a diagnostic test of a sample of red bone marrow, or a bone marrow transplant, a treatment in which a donor’s healthy bone marrow—and its stem cells—replaces the faulty bone marrow of a patient. These tests and procedures are often used to assist in the diagnosis and treatment of various severe forms of anemia, such as thalassemia major and sickle cell anemia, as well as some types of cancer, specifically leukemia. In the past, when a bone marrow sample or transplant was necessary, the procedure would have required inserting a large-bore needle into the region near the iliac crest of the pelvic bones (os coxae). This location was preferred, since its location close to the body surface makes it more accessible, and it is relatively isolated from most vital organs. Unfortunately, the procedure is quite painful. Now, direct sampling of bone marrow can often be avoided. In many cases, stem cells can be isolated in just a few hours from a sample of a patient’s blood. The isolated stem cells are then grown in culture using the appropriate hemopoietic growth factors, and analyzed or sometimes frozen for later use. For an individual requiring a transplant, a matching donor is essential to prevent the immune system from destroying the donor cells—a phenomenon known as tissue rejection. To treat patients with bone marrow transplants, it is first necessary to destroy the patient’s own diseased marrow through radiation and/or chemotherapy. Donor bone marrow stem cells are then intravenously infused. From the bloodstream, they establish themselves in the recipient’s bone marrow. Erythrocytes - Describe the anatomy of erythrocytes - Discuss the various steps in the lifecycle of an erythrocyte - Explain the composition and function of hemoglobin The erythrocyte, commonly known as a red blood cell (or RBC), is by far the most common formed element: A single drop of blood contains millions of erythrocytes and just thousands of leukocytes. Specifically, males have about 5.4 million erythrocytes per microliter (µL) of blood, and females have approximately 4.8 million per µL. In fact, erythrocytes are estimated to make up about 25 percent of the total cells in the body. As you can imagine, they are quite small cells, with a mean diameter of only about 7–8 micrometers (µm) (Figure 18.5). The primary functions of erythrocytes are to pick up inhaled oxygen from the lungs and transport it to the body’s tissues, and to pick up some (about 24 percent) carbon dioxide waste at the tissues and transport it to the lungs for exhalation. Erythrocytes remain within the vascular network. Although leukocytes typically leave the blood vessels to perform their defensive functions, movement of erythrocytes from the blood vessels is abnormal. Figure 18.5 Summary of Formed Elements in Blood Shape and Structure of Erythrocytes As an erythrocyte matures in the red bone marrow, it extrudes its nucleus and most of its other organelles. During the first day or two that it is in the circulation, an immature erythrocyte, known as a reticulocyte, will still typically contain remnants of organelles. Reticulocytes should comprise approximately 1–2 percent of the erythrocyte count and provide a rough estimate of the rate of RBC production, with abnormally low or high rates indicating deviations in the production of these cells. These remnants, primarily of networks (reticulum) of ribosomes, are quickly shed, however, and mature, circulating erythrocytes have few internal cellular structural components. Lacking mitochondria, for example, they rely on anaerobic respiration. This means that they do not utilize any of the oxygen they are transporting, so they can deliver it all to the tissues. They also lack endoplasmic reticula and do not synthesize proteins. Erythrocytes do, however, contain some structural proteins that help the blood cells maintain their unique structure and enable them to change their shape to squeeze through capillaries. This includes the protein spectrin, a cytoskeletal protein element. Erythrocytes are biconcave disks; that is, they are plump at their periphery and very thin in the center (Figure 18.6). Since they lack most organelles, there is more interior space for the presence of the hemoglobin molecules that, as you will see shortly, transport gases. The biconcave shape also provides a greater surface area across which gas exchange can occur, relative to its volume; a sphere of a similar diameter would have a lower surface area-to-volume ratio. In the capillaries, the oxygen carried by the erythrocytes can diffuse into the plasma and then through the capillary walls to reach the cells, whereas some of the carbon dioxide produced by the cells as a waste product diffuses into the capillaries to be picked up by the erythrocytes. Capillary beds are extremely narrow, slowing the passage of the erythrocytes and providing an extended opportunity for gas exchange to occur. However, the space within capillaries can be so minute that, despite their own small size, erythrocytes may have to fold in on themselves if they are to make their way through. Fortunately, their structural proteins like spectrin are flexible, allowing them to bend over themselves to a surprising degree, then spring back again when they enter a wider vessel. In wider vessels, erythrocytes may stack up much like a roll of coins, forming a rouleaux, from the French word for “roll.” Figure 18.6 Shape of Red Blood Cells Erythrocytes are biconcave discs with very shallow centers. This shape optimizes the ratio of surface area to volume, facilitating gas exchange. It also enables them to fold up as they move through narrow blood vessels. Hemoglobin Hemoglobin is a large molecule made up of proteins and iron. It consists of four folded chains of a protein called globin, designated alpha 1 and 2, and beta 1 and 2 (Figure 18.7a). Each of these globin molecules is bound to a red pigment molecule called heme, which contains an ion of iron (Fe2+) (Figure 18.7b). Figure 18.7 Hemoglobin (a) A molecule of hemoglobin contains four globin proteins, each of which is bound to one molecule of the iron-containing pigment heme. (b) A single erythrocyte can contain 300 million hemoglobin molecules, and thus more than 1 billion oxygen molecules. Each iron ion in the heme can bind to one oxygen molecule; therefore, each hemoglobin molecule can transport four oxygen molecules. An individual erythrocyte may contain about 300 million hemoglobin molecules, and therefore can bind to and transport up to 1.2 billion oxygen molecules (see Figure 18.7b). In the lungs, hemoglobin picks up oxygen, which binds to the iron ions, forming oxyhemoglobin. The bright red, oxygenated hemoglobin travels to the body tissues, where it releases some of the oxygen molecules, becoming darker red deoxyhemoglobin, sometimes referred to as reduced hemoglobin. Oxygen release depends on the need for oxygen in the surrounding tissues, so hemoglobin rarely if ever leaves all of its oxygen behind. In the capillaries, carbon dioxide enters the bloodstream. About 76 percent dissolves in the plasma, some of it remaining as dissolved CO2, and the remainder forming bicarbonate ion. About 23–24 percent of it binds to the amino acids in hemoglobin, forming a molecule known as carbaminohemoglobin. From the capillaries, the hemoglobin carries carbon dioxide back to the lungs, where it releases it for exchange of oxygen. Changes in the levels of RBCs can have significant effects on the body’s ability to effectively deliver oxygen to the tissues. Ineffective hematopoiesis results in insufficient numbers of RBCs and results in one of several forms of anemia. An overproduction of RBCs produces a condition called polycythemia. The primary drawback with polycythemia is not a failure to directly deliver enough oxygen to the tissues, but rather the increased viscosity of the blood, which makes it more difficult for the heart to circulate the blood. In patients with insufficient hemoglobin, the tissues may not receive sufficient oxygen, resulting in another form of anemia. In determining oxygenation of tissues, the value of greatest interest in healthcare is the percent saturation; that is, the percentage of hemoglobin sites occupied by oxygen in a patient’s blood. Clinically this value is commonly referred to simply as “percent sat.” Percent saturation is normally monitored using a device known as a pulse oximeter, which is applied to a thin part of the body, typically the tip of the patient’s finger. The device works by sending two different wavelengths of light (one red, the other infrared) through the finger and measuring the light with a photodetector as it exits. Hemoglobin absorbs light differentially depending upon its saturation with oxygen. The machine calibrates the amount of light received by the photodetector against the amount absorbed by the partially oxygenated hemoglobin and presents the data as percent saturation. Normal pulse oximeter readings range from 95–100 percent. Lower percentages reflect hypoxemia, or low blood oxygen. The term hypoxia is more generic and simply refers to low oxygen levels. Oxygen levels are also directly monitored from free oxygen in the plasma typically following an arterial stick. When this method is applied, the amount of oxygen present is expressed in terms of partial pressure of oxygen or simply pO2 and is typically recorded in units of millimeters of mercury, mm Hg. The kidneys filter about 180 liters (~380 pints) of blood in an average adult each day, or about 20 percent of the total resting volume, and thus serve as ideal sites for receptors that determine oxygen saturation. In response to hypoxemia, less oxygen will exit the vessels supplying the kidney, resulting in hypoxia (low oxygen concentration) in the tissue fluid of the kidney where oxygen concentration is actually monitored. Interstitial fibroblasts within the kidney secrete EPO, thereby increasing erythrocyte production and restoring oxygen levels. In a classic negative-feedback loop, as oxygen saturation rises, EPO secretion falls, and vice versa, thereby maintaining homeostasis. Populations dwelling at high elevations, with inherently lower levels of oxygen in the atmosphere, naturally maintain a hematocrit higher than people living at sea level. Consequently, people traveling to high elevations may experience symptoms of hypoxemia, such as fatigue, headache, and shortness of breath, for a few days after their arrival. In response to the hypoxemia, the kidneys secrete EPO to step up the production of erythrocytes until homeostasis is achieved once again. To avoid the symptoms of hypoxemia, or altitude sickness, mountain climbers typically rest for several days to a week or more at a series of camps situated at increasing elevations to allow EPO levels and, consequently, erythrocyte counts to rise. When climbing the tallest peaks, such as Mt. Everest and K2 in the Himalayas, many mountain climbers rely upon bottled oxygen as they near the summit. Lifecycle of Erythrocytes Production of erythrocytes in the marrow occurs at the staggering rate of more than 2 million cells per second. For this production to occur, a number of raw materials must be present in adequate amounts. These include the same nutrients that are essential to the production and maintenance of any cell, such as glucose, lipids, and amino acids. However, erythrocyte production also requires several trace elements: - Iron. We have said that each heme group in a hemoglobin molecule contains an ion of the trace mineral iron. On average, less than 20 percent of the iron we consume is absorbed. Heme iron, from animal foods such as meat, poultry, and fish, is absorbed more efficiently than non-heme iron from plant foods. Upon absorption, iron becomes part of the body’s total iron pool. The bone marrow, liver, and spleen can store iron in the protein compounds ferritin and hemosiderin. Ferroportin transports the iron across the intestinal cell plasma membranes and from its storage sites into tissue fluid where it enters the blood. When EPO stimulates the production of erythrocytes, iron is released from storage, bound to transferrin, and carried to the red marrow where it attaches to erythrocyte precursors. - Copper. A trace mineral, copper is a component of two plasma proteins, hephaestin and ceruloplasmin. Without these, hemoglobin could not be adequately produced. Located in intestinal villi, hephaestin enables iron to be absorbed by intestinal cells. Ceruloplasmin transports copper. Both enable the oxidation of iron from Fe2+ to Fe3+, a form in which it can be bound to its transport protein, transferrin, for transport to body cells. In a state of copper deficiency, the transport of iron for heme synthesis decreases, and iron can accumulate in tissues, where it can eventually lead to organ damage. - Zinc. The trace mineral zinc functions as a co-enzyme that facilitates the synthesis of the heme portion of hemoglobin. - B vitamins. The B vitamins folate and vitamin B12 function as co-enzymes that facilitate DNA synthesis. Thus, both are critical for the synthesis of new cells, including erythrocytes. Erythrocytes live up to 120 days in the circulation, after which the worn-out cells are removed by a type of myeloid phagocytic cell called a macrophage, located primarily within the bone marrow, liver, and spleen. The components of the degraded erythrocytes’ hemoglobin are further processed as follows: - Globin, the protein portion of hemoglobin, is broken down into amino acids, which can be sent back to the bone marrow to be used in the production of new erythrocytes. Hemoglobin that is not phagocytized is broken down in the circulation, releasing alpha and beta chains that are removed from circulation by the kidneys. - The iron contained in the heme portion of hemoglobin may be stored in the liver or spleen, primarily in the form of ferritin or hemosiderin, or carried through the bloodstream by transferrin to the red bone marrow for recycling into new erythrocytes. - The non-iron portion of heme is degraded into the waste product biliverdin, a green pigment, and then into another waste product, bilirubin, a yellow pigment. Bilirubin binds to albumin and travels in the blood to the liver, which uses it in the manufacture of bile, a compound released into the intestines to help emulsify dietary fats. In the large intestine, bacteria breaks the bilirubin apart from the bile and converts it to urobilinogen and then into stercobilin. It is then eliminated from the body in the feces. Broad-spectrum antibiotics typically eliminate these bacteria as well and may alter the color of feces. The kidneys also remove any circulating bilirubin and other related metabolic byproducts such as urobilins and secrete them into the urine. The breakdown pigments formed from the destruction of hemoglobin can be seen in a variety of situations. At the site of an injury, biliverdin from damaged RBCs produces some of the dramatic colors associated with bruising. With a failing liver, bilirubin cannot be removed effectively from circulation and causes the body to assume a yellowish tinge associated with jaundice. Stercobilins within the feces produce the typical brown color associated with this waste. And the yellow of urine is associated with the urobilins. The erythrocyte lifecycle is summarized in Figure 18.8. Figure 18.8 Erythrocyte Lifecycle Erythrocytes are produced in the bone marrow and sent into the circulation. At the end of their lifecycle, they are destroyed by macrophages, and their components are recycled. Disorders of Erythrocytes The size, shape, and number of erythrocytes, and the number of hemoglobin molecules can have a major impact on a person’s health. When the number of RBCs or hemoglobin is deficient, the general condition is called anemia. There are more than 400 types of anemia and more than 3.5 million Americans suffer from this condition. Anemia can be broken down into three major groups: those caused by blood loss, those caused by faulty or decreased RBC production, and those caused by excessive destruction of RBCs. Clinicians often use two groupings in diagnosis: The kinetic approach focuses on evaluating the production, destruction, and removal of RBCs, whereas the morphological approach examines the RBCs themselves, paying particular emphasis to their size. A common test is the mean corpuscle volume (MCV), which measures size. Normal-sized cells are referred to as normocytic, smaller-than-normal cells are referred to as microcytic, and larger-than-normal cells are referred to as macrocytic. Reticulocyte counts are also important and may reveal inadequate production of RBCs. The effects of the various anemias are widespread, because reduced numbers of RBCs or hemoglobin will result in lower levels of oxygen being delivered to body tissues. Since oxygen is required for tissue functioning, anemia produces fatigue, lethargy, and an increased risk for infection. An oxygen deficit in the brain impairs the ability to think clearly, and may prompt headaches and irritability. Lack of oxygen leaves the patient short of breath, even as the heart and lungs work harder in response to the deficit. Blood loss anemias are fairly straightforward. In addition to bleeding from wounds or other lesions, these forms of anemia may be due to ulcers, hemorrhoids, inflammation of the stomach (gastritis), and some cancers of the gastrointestinal tract. The excessive use of aspirin or other nonsteroidal anti-inflammatory drugs such as ibuprofen can trigger ulceration and gastritis. Excessive menstruation and loss of blood during childbirth are also potential causes. Anemias caused by faulty or decreased RBC production include sickle cell anemia, iron deficiency anemia, vitamin deficiency anemia, and diseases of the bone marrow and stem cells. - A characteristic change in the shape of erythrocytes is seen in sickle cell disease (also referred to as sickle cell anemia). A genetic disorder, it is caused by production of an abnormal type of hemoglobin, called hemoglobin S, which delivers less oxygen to tissues and causes erythrocytes to assume a sickle (or crescent) shape, especially at low oxygen concentrations (Figure 18.9). These abnormally shaped cells can then become lodged in narrow capillaries because they are unable to fold in on themselves to squeeze through, blocking blood flow to tissues and causing a variety of serious problems from painful joints to delayed growth and even blindness and cerebrovascular accidents (strokes). Sickle cell anemia is a genetic condition particularly found in individuals of African descent. Figure 18.9 Sickle Cells Sickle cell anemia is caused by a mutation in one of the hemoglobin genes. Erythrocytes produce an abnormal type of hemoglobin, which causes the cell to take on a sickle or crescent shape. (credit: Janice Haney Carr) - Iron deficiency anemia is the most common type and results when the amount of available iron is insufficient to allow production of sufficient heme. This condition can occur in individuals with a deficiency of iron in the diet and is especially common in teens and children as well as in vegans and vegetarians. Additionally, iron deficiency anemia may be caused by either an inability to absorb and transport iron or slow, chronic bleeding. - Vitamin-deficient anemias generally involve insufficient vitamin B12 and folate. - Megaloblastic anemia involves a deficiency of vitamin B12 and/or folate, and often involves diets deficient in these essential nutrients. Lack of meat or a viable alternate source, and overcooking or eating insufficient amounts of vegetables may lead to a lack of folate. - Pernicious anemia is caused by poor absorption of vitamin B12 and is often seen in patients with Crohn’s disease (a severe intestinal disorder often treated by surgery), surgical removal of the intestines or stomach (common in some weight loss surgeries), intestinal parasites, and AIDS. - Pregnancies, some medications, excessive alcohol consumption, and some diseases such as celiac disease are also associated with vitamin deficiencies. It is essential to provide sufficient folic acid during the early stages of pregnancy to reduce the risk of neurological defects, including spina bifida, a failure of the neural tube to close. - Assorted disease processes can also interfere with the production and formation of RBCs and hemoglobin. If myeloid stem cells are defective or replaced by cancer cells, there will be insufficient quantities of RBCs produced. - Aplastic anemia is the condition in which there are deficient numbers of RBC stem cells. Aplastic anemia is often inherited, or it may be triggered by radiation, medication, chemotherapy, or infection. - Thalassemia is an inherited condition typically occurring in individuals from the Middle East, the Mediterranean, African, and Southeast Asia, in which maturation of the RBCs does not proceed normally. The most severe form is called Cooley’s anemia. - Lead exposure from industrial sources or even dust from paint chips of iron-containing paints or pottery that has not been properly glazed may also lead to destruction of the red marrow. - Various disease processes also can lead to anemias. These include chronic kidney diseases often associated with a decreased production of EPO, hypothyroidism, some forms of cancer, lupus, and rheumatoid arthritis. In contrast to anemia, an elevated RBC count is called polycythemia and is detected in a patient’s elevated hematocrit. It can occur transiently in a person who is dehydrated; when water intake is inadequate or water losses are excessive, the plasma volume falls. As a result, the hematocrit rises. For reasons mentioned earlier, a mild form of polycythemia is chronic but normal in people living at high altitudes. Some elite athletes train at high elevations specifically to induce this phenomenon. Finally, a type of bone marrow disease called polycythemia vera (from the Greek vera = “true”) causes an excessive production of immature erythrocytes. Polycythemia vera can dangerously elevate the viscosity of blood, raising blood pressure and making it more difficult for the heart to pump blood throughout the body. It is a relatively rare disease that occurs more often in men than women, and is more likely to be present in elderly patients those over 60 years of age. Leukocytes and Platelets - Describe the general characteristics of leukocytes - Classify leukocytes according to their lineage, their main structural features, and their primary functions - Discuss the most common malignancies involving leukocytes - Identify the lineage, basic structure, and function of platelets The leukocyte, commonly known as a white blood cell (or WBC), is a major component of the body’s defenses against disease. Leukocytes protect the body against invading microorganisms and body cells with mutated DNA, and they clean up debris. Platelets are essential for the repair of blood vessels when damage to them has occurred; they also provide growth factors for healing and repair. See Figure 18.5 for a summary of leukocytes and platelets. Characteristics of Leukocytes Although leukocytes and erythrocytes both originate from hematopoietic stem cells in the bone marrow, they are very different from each other in many significant ways. For instance, leukocytes are far less numerous than erythrocytes: Typically there are only 5000 to 10,000 per µL. They are also larger than erythrocytes and are the only formed elements that are complete cells, possessing a nucleus and organelles. And although there is just one type of erythrocyte, there are many types of leukocytes. Most of these types have a much shorter lifespan than that of erythrocytes, some as short as a few hours or even a few minutes in the case of acute infection. One of the most distinctive characteristics of leukocytes is their movement. Whereas erythrocytes spend their days circulating within the blood vessels, leukocytes routinely leave the bloodstream to perform their defensive functions in the body’s tissues. For leukocytes, the vascular network is simply a highway they travel and soon exit to reach their true destination. When they arrive, they are often given distinct names, such as macrophage or microglia, depending on their function. As shown in Figure 18.10, they leave the capillaries—the smallest blood vessels—or other small vessels through a process known as emigration(from the Latin for “removal”) or diapedesis (dia- = “through”; -pedan = “to leap”) in which they squeeze through adjacent cells in a blood vessel wall. Once they have exited the capillaries, some leukocytes will take up fixed positions in lymphatic tissue, bone marrow, the spleen, the thymus, or other organs. Others will move about through the tissue spaces very much like amoebas, continuously extending their plasma membranes, sometimes wandering freely, and sometimes moving toward the direction in which they are drawn by chemical signals. This attracting of leukocytes occurs because of positive chemotaxis (literally “movement in response to chemicals”), a phenomenon in which injured or infected cells and nearby leukocytes emit the equivalent of a chemical “911” call, attracting more leukocytes to the site. In clinical medicine, the differential counts of the types and percentages of leukocytes present are often key indicators in making a diagnosis and selecting a treatment. Figure 18.10 Emigration Leukocytes exit the blood vessel and then move through the connective tissue of the dermis toward the site of a wound. Some leukocytes, such as the eosinophil and neutrophil, are characterized as granular leukocytes. They release chemicals from their granules that destroy pathogens; they are also capable of phagocytosis. The monocyte, an agranular leukocyte, differentiates into a macrophage that then phagocytizes the pathogens. Classification of Leukocytes When scientists first began to observe stained blood slides, it quickly became evident that leukocytes could be divided into two groups, according to whether their cytoplasm contained highly visible granules: - Granular leukocytes contain abundant granules within the cytoplasm. They include neutrophils, eosinophils, and basophils (you can view their lineage from myeloid stem cells in Figure 18.4). - While granules are not totally lacking in agranular leukocytes, they are far fewer and less obvious. Agranular leukocytes include monocytes, which mature into macrophages that are phagocytic, and lymphocytes, which arise from the lymphoid stem cell line. Granular Leukocytes We will consider the granular leukocytes in order from most common to least common. All of these are produced in the red bone marrow and have a short lifespan of hours to days. They typically have a lobed nucleus and are classified according to which type of stain best highlights their granules (Figure 18.11). Figure 18.11 Granular Leukocytes A neutrophil has small granules that stain light lilac and a nucleus with two to five lobes. An eosinophil’s granules are slightly larger and stain reddish-orange, and its nucleus has two to three lobes. A basophil has large granules that stain dark blue to purple and a two-lobed nucleus. The most common of all the leukocytes, neutrophils will normally comprise 50–70 percent of total leukocyte count. They are 10–12 µm in diameter, significantly larger than erythrocytes. They are called neutrophils because their granules show up most clearly with stains that are chemically neutral (neither acidic nor basic). The granules are numerous but quite fine and normally appear light lilac. The nucleus has a distinct lobed appearance and may have two to five lobes, the number increasing with the age of the cell. Older neutrophils have increasing numbers of lobes and are often referred to as polymorphonuclear (a nucleus with many forms), or simply “polys.” Younger and immature neutrophils begin to develop lobes and are known as “bands.” Neutrophils are rapid responders to the site of infection and are efficient phagocytes with a preference for bacteria. Their granules include lysozyme, an enzyme capable of lysing, or breaking down, bacterial cell walls; oxidants such as hydrogen peroxide; and defensins, proteins that bind to and puncture bacterial and fungal plasma membranes, so that the cell contents leak out. Abnormally high counts of neutrophils indicate infection and/or inflammation, particularly triggered by bacteria, but are also found in burn patients and others experiencing unusual stress. A burn injury increases the proliferation of neutrophils in order to fight off infection that can result from the destruction of the barrier of the skin. Low counts may be caused by drug toxicity and other disorders, and may increase an individual’s susceptibility to infection. Eosinophils typically represent 2–4 percent of total leukocyte count. They are also 10–12 µm in diameter. The granules of eosinophils stain best with an acidic stain known as eosin. The nucleus of the eosinophil will typically have two to three lobes and, if stained properly, the granules will have a distinct red to orange color. The granules of eosinophils include antihistamine molecules, which counteract the activities of histamines, inflammatory chemicals produced by basophils and mast cells. Some eosinophil granules contain molecules toxic to parasitic worms, which can enter the body through the integument, or when an individual consumes raw or undercooked fish or meat. Eosinophils are also capable of phagocytosis and are particularly effective when antibodies bind to the target and form an antigen-antibody complex. High counts of eosinophils are typical of patients experiencing allergies, parasitic worm infestations, and some autoimmune diseases. Low counts may be due to drug toxicity and stress. Basophils are the least common leukocytes, typically comprising less than one percent of the total leukocyte count. They are slightly smaller than neutrophils and eosinophils at 8–10 µm in diameter. The granules of basophils stain best with basic (alkaline) stains. Basophils contain large granules that pick up a dark blue stain and are so common they may make it difficult to see the two-lobed nucleus. In general, basophils intensify the inflammatory response. They share this trait with mast cells. In the past, mast cells were considered to be basophils that left the circulation. However, this appears not to be the case, as the two cell types develop from different lineages. The granules of basophils release histamines, which contribute to inflammation, and heparin, which opposes blood clotting. High counts of basophils are associated with allergies, parasitic infections, and hypothyroidism. Low counts are associated with pregnancy, stress, and hyperthyroidism. Agranular Leukocytes Agranular leukocytes contain smaller, less-visible granules in their cytoplasm than do granular leukocytes. The nucleus is simple in shape, sometimes with an indentation but without distinct lobes. There are two major types of agranulocytes: lymphocytes and monocytes (see Figure 18.4). Lymphocytes are the only formed element of blood that arises from lymphoid stem cells. Although they form initially in the bone marrow, much of their subsequent development and reproduction occurs in the lymphatic tissues. Lymphocytes are the second most common type of leukocyte, accounting for about 20–30 percent of all leukocytes, and are essential for the immune response. The size range of lymphocytes is quite extensive, with some authorities recognizing two size classes and others three. Typically, the large cells are 10–14 µm and have a smaller nucleus-to-cytoplasm ratio and more granules. The smaller cells are typically 6–9 µm with a larger volume of nucleus to cytoplasm, creating a “halo” effect. A few cells may fall outside these ranges, at 14–17 µm. This finding has led to the three size range classification. The three major groups of lymphocytes include natural killer cells, B cells, and T cells. Natural killer (NK) cells are capable of recognizing cells that do not express “self” proteins on their plasma membrane or that contain foreign or abnormal markers. These “nonself” cells include cancer cells, cells infected with a virus, and other cells with atypical surface proteins. Thus, they provide generalized, nonspecific immunity. The larger lymphocytes are typically NK cells. B cells and T cells, also called B lymphocytes and T lymphocytes, play prominent roles in defending the body against specific pathogens (disease-causing microorganisms) and are involved in specific immunity. One form of B cells (plasma cells) produces the antibodies or immunoglobulins that bind to specific foreign or abnormal components of plasma membranes. This is also referred to as humoral (body fluid) immunity. T cells provide cellular-level immunity by physically attacking foreign or diseased cells. A memory cell is a variety of both B and T cells that forms after exposure to a pathogen and mounts rapid responses upon subsequent exposures. Unlike other leukocytes, memory cells live for many years. B cells undergo a maturation process in the bone marrow, whereas T cells undergo maturation in the thymus. This site of the maturation process gives rise to the name B and T cells. The functions of lymphocytes are complex and will be covered in detail in the chapter covering the lymphatic system and immunity. Smaller lymphocytes are either B or T cells, although they cannot be differentiated in a normal blood smear. Abnormally high lymphocyte counts are characteristic of viral infections as well as some types of cancer. Abnormally low lymphocyte counts are characteristic of prolonged (chronic) illness or immunosuppression, including that caused by HIV infection and drug therapies that often involve steroids. Monocytes originate from myeloid stem cells. They normally represent 2–8 percent of the total leukocyte count. They are typically easily recognized by their large size of 12–20 µm and indented or horseshoe-shaped nuclei. Macrophages are monocytes that have left the circulation and phagocytize debris, foreign pathogens, worn-out erythrocytes, and many other dead, worn out, or damaged cells. Macrophages also release antimicrobial defensins and chemotactic chemicals that attract other leukocytes to the site of an infection. Some macrophages occupy fixed locations, whereas others wander through the tissue fluid. Abnormally high counts of monocytes are associated with viral or fungal infections, tuberculosis, and some forms of leukemia and other chronic diseases. Abnormally low counts are typically caused by suppression of the bone marrow. Lifecycle of Leukocytes Most leukocytes have a relatively short lifespan, typically measured in hours or days. Production of all leukocytes begins in the bone marrow under the influence of CSFs and interleukins. Secondary production and maturation of lymphocytes occurs in specific regions of lymphatic tissue known as germinal centers. Lymphocytes are fully capable of mitosis and may produce clones of cells with identical properties. This capacity enables an individual to maintain immunity throughout life to many threats that have been encountered in the past. Disorders of Leukocytes Leukopenia is a condition in which too few leukocytes are produced. If this condition is pronounced, the individual may be unable to ward off disease. Excessive leukocyte proliferation is known as leukocytosis. Although leukocyte counts are high, the cells themselves are often nonfunctional, leaving the individual at increased risk for disease. Leukemia is a cancer involving an abundance of leukocytes. It may involve only one specific type of leukocyte from either the myeloid line (myelocytic leukemia) or the lymphoid line (lymphocytic leukemia). In chronic leukemia, mature leukocytes accumulate and fail to die. In acute leukemia, there is an overproduction of young, immature leukocytes. In both conditions the cells do not function properly. Lymphoma is a form of cancer in which masses of malignant T and/or B lymphocytes collect in lymph nodes, the spleen, the liver, and other tissues. As in leukemia, the malignant leukocytes do not function properly, and the patient is vulnerable to infection. Some forms of lymphoma tend to progress slowly and respond well to treatment. Others tend to progress quickly and require aggressive treatment, without which they are rapidly fatal. Platelets You may occasionally see platelets referred to as thrombocytes, but because this name suggests they are a type of cell, it is not accurate. A platelet is not a cell but rather a fragment of the cytoplasm of a cell called a megakaryocyte that is surrounded by a plasma membrane. Megakaryocytes are descended from myeloid stem cells (see Figure 18.4) and are large, typically 50–100 µm in diameter, and contain an enlarged, lobed nucleus. As noted earlier, thrombopoietin, a glycoprotein secreted by the kidneys and liver, stimulates the proliferation of megakaryoblasts, which mature into megakaryocytes. These remain within bone marrow tissue (Figure 18.12) and ultimately form platelet-precursor extensions that extend through the walls of bone marrow capillaries to release into the circulation thousands of cytoplasmic fragments, each enclosed by a bit of plasma membrane. These enclosed fragments are platelets. Each megakarocyte releases 2000–3000 platelets during its lifespan. Following platelet release, megakaryocyte remnants, which are little more than a cell nucleus, are consumed by macrophages. Platelets are relatively small, 2–4 µm in diameter, but numerous, with typically 150,000–160,000 per µL of blood. After entering the circulation, approximately one-third migrate to the spleen for storage for later release in response to any rupture in a blood vessel. They then become activated to perform their primary function, which is to limit blood loss. Platelets remain only about 10 days, then are phagocytized by macrophages. Platelets are critical to hemostasis, the stoppage of blood flow following damage to a vessel. They also secrete a variety of growth factors essential for growth and repair of tissue, particularly connective tissue. Infusions of concentrated platelets are now being used in some therapies to stimulate healing. Disorders of Platelets Thrombocytosis is a condition in which there are too many platelets. This may trigger formation of unwanted blood clots (thrombosis), a potentially fatal disorder. If there is an insufficient number of platelets, called thrombocytopenia, blood may not clot properly, and excessive bleeding may result. Figure 18.12 Platelets Platelets are derived from cells called megakaryocytes. INTERACTIVE LINK Figure 18.13 Leukocytes (Micrographs provided by the Regents of University of Michigan Medical School © 2012) View University of Michigan Webscopes at http://virtualslides.med.umich.edu/Histology/Cardiovascular%20System/081-2_HISTO_40X.svs/view.apml?cwidth=860&cheight=733&chost=virtualslides.med.umich.edu&listview=1&title=&csis=1 and explore the blood slides in greater detail. The Webscope feature allows you to move the slides as you would with a mechanical stage. You can increase and decrease the magnification. There is a chance to review each of the leukocytes individually after you have attempted to identify them from the first two blood smears. In addition, there are a few multiple choice questions. Are you able to recognize and identify the various formed elements? You will need to do this is a systematic manner, scanning along the image. The standard method is to use a grid, but this is not possible with this resource. Try constructing a simple table with each leukocyte type and then making a mark for each cell type you identify. Attempt to classify at least 50 and perhaps as many as 100 different cells. Based on the percentage of cells that you count, do the numbers represent a normal blood smear or does something appear to be abnormal? Hemostasis - Describe the three mechanisms involved in hemostasis - Explain how the extrinsic and intrinsic coagulation pathways lead to the common pathway, and the coagulation factors involved in each - Discuss disorders affecting hemostasis Platelets are key players in hemostasis, the process by which the body seals a ruptured blood vessel and prevents further loss of blood. Although rupture of larger vessels usually requires medical intervention, hemostasis is quite effective in dealing with small, simple wounds. There are three steps to the process: vascular spasm, the formation of a platelet plug, and coagulation (blood clotting). Failure of any of these steps will result in hemorrhage—excessive bleeding. Vascular Spasm When a vessel is severed or punctured, or when the wall of a vessel is damaged, vascular spasm occurs. In vascular spasm, the smooth muscle in the walls of the vessel contracts dramatically. This smooth muscle has both circular layers; larger vessels also have longitudinal layers. The circular layers tend to constrict the flow of blood, whereas the longitudinal layers, when present, draw the vessel back into the surrounding tissue, often making it more difficult for a surgeon to locate, clamp, and tie off a severed vessel. The vascular spasm response is believed to be triggered by several chemicals called endothelins that are released by vessel-lining cells and by pain receptors in response to vessel injury. This phenomenon typically lasts for up to 30 minutes, although it can last for hours. Formation of the Platelet Plug In the second step, platelets, which normally float free in the plasma, encounter the area of vessel rupture with the exposed underlying connective tissue and collagenous fibers. The platelets begin to clump together, become spiked and sticky, and bind to the exposed collagen and endothelial lining. This process is assisted by a glycoprotein in the blood plasma called von Willebrand factor, which helps stabilize the growing platelet plug. As platelets collect, they simultaneously release chemicals from their granules into the plasma that further contribute to hemostasis. Among the substances released by the platelets are: - adenosine diphosphate (ADP), which helps additional platelets to adhere to the injury site, reinforcing and expanding the platelet plug - serotonin, which maintains vasoconstriction - prostaglandins and phospholipids, which also maintain vasoconstriction and help to activate further clotting chemicals, as discussed next A platelet plug can temporarily seal a small opening in a blood vessel. Plug formation, in essence, buys the body time while more sophisticated and durable repairs are being made. In a similar manner, even modern naval warships still carry an assortment of wooden plugs to temporarily repair small breaches in their hulls until permanent repairs can be made. Coagulation Those more sophisticated and more durable repairs are collectively called coagulation, the formation of a blood clot. The process is sometimes characterized as a cascade, because one event prompts the next as in a multi-level waterfall. The result is the production of a gelatinous but robust clot made up of a mesh of fibrin—an insoluble filamentous protein derived from fibrinogen, the plasma protein introduced earlier—in which platelets and blood cells are trapped. Figure 18.14 summarizes the three steps of hemostasis. Figure 18.14 Hemostasis (a) An injury to a blood vessel initiates the process of hemostasis. Blood clotting involves three steps. First, vascular spasm constricts the flow of blood. Next, a platelet plug forms to temporarily seal small openings in the vessel. Coagulation then enables the repair of the vessel wall once the leakage of blood has stopped. (b) The synthesis of fibrin in blood clots involves either an intrinsic pathway or an extrinsic pathway, both of which lead to a common pathway. (credit a: Kevin MacKenzie) Clotting Factors Involved in Coagulation In the coagulation cascade, chemicals called clotting factors (or coagulation factors) prompt reactions that activate still more coagulation factors. The process is complex, but is initiated along two basic pathways: - The extrinsic pathway, which normally is triggered by trauma. - The intrinsic pathway, which begins in the bloodstream and is triggered by internal damage to the wall of the vessel. Both of these merge into a third pathway, referred to as the common pathway (see Figure 18.14b). All three pathways are dependent upon the 12 known clotting factors, including Ca2+ and vitamin K (Table 18.1). Clotting factors are secreted primarily by the liver and the platelets. The liver requires the fat-soluble vitamin K to produce many of them. Vitamin K (along with biotin and folate) is somewhat unusual among vitamins in that it is not only consumed in the diet but is also synthesized by bacteria residing in the large intestine. The calcium ion, considered factor IV, is derived from the diet and from the breakdown of bone. Some recent evidence indicates that activation of various clotting factors occurs on specific receptor sites on the surfaces of platelets. The 12 clotting factors are numbered I through XIII according to the order of their discovery. Factor VI was once believed to be a distinct clotting factor, but is now thought to be identical to factor V. Rather than renumber the other factors, factor VI was allowed to remain as a placeholder and also a reminder that knowledge changes over time. Clotting Factors \| Factor number \| Name \| Type of molecule \| Source \| Pathway(s) \| \|---\|---\|---\|---\|---\| \| I \| Fibrinogen \| Plasma protein \| Liver \| Common; converted into fibrin \| \| II \| Prothrombin \| Plasma protein \| Liver* \| Common; converted into thrombin \| \| III \| Tissue thromboplastin or tissue factor \| Lipoprotein mixture \| Damaged cells and platelets \| Extrinsic \| \| IV \| Calcium ions \| Inorganic ions in plasma \| Diet, platelets, bone matrix \| Entire process \| \| V \| Proaccelerin \| Plasma protein \| Liver, platelets \| Extrinsic and intrinsic \| \| VI \| Not used \| Not used \| Not used \| Not used \| \| VII \| Proconvertin \| Plasma protein \| Liver * \| Extrinsic \| \| VIII \| Antihemolytic factor A \| Plasma protein factor \| Platelets and endothelial cells \| Intrinsic; deficiency results in hemophilia A \| \| IX \| Antihemolytic factor B (plasma thromboplastin component) \| Plasma protein \| Liver* \| Intrinsic; deficiency results in hemophilia B \| \| X \| Stuart–Prower factor (thrombokinase) \| Protein \| Liver* \| Extrinsic and intrinsic \| \| XI \| Antihemolytic factor C (plasma thromboplastin antecedent) \| Plasma protein \| Liver \| Intrinsic; deficiency results in hemophilia C \| \| XII \| Hageman factor \| Plasma protein \| Liver \| Intrinsic; initiates clotting in vitro also activates plasmin \| \| XIII \| Fibrin-stabilizing factor \| Plasma protein \| Liver, platelets \| Stabilizes fibrin; slows fibrinolysis \| Table 18.1 *Vitamin K required. Extrinsic Pathway The quicker responding and more direct extrinsic pathway (also known as the tissue factor pathway) begins when damage occurs to the surrounding tissues, such as in a traumatic injury. Upon contact with blood plasma, the damaged extravascular cells, which are extrinsic to the bloodstream, release factor III (thromboplastin). Sequentially, Ca2+ then factor VII (proconvertin), which is activated by factor III, are added, forming an enzyme complex. This enzyme complex leads to activation of factor X (Stuart–Prower factor), which activates the common pathway discussed below. The events in the extrinsic pathway are completed in a matter of seconds. Intrinsic Pathway The intrinsic pathway (also known as the contact activation pathway) is longer and more complex. In this case, the factors involved are intrinsic to (present within) the bloodstream. The pathway can be prompted by damage to the tissues, resulting from internal factors such as arterial disease; however, it is most often initiated when factor XII (Hageman factor) comes into contact with foreign materials, such as when a blood sample is put into a glass test tube. Within the body, factor XII is typically activated when it encounters negatively charged molecules, such as inorganic polymers and phosphate produced earlier in the series of intrinsic pathway reactions. Factor XII sets off a series of reactions that in turn activates factor XI (antihemolytic factor C or plasma thromboplastin antecedent) then factor IX (antihemolytic factor B or plasma thromboplasmin). In the meantime, chemicals released by the platelets increase the rate of these activation reactions. Finally, factor VIII (antihemolytic factor A) from the platelets and endothelial cells combines with factor IX (antihemolytic factor B or plasma thromboplasmin) to form an enzyme complex that activates factor X (Stuart–Prower factor or thrombokinase), leading to the common pathway. The events in the intrinsic pathway are completed in a few minutes. Common Pathway Both the intrinsic and extrinsic pathways lead to the common pathway, in which fibrin is produced to seal off the vessel. Once factor X has been activated by either the intrinsic or extrinsic pathway, the enzyme prothrombinase converts factor II, the inactive enzyme prothrombin, into the active enzyme thrombin. (Note that if the enzyme thrombin were not normally in an inactive form, clots would form spontaneously, a condition not consistent with life.) Then, thrombin converts factor I, the soluble fibrinogen, into the insoluble fibrin protein strands. Factor XIII then stabilizes the fibrin clot. Fibrinolysis The stabilized clot is acted upon by contractile proteins within the platelets. As these proteins contract, they pull on the fibrin threads, bringing the edges of the clot more tightly together, somewhat as we do when tightening loose shoelaces (see Figure 18.14a). This process also wrings out of the clot a small amount of fluid called serum, which is blood plasma without its clotting factors. To restore normal blood flow as the vessel heals, the clot must eventually be removed. Fibrinolysis is the gradual degradation of the clot. Again, there is a fairly complicated series of reactions that involves factor XII and protein-catabolizing enzymes. During this process, the inactive protein plasminogen is converted into the active plasmin, which gradually breaks down the fibrin of the clot. Additionally, bradykinin, a vasodilator, is released, reversing the effects of the serotonin and prostaglandins from the platelets. This allows the smooth muscle in the walls of the vessels to relax and helps to restore the circulation. Plasma Anticoagulants An anticoagulant is any substance that opposes coagulation. Several circulating plasma anticoagulants play a role in limiting the coagulation process to the region of injury and restoring a normal, clot-free condition of blood. For instance, a cluster of proteins collectively referred to as the protein C system inactivates clotting factors involved in the intrinsic pathway. TFPI (tissue factor pathway inhibitor) inhibits the conversion of the inactive factor VII to the active form in the extrinsic pathway. Antithrombin inactivates factor X and opposes the conversion of prothrombin (factor II) to thrombin in the common pathway. And as noted earlier, basophils release heparin, a short-acting anticoagulant that also opposes prothrombin. Heparin is also found on the surfaces of cells lining the blood vessels. A pharmaceutical form of heparin is often administered therapeutically, for example, in surgical patients at risk for blood clots. INTERACTIVE LINK View these animations to explore the intrinsic, extrinsic, and common pathways that are involved the process of coagulation. The coagulation cascade restores hemostasis by activating coagulation factors in the presence of an injury. How does the endothelium of the blood vessel walls prevent the blood from coagulating as it flows through the blood vessels? Disorders of Clotting Either an insufficient or an excessive production of platelets can lead to severe disease or death. As discussed earlier, an insufficient number of platelets, called thrombocytopenia, typically results in the inability of blood to form clots. This can lead to excessive bleeding, even from minor wounds. Another reason for failure of the blood to clot is the inadequate production of functional amounts of one or more clotting factors. This is the case in the genetic disorder hemophilia, which is actually a group of related disorders, the most common of which is hemophilia A, accounting for approximately 80 percent of cases. This disorder results in the inability to synthesize sufficient quantities of factor VIII. Hemophilia B is the second most common form, accounting for approximately 20 percent of cases. In this case, there is a deficiency of factor IX. Both of these defects are linked to the X chromosome and are typically passed from a healthy (carrier) mother to her male offspring, since males are XY. Females would need to inherit a defective gene from each parent to manifest the disease, since they are XX. Patients with hemophilia bleed from even minor internal and external wounds, and leak blood into joint spaces after exercise and into urine and stool. Hemophilia C is a rare condition that is triggered by an autosomal (not sex) chromosome that renders factor XI nonfunctional. It is not a true recessive condition, since even individuals with a single copy of the mutant gene show a tendency to bleed. Regular infusions of clotting factors isolated from healthy donors can help prevent bleeding in hemophiliac patients. At some point, genetic therapy will become a viable option. In contrast to the disorders characterized by coagulation failure is thrombocytosis, also mentioned earlier, a condition characterized by excessive numbers of platelets that increases the risk for excessive clot formation, a condition known as thrombosis. A thrombus (plural = thrombi) is an aggregation of platelets, erythrocytes, and even WBCs typically trapped within a mass of fibrin strands. While the formation of a clot is normal following the hemostatic mechanism just described, thrombi can form within an intact or only slightly damaged blood vessel. In a large vessel, a thrombus will adhere to the vessel wall and decrease the flow of blood, and is referred to as a mural thrombus. In a small vessel, it may actually totally block the flow of blood and is termed an occlusive thrombus. Thrombi are most commonly caused by vessel damage to the endothelial lining, which activates the clotting mechanism. These may include venous stasis, when blood in the veins, particularly in the legs, remains stationary for long periods. This is one of the dangers of long airplane flights in crowded conditions and may lead to deep vein thrombosis or atherosclerosis, an accumulation of debris in arteries. Thrombophilia, also called hypercoagulation, is a condition in which there is a tendency to form thrombosis. This may be familial (genetic) or acquired. Acquired forms include the autoimmune disease lupus, immune reactions to heparin, polycythemia vera, thrombocytosis, sickle cell disease, pregnancy, and even obesity. A thrombus can seriously impede blood flow to or from a region and will cause a local increase in blood pressure. If flow is to be maintained, the heart will need to generate a greater pressure to overcome the resistance. When a portion of a thrombus breaks free from the vessel wall and enters the circulation, it is referred to as an embolus. An embolus that is carried through the bloodstream can be large enough to block a vessel critical to a major organ. When it becomes trapped, an embolus is called an embolism. In the heart, brain, or lungs, an embolism may accordingly cause a heart attack, a stroke, or a pulmonary embolism. These are medical emergencies. Among the many known biochemical activities of aspirin is its role as an anticoagulant. Aspirin (acetylsalicylic acid) is very effective at inhibiting the aggregation of platelets. It is routinely administered during a heart attack or stroke to reduce the adverse effects. Physicians sometimes recommend that patients at risk for cardiovascular disease take a low dose of aspirin on a daily basis as a preventive measure. However, aspirin can also lead to serious side effects, including increasing the risk of ulcers. A patient is well advised to consult a physician before beginning any aspirin regimen. A class of drugs collectively known as thrombolytic agents can help speed up the degradation of an abnormal clot. If a thrombolytic agent is administered to a patient within 3 hours following a thrombotic stroke, the patient’s prognosis improves significantly. However, some strokes are not caused by thrombi, but by hemorrhage. Thus, the cause must be determined before treatment begins. Tissue plasminogen activator is an enzyme that catalyzes the conversion of plasminogen to plasmin, the primary enzyme that breaks down clots. It is released naturally by endothelial cells but is also used in clinical medicine. New research is progressing using compounds isolated from the venom of some species of snakes, particularly vipers and cobras, which may eventually have therapeutic value as thrombolytic agents. Blood Typing - Describe the two basic physiological consequences of transfusion of incompatible blood - Compare and contrast ABO and Rh blood groups - Identify which blood groups may be safely transfused into patients with different ABO types - Discuss the pathophysiology of hemolytic disease of the newborn Blood transfusions in humans were risky procedures until the discovery of the major human blood groups by Karl Landsteiner, an Austrian biologist and physician, in 1900. Until that point, physicians did not understand that death sometimes followed blood transfusions, when the type of donor blood infused into the patient was incompatible with the patient’s own blood. Blood groups are determined by the presence or absence of specific marker molecules on the plasma membranes of erythrocytes. With their discovery, it became possible for the first time to match patient-donor blood types and prevent transfusion reactions and deaths. Antigens, Antibodies, and Transfusion Reactions Antigens are substances that the body does not recognize as belonging to the “self” and that therefore trigger a defensive response from the leukocytes of the immune system. (Seek more content for additional information on immunity.) Here, we will focus on the role of immunity in blood transfusion reactions. With RBCs in particular, you may see the antigens referred to as isoantigens or agglutinogens (surface antigens) and the antibodies referred to as isoantibodies or agglutinins. In this chapter, we will use the more common terms antigens and antibodies. Antigens are generally large proteins, but may include other classes of organic molecules, including carbohydrates, lipids, and nucleic acids. Following an infusion of incompatible blood, erythrocytes with foreign antigens appear in the bloodstream and trigger an immune response. Proteins called antibodies (immunoglobulins), which are produced by certain B lymphocytes called plasma cells, attach to the antigens on the plasma membranes of the infused erythrocytes and cause them to adhere to one another. - Because the arms of the Y-shaped antibodies attach randomly to more than one nonself erythrocyte surface, they form clumps of erythrocytes. This process is called agglutination. - The clumps of erythrocytes block small blood vessels throughout the body, depriving tissues of oxygen and nutrients. - As the erythrocyte clumps are degraded, in a process called hemolysis, their hemoglobin is released into the bloodstream. This hemoglobin travels to the kidneys, which are responsible for filtration of the blood. However, the load of hemoglobin released can easily overwhelm the kidney’s capacity to clear it, and the patient can quickly develop kidney failure. More than 50 antigens have been identified on erythrocyte membranes, but the most significant in terms of their potential harm to patients are classified in two groups: the ABO blood group and the Rh blood group. The ABO Blood Group Although the ABO blood group name consists of three letters, ABO blood typing designates the presence or absence of just two antigens, A and B. Both are glycoproteins. People whose erythrocytes have A antigens on their erythrocyte membrane surfaces are designated blood type A, and those whose erythrocytes have B antigens are blood type B. People can also have both A and B antigens on their erythrocytes, in which case they are blood type AB. People with neither A nor B antigens are designated blood type O. ABO blood types are genetically determined. Normally the body must be exposed to a foreign antigen before an antibody can be produced. This is not the case for the ABO blood group. Individuals with type A blood—without any prior exposure to incompatible blood—have preformed antibodies to the B antigen circulating in their blood plasma. These antibodies, referred to as anti-B antibodies, will cause agglutination and hemolysis if they ever encounter erythrocytes with B antigens. Similarly, an individual with type B blood has pre-formed anti-A antibodies. Individuals with type AB blood, which has both antigens, do not have preformed antibodies to either of these. People with type O blood lack antigens A and B on their erythrocytes, but both anti-A and anti-B antibodies circulate in their blood plasma. Rh Blood Groups The Rh blood group is classified according to the presence or absence of a second erythrocyte antigen identified as Rh. (It was first discovered in a type of primate known as a rhesus macaque, which is often used in research, because its blood is similar to that of humans.) Although dozens of Rh antigens have been identified, only one, designated D, is clinically important. Those who have the Rh D antigen present on their erythrocytes—about 85 percent of Americans—are described as Rh positive (Rh+) and those who lack it are Rh negative (Rh−). Note that the Rh group is distinct from the ABO group, so any individual, no matter their ABO blood type, may have or lack this Rh antigen. When identifying a patient’s blood type, the Rh group is designated by adding the word positive or negative to the ABO type. For example, A positive (A+) means ABO group A blood with the Rh antigen present, and AB negative (AB−) means ABO group AB blood without the Rh antigen. Table 18.2 summarizes the distribution of the ABO and Rh blood types within the United States. Summary of ABO and Rh Blood Types within the United States \| Blood Type \| African-Americans \| Asian-Americans \| Caucasian-Americans \| Latino/Latina-Americans \| \|---\|---\|---\|---\|---\| \| A+ \| 24 \| 27 \| 33 \| 29 \| \| A− \| 2 \| 0.5 \| 7 \| 2 \| \| B+ \| 18 \| 25 \| 9 \| 9 \| \| B− \| 1 \| 0.4 \| 2 \| 1 \| \| AB+ \| 4 \| 7 \| 3 \| 2 \| \| AB− \| 0.3 \| 0.1 \| 1 \| 0.2 \| \| O+ \| 47 \| 39 \| 37 \| 53 \| \| O− \| 4 \| 1 \| 8 \| 4 \| Table 18.2 n contrast to the ABO group antibodies, which are preformed, antibodies to the Rh antigen are produced only in Rh− individuals after exposure to the antigen. This process, called sensitization, occurs following a transfusion with Rh-incompatible blood or, more commonly, with the birth of an Rh+ baby to an Rh− mother. Problems are rare in a first pregnancy, since the baby’s Rh+cells rarely cross the placenta (the organ of gas and nutrient exchange between the baby and the mother). However, during or immediately after birth, the Rh− mother can be exposed to the baby’s Rh+ cells (Figure 18.15). Research has shown that this occurs in about 13−14 percent of such pregnancies. After exposure, the mother’s immune system begins to generate anti-Rh antibodies. If the mother should then conceive another Rh+ baby, the Rh antibodies she has produced can cross the placenta into the fetal bloodstream and destroy the fetal RBCs. This condition, known as hemolytic disease of the newborn (HDN) or erythroblastosis fetalis, may cause anemia in mild cases, but the agglutination and hemolysis can be so severe that without treatment the fetus may die in the womb or shortly after birth. Figure 18.15 Erythroblastosis Fetalis The first exposure of an Rh− mother to Rh+ erythrocytes during pregnancy induces sensitization. Anti-Rh antibodies begin to circulate in the mother’s bloodstream. A second exposure occurs with a subsequent pregnancy with an Rh+ fetus in the uterus. Maternal anti-Rh antibodies may cross the placenta and enter the fetal bloodstream, causing agglutination and hemolysis of fetal erythrocytes. A drug known as RhoGAM, short for Rh immune globulin, can temporarily prevent the development of Rh antibodies in the Rh−mother, thereby averting this potentially serious disease for the fetus. RhoGAM antibodies destroy any fetal Rh+ erythrocytes that may cross the placental barrier. RhoGAM is normally administered to Rh− mothers during weeks 26−28 of pregnancy and within 72 hours following birth. It has proven remarkably effective in decreasing the incidence of HDN. Earlier we noted that the incidence of HDN in an Rh+ subsequent pregnancy to an Rh− mother is about 13–14 percent without preventive treatment. Since the introduction of RhoGAM in 1968, the incidence has dropped to about 0.1 percent in the United States. Determining ABO Blood Types Clinicians are able to determine a patient’s blood type quickly and easily using commercially prepared antibodies. An unknown blood sample is allocated into separate wells. Into one well a small amount of anti-A antibody is added, and to another a small amount of anti-B antibody. If the antigen is present, the antibodies will cause visible agglutination of the cells (Figure 18.16). The blood should also be tested for Rh antibodies. Figure 18.16 Cross Matching Blood Types This sample of a commercially produced “bedside” card enables quick typing of both a recipient’s and donor’s blood before transfusion. The card contains three reaction sites or wells. One is coated with an anti-A antibody, one with an anti-B antibody, and one with an anti-D antibody (tests for the presence of Rh factor D). Mixing a drop of blood and saline into each well enables the blood to interact with a preparation of type-specific antibodies, also called anti-seras. Agglutination of RBCs in a given site indicates a positive identification of the blood antigens, in this case A and Rh antigens for blood type A+. For the purpose of transfusion, the donor’s and recipient’s blood types must match. ABO Transfusion Protocols To avoid transfusion reactions, it is best to transfuse only matching blood types; that is, a type B+ recipient should ideally receive blood only from a type B+ donor and so on. That said, in emergency situations, when acute hemorrhage threatens the patient’s life, there may not be time for cross matching to identify blood type. In these cases, blood from a universal donor—an individual with type O− blood—may be transfused. Recall that type O erythrocytes do not display A or B antigens. Thus, anti-A or anti-B antibodies that might be circulating in the patient’s blood plasma will not encounter any erythrocyte surface antigens on the donated blood and therefore will not be provoked into a response. One problem with this designation of universal donor is if the O− individual had prior exposure to Rh antigen, Rh antibodies may be present in the donated blood. Also, introducing type O blood into an individual with type A, B, or AB blood will nevertheless introduce antibodies against both A and B antigens, as these are always circulating in the type O blood plasma. This may cause problems for the recipient, but because the volume of blood transfused is much lower than the volume of the patient’s own blood, the adverse effects of the relatively few infused plasma antibodies are typically limited. Rh factor also plays a role. If Rh− individuals receiving blood have had prior exposure to Rh antigen, antibodies for this antigen may be present in the blood and trigger agglutination to some degree. Although it is always preferable to cross match a patient’s blood before transfusing, in a true life-threatening emergency situation, this is not always possible, and these procedures may be implemented. A patient with blood type AB+ is known as the universal recipient. This patient can theoretically receive any type of blood, because the patient’s own blood—having both A and B antigens on the erythrocyte surface—does not produce anti-A or anti-B antibodies. In addition, an Rh+ patient can receive both Rh+ and Rh− blood. However, keep in mind that the donor’s blood will contain circulating antibodies, again with possible negative implications. Figure 18.17 summarizes the blood types and compatibilities. At the scene of multiple-vehicle accidents, military engagements, and natural or human-caused disasters, many victims may suffer simultaneously from acute hemorrhage, yet type O blood may not be immediately available. In these circumstances, medics may at least try to replace some of the volume of blood that has been lost. This is done by intravenous administration of a saline solution that provides fluids and electrolytes in proportions equivalent to those of normal blood plasma. Research is ongoing to develop a safe and effective artificial blood that would carry out the oxygen-carrying function of blood without the RBCs, enabling transfusions in the field without concern for incompatibility. These blood substitutes normally contain hemoglobin- as well as perfluorocarbon-based oxygen carriers. Figure 18.17 ABO Blood Group This chart summarizes the characteristics of the blood types in the ABO blood group. See the text for more on the concept of a universal donor or recipient. Key Terms - ABO blood group - blood-type classification based on the presence or absence of A and B glycoproteins on the erythrocyte membrane surface - agglutination - clustering of cells into masses linked by antibodies - agranular leukocytes - leukocytes with few granules in their cytoplasm; specifically, monocytes, lymphocytes, and NK cells - albumin - most abundant plasma protein, accounting for most of the osmotic pressure of plasma - anemia - deficiency of red blood cells or hemoglobin - antibodies - (also, immunoglobulins or gamma globulins) antigen-specific proteins produced by specialized B lymphocytes that protect the body by binding to foreign objects such as bacteria and viruses - anticoagulant - substance such as heparin that opposes coagulation - antithrombin - anticoagulant that inactivates factor X and opposes the conversion of prothrombin (factor II) into thrombin in the common pathway - B lymphocytes - (also, B cells) lymphocytes that defend the body against specific pathogens and thereby provide specific immunity - basophils - granulocytes that stain with a basic (alkaline) stain and store histamine and heparin - bilirubin - yellowish bile pigment produced when iron is removed from heme and is further broken down into waste products - biliverdin - green bile pigment produced when the non-iron portion of heme is degraded into a waste product; converted to bilirubin in the liver - blood - liquid connective tissue composed of formed elements—erythrocytes, leukocytes, and platelets—and a fluid extracellular matrix called plasma; component of the cardiovascular system - bone marrow biopsy - diagnostic test of a sample of red bone marrow - bone marrow transplant - treatment in which a donor’s healthy bone marrow with its stem cells replaces diseased or damaged bone marrow of a patient - buffy coat - thin, pale layer of leukocytes and platelets that separates the erythrocytes from the plasma in a sample of centrifuged blood - carbaminohemoglobin - compound of carbon dioxide and hemoglobin, and one of the ways in which carbon dioxide is carried in the blood - clotting factors - group of 12 identified substances active in coagulation - coagulation - formation of a blood clot; part of the process of hemostasis - colony-stimulating factors (CSFs) - glycoproteins that trigger the proliferation and differentiation of myeloblasts into granular leukocytes (basophils, neutrophils, and eosinophils) - common pathway - final coagulation pathway activated either by the intrinsic or the extrinsic pathway, and ending in the formation of a blood clot - cross matching - blood test for identification of blood type using antibodies and small samples of blood - cytokines - class of proteins that act as autocrine or paracrine signaling molecules; in the cardiovascular system, they stimulate the proliferation of progenitor cells and help to stimulate both nonspecific and specific resistance to disease - defensins - antimicrobial proteins released from neutrophils and macrophages that create openings in the plasma membranes to kill cells - deoxyhemoglobin - molecule of hemoglobin without an oxygen molecule bound to it - diapedesis - (also, emigration) process by which leukocytes squeeze through adjacent cells in a blood vessel wall to enter tissues - embolus - thrombus that has broken free from the blood vessel wall and entered the circulation - emigration - (also, diapedesis) process by which leukocytes squeeze through adjacent cells in a blood vessel wall to enter tissues - eosinophils - granulocytes that stain with eosin; they release antihistamines and are especially active against parasitic worms - erythrocyte - (also, red blood cell) mature myeloid blood cell that is composed mostly of hemoglobin and functions primarily in the transportation of oxygen and carbon dioxide - erythropoietin (EPO) - glycoprotein that triggers the bone marrow to produce RBCs; secreted by the kidney in response to low oxygen levels - extrinsic pathway - initial coagulation pathway that begins with tissue damage and results in the activation of the common pathway - ferritin - protein-containing storage form of iron found in the bone marrow, liver, and spleen - fibrin - insoluble, filamentous protein that forms the structure of a blood clot - fibrinogen - plasma protein produced in the liver and involved in blood clotting - fibrinolysis - gradual degradation of a blood clot - formed elements - cellular components of blood; that is, erythrocytes, leukocytes, and platelets - globin - heme-containing globular protein that is a constituent of hemoglobin - globulins - heterogeneous group of plasma proteins that includes transport proteins, clotting factors, immune proteins, and others - granular leukocytes - leukocytes with abundant granules in their cytoplasm; specifically, neutrophils, eosinophils, and basophils - hematocrit - (also, packed cell volume) volume percentage of erythrocytes in a sample of centrifuged blood - heme - red, iron-containing pigment to which oxygen binds in hemoglobin - hemocytoblast - hemopoietic stem cell that gives rise to the formed elements of blood - hemoglobin - oxygen-carrying compound in erythrocytes - hemolysis - destruction (lysis) of erythrocytes and the release of their hemoglobin into circulation - hemolytic disease of the newborn (HDN) - (also, erythroblastosis fetalis) disorder causing agglutination and hemolysis in an Rh+ fetus or newborn of an Rh− mother - hemophilia - genetic disorder characterized by inadequate synthesis of clotting factors - hemopoiesis - production of the formed elements of blood - hemopoietic growth factors - chemical signals including erythropoietin, thrombopoietin, colony-stimulating factors, and interleukins that regulate the differentiation and proliferation of particular blood progenitor cells - hemopoietic stem cell - type of pluripotent stem cell that gives rise to the formed elements of blood (hemocytoblast) - hemorrhage - excessive bleeding - hemosiderin - protein-containing storage form of iron found in the bone marrow, liver, and spleen - hemostasis - physiological process by which bleeding ceases - heparin - short-acting anticoagulant stored in mast cells and released when tissues are injured, opposes prothrombin - hypoxemia - below-normal level of oxygen saturation of blood (typically <95 percent) - immunoglobulins - (also, antibodies or gamma globulins) antigen-specific proteins produced by specialized B lymphocytes that protect the body by binding to foreign objects such as bacteria and viruses - interleukins - signaling molecules that may function in hemopoiesis, inflammation, and specific immune responses - intrinsic pathway - initial coagulation pathway that begins with vascular damage or contact with foreign substances, and results in the activation of the common pathway - leukemia - cancer involving leukocytes - leukocyte - (also, white blood cell) colorless, nucleated blood cell, the chief function of which is to protect the body from disease - leukocytosis - excessive leukocyte proliferation - leukopenia - below-normal production of leukocytes - lymphocytes - agranular leukocytes of the lymphoid stem cell line, many of which function in specific immunity - lymphoid stem cells - type of hemopoietic stem cells that gives rise to lymphocytes, including various T cells, B cells, and NK cells, all of which function in immunity - lymphoma - form of cancer in which masses of malignant T and/or B lymphocytes collect in lymph nodes, the spleen, the liver, and other tissues - lysozyme - digestive enzyme with bactericidal properties - macrophage - phagocytic cell of the myeloid lineage; a matured monocyte - megakaryocyte - bone marrow cell that produces platelets - memory cell - type of B or T lymphocyte that forms after exposure to a pathogen - monocytes - agranular leukocytes of the myeloid stem cell line that circulate in the bloodstream; tissue monocytes are macrophages - myeloid stem cells - type of hemopoietic stem cell that gives rise to some formed elements, including erythrocytes, megakaryocytes that produce platelets, and a myeloblast lineage that gives rise to monocytes and three forms of granular leukocytes (neutrophils, eosinophils, and basophils) - natural killer (NK) cells - cytotoxic lymphocytes capable of recognizing cells that do not express “self” proteins on their plasma membrane or that contain foreign or abnormal markers; provide generalized, nonspecific immunity - neutrophils - granulocytes that stain with a neutral dye and are the most numerous of the leukocytes; especially active against bacteria - oxyhemoglobin - molecule of hemoglobin to which oxygen is bound - packed cell volume (PCV) - (also, hematocrit) volume percentage of erythrocytes present in a sample of centrifuged blood - plasma - in blood, the liquid extracellular matrix composed mostly of water that circulates the formed elements and dissolved materials throughout the cardiovascular system - plasmin - blood protein active in fibrinolysis - platelet plug - accumulation and adhesion of platelets at the site of blood vessel injury - platelets - (also, thrombocytes) one of the formed elements of blood that consists of cell fragments broken off from megakaryocytes - pluripotent stem cell - stem cell that derives from totipotent stem cells and is capable of differentiating into many, but not all, cell types - polycythemia - elevated level of hemoglobin, whether adaptive or pathological - polymorphonuclear - having a lobed nucleus, as seen in some leukocytes - positive chemotaxis - process in which a cell is attracted to move in the direction of chemical stimuli - red blood cells (RBCs) - (also, erythrocytes) one of the formed elements of blood that transports oxygen - reticulocyte - immature erythrocyte that may still contain fragments of organelles - Rh blood group - blood-type classification based on the presence or absence of the antigen Rh on the erythrocyte membrane surface - serum - blood plasma that does not contain clotting factors - sickle cell disease - (also, sickle cell anemia) inherited blood disorder in which hemoglobin molecules are malformed, leading to the breakdown of RBCs that take on a characteristic sickle shape - T lymphocytes - (also, T cells) lymphocytes that provide cellular-level immunity by physically attacking foreign or diseased cells - thalassemia - inherited blood disorder in which maturation of RBCs does not proceed normally, leading to abnormal formation of hemoglobin and the destruction of RBCs - thrombin - enzyme essential for the final steps in formation of a fibrin clot - thrombocytes - platelets, one of the formed elements of blood that consists of cell fragments broken off from megakaryocytes - thrombocytopenia - condition in which there are too few platelets, resulting in abnormal bleeding (hemophilia) - thrombocytosis - condition in which there are too many platelets, resulting in abnormal clotting (thrombosis) - thrombopoietin - hormone secreted by the liver and kidneys that prompts the development of megakaryocytes into thrombocytes (platelets) - thrombosis - excessive clot formation - thrombus - aggregation of fibrin, platelets, and erythrocytes in an intact artery or vein - tissue factor - protein thromboplastin, which initiates the extrinsic pathway when released in response to tissue damage - totipotent stem cell - embryonic stem cell that is capable of differentiating into any and all cells of the body; enabling the full development of an organism - transferrin - plasma protein that binds reversibly to iron and distributes it throughout the body - universal donor - individual with type O− blood - universal recipient - individual with type AB+ blood - vascular spasm - initial step in hemostasis, in which the smooth muscle in the walls of the ruptured or damaged blood vessel contracts - white blood cells (WBCs) - (also, leukocytes) one of the formed elements of blood that provides defense against disease agents and foreign materials Chapter Review 18.1 An Overview of Blood Blood is a fluid connective tissue critical to the transportation of nutrients, gases, and wastes throughout the body; to defend the body against infection and other threats; and to the homeostatic regulation of pH, temperature, and other internal conditions. Blood is composed of formed elements—erythrocytes, leukocytes, and cell fragments called platelets—and a fluid extracellular matrix called plasma. More than 90 percent of plasma is water. The remainder is mostly plasma proteins—mainly albumin, globulins, and fibrinogen—and other dissolved solutes such as glucose, lipids, electrolytes, and dissolved gases. Because of the formed elements and the plasma proteins and other solutes, blood is sticky and more viscous than water. It is also slightly alkaline, and its temperature is slightly higher than normal body temperature. 18.2 Production of the Formed Elements Through the process of hemopoiesis, the formed elements of blood are continually produced, replacing the relatively short-lived erythrocytes, leukocytes, and platelets. Hemopoiesis begins in the red bone marrow, with hemopoietic stem cells that differentiate into myeloid and lymphoid lineages. Myeloid stem cells give rise to most of the formed elements. Lymphoid stem cells give rise only to the various lymphocytes designated as B and T cells, and NK cells. Hemopoietic growth factors, including erythropoietin, thrombopoietin, colony-stimulating factors, and interleukins, promote the proliferation and differentiation of formed elements. 18.3 Erythrocytes The most abundant formed elements in blood, erythrocytes are red, biconcave disks packed with an oxygen-carrying compound called hemoglobin. The hemoglobin molecule contains four globin proteins bound to a pigment molecule called heme, which contains an ion of iron. In the bloodstream, iron picks up oxygen in the lungs and drops it off in the tissues; the amino acids in hemoglobin then transport carbon dioxide from the tissues back to the lungs. Erythrocytes live only 120 days on average, and thus must be continually replaced. Worn-out erythrocytes are phagocytized by macrophages and their hemoglobin is broken down. The breakdown products are recycled or removed as wastes: Globin is broken down into amino acids for synthesis of new proteins; iron is stored in the liver or spleen or used by the bone marrow for production of new erythrocytes; and the remnants of heme are converted into bilirubin, or other waste products that are taken up by the liver and excreted in the bile or removed by the kidneys. Anemia is a deficiency of RBCs or hemoglobin, whereas polycythemia is an excess of RBCs. 18.4 Leukocytes and Platelets Leukocytes function in body defenses. They squeeze out of the walls of blood vessels through emigration or diapedesis, then may move through tissue fluid or become attached to various organs where they fight against pathogenic organisms, diseased cells, or other threats to health. Granular leukocytes, which include neutrophils, eosinophils, and basophils, originate with myeloid stem cells, as do the agranular monocytes. The other agranular leukocytes, NK cells, B cells, and T cells, arise from the lymphoid stem cell line. The most abundant leukocytes are the neutrophils, which are first responders to infections, especially with bacteria. About 20–30 percent of all leukocytes are lymphocytes, which are critical to the body’s defense against specific threats. Leukemia and lymphoma are malignancies involving leukocytes. Platelets are fragments of cells known as megakaryocytes that dwell within the bone marrow. While many platelets are stored in the spleen, others enter the circulation and are essential for hemostasis; they also produce several growth factors important for repair and healing. 18.5 Hemostasis Hemostasis is the physiological process by which bleeding ceases. Hemostasis involves three basic steps: vascular spasm, the formation of a platelet plug, and coagulation, in which clotting factors promote the formation of a fibrin clot. Fibrinolysis is the process in which a clot is degraded in a healing vessel. Anticoagulants are substances that oppose coagulation. They are important in limiting the extent and duration of clotting. Inadequate clotting can result from too few platelets, or inadequate production of clotting factors, for instance, in the genetic disorder hemophilia. Excessive clotting, called thrombosis, can be caused by excessive numbers of platelets. A thrombus is a collection of fibrin, platelets, and erythrocytes that has accumulated along the lining of a blood vessel, whereas an embolus is a thrombus that has broken free from the vessel wall and is circulating in the bloodstream. 18.6 Blood Typing Antigens are nonself molecules, usually large proteins, which provoke an immune response. In transfusion reactions, antibodies attach to antigens on the surfaces of erythrocytes and cause agglutination and hemolysis. ABO blood group antigens are designated A and B. People with type A blood have A antigens on their erythrocytes, whereas those with type B blood have B antigens. Those with AB blood have both A and B antigens, and those with type O blood have neither A nor B antigens. The blood plasma contains preformed antibodies against the antigens not present on a person’s erythrocytes. A second group of blood antigens is the Rh group, the most important of which is Rh D. People with Rh− blood do not have this antigen on their erythrocytes, whereas those who are Rh+ do. About 85 percent of Americans are Rh+. When a woman who is Rh− becomes pregnant with an Rh+ fetus, her body may begin to produce anti-Rh antibodies. If she subsequently becomes pregnant with a second Rh+ fetus and is not treated preventively with RhoGAM, the fetus will be at risk for an antigen-antibody reaction, including agglutination and hemolysis. This is known as hemolytic disease of the newborn. Cross matching to determine blood type is necessary before transfusing blood, unless the patient is experiencing hemorrhage that is an immediate threat to life, in which case type O− blood may be transfused. Interactive Link Questions Visit this site for a list of normal levels established for many of the substances found in a sample of blood. Serum, one of the specimen types included, refers to a sample of plasma after clotting factors have been removed. What types of measurements are given for levels of glucose in the blood? 2.Watch this video to see doctors discuss the dangers of blood doping in sports. What are the some potential side effects of blood doping? 3.Figure 18.13 Are you able to recognize and identify the various formed elements? You will need to do this is a systematic manner, scanning along the image. The standard method is to use a grid, but this is not possible with this resource. Try constructing a simple table with each leukocyte type and then making a mark for each cell type you identify. Attempt to classify at least 50 and perhaps as many as 100 different cells. Based on the percentage of cells that you count, do the numbers represent a normal blood smear or does something appear to be abnormal? 4.View these animations to explore the intrinsic, extrinsic, and common pathways that are involved the process of coagulation. The coagulation cascade restores hemostasis by activating coagulation factors in the presence of an injury. How does the endothelium of the blood vessel walls prevent the blood from coagulating as it flows through the blood vessels? Review Questions Which of the following statements about blood is true? - Blood is about 92 percent water. - Blood is slightly more acidic than water. - Blood is slightly more viscous than water. - Blood is slightly more salty than seawater. Which of the following statements about albumin is true? - It draws water out of the blood vessels and into the body’s tissues. - It is the most abundant plasma protein. - It is produced by specialized leukocytes called plasma cells. - All of the above are true. Which of the following plasma proteins is not produced by the liver? - fibrinogen - alpha globulin - beta globulin - immunoglobulin Which of the formed elements arise from myeloid stem cells? - B cells - natural killer cells - platelets - all of the above Which of the following statements about erythropoietin is true? - It facilitates the proliferation and differentiation of the erythrocyte lineage. - It is a hormone produced by the thyroid gland. - It is a hemopoietic growth factor that prompts lymphoid stem cells to leave the bone marrow. - Both a and b are true. Interleukins are associated primarily with which of the following? - production of various lymphocytes - immune responses - inflammation - all of the above Which of the following statements about mature, circulating erythrocytes is true? - They have no nucleus. - They are packed with mitochondria. - They survive for an average of 4 days. - All of the above A molecule of hemoglobin ________. - is shaped like a biconcave disk packed almost entirely with iron - contains four glycoprotein units studded with oxygen - consists of four globin proteins, each bound to a molecule of heme - can carry up to 120 molecules of oxygen The production of healthy erythrocytes depends upon the availability of ________. - copper - zinc - vitamin B12 - copper, zinc, and vitamin B12 Aging and damaged erythrocytes are removed from the circulation by ________. - myeoblasts - monocytes - macrophages - mast cells A patient has been suffering for 2 months with a chronic, watery diarrhea. A blood test is likely to reveal ________. - a hematocrit below 30 percent - hypoxemia - anemia - polycythemia The process by which leukocytes squeeze through adjacent cells in a blood vessel wall is called ________. - leukocytosis - positive chemotaxis - emigration - cytoplasmic extending Which of the following describes a neutrophil? - abundant, agranular, especially effective against cancer cells - abundant, granular, especially effective against bacteria - rare, agranular, releases antimicrobial defensins - rare, granular, contains multiple granules packed with histamine T and B lymphocytes ________. - are polymorphonuclear - are involved with specific immune function - proliferate excessively in leukopenia - are most active against parasitic worms A patient has been experiencing severe, persistent allergy symptoms that are reduced when she takes an antihistamine. Before the treatment, this patient was likely to have had increased activity of which leukocyte? - basophils - neutrophils - monocytes - natural killer cells Thrombocytes are more accurately called ________. - clotting factors - megakaryoblasts - megakaryocytes - platelets The first step in hemostasis is ________. - vascular spasm - conversion of fibrinogen to fibrin - activation of the intrinsic pathway - activation of the common pathway Prothrombin is converted to thrombin during the ________. - intrinsic pathway - extrinsic pathway - common pathway - formation of the platelet plug Hemophilia is characterized by ________. - inadequate production of heparin - inadequate production of clotting factors - excessive production of fibrinogen - excessive production of platelets The process in which antibodies attach to antigens, causing the formation of masses of linked cells, is called ________. - sensitization - coagulation - agglutination - hemolysis People with ABO blood type O ________. - have both antigens A and B on their erythrocytes - lack both antigens A and B on their erythrocytes - have neither anti-A nor anti-B antibodies circulating in their blood plasma - are considered universal recipients Hemolytic disease of the newborn is a risk during a subsequent pregnancy in which ________. - a type AB mother is carrying a type O fetus - a type O mother is carrying a type AB fetus - an Rh+ mother is carrying an Rh− fetus - an Rh− mother is carrying a second Rh+ fetus Critical Thinking Questions A patient’s hematocrit is 42 percent. Approximately what percentage of the patient’s blood is plasma? 28.Why would it be incorrect to refer to the formed elements as cells? 29.True or false: The buffy coat is the portion of a blood sample that is made up of its proteins. 30.Myelofibrosis is a disorder in which inflammation and scar tissue formation in the bone marrow impair hemopoiesis. One sign is an enlarged spleen. Why? 31.Would you expect a patient with a form of cancer called acute myelogenous leukemia to experience impaired production of erythrocytes, or impaired production of lymphocytes? Explain your choice. 32.A young woman has been experiencing unusually heavy menstrual bleeding for several years. She follows a strict vegan diet (no animal foods). She is at risk for what disorder, and why? 33.A patient has thalassemia, a genetic disorder characterized by abnormal synthesis of globin proteins and excessive destruction of erythrocytes. This patient is jaundiced and is found to have an excessive level of bilirubin in his blood. Explain the connection. 34.One of the more common adverse effects of cancer chemotherapy is the destruction of leukocytes. Before his next scheduled chemotherapy treatment, a patient undergoes a blood test called an absolute neutrophil count (ANC), which reveals that his neutrophil count is 1900 cells per microliter. Would his healthcare team be likely to proceed with his chemotherapy treatment? Why? 35.A patient was admitted to the burn unit the previous evening suffering from a severe burn involving his left upper extremity and shoulder. A blood test reveals that he is experiencing leukocytosis. Why is this an expected finding? 36.A lab technician collects a blood sample in a glass tube. After about an hour, she harvests serum to continue her blood analysis. Explain what has happened during the hour that the sample was in the glass tube. 37.Explain why administration of a thrombolytic agent is a first intervention for someone who has suffered a thrombotic stroke. 38.Following a motor vehicle accident, a patient is rushed to the emergency department with multiple traumatic injuries, causing severe bleeding. The patient’s condition is critical, and there is no time for determining his blood type. What type of blood is transfused, and why? 39.In preparation for a scheduled surgery, a patient visits the hospital lab for a blood draw. The technician collects a blood sample and performs a test to determine its type. She places a sample of the patient’s blood in two wells. To the first well she adds anti-A antibody. To the second she adds anti-B antibody. Both samples visibly agglutinate. Has the technician made an error, or is this a normal response? If normal, what blood type does this indicate?	oercommons	2025-03-18T00:35:13.924651	10/14/2019	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/58764/overview", "title": "Anatomy and Physiology, Fluids and Transport, The Cardiovascular System: Blood", "author": null }
https://oercommons.org/courseware/lesson/56354/overview	The Tissue Level of Organization Introduction Figure 4.1 Micrograph of Cervical Tissue This figure is a view of the regular architecture of normal tissue contrasted with the irregular arrangement of cancerous cells. (credit: “Haymanj”/Wikimedia Commons) CHAPTER OBJECTIVES After studying this chapter, you will be able to: - Identify the main tissue types and discuss their roles in the human body - Identify the four types of tissue membranes and the characteristics of each that make them functional - Explain the functions of various epithelial tissues and how their forms enable their functions - Explain the functions of various connective tissues and how their forms enable their functions - Describe the characteristics of muscle tissue and how these enable function - Discuss the characteristics of nervous tissue and how these enable information processing and control of muscular and glandular activities The body contains at least 200 distinct cell types. These cells contain essentially the same internal structures yet they vary enormously in shape and function. The different types of cells are not randomly distributed throughout the body; rather they occur in organized layers, a level of organization referred to as tissue. The micrograph that opens this chapter shows the high degree of organization among different types of cells in the tissue of the cervix. You can also see how that organization breaks down when cancer takes over the regular mitotic functioning of a cell. The variety in shape reflects the many different roles that cells fulfill in your body. The human body starts as a single cell at fertilization. As this fertilized egg divides, it gives rise to trillions of cells, each built from the same blueprint, but organizing into tissues and becoming irreversibly committed to a developmental pathway. Types of Tissues - Identify the four main tissue types - Discuss the functions of each tissue type - Relate the structure of each tissue type to their function - Discuss the embryonic origin of tissue - Identify the three major germ layers - Identify the main types of tissue membranes The term tissue is used to describe a group of cells found together in the body. The cells within a tissue share a common embryonic origin. Microscopic observation reveals that the cells in a tissue share morphological features and are arranged in an orderly pattern that achieves the tissue’s functions. From the evolutionary perspective, tissues appear in more complex organisms. For example, multicellular protists, ancient eukaryotes, do not have cells organized into tissues. Although there are many types of cells in the human body, they are organized into four broad categories of tissues: epithelial, connective, muscle, and nervous. Each of these categories is characterized by specific functions that contribute to the overall health and maintenance of the body. A disruption of the structure is a sign of injury or disease. Such changes can be detected through histology, the microscopic study of tissue appearance, organization, and function. The Four Types of Tissues Epithelial tissue, also referred to as epithelium, refers to the sheets of cells that cover exterior surfaces of the body, lines internal cavities and passageways, and forms certain glands. Connective tissue, as its name implies, binds the cells and organs of the body together and functions in the protection, support, and integration of all parts of the body. Muscle tissue is excitable, responding to stimulation and contracting to provide movement, and occurs as three major types: skeletal (voluntary) muscle, smooth muscle, and cardiac muscle in the heart. Nervous tissue is also excitable, allowing the propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of the body (Figure 4.2). The next level of organization is the organ, where several types of tissues come together to form a working unit. Just as knowing the structure and function of cells helps you in your study of tissues, knowledge of tissues will help you understand how organs function. The epithelial and connective tissues are discussed in detail in this chapter. Muscle and nervous tissues will be discussed only briefly in this chapter. Figure 4.2 Four Types of Tissue: Body The four types of tissues are exemplified in nervous tissue, stratified squamous epithelial tissue, cardiac muscle tissue, and connective tissue in small intestine. Clockwise from nervous tissue, LM × 872, LM × 282, LM × 460, LM × 800. (Micrographs provided by the Regents of University of Michigan Medical School © 2012) Embryonic Origin of Tissues The zygote, or fertilized egg, is a single cell formed by the fusion of an egg and sperm. After fertilization the zygote gives rise to rapid mitotic cycles, generating many cells to form the embryo. The first embryonic cells generated have the ability to differentiate into any type of cell in the body and, as such, are called totipotent, meaning each has the capacity to divide, differentiate, and develop into a new organism. As cell proliferation progresses, three major cell lineages are established within the embryo. As explained in a later chapter, each of these lineages of embryonic cells forms the distinct germ layers from which all the tissues and organs of the human body eventually form. Each germ layer is identified by its relative position: ectoderm (ecto- = “outer”), mesoderm (meso- = “middle”), and endoderm (endo- = “inner”). Figure 4.3 shows the types of tissues and organs associated with the each of the three germ layers. Note that epithelial tissue originates in all three layers, whereas nervous tissue derives primarily from the ectoderm and muscle tissue from mesoderm. Figure 4.3 Embryonic Origin of Tissues and Major Organs INTERACTIVE LINK View this slideshow to learn more about stem cells. How do somatic stem cells differ from embryonic stem cells? Tissue Membranes A tissue membrane is a thin layer or sheet of cells that covers the outside of the body (for example, skin), the organs (for example, pericardium), internal passageways that lead to the exterior of the body (for example, abdominal mesenteries), and the lining of the moveable joint cavities. There are two basic types of tissue membranes: connective tissue and epithelial membranes (Figure 4.4). Figure 4.4 Tissue Membranes The two broad categories of tissue membranes in the body are (1) connective tissue membranes, which include synovial membranes, and (2) epithelial membranes, which include mucous membranes, serous membranes, and the cutaneous membrane, in other words, the skin. Connective Tissue Membranes The connective tissue membrane is formed solely from connective tissue. These membranes encapsulate organs, such as the kidneys, and line our movable joints. A synovial membrane is a type of connective tissue membrane that lines the cavity of a freely movable joint. For example, synovial membranes surround the joints of the shoulder, elbow, and knee. Fibroblasts in the inner layer of the synovial membrane release hyaluronan into the joint cavity. The hyaluronan effectively traps available water to form the synovial fluid, a natural lubricant that enables the bones of a joint to move freely against one another without much friction. This synovial fluid readily exchanges water and nutrients with blood, as do all body fluids. Epithelial Membranes The epithelial membrane is composed of epithelium attached to a layer of connective tissue, for example, your skin. The mucous membrane is also a composite of connective and epithelial tissues. Sometimes called mucosae, these epithelial membranes line the body cavities and hollow passageways that open to the external environment, and include the digestive, respiratory, excretory, and reproductive tracts. Mucous, produced by the epithelial exocrine glands, covers the epithelial layer. The underlying connective tissue, called the lamina propria (literally “own layer”), help support the fragile epithelial layer. A serous membrane is an epithelial membrane composed of mesodermally derived epithelium called the mesothelium that is supported by connective tissue. These membranes line the coelomic cavities of the body, that is, those cavities that do not open to the outside, and they cover the organs located within those cavities. They are essentially membranous bags, with mesothelium lining the inside and connective tissue on the outside. Serous fluid secreted by the cells of the thin squamous mesothelium lubricates the membrane and reduces abrasion and friction between organs. Serous membranes are identified according locations. Three serous membranes line the thoracic cavity; the two pleura that cover the lungs and the pericardium that covers the heart. A fourth, the peritoneum, is the serous membrane in the abdominal cavity that covers abdominal organs and forms double sheets of mesenteries that suspend many of the digestive organs. The skin is an epithelial membrane also called the cutaneous membrane. It is a stratified squamous epithelial membrane resting on top of connective tissue. The apical surface of this membrane is exposed to the external environment and is covered with dead, keratinized cells that help protect the body from desiccation and pathogens. Epithelial Tissue - Explain the structure and function of epithelial tissue - Distinguish between tight junctions, anchoring junctions, and gap junctions - Distinguish between simple epithelia and stratified epithelia, as well as between squamous, cuboidal, and columnar epithelia - Describe the structure and function of endocrine and exocrine glands and their respective secretions Most epithelial tissues are essentially large sheets of cells covering all the surfaces of the body exposed to the outside world and lining the outside of organs. Epithelium also forms much of the glandular tissue of the body. Skin is not the only area of the body exposed to the outside. Other areas include the airways, the digestive tract, as well as the urinary and reproductive systems, all of which are lined by an epithelium. Hollow organs and body cavities that do not connect to the exterior of the body, which includes, blood vessels and serous membranes, are lined by endothelium (plural = endothelia), which is a type of epithelium. Epithelial cells derive from all three major embryonic layers. The epithelia lining the skin, parts of the mouth and nose, and the anus develop from the ectoderm. Cells lining the airways and most of the digestive system originate in the endoderm. The epithelium that lines vessels in the lymphatic and cardiovascular system derives from the mesoderm and is called an endothelium. All epithelia share some important structural and functional features. This tissue is highly cellular, with little or no extracellular material present between cells. Adjoining cells form a specialized intercellular connection between their cell membranes called a cell junction. The epithelial cells exhibit polarity with differences in structure and function between the exposed or apicalfacing surface of the cell and the basal surface close to the underlying body structures. The basal lamina, a mixture of glycoproteins and collagen, provides an attachment site for the epithelium, separating it from underlying connective tissue. The basal lamina attaches to a reticular lamina, which is secreted by the underlying connective tissue, forming a basement membrane that helps hold it all together. Epithelial tissues are nearly completely avascular. For instance, no blood vessels cross the basement membrane to enter the tissue, and nutrients must come by diffusion or absorption from underlying tissues or the surface. Many epithelial tissues are capable of rapidly replacing damaged and dead cells. Sloughing off of damaged or dead cells is a characteristic of surface epithelium and allows our airways and digestive tracts to rapidly replace damaged cells with new cells. Generalized Functions of Epithelial Tissue Epithelial tissues provide the body’s first line of protection from physical, chemical, and biological wear and tear. The cells of an epithelium act as gatekeepers of the body controlling permeability and allowing selective transfer of materials across a physical barrier. All substances that enter the body must cross an epithelium. Some epithelia often include structural features that allow the selective transport of molecules and ions across their cell membranes. Many epithelial cells are capable of secretion and release mucous and specific chemical compounds onto their apical surfaces. The epithelium of the small intestine releases digestive enzymes, for example. Cells lining the respiratory tract secrete mucous that traps incoming microorganisms and particles. A glandular epithelium contains many secretory cells. The Epithelial Cell Epithelial cells are typically characterized by the polarized distribution of organelles and membrane-bound proteins between their basal and apical surfaces. Particular structures found in some epithelial cells are an adaptation to specific functions. Certain organelles are segregated to the basal sides, whereas other organelles and extensions, such as cilia, when present, are on the apical surface. Cilia are microscopic extensions of the apical cell membrane that are supported by microtubules. They beat in unison and move fluids as well as trapped particles. Ciliated epithelium lines the ventricles of the brain where it helps circulate the cerebrospinal fluid. The ciliated epithelium of your airway forms a mucociliary escalator that sweeps particles of dust and pathogens trapped in the secreted mucous toward the throat. It is called an escalator because it continuously pushes mucous with trapped particles upward. In contrast, nasal cilia sweep the mucous blanket down towards your throat. In both cases, the transported materials are usually swallowed, and end up in the acidic environment of your stomach. Cell to Cell Junctions Cells of epithelia are closely connected and are not separated by intracellular material. Three basic types of connections allow varying degrees of interaction between the cells: tight junctions, anchoring junctions, and gap junctions (Figure 4.5). Figure 4.5 Types of Cell Junctions The three basic types of cell-to-cell junctions are tight junctions, gap junctions, and anchoring junctions. At one end of the spectrum is the tight junction, which separates the cells into apical and basal compartments. When two adjacent epithelial cells form a tight junction, there is no extracellular space between them and the movement of substances through the extracellular space between the cells is blocked. This enables the epithelia to act as selective barriers. An anchoring junction includes several types of cell junctions that help stabilize epithelial tissues. Anchoring junctions are common on the lateral and basal surfaces of cells where they provide strong and flexible connections. There are three types of anchoring junctions: desmosomes, hemidesmosomes, and adherens. Desmosomes occur in patches on the membranes of cells. The patches are structural proteins on the inner surface of the cell’s membrane. The adhesion molecule, cadherin, is embedded in these patches and projects through the cell membrane to link with the cadherin molecules of adjacent cells. These connections are especially important in holding cells together. Hemidesmosomes, which look like half a desmosome, link cells to the extracellular matrix, for example, the basal lamina. While similar in appearance to desmosomes, they include the adhesion proteins called integrins rather than cadherins. Adherens junctions use either cadherins or integrins depending on whether they are linking to other cells or matrix. The junctions are characterized by the presence of the contractile protein actin located on the cytoplasmic surface of the cell membrane. The actin can connect isolated patches or form a belt-like structure inside the cell. These junctions influence the shape and folding of the epithelial tissue. In contrast with the tight and anchoring junctions, a gap junction forms an intercellular passageway between the membranes of adjacent cells to facilitate the movement of small molecules and ions between the cytoplasm of adjacent cells. These junctions allow electrical and metabolic coupling of adjacent cells, which coordinates function in large groups of cells. Classification of Epithelial Tissues Epithelial tissues are classified according to the shape of the cells and number of the cell layers formed (Figure 4.6). Cell shapes can be squamous (flattened and thin), cuboidal (boxy, as wide as it is tall), or columnar (rectangular, taller than it is wide). Similarly, the number of cell layers in the tissue can be one—where every cell rests on the basal lamina—which is a simple epithelium, or more than one, which is a stratified epithelium and only the basal layer of cells rests on the basal lamina. Pseudostratified (pseudo- = “false”) describes tissue with a single layer of irregularly shaped cells that give the appearance of more than one layer. Transitional describes a form of specialized stratified epithelium in which the shape of the cells can vary. Figure 4.6 Cells of Epithelial Tissue Simple epithelial tissue is organized as a single layer of cells and stratified epithelial tissue is formed by several layers of cells. Simple Epithelium The shape of the cells in the single cell layer of simple epithelium reflects the functioning of those cells. The cells in simple squamous epithelium have the appearance of thin scales. Squamous cell nuclei tend to be flat, horizontal, and elliptical, mirroring the form of the cell. The endothelium is the epithelial tissue that lines vessels of the lymphatic and cardiovascular system, and it is made up of a single layer of squamous cells. Simple squamous epithelium, because of the thinness of the cell, is present where rapid passage of chemical compounds is observed. The alveoli of lungs where gases diffuse, segments of kidney tubules, and the lining of capillaries are also made of simple squamous epithelial tissue. The mesothelium is a simple squamous epithelium that forms the surface layer of the serous membrane that lines body cavities and internal organs. Its primary function is to provide a smooth and protective surface. Mesothelial cells are squamous epithelial cells that secrete a fluid that lubricates the mesothelium. In simple cuboidal epithelium, the nucleus of the box-like cells appears round and is generally located near the center of the cell. These epithelia are active in the secretion and absorptions of molecules. Simple cuboidal epithelia are observed in the lining of the kidney tubules and in the ducts of glands. In simple columnar epithelium, the nucleus of the tall column-like cells tends to be elongated and located in the basal end of the cells. Like the cuboidal epithelia, this epithelium is active in the absorption and secretion of molecules. Simple columnar epithelium forms the lining of some sections of the digestive system and parts of the female reproductive tract. Ciliated columnar epithelium is composed of simple columnar epithelial cells with cilia on their apical surfaces. These epithelial cells are found in the lining of the fallopian tubes and parts of the respiratory system, where the beating of the cilia helps remove particulate matter. Pseudostratified columnar epithelium is a type of epithelium that appears to be stratified but instead consists of a single layer of irregularly shaped and differently sized columnar cells. In pseudostratified epithelium, nuclei of neighboring cells appear at different levels rather than clustered in the basal end. The arrangement gives the appearance of stratification; but in fact all the cells are in contact with the basal lamina, although some do not reach the apical surface. Pseudostratified columnar epithelium is found in the respiratory tract, where some of these cells have cilia. Both simple and pseudostratified columnar epithelia are heterogeneous epithelia because they include additional types of cells interspersed among the epithelial cells. For example, a goblet cell is a mucous-secreting unicellular “gland” interspersed between the columnar epithelial cells of mucous membranes (Figure 4.7). Figure 4.7 Goblet Cell (a) In the lining of the small intestine, columnar epithelium cells are interspersed with goblet cells. (b) The arrows in this micrograph point to the mucous-secreting goblet cells. LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK View the University of Michigan WebScope to explore the tissue sample in greater detail. Stratified Epithelium A stratified epithelium consists of several stacked layers of cells. This epithelium protects against physical and chemical wear and tear. The stratified epithelium is named by the shape of the most apical layer of cells, closest to the free space. Stratified squamous epithelium is the most common type of stratified epithelium in the human body. The apical cells are squamous, whereas the basal layer contains either columnar or cuboidal cells. The top layer may be covered with dead cells filled with keratin. Mammalian skin is an example of this dry, keratinized, stratified squamous epithelium. The lining of the mouth cavity is an example of an unkeratinized, stratified squamous epithelium. Stratified cuboidal epithelium and stratified columnar epithelium can also be found in certain glands and ducts, but are uncommon in the human body. Another kind of stratified epithelium is transitional epithelium, so-called because of the gradual changes in the shapes of the apical cells as the bladder fills with urine. It is found only in the urinary system, specifically the ureters and urinary bladder. When the bladder is empty, this epithelium is convoluted and has cuboidal apical cells with convex, umbrella shaped, apical surfaces. As the bladder fills with urine, this epithelium loses its convolutions and the apical cells transition from cuboidal to squamous. It appears thicker and more multi-layered when the bladder is empty, and more stretched out and less stratified when the bladder is full and distended. Figure 4.8 summarizes the different categories of epithelial cell tissue cells. Figure 4.8 Summary of Epithelial Tissue Cells INTERACTIVE LINK Watch this video to find out more about the anatomy of epithelial tissues. Where in the body would one find non-keratinizing stratified squamous epithelium? Glandular Epithelium A gland is a structure made up of one or more cells modified to synthesize and secrete chemical substances. Most glands consist of groups of epithelial cells. A gland can be classified as an endocrine gland, a ductless gland that releases secretions directly into surrounding tissues and fluids (endo- = “inside”), or an exocrine gland whose secretions leave through a duct that opens directly, or indirectly, to the external environment (exo- = “outside”). Endocrine Glands The secretions of endocrine glands are called hormones. Hormones are released into the interstitial fluid, diffused into the bloodstream, and delivered to targets, in other words, cells that have receptors to bind the hormones. The endocrine system is part of a major regulatory system coordinating the regulation and integration of body responses. A few examples of endocrine glands include the anterior pituitary, thymus, adrenal cortex, and gonads. Exocrine Glands Exocrine glands release their contents through a duct that leads to the epithelial surface. Mucous, sweat, saliva, and breast milk are all examples of secretions from exocrine glands. They are all discharged through tubular ducts. Secretions into the lumen of the gastrointestinal tract, technically outside of the body, are of the exocrine category. Glandular Structure Exocrine glands are classified as either unicellular or multicellular. The unicellular glands are scattered single cells, such as goblet cells, found in the mucous membranes of the small and large intestine. The multicellular exocrine glands known as serous glands develop from simple epithelium to form a secretory surface that secretes directly into an inner cavity. These glands line the internal cavities of the abdomen and chest and release their secretions directly into the cavities. Other multicellular exocrine glands release their contents through a tubular duct. The duct is single in a simple gland but in compound glands is divided into one or more branches (Figure 4.9). In tubular glands, the ducts can be straight or coiled, whereas tubes that form pockets are alveolar (acinar), such as the exocrine portion of the pancreas. Combinations of tubes and pockets are known as tubuloalveolar (tubuloacinar) compound glands. In a branched gland, a duct is connected to more than one secretory group of cells. Figure 4.9 Types of Exocrine Glands Exocrine glands are classified by their structure. Methods and Types of Secretion Exocrine glands can be classified by their mode of secretion and the nature of the substances released, as well as by the structure of the glands and shape of ducts (Figure 4.10). Merocrine secretion is the most common type of exocrine secretion. The secretions are enclosed in vesicles that move to the apical surface of the cell where the contents are released by exocytosis. For example, watery mucous containing the glycoprotein mucin, a lubricant that offers some pathogen protection is a merocrine secretion. The eccrine glands that produce and secrete sweat are another example. Figure 4.10 Modes of Glandular Secretion (a) In merocrine secretion, the cell remains intact. (b) In apocrine secretion, the apical portion of the cell is released, as well. (c) In holocrine secretion, the cell is destroyed as it releases its product and the cell itself becomes part of the secretion. Apocrine secretion accumulates near the apical portion of the cell. That portion of the cell and its secretory contents pinch off from the cell and are released. Apocrine sweat glands in the axillary and genital areas release fatty secretions that local bacteria break down; this causes body odor. Both merocrine and apocrine glands continue to produce and secrete their contents with little damage caused to the cell because the nucleus and golgi regions remain intact after secretion. In contrast, the process of holocrine secretion involves the rupture and destruction of the entire gland cell. The cell accumulates its secretory products and releases them only when it bursts. New gland cells differentiate from cells in the surrounding tissue to replace those lost by secretion. The sebaceous glands that produce the oils on the skin and hair are holocrine glands/cells (Figure 4.11). Figure 4.11 Sebaceous Glands These glands secrete oils that lubricate and protect the skin. They are holocrine glands and they are destroyed after releasing their contents. New glandular cells form to replace the cells that are lost. LM × 400. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Glands are also named after the products they produce. The serous gland produces watery, blood-plasma-like secretions rich in enzymes such as alpha amylase, whereas the mucous gland releases watery to viscous products rich in the glycoprotein mucin. Both serous and mucous glands are common in the salivary glands of the mouth. Mixed exocrine glands contain both serous and mucous glands and release both types of secretions. Connective Tissue Supports and Protects - Identify and distinguish between the types of connective tissue: proper, supportive, and fluid - Explain the functions of connective tissues As may be obvious from its name, one of the major functions of connective tissue is to connect tissues and organs. Unlike epithelial tissue, which is composed of cells closely packed with little or no extracellular space in between, connective tissue cells are dispersed in a matrix. The matrix usually includes a large amount of extracellular material produced by the connective tissue cells that are embedded within it. The matrix plays a major role in the functioning of this tissue. The major component of the matrix is a ground substance often crisscrossed by protein fibers. This ground substance is usually a fluid, but it can also be mineralized and solid, as in bones. Connective tissues come in a vast variety of forms, yet they typically have in common three characteristic components: cells, large amounts of amorphous ground substance, and protein fibers. The amount and structure of each component correlates with the function of the tissue, from the rigid ground substance in bones supporting the body to the inclusion of specialized cells; for example, a phagocytic cell that engulfs pathogens and also rids tissue of cellular debris. Functions of Connective Tissues Connective tissues perform many functions in the body, but most importantly, they support and connect other tissues; from the connective tissue sheath that surrounds muscle cells, to the tendons that attach muscles to bones, and to the skeleton that supports the positions of the body. Protection is another major function of connective tissue, in the form of fibrous capsules and bones that protect delicate organs and, of course, the skeletal system. Specialized cells in connective tissue defend the body from microorganisms that enter the body. Transport of fluid, nutrients, waste, and chemical messengers is ensured by specialized fluid connective tissues, such as blood and lymph. Adipose cells store surplus energy in the form of fat and contribute to the thermal insulation of the body. Embryonic Connective Tissue All connective tissues derive from the mesodermal layer of the embryo (see Figure 4.3). The first connective tissue to develop in the embryo is mesenchyme, the stem cell line from which all connective tissues are later derived. Clusters of mesenchymal cells are scattered throughout adult tissue and supply the cells needed for replacement and repair after a connective tissue injury. A second type of embryonic connective tissue forms in the umbilical cord, called mucous connective tissue or Wharton’s jelly. This tissue is no longer present after birth, leaving only scattered mesenchymal cells throughout the body. Classification of Connective Tissues The three broad categories of connective tissue are classified according to the characteristics of their ground substance and the types of fibers found within the matrix (Table 4.1). Connective tissue proper includes loose connective tissue and dense connective tissue. Both tissues have a variety of cell types and protein fibers suspended in a viscous ground substance. Dense connective tissue is reinforced by bundles of fibers that provide tensile strength, elasticity, and protection. In loose connective tissue, the fibers are loosely organized, leaving large spaces in between. Supportive connective tissue—bone and cartilage—provide structure and strength to the body and protect soft tissues. A few distinct cell types and densely packed fibers in a matrix characterize these tissues. In bone, the matrix is rigid and described as calcified because of the deposited calcium salts. In fluid connective tissue, in other words, lymph and blood, various specialized cells circulate in a watery fluid containing salts, nutrients, and dissolved proteins. Connective Tissue Proper Fibroblasts are present in all connective tissue proper (Figure 4.12). Fibrocytes, adipocytes, and mesenchymal cells are fixed cells, which means they remain within the connective tissue. Other cells move in and out of the connective tissue in response to chemical signals. Macrophages, mast cells, lymphocytes, plasma cells, and phagocytic cells are found in connective tissue proper but are actually part of the immune system protecting the body. Figure 4.12 Connective Tissue Proper Fibroblasts produce this fibrous tissue. Connective tissue proper includes the fixed cells fibrocytes, adipocytes, and mesenchymal cells. LM × 400. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Cell Types The most abundant cell in connective tissue proper is the fibroblast. Polysaccharides and proteins secreted by fibroblasts combine with extra-cellular fluids to produce a viscous ground substance that, with embedded fibrous proteins, forms the extra-cellular matrix. As you might expect, a fibrocyte, a less active form of fibroblast, is the second most common cell type in connective tissue proper. Adipocytes are cells that store lipids as droplets that fill most of the cytoplasm. There are two basic types of adipocytes: white and brown. The brown adipocytes store lipids as many droplets, and have high metabolic activity. In contrast, white fat adipocytes store lipids as a single large drop and are metabolically less active. Their effectiveness at storing large amounts of fat is witnessed in obese individuals. The number and type of adipocytes depends on the tissue and location, and vary among individuals in the population. The mesenchymal cell is a multipotent adult stem cell. These cells can differentiate into any type of connective tissue cells needed for repair and healing of damaged tissue. The macrophage cell is a large cell derived from a monocyte, a type of blood cell, which enters the connective tissue matrix from the blood vessels. The macrophage cells are an essential component of the immune system, which is the body’s defense against potential pathogens and degraded host cells. When stimulated, macrophages release cytokines, small proteins that act as chemical messengers. Cytokines recruit other cells of the immune system to infected sites and stimulate their activities. Roaming, or free, macrophages move rapidly by amoeboid movement, engulfing infectious agents and cellular debris. In contrast, fixed macrophages are permanent residents of their tissues. The mast cell, found in connective tissue proper, has many cytoplasmic granules. These granules contain the chemical signals histamine and heparin. When irritated or damaged, mast cells release histamine, an inflammatory mediator, which causes vasodilation and increased blood flow at a site of injury or infection, along with itching, swelling, and redness you recognize as an allergic response. Like blood cells, mast cells are derived from hematopoietic stem cells and are part of the immune system. Connective Tissue Fibers and Ground Substance Three main types of fibers are secreted by fibroblasts: collagen fibers, elastic fibers, and reticular fibers. Collagen fiber is made from fibrous protein subunits linked together to form a long and straight fiber. Collagen fibers, while flexible, have great tensile strength, resist stretching, and give ligaments and tendons their characteristic resilience and strength. These fibers hold connective tissues together, even during the movement of the body. Elastic fiber contains the protein elastin along with lesser amounts of other proteins and glycoproteins. The main property of elastin is that after being stretched or compressed, it will return to its original shape. Elastic fibers are prominent in elastic tissues found in skin and the elastic ligaments of the vertebral column. Reticular fiber is also formed from the same protein subunits as collagen fibers; however, these fibers remain narrow and are arrayed in a branching network. They are found throughout the body, but are most abundant in the reticular tissue of soft organs, such as liver and spleen, where they anchor and provide structural support to the parenchyma (the functional cells, blood vessels, and nerves of the organ). All of these fiber types are embedded in ground substance. Secreted by fibroblasts, ground substance is made of polysaccharides, specifically hyaluronic acid, and proteins. These combine to form a proteoglycan with a protein core and polysaccharide branches. The proteoglycan attracts and traps available moisture forming the clear, viscous, colorless matrix you now know as ground substance. Loose Connective Tissue Loose connective tissue is found between many organs where it acts both to absorb shock and bind tissues together. It allows water, salts, and various nutrients to diffuse through to adjacent or imbedded cells and tissues. Adipose tissue consists mostly of fat storage cells, with little extracellular matrix (Figure 4.13). A large number of capillaries allow rapid storage and mobilization of lipid molecules. White adipose tissue is most abundant. It can appear yellow and owes its color to carotene and related pigments from plant food. White fat contributes mostly to lipid storage and can serve as insulation from cold temperatures and mechanical injuries. White adipose tissue can be found protecting the kidneys and cushioning the back of the eye. Brown adipose tissue is more common in infants, hence the term “baby fat.” In adults, there is a reduced amount of brown fat and it is found mainly in the neck and clavicular regions of the body. The many mitochondria in the cytoplasm of brown adipose tissue help explain its efficiency at metabolizing stored fat. Brown adipose tissue is thermogenic, meaning that as it breaks down fats, it releases metabolic heat, rather than producing adenosine triphosphate (ATP), a key molecule used in metabolism. Figure 4.13 Adipose Tissue This is a loose connective tissue that consists of fat cells with little extracellular matrix. It stores fat for energy and provides insulation. LM × 800. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Areolar tissue shows little specialization. It contains all the cell types and fibers previously described and is distributed in a random, web-like fashion. It fills the spaces between muscle fibers, surrounds blood and lymph vessels, and supports organs in the abdominal cavity. Areolar tissue underlies most epithelia and represents the connective tissue component of epithelial membranes, which are described further in a later section. Reticular tissue is a mesh-like, supportive framework for soft organs such as lymphatic tissue, the spleen, and the liver (Figure 4.14). Reticular cells produce the reticular fibers that form the network onto which other cells attach. It derives its name from the Latin reticulus, which means “little net.” Figure 4.14 Reticular Tissue This is a loose connective tissue made up of a network of reticular fibers that provides a supportive framework for soft organs. LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Dense Connective Tissue Dense connective tissue contains more collagen fibers than does loose connective tissue. As a consequence, it displays greater resistance to stretching. There are two major categories of dense connective tissue: regular and irregular. Dense regular connective tissue fibers are parallel to each other, enhancing tensile strength and resistance to stretching in the direction of the fiber orientations. Ligaments and tendons are made of dense regular connective tissue, but in ligaments not all fibers are parallel. Dense regular elastic tissue contains elastin fibers in addition to collagen fibers, which allows the ligament to return to its original length after stretching. The ligaments in the vocal folds and between the vertebrae in the vertebral column are elastic. In dense irregular connective tissue, the direction of fibers is random. This arrangement gives the tissue greater strength in all directions and less strength in one particular direction. In some tissues, fibers crisscross and form a mesh. In other tissues, stretching in several directions is achieved by alternating layers where fibers run in the same orientation in each layer, and it is the layers themselves that are stacked at an angle. The dermis of the skin is an example of dense irregular connective tissue rich in collagen fibers. Dense irregular elastic tissues give arterial walls the strength and the ability to regain original shape after stretching (Figure 4.15). Figure 4.15 Dense Connective Tissue (a) Dense regular connective tissue consists of collagenous fibers packed into parallel bundles. (b) Dense irregular connective tissue consists of collagenous fibers interwoven into a mesh-like network. From top, LM × 1000, LM × 200. (Micrographs provided by the Regents of University of Michigan Medical School © 2012) DISORDERS OF THE... Connective Tissue: Tendinitis Your opponent stands ready as you prepare to hit the serve, but you are confident that you will smash the ball past your opponent. As you toss the ball high in the air, a burning pain shoots across your wrist and you drop the tennis racket. That dull ache in the wrist that you ignored through the summer is now an unbearable pain. The game is over for now. After examining your swollen wrist, the doctor in the emergency room announces that you have developed wrist tendinitis. She recommends icing the tender area, taking non-steroidal anti-inflammatory medication to ease the pain and to reduce swelling, and complete rest for a few weeks. She interrupts your protests that you cannot stop playing. She issues a stern warning about the risk of aggravating the condition and the possibility of surgery. She consoles you by mentioning that well known tennis players such as Venus and Serena Williams and Rafael Nadal have also suffered from tendinitis related injuries. What is tendinitis and how did it happen? Tendinitis is the inflammation of a tendon, the thick band of fibrous connective tissue that attaches a muscle to a bone. The condition causes pain and tenderness in the area around a joint. On rare occasions, a sudden serious injury will cause tendinitis. Most often, the condition results from repetitive motions over time that strain the tendons needed to perform the tasks. Persons whose jobs and hobbies involve performing the same movements over and over again are often at the greatest risk of tendinitis. You hear of tennis and golfer’s elbow, jumper's knee, and swimmer’s shoulder. In all cases, overuse of the joint causes a microtrauma that initiates the inflammatory response. Tendinitis is routinely diagnosed through a clinical examination. In case of severe pain, X-rays can be examined to rule out the possibility of a bone injury. Severe cases of tendinitis can even tear loose a tendon. Surgical repair of a tendon is painful. Connective tissue in the tendon does not have abundant blood supply and heals slowly. While older adults are at risk for tendinitis because the elasticity of tendon tissue decreases with age, active people of all ages can develop tendinitis. Young athletes, dancers, and computer operators; anyone who performs the same movements constantly is at risk for tendinitis. Although repetitive motions are unavoidable in many activities and may lead to tendinitis, precautions can be taken that can lessen the probability of developing tendinitis. For active individuals, stretches before exercising and cross training or changing exercises are recommended. For the passionate athlete, it may be time to take some lessons to improve technique. All of the preventive measures aim to increase the strength of the tendon and decrease the stress put on it. With proper rest and managed care, you will be back on the court to hit that slice-spin serve over the net. INTERACTIVE LINK Watch this animation to learn more about tendonitis, a painful condition caused by swollen or injured tendons. Supportive Connective Tissues Two major forms of supportive connective tissue, cartilage and bone, allow the body to maintain its posture and protect internal organs. Cartilage The distinctive appearance of cartilage is due to polysaccharides called chondroitin sulfates, which bind with ground substance proteins to form proteoglycans. Embedded within the cartilage matrix are chondrocytes, or cartilage cells, and the space they occupy are called lacunae (singular = lacuna). A layer of dense irregular connective tissue, the perichondrium, encapsulates the cartilage. Cartilaginous tissue is avascular, thus all nutrients need to diffuse through the matrix to reach the chondrocytes. This is a factor contributing to the very slow healing of cartilaginous tissues. The three main types of cartilage tissue are hyaline cartilage, fibrocartilage, and elastic cartilage (Figure 4.16). Hyaline cartilage, the most common type of cartilage in the body, consists of short and dispersed collagen fibers and contains large amounts of proteoglycans. Under the microscope, tissue samples appear clear. The surface of hyaline cartilage is smooth. Both strong and flexible, it is found in the rib cage and nose and covers bones where they meet to form moveable joints. It makes up a template of the embryonic skeleton before bone formation. A plate of hyaline cartilage at the ends of bone allows continued growth until adulthood. Fibrocartilage is tough because it has thick bundles of collagen fibers dispersed through its matrix. Menisci in the knee joint and the intervertebral discs are examples of fibrocartilage. Elastic cartilage contains elastic fibers as well as collagen and proteoglycans. This tissue gives rigid support as well as elasticity. Tug gently at your ear lobes, and notice that the lobes return to their initial shape. The external ear contains elastic cartilage. Figure 4.16 Types of Cartilage Cartilage is a connective tissue consisting of collagenous fibers embedded in a firm matrix of chondroitin sulfates. (a) Hyaline cartilage provides support with some flexibility. The example is from dog tissue. (b) Fibrocartilage provides some compressibility and can absorb pressure. (c) Elastic cartilage provides firm but elastic support. From top, LM × 300, LM × 1200, LM × 1016. (Micrographs provided by the Regents of University of Michigan Medical School © 2012) Bone Bone is the hardest connective tissue. It provides protection to internal organs and supports the body. Bone’s rigid extracellular matrix contains mostly collagen fibers embedded in a mineralized ground substance containing hydroxyapatite, a form of calcium phosphate. Both components of the matrix, organic and inorganic, contribute to the unusual properties of bone. Without collagen, bones would be brittle and shatter easily. Without mineral crystals, bones would flex and provide little support. Osteocytes, bone cells like chondrocytes, are located within lacunae. The histology of transverse tissue from long bone shows a typical arrangement of osteocytes in concentric circles around a central canal. Bone is a highly vascularized tissue. Unlike cartilage, bone tissue can recover from injuries in a relatively short time. Cancellous bone looks like a sponge under the microscope and contains empty spaces between trabeculae, or arches of bone proper. It is lighter than compact bone and found in the interior of some bones and at the end of long bones. Compact bone is solid and has greater structural strength. Fluid Connective Tissue Blood and lymph are fluid connective tissues. Cells circulate in a liquid extracellular matrix. The formed elements circulating in blood are all derived from hematopoietic stem cells located in bone marrow (Figure 4.17). Erythrocytes, red blood cells, transport oxygen and some carbon dioxide. Leukocytes, white blood cells, are responsible for defending against potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting. Some white blood cells have the ability to cross the endothelial layer that lines blood vessels and enter adjacent tissues. Nutrients, salts, and wastes are dissolved in the liquid matrix and transported through the body. Lymph contains a liquid matrix and white blood cells. Lymphatic capillaries are extremely permeable, allowing larger molecules and excess fluid from interstitial spaces to enter the lymphatic vessels. Lymph drains into blood vessels, delivering molecules to the blood that could not otherwise directly enter the bloodstream. In this way, specialized lymphatic capillaries transport absorbed fats away from the intestine and deliver these molecules to the blood. Figure 4.17 Blood: A Fluid Connective Tissue Blood is a fluid connective tissue containing erythrocytes and various types of leukocytes that circulate in a liquid extracellular matrix. LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK View the University of Michigan Webscope to explore the tissue sample in greater detail. INTERACTIVE LINK Visit this link to test your connective tissue knowledge with this 10-question quiz. Can you name the 10 tissue types shown in the histology slides? Muscle Tissue and Motion - Identify the three types of muscle tissue - Compare and contrast the functions of each muscle tissue type - Explain how muscle tissue can enable motion Muscle tissue is characterized by properties that allow movement. Muscle cells are excitable; they respond to a stimulus. They are contractile, meaning they can shorten and generate a pulling force. When attached between two movable objects, in other words, bones, contractions of the muscles cause the bones to move. Some muscle movement is voluntary, which means it is under conscious control. For example, a person decides to open a book and read a chapter on anatomy. Other movements are involuntary, meaning they are not under conscious control, such as the contraction of your pupil in bright light. Muscle tissue is classified into three types according to structure and function: skeletal, cardiac, and smooth (Table 4.2). Skeletal muscle is attached to bones and its contraction makes possible locomotion, facial expressions, posture, and other voluntary movements of the body. Forty percent of your body mass is made up of skeletal muscle. Skeletal muscles generate heat as a byproduct of their contraction and thus participate in thermal homeostasis. Shivering is an involuntary contraction of skeletal muscles in response to perceived lower than normal body temperature. The muscle cell, or myocyte, develops from myoblasts derived from the mesoderm. Myocytes and their numbers remain relatively constant throughout life. Skeletal muscle tissue is arranged in bundles surrounded by connective tissue. Under the light microscope, muscle cells appear striated with many nuclei squeezed along the membranes. The striation is due to the regular alternation of the contractile proteins actin and myosin, along with the structural proteins that couple the contractile proteins to connective tissues. The cells are multinucleated as a result of the fusion of the many myoblasts that fuse to form each long muscle fiber. Cardiac muscle forms the contractile walls of the heart. The cells of cardiac muscle, known as cardiomyocytes, also appear striated under the microscope. Unlike skeletal muscle fibers, cardiomyocytes are single cells typically with a single centrally located nucleus. A principal characteristic of cardiomyocytes is that they contract on their own intrinsic rhythms without any external stimulation. Cardiomyocyte attach to one another with specialized cell junctions called intercalated discs. Intercalated discs have both anchoring junctions and gap junctions. Attached cells form long, branching cardiac muscle fibers that are, essentially, a mechanical and electrochemical syncytium allowing the cells to synchronize their actions. The cardiac muscle pumps blood through the body and is under involuntary control. The attachment junctions hold adjacent cells together across the dynamic pressures changes of the cardiac cycle. Smooth muscle tissue contraction is responsible for involuntary movements in the internal organs. It forms the contractile component of the digestive, urinary, and reproductive systems as well as the airways and arteries. Each cell is spindle shaped with a single nucleus and no visible striations (Figure 4.18). Figure 4.18 Muscle Tissue (a) Skeletal muscle cells have prominent striation and nuclei on their periphery. (b) Smooth muscle cells have a single nucleus and no visible striations. (c) Cardiac muscle cells appear striated and have a single nucleus. From top, LM × 1600, LM × 1600, LM × 1600. (Micrographs provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK Watch this video to learn more about muscle tissue. In looking through a microscope how could you distinguish skeletal muscle tissue from smooth muscle? Nervous Tissue Mediates Perception and Response By the end of this section, you will be able to:- Identify the classes of cells that make up nervous tissue - Discuss how nervous tissue mediates perception and response Nervous tissue is characterized as being excitable and capable of sending and receiving electrochemical signals that provide the body with information. Two main classes of cells make up nervous tissue: the neuron and neuroglia (Figure 4.19). Neurons propagate information via electrochemical impulses, called action potentials, which are biochemically linked to the release of chemical signals. Neuroglia play an essential role in supporting neurons and modulating their information propagation. Figure 4.19 The Neuron The cell body of a neuron, also called the soma, contains the nucleus and mitochondria. The dendrites transfer the nerve impulse to the soma. The axon carries the action potential away to another excitable cell. LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK Follow this link to learn more about nervous tissue. What are the main parts of a nerve cell? Neurons display distinctive morphology, well suited to their role as conducting cells, with three main parts. The cell body includes most of the cytoplasm, the organelles, and the nucleus. Dendrites branch off the cell body and appear as thin extensions. A long “tail,” the axon, extends from the neuron body and can be wrapped in an insulating layer known as myelin, which is formed by accessory cells. The synapse is the gap between nerve cells, or between a nerve cell and its target, for example, a muscle or a gland, across which the impulse is transmitted by chemical compounds known as neurotransmitters. Neurons categorized as multipolar neurons have several dendrites and a single prominent axon. Bipolar neurons possess a single dendrite and axon with the cell body, while unipolar neurons have only a single process extending out from the cell body, which divides into a functional dendrite and into a functional axon. When a neuron is sufficiently stimulated, it generates an action potential that propagates down the axon towards the synapse. If enough neurotransmitters are released at the synapse to stimulate the next neuron or target, a response is generated. The second class of neural cells comprises the neuroglia or glial cells, which have been characterized as having a simple support role. The word “glia” comes from the Greek word for glue. Recent research is shedding light on the more complex role of neuroglia in the function of the brain and nervous system. Astrocyte cells, named for their distinctive star shape, are abundant in the central nervous system. The astrocytes have many functions, including regulation of ion concentration in the intercellular space, uptake and/or breakdown of some neurotransmitters, and formation of the blood-brain barrier, the membrane that separates the circulatory system from the brain. Microglia protect the nervous system against infection but are not nervous tissue because they are related to macrophages. Oligodendrocyte cells produce myelin in the central nervous system (brain and spinal cord) while the Schwann cell produces myelin in the peripheral nervous system (Figure 4.20). Figure 4.20 Nervous Tissue Nervous tissue is made up of neurons and neuroglia. The cells of nervous tissue are specialized to transmit and receive impulses. LM × 872. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Tissue Injury and Aging - Identify the cardinal signs of inflammation - List the body’s response to tissue injury - Explain the process of tissue repair - Discuss the progressive impact of aging on tissue - Describe cancerous mutations’ effect on tissue Tissues of all types are vulnerable to injury and, inevitably, aging. In the former case, understanding how tissues respond to damage can guide strategies to aid repair. In the latter case, understanding the impact of aging can help in the search for ways to diminish its effects. Tissue Injury and Repair Inflammation is the standard, initial response of the body to injury. Whether biological, chemical, physical, or radiation burns, all injuries lead to the same sequence of physiological events. Inflammation limits the extent of injury, partially or fully eliminates the cause of injury, and initiates repair and regeneration of damaged tissue. Necrosis, or accidental cell death, causes inflammation. Apoptosis is programmed cell death, a normal step-by-step process that destroys cells no longer needed by the body. By mechanisms still under investigation, apoptosis does not initiate the inflammatory response. Acute inflammation resolves over time by the healing of tissue. If inflammation persists, it becomes chronic and leads to diseased conditions. Arthritis and tuberculosis are examples of chronic inflammation. The suffix “-itis” denotes inflammation of a specific organ or type, for example, peritonitis is the inflammation of the peritoneum, and meningitis refers to the inflammation of the meninges, the tough membranes that surround the central nervous system The four cardinal signs of inflammation—redness, swelling, pain, and local heat—were first recorded in antiquity. Cornelius Celsus is credited with documenting these signs during the days of the Roman Empire, as early as the first century AD. A fifth sign, loss of function, may also accompany inflammation. Upon tissue injury, damaged cells release inflammatory chemical signals that evoke local vasodilation, the widening of the blood vessels. Increased blood flow results in apparent redness and heat. In response to injury, mast cells present in tissue degranulate, releasing the potent vasodilator histamine. Increased blood flow and inflammatory mediators recruit white blood cells to the site of inflammation. The endothelium lining the local blood vessel becomes “leaky” under the influence of histamine and other inflammatory mediators allowing neutrophils, macrophages, and fluid to move from the blood into the interstitial tissue spaces. The excess liquid in tissue causes swelling, more properly called edema. The swollen tissues squeezing pain receptors cause the sensation of pain. Prostaglandins released from injured cells also activate pain neurons. Non-steroidal anti-inflammatory drugs (NSAIDs) reduce pain because they inhibit the synthesis of prostaglandins. High levels of NSAIDs reduce inflammation. Antihistamines decrease allergies by blocking histamine receptors and as a result the histamine response. After containment of an injury, the tissue repair phase starts with removal of toxins and waste products. Clotting (coagulation) reduces blood loss from damaged blood vessels and forms a network of fibrin proteins that trap blood cells and bind the edges of the wound together. A scab forms when the clot dries, reducing the risk of infection. Sometimes a mixture of dead leukocytes and fluid called pus accumulates in the wound. As healing progresses, fibroblasts from the surrounding connective tissues replace the collagen and extracellular material lost by the injury. Angiogenesis, the growth of new blood vessels, results in vascularization of the new tissue known as granulation tissue. The clot retracts pulling the edges of the wound together, and it slowly dissolves as the tissue is repaired. When a large amount of granulation tissue forms and capillaries disappear, a pale scar is often visible in the healed area. A primary union describes the healing of a wound where the edges are close together. When there is a gaping wound, it takes longer to refill the area with cells and collagen. The process called secondary unionoccurs as the edges of the wound are pulled together by what is called wound contraction. When a wound is more than one quarter of an inch deep, sutures (stitches) are recommended to promote a primary union and avoid the formation of a disfiguring scar. Regeneration is the addition of new cells of the same type as the ones that were injured (Figure 4.21). Figure 4.21 Tissue Healing During wound repair, collagen fibers are laid down randomly by fibroblasts that move into repair the area. INTERACTIVE LINK Watch this video to see a hand heal. Over what period of time do you think these images were taken? Tissue and Aging According to poet Ralph Waldo Emerson, “The surest poison is time.” In fact, biology confirms that many functions of the body decline with age. All the cells, tissues, and organs are affected by senescence, with noticeable variability between individuals owing to different genetic makeup and lifestyles. The outward signs of aging are easily recognizable. The skin and other tissues become thinner and drier, reducing their elasticity, contributing to wrinkles and high blood pressure. Hair turns gray because follicles produce less melanin, the brown pigment of hair and the iris of the eye. The face looks flabby because elastic and collagen fibers decrease in connective tissue and muscle tone is lost. Glasses and hearing aids may become parts of life as the senses slowly deteriorate, all due to reduced elasticity. Overall height decreases as the bones lose calcium and other minerals. With age, fluid decreases in the fibrous cartilage disks intercalated between the vertebrae in the spine. Joints lose cartilage and stiffen. Many tissues, including those in muscles, lose mass through a process called atrophy. Lumps and rigidity become more widespread. As a consequence, the passageways, blood vessels, and airways become more rigid. The brain and spinal cord lose mass. Nerves do not transmit impulses with the same speed and frequency as in the past. Some loss of thought clarity and memory can accompany aging. More severe problems are not necessarily associated with the aging process and may be symptoms of underlying illness. As exterior signs of aging increase, so do the interior signs, which are not as noticeable. The incidence of heart diseases, respiratory syndromes, and type 2 diabetes increases with age, though these are not necessarily age-dependent effects. Wound healing is slower in the elderly, accompanied by a higher frequency of infection as the capacity of the immune system to fend off pathogen declines. Aging is also apparent at the cellular level because all cells experience changes with aging. Telomeres, regions of the chromosomes necessary for cell division, shorten each time cells divide. As they do, cells are less able to divide and regenerate. Because of alterations in cell membranes, transport of oxygen and nutrients into the cell and removal of carbon dioxide and waste products from the cell are not as efficient in the elderly. Cells may begin to function abnormally, which may lead to diseases associated with aging, including arthritis, memory issues, and some cancers. The progressive impact of aging on the body varies considerably among individuals, but Studies indicate, however, that exercise and healthy lifestyle choices can slow down the deterioration of the body that comes with old age. HOMEOSTATIC IMBALANCES Tissues and Cancer Cancer is a generic term for many diseases in which cells escape regulatory signals. Uncontrolled growth, invasion into adjacent tissues, and colonization of other organs, if not treated early enough, are its hallmarks. Health suffers when tumors “rob” blood supply from the “normal” organs. A mutation is defined as a permanent change in the DNA of a cell. Epigenetic modifications, changes that do not affect the code of the DNA but alter how the DNA is decoded, are also known to generate abnormal cells. Alterations in the genetic material may be caused by environmental agents, infectious agents, or errors in the replication of DNA that accumulate with age. Many mutations do not cause any noticeable change in the functions of a cell. However, if the modification affects key proteins that have an impact on the cell’s ability to proliferate in an orderly fashion, the cell starts to divide abnormally. As changes in cells accumulate, they lose their ability to form regular tissues. A tumor, a mass of cells displaying abnormal architecture, forms in the tissue. Many tumors are benign, meaning they do not metastasize nor cause disease. A tumor becomes malignant, or cancerous, when it breaches the confines of its tissue, promotes angiogenesis, attracts the growth of capillaries, and metastasizes to other organs (Figure 4.22). The specific names of cancers reflect the tissue of origin. Cancers derived from epithelial cells are referred to as carcinomas. Cancer in myeloid tissue or blood cells form myelomas. Leukemias are cancers of white blood cells, whereas sarcomas derive from connective tissue. Cells in tumors differ both in structure and function. Some cells, called cancer stem cells, appear to be a subtype of cell responsible for uncontrolled growth. Recent research shows that contrary to what was previously assumed, tumors are not disorganized masses of cells, but have their own structures. Figure 4.22 Development of Cancer Note the change in cell size, nucleus size, and organization in the tissue. INTERACTIVE LINK Watch this video to learn more about tumors. What is a tumor? Cancer treatments vary depending on the disease’s type and stage. Traditional approaches, including surgery, radiation, chemotherapy, and hormonal therapy, aim to remove or kill rapidly dividing cancer cells, but these strategies have their limitations. Depending on a tumor’s location, for example, cancer surgeons may be unable to remove it. Radiation and chemotherapy are difficult, and it is often impossible to target only the cancer cells. The treatments inevitably destroy healthy tissue as well. To address this, researchers are working on pharmaceuticals that can target specific proteins implicated in cancer-associated molecular pathways. Key Terms - adipocytes - lipid storage cells - adipose tissue - specialized areolar tissue rich in stored fat - anchoring junction - mechanically attaches adjacent cells to each other or to the basement membrane - apical - that part of a cell or tissue which, in general, faces an open space - apocrine secretion - release of a substance along with the apical portion of the cell - apoptosis - programmed cell death - areolar tissue - (also, loose connective tissue) a type of connective tissue proper that shows little specialization with cells dispersed in the matrix - astrocyte - star-shaped cell in the central nervous system that regulates ions and uptake and/or breakdown of some neurotransmitters and contributes to the formation of the blood-brain barrier - atrophy - loss of mass and function - basal lamina - thin extracellular layer that lies underneath epithelial cells and separates them from other tissues - basement membrane - in epithelial tissue, a thin layer of fibrous material that anchors the epithelial tissue to the underlying connective tissue; made up of the basal lamina and reticular lamina - cardiac muscle - heart muscle, under involuntary control, composed of striated cells that attach to form fibers, each cell contains a single nucleus, contracts autonomously - cell junction - point of cell-to-cell contact that connects one cell to another in a tissue - chondrocytes - cells of the cartilage - clotting - also called coagulation; complex process by which blood components form a plug to stop bleeding - collagen fiber - flexible fibrous proteins that give connective tissue tensile strength - connective tissue - type of tissue that serves to hold in place, connect, and integrate the body’s organs and systems - connective tissue membrane - connective tissue that encapsulates organs and lines movable joints - connective tissue proper - connective tissue containing a viscous matrix, fibers, and cells. - cutaneous membrane - skin; epithelial tissue made up of a stratified squamous epithelial cells that cover the outside of the body - dense connective tissue - connective tissue proper that contains many fibers that provide both elasticity and protection - ectoderm - outermost embryonic germ layer from which the epidermis and the nervous tissue derive - elastic cartilage - type of cartilage, with elastin as the major protein, characterized by rigid support as well as elasticity - elastic fiber - fibrous protein within connective tissue that contains a high percentage of the protein elastin that allows the fibers to stretch and return to original size - endocrine gland - groups of cells that release chemical signals into the intercellular fluid to be picked up and transported to their target organs by blood - endoderm - innermost embryonic germ layer from which most of the digestive system and lower respiratory system derive - endothelium - tissue that lines vessels of the lymphatic and cardiovascular system, made up of a simple squamous epithelium - epithelial membrane - epithelium attached to a layer of connective tissue - epithelial tissue - type of tissue that serves primarily as a covering or lining of body parts, protecting the body; it also functions in absorption, transport, and secretion - exocrine gland - group of epithelial cells that secrete substances through ducts that open to the skin or to internal body surfaces that lead to the exterior of the body - fibroblast - most abundant cell type in connective tissue, secretes protein fibers and matrix into the extracellular space - fibrocartilage - tough form of cartilage, made of thick bundles of collagen fibers embedded in chondroitin sulfate ground substance - fibrocyte - less active form of fibroblast - fluid connective tissue - specialized cells that circulate in a watery fluid containing salts, nutrients, and dissolved proteins - gap junction - allows cytoplasmic communications to occur between cells - goblet cell - unicellular gland found in columnar epithelium that secretes mucous - ground substance - fluid or semi-fluid portion of the matrix - histamine - chemical compound released by mast cells in response to injury that causes vasodilation and endothelium permeability - histology - microscopic study of tissue architecture, organization, and function - holocrine secretion - release of a substance caused by the rupture of a gland cell, which becomes part of the secretion - hyaline cartilage - most common type of cartilage, smooth and made of short collagen fibers embedded in a chondroitin sulfate ground substance - inflammation - response of tissue to injury - lacunae - (singular = lacuna) small spaces in bone or cartilage tissue that cells occupy - lamina propria - areolar connective tissue underlying a mucous membrane - loose connective tissue - (also, areolar tissue) type of connective tissue proper that shows little specialization with cells dispersed in the matrix - matrix - extracellular material which is produced by the cells embedded in it, containing ground substance and fibers - merocrine secretion - release of a substance from a gland via exocytosis - mesenchymal cell - adult stem cell from which most connective tissue cells are derived - mesenchyme - embryonic tissue from which connective tissue cells derive - mesoderm - middle embryonic germ layer from which connective tissue, muscle tissue, and some epithelial tissue derive - mesothelium - simple squamous epithelial tissue which covers the major body cavities and is the epithelial portion of serous membranes - mucous connective tissue - specialized loose connective tissue present in the umbilical cord - mucous gland - group of cells that secrete mucous, a thick, slippery substance that keeps tissues moist and acts as a lubricant - mucous membrane - tissue membrane that is covered by protective mucous and lines tissue exposed to the outside environment - muscle tissue - type of tissue that is capable of contracting and generating tension in response to stimulation; produces movement. - myelin - layer of lipid inside some neuroglial cells that wraps around the axons of some neurons - myocyte - muscle cells - necrosis - accidental death of cells and tissues - nervous tissue - type of tissue that is capable of sending and receiving impulses through electrochemical signals. - neuroglia - supportive neural cells - neuron - excitable neural cell that transfer nerve impulses - oligodendrocyte - neuroglial cell that produces myelin in the brain - parenchyma - functional cells of a gland or organ, in contrast with the supportive or connective tissue of a gland or organ - primary union - condition of a wound where the wound edges are close enough to be brought together and fastened if necessary, allowing quicker and more thorough healing - pseudostratified columnar epithelium - tissue that consists of a single layer of irregularly shaped and sized cells that give the appearance of multiple layers; found in ducts of certain glands and the upper respiratory tract - reticular fiber - fine fibrous protein, made of collagen subunits, which cross-link to form supporting “nets” within connective tissue - reticular lamina - matrix containing collagen and elastin secreted by connective tissue; a component of the basement membrane - reticular tissue - type of loose connective tissue that provides a supportive framework to soft organs, such as lymphatic tissue, spleen, and the liver - Schwann cell - neuroglial cell that produces myelin in the peripheral nervous system - secondary union - wound healing facilitated by wound contraction - serous gland - group of cells within the serous membrane that secrete a lubricating substance onto the surface - serous membrane - type of tissue membrane that lines body cavities and lubricates them with serous fluid - simple columnar epithelium - tissue that consists of a single layer of column-like cells; promotes secretion and absorption in tissues and organs - simple cuboidal epithelium - tissue that consists of a single layer of cube-shaped cells; promotes secretion and absorption in ducts and tubules - simple squamous epithelium - tissue that consists of a single layer of flat scale-like cells; promotes diffusion and filtration across surface - skeletal muscle - usually attached to bone, under voluntary control, each cell is a fiber that is multinucleated and striated - smooth muscle - under involuntary control, moves internal organs, cells contain a single nucleus, are spindle-shaped, and do not appear striated; each cell is a fiber - stratified columnar epithelium - tissue that consists of two or more layers of column-like cells, contains glands and is found in some ducts - stratified cuboidal epithelium - tissue that consists of two or more layers of cube-shaped cells, found in some ducts - stratified squamous epithelium - tissue that consists of multiple layers of cells with the most apical being flat scale-like cells; protects surfaces from abrasion - striation - alignment of parallel actin and myosin filaments which form a banded pattern - supportive connective tissue - type of connective tissue that provides strength to the body and protects soft tissue - synovial membrane - connective tissue membrane that lines the cavities of freely movable joints, producing synovial fluid for lubrication - tight junction - forms an impermeable barrier between cells - tissue - group of cells that are similar in form and perform related functions - tissue membrane - thin layer or sheet of cells that covers the outside of the body, organs, and internal cavities - totipotent - embryonic cells that have the ability to differentiate into any type of cell and organ in the body - transitional epithelium - form of stratified epithelium found in the urinary tract, characterized by an apical layer of cells that change shape in response to the presence of urine - vasodilation - widening of blood vessels - wound contraction - process whereby the borders of a wound are physically drawn together Chapter Review 4.1 Types of Tissues The human body contains more than 200 types of cells that can all be classified into four types of tissues: epithelial, connective, muscle, and nervous. Epithelial tissues act as coverings controlling the movement of materials across the surface. Connective tissue integrates the various parts of the body and provides support and protection to organs. Muscle tissue allows the body to move. Nervous tissues propagate information. The study of the shape and arrangement of cells in tissue is called histology. All cells and tissues in the body derive from three germ layers in the embryo: the ectoderm, mesoderm, and endoderm. Different types of tissues form membranes that enclose organs, provide a friction-free interaction between organs, and keep organs together. Synovial membranes are connective tissue membranes that protect and line the joints. Epithelial membranes are formed from epithelial tissue attached to a layer of connective tissue. There are three types of epithelial membranes: mucous, which contain glands; serous, which secrete fluid; and cutaneous which makes up the skin. 4.2 Epithelial Tissue In epithelial tissue, cells are closely packed with little or no extracellular matrix except for the basal lamina that separates the epithelium from underlying tissue. The main functions of epithelia are protection from the environment, coverage, secretion and excretion, absorption, and filtration. Cells are bound together by tight junctions that form an impermeable barrier. They can also be connected by gap junctions, which allow free exchange of soluble molecules between cells, and anchoring junctions, which attach cell to cell or cell to matrix. The different types of epithelial tissues are characterized by their cellular shapes and arrangements: squamous, cuboidal, or columnar epithelia. Single cell layers form simple epithelia, whereas stacked cells form stratified epithelia. Very few capillaries penetrate these tissues. Glands are secretory tissues and organs that are derived from epithelial tissues. Exocrine glands release their products through ducts. Endocrine glands secrete hormones directly into the interstitial fluid and blood stream. Glands are classified both according to the type of secretion and by their structure. Merocrine glands secrete products as they are synthesized. Apocrine glands release secretions by pinching off the apical portion of the cell, whereas holocrine gland cells store their secretions until they rupture and release their contents. In this case, the cell becomes part of the secretion. 4.3 Connective Tissue Supports and Protects Connective tissue is a heterogeneous tissue with many cell shapes and tissue architecture. Structurally, all connective tissues contain cells that are embedded in an extracellular matrix stabilized by proteins. The chemical nature and physical layout of the extracellular matrix and proteins vary enormously among tissues, reflecting the variety of functions that connective tissue fulfills in the body. Connective tissues separate and cushion organs, protecting them from shifting or traumatic injury. Connect tissues provide support and assist movement, store and transport energy molecules, protect against infections, and contribute to temperature homeostasis. Many different cells contribute to the formation of connective tissues. They originate in the mesodermal germ layer and differentiate from mesenchyme and hematopoietic tissue in the bone marrow. Fibroblasts are the most abundant and secrete many protein fibers, adipocytes specialize in fat storage, hematopoietic cells from the bone marrow give rise to all the blood cells, chondrocytes form cartilage, and osteocytes form bone. The extracellular matrix contains fluid, proteins, polysaccharide derivatives, and, in the case of bone, mineral crystals. Protein fibers fall into three major groups: collagen fibers that are thick, strong, flexible, and resist stretch; reticular fibers that are thin and form a supportive mesh; and elastin fibers that are thin and elastic. The major types of connective tissue are connective tissue proper, supportive tissue, and fluid tissue. Loose connective tissue proper includes adipose tissue, areolar tissue, and reticular tissue. These serve to hold organs and other tissues in place and, in the case of adipose tissue, isolate and store energy reserves. The matrix is the most abundant feature for loose tissue although adipose tissue does not have much extracellular matrix. Dense connective tissue proper is richer in fibers and may be regular, with fibers oriented in parallel as in ligaments and tendons, or irregular, with fibers oriented in several directions. Organ capsules (collagenous type) and walls of arteries (elastic type) contain dense irregular connective tissue. Cartilage and bone are supportive tissue. Cartilage contains chondrocytes and is somewhat flexible. Hyaline cartilage is smooth and clear, covers joints, and is found in the growing portion of bones. Fibrocartilage is tough because of extra collagen fibers and forms, among other things, the intervertebral discs. Elastic cartilage can stretch and recoil to its original shape because of its high content of elastic fibers. The matrix contains very few blood vessels. Bones are made of a rigid, mineralized matrix containing calcium salts, crystals, and osteocytes lodged in lacunae. Bone tissue is highly vascularized. Cancellous bone is spongy and less solid than compact bone. Fluid tissue, for example blood and lymph, is characterized by a liquid matrix and no supporting fibers. 4.4 Muscle Tissue and Motion The three types of muscle cells are skeletal, cardiac, and smooth. Their morphologies match their specific functions in the body. Skeletal muscle is voluntary and responds to conscious stimuli. The cells are striated and multinucleated appearing as long, unbranched cylinders. Cardiac muscle is involuntary and found only in the heart. Each cell is striated with a single nucleus and they attach to one another to form long fibers. Cells are attached to one another at intercalated disks. The cells are interconnected physically and electrochemically to act as a syncytium. Cardiac muscle cells contract autonomously and involuntarily. Smooth muscle is involuntary. Each cell is a spindle-shaped fiber and contains a single nucleus. No striations are evident because the actin and myosin filaments do not align in the cytoplasm. 4.5 Nervous Tissue Mediates Perception and Response The most prominent cell of the nervous tissue, the neuron, is characterized mainly by its ability to receive stimuli and respond by generating an electrical signal, known as an action potential, which can travel rapidly over great distances in the body. A typical neuron displays a distinctive morphology: a large cell body branches out into short extensions called dendrites, which receive chemical signals from other neurons, and a long tail called an axon, which relays signals away from the cell to other neurons, muscles, or glands. Many axons are wrapped by a myelin sheath, a lipid derivative that acts as an insulator and speeds up the transmission of the action potential. Other cells in the nervous tissue, the neuroglia, include the astrocytes, microglia, oligodendrocytes, and Schwann cells. 4.6 Tissue Injury and Aging Inflammation is the classic response of the body to injury and follows a common sequence of events. The area is red, feels warm to the touch, swells, and is painful. Injured cells, mast cells, and resident macrophages release chemical signals that cause vasodilation and fluid leakage in the surrounding tissue. The repair phase includes blood clotting, followed by regeneration of tissue as fibroblasts deposit collagen. Some tissues regenerate more readily than others. Epithelial and connective tissues replace damaged or dead cells from a supply of adult stem cells. Muscle and nervous tissues undergo either slow regeneration or do not repair at all. Age affects all the tissues and organs of the body. Damaged cells do not regenerate as rapidly as in younger people. Perception of sensation and effectiveness of response are lost in the nervous system. Muscles atrophy, and bones lose mass and become brittle. Collagen decreases in some connective tissue, and joints stiffen. Interactive Link Questions View this slideshow to learn more about stem cells. How do somatic stem cells differ from embryonic stem cells? 2.Watch this video to find out more about the anatomy of epithelial tissues. Where in the body would one find non-keratinizing stratified squamous epithelium? 3.Visit this link to test your connective tissue knowledge with this 10-question quiz. Can you name the 10 tissue types shown in the histology slides? 4.Watch this video to learn more about muscle tissue. In looking through a microscope how could you distinguish skeletal muscle tissue from smooth muscle? 5.Follow this link to learn more about nervous tissue. What are the main parts of a nerve cell? 6.Watch this video to see a hand heal. Over what period of time do you think these images were taken? 7.Watch this video to learn more about tumors. What is a tumor? Review Questions Which of the following is not a type of tissue? - muscle - nervous - embryonic - epithelial The process by which a less specialized cell matures into a more specialized cell is called ________. - differentiation - maturation - modification - specialization Differentiated cells in a developing embryo derive from ________. - endothelium, mesothelium, and epithelium - ectoderm, mesoderm, and endoderm - connective tissue, epithelial tissue, and muscle tissue - epidermis, mesoderm, and endothelium Which of the following lines the body cavities exposed to the external environment? - mesothelium - lamina propria - mesenteries - mucosa In observing epithelial cells under a microscope, the cells are arranged in a single layer and look tall and narrow, and the nucleus is located close to the basal side of the cell. The specimen is what type of epithelial tissue? - columnar - stratified - squamous - transitional Which of the following is the epithelial tissue that lines the interior of blood vessels? - columnar - pseudostratified - simple squamous - transitional Which type of epithelial tissue specializes in moving particles across its surface and is found in airways and lining of the oviduct? - transitional - stratified columnar - pseudostratified ciliated columnar - stratified squamous The ________ exocrine gland stores its secretion until the glandular cell ruptures, whereas the ________ gland releases its apical region and reforms. - holocrine; apocrine - eccrine; endocrine - apocrine; holocrine - eccrine; apocrine Connective tissue is made of which three essential components? - cells, ground substance, and carbohydrate fibers - cells, ground substance, and protein fibers - collagen, ground substance, and protein fibers - matrix, ground substance, and fluid Under the microscope, a tissue specimen shows cells located in spaces scattered in a transparent background. This is probably ________. - loose connective tissue - a tendon - bone - hyaline cartilage Which connective tissue specializes in storage of fat? - tendon - adipose tissue - reticular tissue - dense connective tissue Ligaments connect bones together and withstand a lot of stress. What type of connective tissue should you expect ligaments to contain? - areolar tissue - adipose tissue - dense regular connective tissue - dense irregular connective tissue In adults, new connective tissue cells originate from the ________. - mesoderm - mesenchyme - ectoderm - endoderm In bone, the main cells are ________. - fibroblasts - chondrocytes - lymphocytes - osteocytes Striations, cylindrical cells, and multiple nuclei are observed in ________. - skeletal muscle only - cardiac muscle only - smooth muscle only - skeletal and cardiac muscles The cells of muscles, myocytes, develop from ________. - myoblasts - endoderm - fibrocytes - chondrocytes Skeletal muscle is composed of very hard working cells. Which organelles do you expect to find in abundance in skeletal muscle cell? - nuclei - striations - golgi bodies - mitochondria The cells responsible for the transmission of the nerve impulse are ________. - neurons - oligodendrocytes - astrocytes - microglia The nerve impulse travels down a(n) ________, away from the cell body. - dendrite - axon - microglia - collagen fiber Which of the following central nervous system cells regulate ions, regulate the uptake and/or breakdown of some neurotransmitters, and contribute to the formation of the blood-brain barrier? - microglia - neuroglia - oligodendrocytes - astrocytes Which of the following processes is not a cardinal sign of inflammation? - redness - heat - fever - swelling When a mast cell reacts to an irritation, which of the following chemicals does it release? - collagen - histamine - hyaluronic acid - meylin Atrophy refers to ________. - loss of elasticity - loss of mass - loss of rigidity - loss of permeability Individuals can slow the rate of aging by modifying all of these lifestyle aspects except for ________. - diet - exercise - genetic factors - stress Critical Thinking Questions Identify the four types of tissue in the body, and describe the major functions of each tissue. 33.The zygote is described as totipotent because it ultimately gives rise to all the cells in your body including the highly specialized cells of your nervous system. Describe this transition, discussing the steps and processes that lead to these specialized cells. 34.What is the function of synovial membranes? 35.The structure of a tissue usually is optimized for its function. Describe how the structure of the mucosa and its cells match its function of nutrient absorption. 36.One of the main functions of connective tissue is to integrate organs and organ systems in the body. Discuss how blood fulfills this role. 37.Why does an injury to cartilage, especially hyaline cartilage, heal much more slowly than a bone fracture? 38.You are watching cells in a dish spontaneously contract. They are all contracting at different rates; some fast, some slow. After a while, several cells link up and they begin contracting in synchrony. Discuss what is going on and what type of cells you are looking at. 39.Why does skeletal muscle look striated? 40.Which morphological adaptations of neurons make them suitable for the transmission of nerve impulse? 41.What are the functions of astrocytes? 42.Why is it important to watch for increased redness, swelling and pain after a cut or abrasion has been cleaned and bandaged? 43.Aspirin is a non-steroidal anti-inflammatory drug (NSAID) that inhibits the formation of blood clots and is taken regularly by individuals with a heart condition. Steroids such as cortisol are used to control some autoimmune diseases and severe arthritis by down-regulating the inflammatory response. After reading the role of inflammation in the body’s response to infection, can you predict an undesirable consequence of taking anti-inflammatory drugs on a regular basis? 44.As an individual ages, a constellation of symptoms begins the decline to the point where an individual’s functioning is compromised. Identify and discuss two factors that have a role in factors leading to the compromised situation. 45.Discuss changes that occur in cells as a person ages.	oercommons	2025-03-18T00:35:14.027531	07/23/2019	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/56354/overview", "title": "Anatomy and Physiology, Levels of Organization, The Tissue Level of Organization", "author": null }
https://oercommons.org/courseware/lesson/58770/overview	The Respiratory System Introduction Figure 22.1 Mountain Climbers The thin air at high elevations can strain the human respiratory system. (credit: “bortescristian”/flickr.com) CHAPTER OBJECTIVES After studying this chapter, you will be able to: - List the structures of the respiratory system - List the major functions of the respiratory system - Outline the forces that allow for air movement into and out of the lungs - Outline the process of gas exchange - Summarize the process of oxygen and carbon dioxide transport within the respiratory system - Create a flow chart illustrating how respiration is controlled - Discuss how the respiratory system responds to exercise - Describe the development of the respiratory system in the embryo Hold your breath. Really! See how long you can hold your breath as you continue reading…How long can you do it? Chances are you are feeling uncomfortable already. A typical human cannot survive without breathing for more than 3 minutes, and even if you wanted to hold your breath longer, your autonomic nervous system would take control. This is because every cell in the body needs to run the oxidative stages of cellular respiration, the process by which energy is produced in the form of adenosine triphosphate (ATP). For oxidative phosphorylation to occur, oxygen is used as a reactant and carbon dioxide is released as a waste product. You may be surprised to learn that although oxygen is a critical need for cells, it is actually the accumulation of carbon dioxide that primarily drives your need to breathe. Carbon dioxide is exhaled and oxygen is inhaled through the respiratory system, which includes muscles to move air into and out of the lungs, passageways through which air moves, and microscopic gas exchange surfaces covered by capillaries. The circulatory system transports gases from the lungs to tissues throughout the body and vice versa. A variety of diseases can affect the respiratory system, such as asthma, emphysema, chronic obstruction pulmonary disorder (COPD), and lung cancer. All of these conditions affect the gas exchange process and result in labored breathing and other difficulties. Organs and Structures of the Respiratory System - List the structures that make up the respiratory system - Describe how the respiratory system processes oxygen and CO2 - Compare and contrast the functions of upper respiratory tract with the lower respiratory tract The major organs of the respiratory system function primarily to provide oxygen to body tissues for cellular respiration, remove the waste product carbon dioxide, and help to maintain acid-base balance. Portions of the respiratory system are also used for non-vital functions, such as sensing odors, speech production, and for straining, such as during childbirth or coughing (Figure 22.2). Figure 22.2 Major Respiratory Structures The major respiratory structures span the nasal cavity to the diaphragm. Functionally, the respiratory system can be divided into a conducting zone and a respiratory zone. The conducting zone of the respiratory system includes the organs and structures not directly involved in gas exchange. The gas exchange occurs in the respiratory zone. Conducting Zone The major functions of the conducting zone are to provide a route for incoming and outgoing air, remove debris and pathogens from the incoming air, and warm and humidify the incoming air. Several structures within the conducting zone perform other functions as well. The epithelium of the nasal passages, for example, is essential to sensing odors, and the bronchial epithelium that lines the lungs can metabolize some airborne carcinogens. The Nose and its Adjacent Structures The major entrance and exit for the respiratory system is through the nose. When discussing the nose, it is helpful to divide it into two major sections: the external nose, and the nasal cavity or internal nose. The external nose consists of the surface and skeletal structures that result in the outward appearance of the nose and contribute to its numerous functions (Figure 22.3). The root is the region of the nose located between the eyebrows. The bridge is the part of the nose that connects the root to the rest of the nose. The dorsum nasi is the length of the nose. The apex is the tip of the nose. On either side of the apex, the nostrils are formed by the alae (singular = ala). An ala is a cartilaginous structure that forms the lateral side of each naris (plural = nares), or nostril opening. The philtrum is the concave surface that connects the apex of the nose to the upper lip. Figure 22.3 Nose This illustration shows features of the external nose (top) and skeletal features of the nose (bottom). Underneath the thin skin of the nose are its skeletal features (see Figure 22.3, lower illustration). While the root and bridge of the nose consist of bone, the protruding portion of the nose is composed of cartilage. As a result, when looking at a skull, the nose is missing. The nasal bone is one of a pair of bones that lies under the root and bridge of the nose. The nasal bone articulates superiorly with the frontal bone and laterally with the maxillary bones. Septal cartilage is flexible hyaline cartilage connected to the nasal bone, forming the dorsum nasi. The alar cartilage consists of the apex of the nose; it surrounds the naris. The nares open into the nasal cavity, which is separated into left and right sections by the nasal septum (Figure 22.4). The nasal septum is formed anteriorly by a portion of the septal cartilage (the flexible portion you can touch with your fingers) and posteriorly by the perpendicular plate of the ethmoid bone (a cranial bone located just posterior to the nasal bones) and the thin vomer bones (whose name refers to its plough shape). Each lateral wall of the nasal cavity has three bony projections, called the superior, middle, and inferior nasal conchae. The inferior conchae are separate bones, whereas the superior and middle conchae are portions of the ethmoid bone. Conchae serve to increase the surface area of the nasal cavity and to disrupt the flow of air as it enters the nose, causing air to bounce along the epithelium, where it is cleaned and warmed. The conchae and meatuses also conserve water and prevent dehydration of the nasal epithelium by trapping water during exhalation. The floor of the nasal cavity is composed of the palate. The hard palate at the anterior region of the nasal cavity is composed of bone. The soft palate at the posterior portion of the nasal cavity consists of muscle tissue. Air exits the nasal cavities via the internal nares and moves into the pharynx. Figure 22.4 Upper Airway Several bones that help form the walls of the nasal cavity have air-containing spaces called the paranasal sinuses, which serve to warm and humidify incoming air. Sinuses are lined with a mucosa. Each paranasal sinus is named for its associated bone: frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal sinus. The sinuses produce mucus and lighten the weight of the skull. The nares and anterior portion of the nasal cavities are lined with mucous membranes, containing sebaceous glands and hair follicles that serve to prevent the passage of large debris, such as dirt, through the nasal cavity. An olfactory epithelium used to detect odors is found deeper in the nasal cavity. The conchae, meatuses, and paranasal sinuses are lined by respiratory epithelium composed of pseudostratified ciliated columnar epithelium (Figure 22.5). The epithelium contains goblet cells, one of the specialized, columnar epithelial cells that produce mucus to trap debris. The cilia of the respiratory epithelium help remove the mucus and debris from the nasal cavity with a constant beating motion, sweeping materials towards the throat to be swallowed. Interestingly, cold air slows the movement of the cilia, resulting in accumulation of mucus that may in turn lead to a runny nose during cold weather. This moist epithelium functions to warm and humidify incoming air. Capillaries located just beneath the nasal epithelium warm the air by convection. Serous and mucus-producing cells also secrete the lysozyme enzyme and proteins called defensins, which have antibacterial properties. Immune cells that patrol the connective tissue deep to the respiratory epithelium provide additional protection. Figure 22.5 Pseudostratified Ciliated Columnar Epithelium Respiratory epithelium is pseudostratified ciliated columnar epithelium. Seromucous glands provide lubricating mucus. LM × 680. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK View the University of Michigan WebScope to explore the tissue sample in greater detail. Pharynx The pharynx is a tube formed by skeletal muscle and lined by mucous membrane that is continuous with that of the nasal cavities (see Figure 22.4). The pharynx is divided into three major regions: the nasopharynx, the oropharynx, and the laryngopharynx (Figure 22.6). Figure 22.6 Divisions of the Pharynx The pharynx is divided into three regions: the nasopharynx, the oropharynx, and the laryngopharynx. The nasopharynx is flanked by the conchae of the nasal cavity, and it serves only as an airway. At the top of the nasopharynx are the pharyngeal tonsils. A pharyngeal tonsil, also called an adenoid, is an aggregate of lymphoid reticular tissue similar to a lymph node that lies at the superior portion of the nasopharynx. The function of the pharyngeal tonsil is not well understood, but it contains a rich supply of lymphocytes and is covered with ciliated epithelium that traps and destroys invading pathogens that enter during inhalation. The pharyngeal tonsils are large in children, but interestingly, tend to regress with age and may even disappear. The uvula is a small bulbous, teardrop-shaped structure located at the apex of the soft palate. Both the uvula and soft palate move like a pendulum during swallowing, swinging upward to close off the nasopharynx to prevent ingested materials from entering the nasal cavity. In addition, auditory (Eustachian) tubes that connect to each middle ear cavity open into the nasopharynx. This connection is why colds often lead to ear infections. The oropharynx is a passageway for both air and food. The oropharynx is bordered superiorly by the nasopharynx and anteriorly by the oral cavity. The fauces is the opening at the connection between the oral cavity and the oropharynx. As the nasopharynx becomes the oropharynx, the epithelium changes from pseudostratified ciliated columnar epithelium to stratified squamous epithelium. The oropharynx contains two distinct sets of tonsils, the palatine and lingual tonsils. A palatine tonsil is one of a pair of structures located laterally in the oropharynx in the area of the fauces. The lingual tonsil is located at the base of the tongue. Similar to the pharyngeal tonsil, the palatine and lingual tonsils are composed of lymphoid tissue, and trap and destroy pathogens entering the body through the oral or nasal cavities. The laryngopharynx is inferior to the oropharynx and posterior to the larynx. It continues the route for ingested material and air until its inferior end, where the digestive and respiratory systems diverge. The stratified squamous epithelium of the oropharynx is continuous with the laryngopharynx. Anteriorly, the laryngopharynx opens into the larynx, whereas posteriorly, it enters the esophagus. Larynx The larynx is a cartilaginous structure inferior to the laryngopharynx that connects the pharynx to the trachea and helps regulate the volume of air that enters and leaves the lungs (Figure 22.7). The structure of the larynx is formed by several pieces of cartilage. Three large cartilage pieces—the thyroid cartilage (anterior), epiglottis (superior), and cricoid cartilage (inferior)—form the major structure of the larynx. The thyroid cartilage is the largest piece of cartilage that makes up the larynx. The thyroid cartilage consists of the laryngeal prominence, or “Adam’s apple,” which tends to be more prominent in males. The thick cricoid cartilage forms a ring, with a wide posterior region and a thinner anterior region. Three smaller, paired cartilages—the arytenoids, corniculates, and cuneiforms—attach to the epiglottis and the vocal cords and muscle that help move the vocal cords to produce speech. Figure 22.7 Larynx The larynx extends from the laryngopharynx and the hyoid bone to the trachea. The epiglottis, attached to the thyroid cartilage, is a very flexible piece of elastic cartilage that covers the opening of the trachea (see Figure 22.4). When in the “closed” position, the unattached end of the epiglottis rests on the glottis. The glottis is composed of the vestibular folds, the true vocal cords, and the space between these folds (Figure 22.8). A vestibular fold, or false vocal cord, is one of a pair of folded sections of mucous membrane. A true vocal cord is one of the white, membranous folds attached by muscle to the thyroid and arytenoid cartilages of the larynx on their outer edges. The inner edges of the true vocal cords are free, allowing oscillation to produce sound. The size of the membranous folds of the true vocal cords differs between individuals, producing voices with different pitch ranges. Folds in males tend to be larger than those in females, which create a deeper voice. The act of swallowing causes the pharynx and larynx to lift upward, allowing the pharynx to expand and the epiglottis of the larynx to swing downward, closing the opening to the trachea. These movements produce a larger area for food to pass through, while preventing food and beverages from entering the trachea. Figure 22.8 Vocal Cords The true vocal cords and vestibular folds of the larynx are viewed inferiorly from the laryngopharynx. Continuous with the laryngopharynx, the superior portion of the larynx is lined with stratified squamous epithelium, transitioning into pseudostratified ciliated columnar epithelium that contains goblet cells. Similar to the nasal cavity and nasopharynx, this specialized epithelium produces mucus to trap debris and pathogens as they enter the trachea. The cilia beat the mucus upward towards the laryngopharynx, where it can be swallowed down the esophagus. Trachea The trachea (windpipe) extends from the larynx toward the lungs (Figure 22.9a). The trachea is formed by 16 to 20 stacked, C-shaped pieces of hyaline cartilage that are connected by dense connective tissue. The trachealis muscle and elastic connective tissue together form the fibroelastic membrane, a flexible membrane that closes the posterior surface of the trachea, connecting the C-shaped cartilages. The fibroelastic membrane allows the trachea to stretch and expand slightly during inhalation and exhalation, whereas the rings of cartilage provide structural support and prevent the trachea from collapsing. In addition, the trachealis muscle can be contracted to force air through the trachea during exhalation. The trachea is lined with pseudostratified ciliated columnar epithelium, which is continuous with the larynx. The esophagus borders the trachea posteriorly. Figure 22.9 Trachea (a) The tracheal tube is formed by stacked, C-shaped pieces of hyaline cartilage. (b) The layer visible in this cross-section of tracheal wall tissue between the hyaline cartilage and the lumen of the trachea is the mucosa, which is composed of pseudostratified ciliated columnar epithelium that contains goblet cells. LM × 1220. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Bronchial Tree The trachea branches into the right and left primary bronchi at the carina. These bronchi are also lined by pseudostratified ciliated columnar epithelium containing mucus-producing goblet cells (Figure 22.9b). The carina is a raised structure that contains specialized nervous tissue that induces violent coughing if a foreign body, such as food, is present. Rings of cartilage, similar to those of the trachea, support the structure of the bronchi and prevent their collapse. The primary bronchi enter the lungs at the hilum, a concave region where blood vessels, lymphatic vessels, and nerves also enter the lungs. The bronchi continue to branch into bronchial a tree. A bronchial tree (or respiratory tree) is the collective term used for these multiple-branched bronchi. The main function of the bronchi, like other conducting zone structures, is to provide a passageway for air to move into and out of each lung. In addition, the mucous membrane traps debris and pathogens. A bronchiole branches from the tertiary bronchi. Bronchioles, which are about 1 mm in diameter, further branch until they become the tiny terminal bronchioles, which lead to the structures of gas exchange. There are more than 1000 terminal bronchioles in each lung. The muscular walls of the bronchioles do not contain cartilage like those of the bronchi. This muscular wall can change the size of the tubing to increase or decrease airflow through the tube. Respiratory Zone In contrast to the conducting zone, the respiratory zone includes structures that are directly involved in gas exchange. The respiratory zone begins where the terminal bronchioles join a respiratory bronchiole, the smallest type of bronchiole (Figure 22.10), which then leads to an alveolar duct, opening into a cluster of alveoli. Figure 22.10 Respiratory Zone Bronchioles lead to alveolar sacs in the respiratory zone, where gas exchange occurs. Alveoli An alveolar duct is a tube composed of smooth muscle and connective tissue, which opens into a cluster of alveoli. An alveolus is one of the many small, grape-like sacs that are attached to the alveolar ducts. An alveolar sac is a cluster of many individual alveoli that are responsible for gas exchange. An alveolus is approximately 200 μm in diameter with elastic walls that allow the alveolus to stretch during air intake, which greatly increases the surface area available for gas exchange. Alveoli are connected to their neighbors by alveolar pores, which help maintain equal air pressure throughout the alveoli and lung (Figure 22.11). Figure 22.11 Structures of the Respiratory Zone (a) The alveolus is responsible for gas exchange. (b) A micrograph shows the alveolar structures within lung tissue. LM × 178. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) The alveolar wall consists of three major cell types: type I alveolar cells, type II alveolar cells, and alveolar macrophages. A type I alveolar cell is a squamous epithelial cell of the alveoli, which constitute up to 97 percent of the alveolar surface area. These cells are about 25 nm thick and are highly permeable to gases. A type II alveolar cell is interspersed among the type I cells and secretes pulmonary surfactant, a substance composed of phospholipids and proteins that reduces the surface tension of the alveoli. Roaming around the alveolar wall is the alveolar macrophage, a phagocytic cell of the immune system that removes debris and pathogens that have reached the alveoli. The simple squamous epithelium formed by type I alveolar cells is attached to a thin, elastic basement membrane. This epithelium is extremely thin and borders the endothelial membrane of capillaries. Taken together, the alveoli and capillary membranes form a respiratory membrane that is approximately 0.5 μm (micrometers) thick. The respiratory membrane allows gases to cross by simple diffusion, allowing oxygen to be picked up by the blood for transport and CO2 to be released into the air of the alveoli. DISEASES OF THE... Respiratory System: Asthma Asthma is common condition that affects the lungs in both adults and children. Approximately 8.2 percent of adults (18.7 million) and 9.4 percent of children (7 million) in the United States suffer from asthma. In addition, asthma is the most frequent cause of hospitalization in children. Asthma is a chronic disease characterized by inflammation and edema of the airway, and bronchospasms (that is, constriction of the bronchioles), which can inhibit air from entering the lungs. In addition, excessive mucus secretion can occur, which further contributes to airway occlusion (Figure 22.12). Cells of the immune system, such as eosinophils and mononuclear cells, may also be involved in infiltrating the walls of the bronchi and bronchioles. Bronchospasms occur periodically and lead to an “asthma attack.” An attack may be triggered by environmental factors such as dust, pollen, pet hair, or dander, changes in the weather, mold, tobacco smoke, and respiratory infections, or by exercise and stress. Figure 22.12 Normal and Bronchial Asthma Tissues (a) Normal lung tissue does not have the characteristics of lung tissue during (b) an asthma attack, which include thickened mucosa, increased mucus-producing goblet cells, and eosinophil infiltrates. Symptoms of an asthma attack involve coughing, shortness of breath, wheezing, and tightness of the chest. Symptoms of a severe asthma attack that requires immediate medical attention would include difficulty breathing that results in blue (cyanotic) lips or face, confusion, drowsiness, a rapid pulse, sweating, and severe anxiety. The severity of the condition, frequency of attacks, and identified triggers influence the type of medication that an individual may require. Longer-term treatments are used for those with more severe asthma. Short-term, fast-acting drugs that are used to treat an asthma attack are typically administered via an inhaler. For young children or individuals who have difficulty using an inhaler, asthma medications can be administered via a nebulizer. In many cases, the underlying cause of the condition is unknown. However, recent research has demonstrated that certain viruses, such as human rhinovirus C (HRVC), and the bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae that are contracted in infancy or early childhood, may contribute to the development of many cases of asthma. INTERACTIVE LINK Visit this site to learn more about what happens during an asthma attack. What are the three changes that occur inside the airways during an asthma attack? The Lungs - Describe the overall function of the lung - Summarize the blood flow pattern associated with the lungs - Outline the anatomy of the blood supply to the lungs - Describe the pleura of the lungs and their function A major organ of the respiratory system, each lung houses structures of both the conducting and respiratory zones. The main function of the lungs is to perform the exchange of oxygen and carbon dioxide with air from the atmosphere. To this end, the lungs exchange respiratory gases across a very large epithelial surface area—about 70 square meters—that is highly permeable to gases. Gross Anatomy of the Lungs The lungs are pyramid-shaped, paired organs that are connected to the trachea by the right and left bronchi; on the inferior surface, the lungs are bordered by the diaphragm. The diaphragm is the flat, dome-shaped muscle located at the base of the lungs and thoracic cavity. The lungs are enclosed by the pleurae, which are attached to the mediastinum. The right lung is shorter and wider than the left lung, and the left lung occupies a smaller volume than the right. The cardiac notch is an indentation on the surface of the left lung, and it allows space for the heart (Figure 22.13). The apex of the lung is the superior region, whereas the base is the opposite region near the diaphragm. The costal surface of the lung borders the ribs. The mediastinal surface faces the midline. Figure 22.13 Gross Anatomy of the Lungs Each lung is composed of smaller units called lobes. Fissures separate these lobes from each other. The right lung consists of three lobes: the superior, middle, and inferior lobes. The left lung consists of two lobes: the superior and inferior lobes. A bronchopulmonary segment is a division of a lobe, and each lobe houses multiple bronchopulmonary segments. Each segment receives air from its own tertiary bronchus and is supplied with blood by its own artery. Some diseases of the lungs typically affect one or more bronchopulmonary segments, and in some cases, the diseased segments can be surgically removed with little influence on neighboring segments. A pulmonary lobule is a subdivision formed as the bronchi branch into bronchioles. Each lobule receives its own large bronchiole that has multiple branches. An interlobular septum is a wall, composed of connective tissue, which separates lobules from one another. Blood Supply and Nervous Innervation of the Lungs The blood supply of the lungs plays an important role in gas exchange and serves as a transport system for gases throughout the body. In addition, innervation by the both the parasympathetic and sympathetic nervous systems provides an important level of control through dilation and constriction of the airway. Blood Supply The major function of the lungs is to perform gas exchange, which requires blood from the pulmonary circulation. This blood supply contains deoxygenated blood and travels to the lungs where erythrocytes, also known as red blood cells, pick up oxygen to be transported to tissues throughout the body. The pulmonary artery is an artery that arises from the pulmonary trunk and carries deoxygenated, arterial blood to the alveoli. The pulmonary artery branches multiple times as it follows the bronchi, and each branch becomes progressively smaller in diameter. One arteriole and an accompanying venule supply and drain one pulmonary lobule. As they near the alveoli, the pulmonary arteries become the pulmonary capillary network. The pulmonary capillary network consists of tiny vessels with very thin walls that lack smooth muscle fibers. The capillaries branch and follow the bronchioles and structure of the alveoli. It is at this point that the capillary wall meets the alveolar wall, creating the respiratory membrane. Once the blood is oxygenated, it drains from the alveoli by way of multiple pulmonary veins, which exit the lungs through the hilum. Nervous Innervation Dilation and constriction of the airway are achieved through nervous control by the parasympathetic and sympathetic nervous systems. The parasympathetic system causes bronchoconstriction, whereas the sympathetic nervous system stimulates bronchodilation. Reflexes such as coughing, and the ability of the lungs to regulate oxygen and carbon dioxide levels, also result from this autonomic nervous system control. Sensory nerve fibers arise from the vagus nerve, and from the second to fifth thoracic ganglia. The pulmonary plexus is a region on the lung root formed by the entrance of the nerves at the hilum. The nerves then follow the bronchi in the lungs and branch to innervate muscle fibers, glands, and blood vessels. Pleura of the Lungs Each lung is enclosed within a cavity that is surrounded by the pleura. The pleura (plural = pleurae) is a serous membrane that surrounds the lung. The right and left pleurae, which enclose the right and left lungs, respectively, are separated by the mediastinum. The pleurae consist of two layers. The visceral pleura is the layer that is superficial to the lungs, and extends into and lines the lung fissures (Figure 22.14). In contrast, the parietal pleura is the outer layer that connects to the thoracic wall, the mediastinum, and the diaphragm. The visceral and parietal pleurae connect to each other at the hilum. The pleural cavity is the space between the visceral and parietal layers. Figure 22.14 Parietal and Visceral Pleurae of the Lungs The pleurae perform two major functions: They produce pleural fluid and create cavities that separate the major organs. Pleural fluid is secreted by mesothelial cells from both pleural layers and acts to lubricate their surfaces. This lubrication reduces friction between the two layers to prevent trauma during breathing, and creates surface tension that helps maintain the position of the lungs against the thoracic wall. This adhesive characteristic of the pleural fluid causes the lungs to enlarge when the thoracic wall expands during ventilation, allowing the lungs to fill with air. The pleurae also create a division between major organs that prevents interference due to the movement of the organs, while preventing the spread of infection. EVERYDAY CONNECTION The Effects of Second-Hand Tobacco Smoke The burning of a tobacco cigarette creates multiple chemical compounds that are released through mainstream smoke, which is inhaled by the smoker, and through sidestream smoke, which is the smoke that is given off by the burning cigarette. Second-hand smoke, which is a combination of sidestream smoke and the mainstream smoke that is exhaled by the smoker, has been demonstrated by numerous scientific studies to cause disease. At least 40 chemicals in sidestream smoke have been identified that negatively impact human health, leading to the development of cancer or other conditions, such as immune system dysfunction, liver toxicity, cardiac arrhythmias, pulmonary edema, and neurological dysfunction. Furthermore, second-hand smoke has been found to harbor at least 250 compounds that are known to be toxic, carcinogenic, or both. Some major classes of carcinogens in second-hand smoke are polyaromatic hydrocarbons (PAHs), N-nitrosamines, aromatic amines, formaldehyde, and acetaldehyde. Tobacco and second-hand smoke are considered to be carcinogenic. Exposure to second-hand smoke can cause lung cancer in individuals who are not tobacco users themselves. It is estimated that the risk of developing lung cancer is increased by up to 30 percent in nonsmokers who live with an individual who smokes in the house, as compared to nonsmokers who are not regularly exposed to second-hand smoke. Children are especially affected by second-hand smoke. Children who live with an individual who smokes inside the home have a larger number of lower respiratory infections, which are associated with hospitalizations, and higher risk of sudden infant death syndrome (SIDS). Second-hand smoke in the home has also been linked to a greater number of ear infections in children, as well as worsening symptoms of asthma. The Process of Breathing - Describe the mechanisms that drive breathing - Discuss how pressure, volume, and resistance are related - List the steps involved in pulmonary ventilation - Discuss the physical factors related to breathing - Discuss the meaning of respiratory volume and capacities - Define respiratory rate - Outline the mechanisms behind the control of breathing - Describe the respiratory centers of the medulla oblongata - Describe the respiratory centers of the pons - Discuss factors that can influence the respiratory rate Pulmonary ventilation is the act of breathing, which can be described as the movement of air into and out of the lungs. The major mechanisms that drive pulmonary ventilation are atmospheric pressure (Patm); the air pressure within the alveoli, called intra-alveolar pressure (Palv); and the pressure within the pleural cavity, called intrapleural pressure (Pip). Mechanisms of Breathing The intra-alveolar and intrapleural pressures are dependent on certain physical features of the lung. However, the ability to breathe—to have air enter the lungs during inspiration and air leave the lungs during expiration—is dependent on the air pressure of the atmosphere and the air pressure within the lungs. Pressure Relationships Inspiration (or inhalation) and expiration (or exhalation) are dependent on the differences in pressure between the atmosphere and the lungs. In a gas, pressure is a force created by the movement of gas molecules that are confined. For example, a certain number of gas molecules in a two-liter container has more room than the same number of gas molecules in a one-liter container (Figure 22.15). In this case, the force exerted by the movement of the gas molecules against the walls of the two-liter container is lower than the force exerted by the gas molecules in the one-liter container. Therefore, the pressure is lower in the two-liter container and higher in the one-liter container. At a constant temperature, changing the volume occupied by the gas changes the pressure, as does changing the number of gas molecules. Boyle’s law describes the relationship between volume and pressure in a gas at a constant temperature. Boyle discovered that the pressure of a gas is inversely proportional to its volume: If volume increases, pressure decreases. Likewise, if volume decreases, pressure increases. Pressure and volume are inversely related (P = k/V). Therefore, the pressure in the one-liter container (one-half the volume of the two-liter container) would be twice the pressure in the two-liter container. Boyle’s law is expressed by the following formula: 𝑃1𝑉1=𝑃2𝑉2P1V1=P2V2 In this formula, P1 represents the initial pressure and V1 represents the initial volume, whereas the final pressure and volume are represented by P2 and V2, respectively. If the two- and one-liter containers were connected by a tube and the volume of one of the containers were changed, then the gases would move from higher pressure (lower volume) to lower pressure (higher volume). Figure 22.15 Boyle's Law In a gas, pressure increases as volume decreases. Pulmonary ventilation is dependent on three types of pressure: atmospheric, intra-alveolar, and intrapleural. Atmospheric pressureis the amount of force that is exerted by gases in the air surrounding any given surface, such as the body. Atmospheric pressure can be expressed in terms of the unit atmosphere, abbreviated atm, or in millimeters of mercury (mm Hg). One atm is equal to 760 mm Hg, which is the atmospheric pressure at sea level. Typically, for respiration, other pressure values are discussed in relation to atmospheric pressure. Therefore, negative pressure is pressure lower than the atmospheric pressure, whereas positive pressure is pressure that it is greater than the atmospheric pressure. A pressure that is equal to the atmospheric pressure is expressed as zero. Intra-alveolar pressure (intrapulmonary pressure) is the pressure of the air within the alveoli, which changes during the different phases of breathing (Figure 22.16). Because the alveoli are connected to the atmosphere via the tubing of the airways (similar to the two- and one-liter containers in the example above), the intrapulmonary pressure of the alveoli always equalizes with the atmospheric pressure. Figure 22.16 Intrapulmonary and Intrapleural Pressure Relationships Intra-alveolar pressure changes during the different phases of the cycle. It equalizes at 760 mm Hg but does not remain at 760 mm Hg. Intrapleural pressure is the pressure of the air within the pleural cavity, between the visceral and parietal pleurae. Similar to intra-alveolar pressure, intrapleural pressure also changes during the different phases of breathing. However, due to certain characteristics of the lungs, the intrapleural pressure is always lower than, or negative to, the intra-alveolar pressure (and therefore also to atmospheric pressure). Although it fluctuates during inspiration and expiration, intrapleural pressure remains approximately –4 mm Hg throughout the breathing cycle. Competing forces within the thorax cause the formation of the negative intrapleural pressure. One of these forces relates to the elasticity of the lungs themselves—elastic tissue pulls the lungs inward, away from the thoracic wall. Surface tension of alveolar fluid, which is mostly water, also creates an inward pull of the lung tissue. This inward tension from the lungs is countered by opposing forces from the pleural fluid and thoracic wall. Surface tension within the pleural cavity pulls the lungs outward. Too much or too little pleural fluid would hinder the creation of the negative intrapleural pressure; therefore, the level must be closely monitored by the mesothelial cells and drained by the lymphatic system. Since the parietal pleura is attached to the thoracic wall, the natural elasticity of the chest wall opposes the inward pull of the lungs. Ultimately, the outward pull is slightly greater than the inward pull, creating the –4 mm Hg intrapleural pressure relative to the intra-alveolar pressure. Transpulmonary pressure is the difference between the intrapleural and intra-alveolar pressures, and it determines the size of the lungs. A higher transpulmonary pressure corresponds to a larger lung. Physical Factors Affecting Ventilation In addition to the differences in pressures, breathing is also dependent upon the contraction and relaxation of muscle fibers of both the diaphragm and thorax. The lungs themselves are passive during breathing, meaning they are not involved in creating the movement that helps inspiration and expiration. This is because of the adhesive nature of the pleural fluid, which allows the lungs to be pulled outward when the thoracic wall moves during inspiration. The recoil of the thoracic wall during expiration causes compression of the lungs. Contraction and relaxation of the diaphragm and intercostals muscles (found between the ribs) cause most of the pressure changes that result in inspiration and expiration. These muscle movements and subsequent pressure changes cause air to either rush in or be forced out of the lungs. Other characteristics of the lungs influence the effort that must be expended to ventilate. Resistance is a force that slows motion, in this case, the flow of gases. The size of the airway is the primary factor affecting resistance. A small tubular diameter forces air through a smaller space, causing more collisions of air molecules with the walls of the airways. The following formula helps to describe the relationship between airway resistance and pressure changes: 𝐹=∆𝑃/𝑅F=∆P/RAs noted earlier, there is surface tension within the alveoli caused by water present in the lining of the alveoli. This surface tension tends to inhibit expansion of the alveoli. However, pulmonary surfactant secreted by type II alveolar cells mixes with that water and helps reduce this surface tension. Without pulmonary surfactant, the alveoli would collapse during expiration. Thoracic wall compliance is the ability of the thoracic wall to stretch while under pressure. This can also affect the effort expended in the process of breathing. In order for inspiration to occur, the thoracic cavity must expand. The expansion of the thoracic cavity directly influences the capacity of the lungs to expand. If the tissues of the thoracic wall are not very compliant, it will be difficult to expand the thorax to increase the size of the lungs. Pulmonary Ventilation The difference in pressures drives pulmonary ventilation because air flows down a pressure gradient, that is, air flows from an area of higher pressure to an area of lower pressure. Air flows into the lungs largely due to a difference in pressure; atmospheric pressure is greater than intra-alveolar pressure, and intra-alveolar pressure is greater than intrapleural pressure. Air flows out of the lungs during expiration based on the same principle; pressure within the lungs becomes greater than the atmospheric pressure. Pulmonary ventilation comprises two major steps: inspiration and expiration. Inspiration is the process that causes air to enter the lungs, and expiration is the process that causes air to leave the lungs (Figure 22.17). A respiratory cycle is one sequence of inspiration and expiration. In general, two muscle groups are used during normal inspiration: the diaphragm and the external intercostal muscles. Additional muscles can be used if a bigger breath is required. When the diaphragm contracts, it moves inferiorly toward the abdominal cavity, creating a larger thoracic cavity and more space for the lungs. Contraction of the external intercostal muscles moves the ribs upward and outward, causing the rib cage to expand, which increases the volume of the thoracic cavity. Due to the adhesive force of the pleural fluid, the expansion of the thoracic cavity forces the lungs to stretch and expand as well. This increase in volume leads to a decrease in intra-alveolar pressure, creating a pressure lower than atmospheric pressure. As a result, a pressure gradient is created that drives air into the lungs. Figure 22.17 Inspiration and Expiration Inspiration and expiration occur due to the expansion and contraction of the thoracic cavity, respectively. The process of normal expiration is passive, meaning that energy is not required to push air out of the lungs. Instead, the elasticity of the lung tissue causes the lung to recoil, as the diaphragm and intercostal muscles relax following inspiration. In turn, the thoracic cavity and lungs decrease in volume, causing an increase in intrapulmonary pressure. The intrapulmonary pressure rises above atmospheric pressure, creating a pressure gradient that causes air to leave the lungs. There are different types, or modes, of breathing that require a slightly different process to allow inspiration and expiration. Quiet breathing, also known as eupnea, is a mode of breathing that occurs at rest and does not require the cognitive thought of the individual. During quiet breathing, the diaphragm and external intercostals must contract. A deep breath, called diaphragmatic breathing, requires the diaphragm to contract. As the diaphragm relaxes, air passively leaves the lungs. A shallow breath, called costal breathing, requires contraction of the intercostal muscles. As the intercostal muscles relax, air passively leaves the lungs. In contrast, forced breathing, also known as hyperpnea, is a mode of breathing that can occur during exercise or actions that require the active manipulation of breathing, such as singing. During forced breathing, inspiration and expiration both occur due to muscle contractions. In addition to the contraction of the diaphragm and intercostal muscles, other accessory muscles must also contract. During forced inspiration, muscles of the neck, including the scalenes, contract and lift the thoracic wall, increasing lung volume. During forced expiration, accessory muscles of the abdomen, including the obliques, contract, forcing abdominal organs upward against the diaphragm. This helps to push the diaphragm further into the thorax, pushing more air out. In addition, accessory muscles (primarily the internal intercostals) help to compress the rib cage, which also reduces the volume of the thoracic cavity. Respiratory Volumes and Capacities Respiratory volume is the term used for various volumes of air moved by or associated with the lungs at a given point in the respiratory cycle. There are four major types of respiratory volumes: tidal, residual, inspiratory reserve, and expiratory reserve (Figure 22.18). Tidal volume (TV) is the amount of air that normally enters the lungs during quiet breathing, which is about 500 milliliters. Expiratory reserve volume (ERV) is the amount of air you can forcefully exhale past a normal tidal expiration, up to 1200 milliliters for men. Inspiratory reserve volume (IRV) is produced by a deep inhalation, past a tidal inspiration. This is the extra volume that can be brought into the lungs during a forced inspiration. Residual volume (RV) is the air left in the lungs if you exhale as much air as possible. The residual volume makes breathing easier by preventing the alveoli from collapsing. Respiratory volume is dependent on a variety of factors, and measuring the different types of respiratory volumes can provide important clues about a person’s respiratory health (Figure 22.19). Figure 22.18 Respiratory Volumes and Capacities These two graphs show (a) respiratory volumes and (b) the combination of volumes that results in respiratory capacity. Figure 22.19 Pulmonary Function Testing Respiratory capacity is the combination of two or more selected volumes, which further describes the amount of air in the lungs during a given time. For example, total lung capacity (TLC) is the sum of all of the lung volumes (TV, ERV, IRV, and RV), which represents the total amount of air a person can hold in the lungs after a forceful inhalation. TLC is about 6000 mL air for men, and about 4200 mL for women. Vital capacity (VC) is the amount of air a person can move into or out of his or her lungs, and is the sum of all of the volumes except residual volume (TV, ERV, and IRV), which is between 4000 and 5000 milliliters. Inspiratory capacity (IC) is the maximum amount of air that can be inhaled past a normal tidal expiration, is the sum of the tidal volume and inspiratory reserve volume. On the other hand, the functional residual capacity (FRC) is the amount of air that remains in the lung after a normal tidal expiration; it is the sum of expiratory reserve volume and residual volume (see Figure 22.18). INTERACTIVE LINK Watch this video to learn more about lung volumes and spirometers. Explain how spirometry test results can be used to diagnose respiratory diseases or determine the effectiveness of disease treatment. In addition to the air that creates respiratory volumes, the respiratory system also contains anatomical dead space, which is air that is present in the airway that never reaches the alveoli and therefore never participates in gas exchange. Alveolar dead spaceinvolves air found within alveoli that are unable to function, such as those affected by disease or abnormal blood flow. Total dead space is the anatomical dead space and alveolar dead space together, and represents all of the air in the respiratory system that is not being used in the gas exchange process. Respiratory Rate and Control of Ventilation Breathing usually occurs without thought, although at times you can consciously control it, such as when you swim under water, sing a song, or blow bubbles. The respiratory rate is the total number of breaths, or respiratory cycles, that occur each minute. Respiratory rate can be an important indicator of disease, as the rate may increase or decrease during an illness or in a disease condition. The respiratory rate is controlled by the respiratory center located within the medulla oblongata in the brain, which responds primarily to changes in carbon dioxide, oxygen, and pH levels in the blood. The normal respiratory rate of a child decreases from birth to adolescence. A child under 1 year of age has a normal respiratory rate between 30 and 60 breaths per minute, but by the time a child is about 10 years old, the normal rate is closer to 18 to 30. By adolescence, the normal respiratory rate is similar to that of adults, 12 to 18 breaths per minute. Ventilation Control Centers The control of ventilation is a complex interplay of multiple regions in the brain that signal the muscles used in pulmonary ventilation to contract (Table 22.1). The result is typically a rhythmic, consistent ventilation rate that provides the body with sufficient amounts of oxygen, while adequately removing carbon dioxide. Summary of Ventilation Regulation \| System component \| Function \| \|---\|---\| \| Medullary respiratory renter \| Sets the basic rhythm of breathing \| \| Ventral respiratory group (VRG) \| Generates the breathing rhythm and integrates data coming into the medulla \| \| Dorsal respiratory group (DRG) \| Integrates input from the stretch receptors and the chemoreceptors in the periphery \| \| Pontine respiratory group (PRG) \| Influences and modifies the medulla oblongata’s functions \| \| Aortic body \| Monitors blood PCO2, PO2, and pH \| \| Carotid body \| Monitors blood PCO2, PO2, and pH \| \| Hypothalamus \| Monitors emotional state and body temperature \| \| Cortical areas of the brain \| Control voluntary breathing \| \| Proprioceptors \| Send impulses regarding joint and muscle movements \| \| Pulmonary irritant reflexes \| Protect the respiratory zones of the system from foreign material \| \| Inflation reflex \| Protects the lungs from over-inflating \| Table 22.1 Neurons that innervate the muscles of the respiratory system are responsible for controlling and regulating pulmonary ventilation. The major brain centers involved in pulmonary ventilation are the medulla oblongata and the pontine respiratory group (Figure 22.20). Figure 22.20 Respiratory Centers of the Brain The medulla oblongata contains the dorsal respiratory group (DRG) and the ventral respiratory group (VRG). The DRG is involved in maintaining a constant breathing rhythm by stimulating the diaphragm and intercostal muscles to contract, resulting in inspiration. When activity in the DRG ceases, it no longer stimulates the diaphragm and intercostals to contract, allowing them to relax, resulting in expiration. The VRG is involved in forced breathing, as the neurons in the VRG stimulate the accessory muscles involved in forced breathing to contract, resulting in forced inspiration. The VRG also stimulates the accessory muscles involved in forced expiration to contract. The second respiratory center of the brain is located within the pons, called the pontine respiratory group, and consists of the apneustic and pneumotaxic centers. The apneustic center is a double cluster of neuronal cell bodies that stimulate neurons in the DRG, controlling the depth of inspiration, particularly for deep breathing. The pneumotaxic center is a network of neurons that inhibits the activity of neurons in the DRG, allowing relaxation after inspiration, and thus controlling the overall rate. Factors That Affect the Rate and Depth of Respiration The respiratory rate and the depth of inspiration are regulated by the medulla oblongata and pons; however, these regions of the brain do so in response to systemic stimuli. It is a dose-response, negative-feedback relationship in which the greater the stimulus, the greater the response. Thus, increasing stimuli results in forced breathing. Multiple systemic factors are involved in stimulating the brain to produce pulmonary ventilation. The major factor that stimulates the medulla oblongata and pons to produce respiration is surprisingly not oxygen concentration, but rather the concentration of carbon dioxide in the blood. As you recall, carbon dioxide is a waste product of cellular respiration and can be toxic. Concentrations of chemicals are sensed by chemoreceptors. A central chemoreceptor is one of the specialized receptors that are located in the brain and brainstem, whereas a peripheral chemoreceptor is one of the specialized receptors located in the carotid arteries and aortic arch. Concentration changes in certain substances, such as carbon dioxide or hydrogen ions, stimulate these receptors, which in turn signal the respiration centers of the brain. In the case of carbon dioxide, as the concentration of CO2 in the blood increases, it readily diffuses across the blood-brain barrier, where it collects in the extracellular fluid. As will be explained in more detail later, increased carbon dioxide levels lead to increased levels of hydrogen ions, decreasing pH. The increase in hydrogen ions in the brain triggers the central chemoreceptors to stimulate the respiratory centers to initiate contraction of the diaphragm and intercostal muscles. As a result, the rate and depth of respiration increase, allowing more carbon dioxide to be expelled, which brings more air into and out of the lungs promoting a reduction in the blood levels of carbon dioxide, and therefore hydrogen ions, in the blood. In contrast, low levels of carbon dioxide in the blood cause low levels of hydrogen ions in the brain, leading to a decrease in the rate and depth of pulmonary ventilation, producing shallow, slow breathing. Another factor involved in influencing the respiratory activity of the brain is systemic arterial concentrations of hydrogen ions. Increasing carbon dioxide levels can lead to increased H+ levels, as mentioned above, as well as other metabolic activities, such as lactic acid accumulation after strenuous exercise. Peripheral chemoreceptors of the aortic arch and carotid arteries sense arterial levels of hydrogen ions. When peripheral chemoreceptors sense decreasing, or more acidic, pH levels, they stimulate an increase in ventilation to remove carbon dioxide from the blood at a quicker rate. Removal of carbon dioxide from the blood helps to reduce hydrogen ions, thus increasing systemic pH. Blood levels of oxygen are also important in influencing respiratory rate. The peripheral chemoreceptors are responsible for sensing large changes in blood oxygen levels. If blood oxygen levels become quite low—about 60 mm Hg or less—then peripheral chemoreceptors stimulate an increase in respiratory activity. The chemoreceptors are only able to sense dissolved oxygen molecules, not the oxygen that is bound to hemoglobin. As you recall, the majority of oxygen is bound by hemoglobin; when dissolved levels of oxygen drop, hemoglobin releases oxygen. Therefore, a large drop in oxygen levels is required to stimulate the chemoreceptors of the aortic arch and carotid arteries. The hypothalamus and other brain regions associated with the limbic system also play roles in influencing the regulation of breathing by interacting with the respiratory centers. The hypothalamus and other regions associated with the limbic system are involved in regulating respiration in response to emotions, pain, and temperature. For example, an increase in body temperature causes an increase in respiratory rate. Feeling excited or the fight-or-flight response will also result in an increase in respiratory rate. DISORDERS OF THE... Respiratory System: Sleep Apnea Sleep apnea is a chronic disorder that can occur in children or adults, and is characterized by the cessation of breathing during sleep. These episodes may last for several seconds or several minutes, and may differ in the frequency with which they are experienced. Sleep apnea leads to poor sleep, which is reflected in the symptoms of fatigue, evening napping, irritability, memory problems, and morning headaches. In addition, many individuals with sleep apnea experience a dry throat in the morning after waking from sleep, which may be due to excessive snoring. There are two types of sleep apnea: obstructive sleep apnea and central sleep apnea. Obstructive sleep apnea is caused by an obstruction of the airway during sleep, which can occur at different points in the airway, depending on the underlying cause of the obstruction. For example, the tongue and throat muscles of some individuals with obstructive sleep apnea may relax excessively, causing the muscles to push into the airway. Another example is obesity, which is a known risk factor for sleep apnea, as excess adipose tissue in the neck region can push the soft tissues towards the lumen of the airway, causing the trachea to narrow. In central sleep apnea, the respiratory centers of the brain do not respond properly to rising carbon dioxide levels and therefore do not stimulate the contraction of the diaphragm and intercostal muscles regularly. As a result, inspiration does not occur and breathing stops for a short period. In some cases, the cause of central sleep apnea is unknown. However, some medical conditions, such as stroke and congestive heart failure, may cause damage to the pons or medulla oblongata. In addition, some pharmacologic agents, such as morphine, can affect the respiratory centers, causing a decrease in the respiratory rate. The symptoms of central sleep apnea are similar to those of obstructive sleep apnea. A diagnosis of sleep apnea is usually done during a sleep study, where the patient is monitored in a sleep laboratory for several nights. The patient’s blood oxygen levels, heart rate, respiratory rate, and blood pressure are monitored, as are brain activity and the volume of air that is inhaled and exhaled. Treatment of sleep apnea commonly includes the use of a device called a continuous positive airway pressure (CPAP) machine during sleep. The CPAP machine has a mask that covers the nose, or the nose and mouth, and forces air into the airway at regular intervals. This pressurized air can help to gently force the airway to remain open, allowing more normal ventilation to occur. Other treatments include lifestyle changes to decrease weight, eliminate alcohol and other sleep apnea–promoting drugs, and changes in sleep position. In addition to these treatments, patients with central sleep apnea may need supplemental oxygen during sleep. Gas Exchange - Compare the composition of atmospheric air and alveolar air - Describe the mechanisms that drive gas exchange - Discuss the importance of sufficient ventilation and perfusion, and how the body adapts when they are insufficient - Discuss the process of external respiration - Describe the process of internal respiration The purpose of the respiratory system is to perform gas exchange. Pulmonary ventilation provides air to the alveoli for this gas exchange process. At the respiratory membrane, where the alveolar and capillary walls meet, gases move across the membranes, with oxygen entering the bloodstream and carbon dioxide exiting. It is through this mechanism that blood is oxygenated and carbon dioxide, the waste product of cellular respiration, is removed from the body. Gas Exchange In order to understand the mechanisms of gas exchange in the lung, it is important to understand the underlying principles of gases and their behavior. In addition to Boyle’s law, several other gas laws help to describe the behavior of gases. Gas Laws and Air Composition Gas molecules exert force on the surfaces with which they are in contact; this force is called pressure. In natural systems, gases are normally present as a mixture of different types of molecules. For example, the atmosphere consists of oxygen, nitrogen, carbon dioxide, and other gaseous molecules, and this gaseous mixture exerts a certain pressure referred to as atmospheric pressure (Table 22.2). Partial pressure (Px) is the pressure of a single type of gas in a mixture of gases. For example, in the atmosphere, oxygen exerts a partial pressure, and nitrogen exerts another partial pressure, independent of the partial pressure of oxygen (Figure 22.21). Total pressure is the sum of all the partial pressures of a gaseous mixture. Dalton’s law describes the behavior of nonreactive gases in a gaseous mixture and states that a specific gas type in a mixture exerts its own pressure; thus, the total pressure exerted by a mixture of gases is the sum of the partial pressures of the gases in the mixture. Partial Pressures of Atmospheric Gases \| Gas \| Percent of total composition \| Partial pressure (mm Hg) \| \|---\|---\|---\| \| Nitrogen (N2) \| 78.6 \| 597.4 \| \| Oxygen (O2) \| 20.9 \| 158.8 \| \| Water (H2O) \| 0.4 \| 3.0 \| \| Carbon dioxide (CO2) \| 0.04 \| 0.3 \| \| Others \| 0.06 \| 0.5 \| \| Total composition/total atmospheric pressure \| 100% \| 760.0 \| Table 22.2 Figure 22.21 Partial and Total Pressures of a Gas Partial pressure is the force exerted by a gas. The sum of the partial pressures of all the gases in a mixture equals the total pressure. Partial pressure is extremely important in predicting the movement of gases. Recall that gases tend to equalize their pressure in two regions that are connected. A gas will move from an area where its partial pressure is higher to an area where its partial pressure is lower. In addition, the greater the partial pressure difference between the two areas, the more rapid is the movement of gases. Solubility of Gases in Liquids Henry’s law describes the behavior of gases when they come into contact with a liquid, such as blood. Henry’s law states that the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that gas. The greater the partial pressure of the gas, the greater the number of gas molecules that will dissolve in the liquid. The concentration of the gas in a liquid is also dependent on the solubility of the gas in the liquid. For example, although nitrogen is present in the atmosphere, very little nitrogen dissolves into the blood, because the solubility of nitrogen in blood is very low. The exception to this occurs in scuba divers; the composition of the compressed air that divers breathe causes nitrogen to have a higher partial pressure than normal, causing it to dissolve in the blood in greater amounts than normal. Too much nitrogen in the bloodstream results in a serious condition that can be fatal if not corrected. Gas molecules establish an equilibrium between those molecules dissolved in liquid and those in air. The composition of air in the atmosphere and in the alveoli differs. In both cases, the relative concentration of gases is nitrogen > oxygen > water vapor > carbon dioxide. The amount of water vapor present in alveolar air is greater than that in atmospheric air (Table 22.3). Recall that the respiratory system works to humidify incoming air, thereby causing the air present in the alveoli to have a greater amount of water vapor than atmospheric air. In addition, alveolar air contains a greater amount of carbon dioxide and less oxygen than atmospheric air. This is no surprise, as gas exchange removes oxygen from and adds carbon dioxide to alveolar air. Both deep and forced breathing cause the alveolar air composition to be changed more rapidly than during quiet breathing. As a result, the partial pressures of oxygen and carbon dioxide change, affecting the diffusion process that moves these materials across the membrane. This will cause oxygen to enter and carbon dioxide to leave the blood more quickly. Composition and Partial Pressures of Alveolar Air \| Gas \| Percent of total composition \| Partial pressure (mm Hg) \| \|---\|---\|---\| \| Nitrogen (N2) \| 74.9 \| 569 \| \| Oxygen (O2) \| 13.7 \| 104 \| \| Water (H2O) \| 6.2 \| 40 \| \| Carbon dioxide (CO2) \| 5.2 \| 47 \| \| Total composition/total alveolar pressure \| 100% \| 760.0 \| Table 22.3 Ventilation and Perfusion Two important aspects of gas exchange in the lung are ventilation and perfusion. Ventilation is the movement of air into and out of the lungs, and perfusion is the flow of blood in the pulmonary capillaries. For gas exchange to be efficient, the volumes involved in ventilation and perfusion should be compatible. However, factors such as regional gravity effects on blood, blocked alveolar ducts, or disease can cause ventilation and perfusion to be imbalanced. The partial pressure of oxygen in alveolar air is about 104 mm Hg, whereas the partial pressure of oxygenated blood in pulmonary veins is about 100 mm Hg. When ventilation is sufficient, oxygen enters the alveoli at a high rate, and the partial pressure of oxygen in the alveoli remains high. In contrast, when ventilation is insufficient, the partial pressure of oxygen in the alveoli drops. Without the large difference in partial pressure between the alveoli and the blood, oxygen does not diffuse efficiently across the respiratory membrane. The body has mechanisms that counteract this problem. In cases when ventilation is not sufficient for an alveolus, the body redirects blood flow to alveoli that are receiving sufficient ventilation. This is achieved by constricting the pulmonary arterioles that serves the dysfunctional alveolus, which redirects blood to other alveoli that have sufficient ventilation. At the same time, the pulmonary arterioles that serve alveoli receiving sufficient ventilation vasodilate, which brings in greater blood flow. Factors such as carbon dioxide, oxygen, and pH levels can all serve as stimuli for adjusting blood flow in the capillary networks associated with the alveoli. Ventilation is regulated by the diameter of the airways, whereas perfusion is regulated by the diameter of the blood vessels. The diameter of the bronchioles is sensitive to the partial pressure of carbon dioxide in the alveoli. A greater partial pressure of carbon dioxide in the alveoli causes the bronchioles to increase their diameter as will a decreased level of oxygen in the blood supply, allowing carbon dioxide to be exhaled from the body at a greater rate. As mentioned above, a greater partial pressure of oxygen in the alveoli causes the pulmonary arterioles to dilate, increasing blood flow. Gas Exchange Gas exchange occurs at two sites in the body: in the lungs, where oxygen is picked up and carbon dioxide is released at the respiratory membrane, and at the tissues, where oxygen is released and carbon dioxide is picked up. External respiration is the exchange of gases with the external environment, and occurs in the alveoli of the lungs. Internal respiration is the exchange of gases with the internal environment, and occurs in the tissues. The actual exchange of gases occurs due to simple diffusion. Energy is not required to move oxygen or carbon dioxide across membranes. Instead, these gases follow pressure gradients that allow them to diffuse. The anatomy of the lung maximizes the diffusion of gases: The respiratory membrane is highly permeable to gases; the respiratory and blood capillary membranes are very thin; and there is a large surface area throughout the lungs. External Respiration The pulmonary artery carries deoxygenated blood into the lungs from the heart, where it branches and eventually becomes the capillary network composed of pulmonary capillaries. These pulmonary capillaries create the respiratory membrane with the alveoli (Figure 22.22). As the blood is pumped through this capillary network, gas exchange occurs. Although a small amount of the oxygen is able to dissolve directly into plasma from the alveoli, most of the oxygen is picked up by erythrocytes (red blood cells) and binds to a protein called hemoglobin, a process described later in this chapter. Oxygenated hemoglobin is red, causing the overall appearance of bright red oxygenated blood, which returns to the heart through the pulmonary veins. Carbon dioxide is released in the opposite direction of oxygen, from the blood to the alveoli. Some of the carbon dioxide is returned on hemoglobin, but can also be dissolved in plasma or is present as a converted form, also explained in greater detail later in this chapter. External respiration occurs as a function of partial pressure differences in oxygen and carbon dioxide between the alveoli and the blood in the pulmonary capillaries. Figure 22.22 External Respiration In external respiration, oxygen diffuses across the respiratory membrane from the alveolus to the capillary, whereas carbon dioxide diffuses out of the capillary into the alveolus. Although the solubility of oxygen in blood is not high, there is a drastic difference in the partial pressure of oxygen in the alveoli versus in the blood of the pulmonary capillaries. This difference is about 64 mm Hg: The partial pressure of oxygen in the alveoli is about 104 mm Hg, whereas its partial pressure in the blood of the capillary is about 40 mm Hg. This large difference in partial pressure creates a very strong pressure gradient that causes oxygen to rapidly cross the respiratory membrane from the alveoli into the blood. The partial pressure of carbon dioxide is also different between the alveolar air and the blood of the capillary. However, the partial pressure difference is less than that of oxygen, about 5 mm Hg. The partial pressure of carbon dioxide in the blood of the capillary is about 45 mm Hg, whereas its partial pressure in the alveoli is about 40 mm Hg. However, the solubility of carbon dioxide is much greater than that of oxygen—by a factor of about 20—in both blood and alveolar fluids. As a result, the relative concentrations of oxygen and carbon dioxide that diffuse across the respiratory membrane are similar. Internal Respiration Internal respiration is gas exchange that occurs at the level of body tissues (Figure 22.23). Similar to external respiration, internal respiration also occurs as simple diffusion due to a partial pressure gradient. However, the partial pressure gradients are opposite of those present at the respiratory membrane. The partial pressure of oxygen in tissues is low, about 40 mm Hg, because oxygen is continuously used for cellular respiration. In contrast, the partial pressure of oxygen in the blood is about 100 mm Hg. This creates a pressure gradient that causes oxygen to dissociate from hemoglobin, diffuse out of the blood, cross the interstitial space, and enter the tissue. Hemoglobin that has little oxygen bound to it loses much of its brightness, so that blood returning to the heart is more burgundy in color. Considering that cellular respiration continuously produces carbon dioxide, the partial pressure of carbon dioxide is lower in the blood than it is in the tissue, causing carbon dioxide to diffuse out of the tissue, cross the interstitial fluid, and enter the blood. It is then carried back to the lungs either bound to hemoglobin, dissolved in plasma, or in a converted form. By the time blood returns to the heart, the partial pressure of oxygen has returned to about 40 mm Hg, and the partial pressure of carbon dioxide has returned to about 45 mm Hg. The blood is then pumped back to the lungs to be oxygenated once again during external respiration. Figure 22.23 Internal Respiration Oxygen diffuses out of the capillary and into cells, whereas carbon dioxide diffuses out of cells and into the capillary. EVERYDAY CONNECTION Hyperbaric Chamber Treatment A type of device used in some areas of medicine that exploits the behavior of gases is hyperbaric chamber treatment. A hyperbaric chamber is a unit that can be sealed and expose a patient to either 100 percent oxygen with increased pressure or a mixture of gases that includes a higher concentration of oxygen than normal atmospheric air, also at a higher partial pressure than the atmosphere. There are two major types of chambers: monoplace and multiplace. Monoplace chambers are typically for one patient, and the staff tending to the patient observes the patient from outside of the chamber (Figure 22.24). Some facilities have special monoplace hyperbaric chambers that allow multiple patients to be treated at once, usually in a sitting or reclining position, to help ease feelings of isolation or claustrophobia. Multiplace chambers are large enough for multiple patients to be treated at one time, and the staff attending these patients is present inside the chamber. In a multiplace chamber, patients are often treated with air via a mask or hood, and the chamber is pressurized. Figure 22.24 Hyperbaric Chamber (credit: “komunews”/flickr.com) Hyperbaric chamber treatment is based on the behavior of gases. As you recall, gases move from a region of higher partial pressure to a region of lower partial pressure. In a hyperbaric chamber, the atmospheric pressure is increased, causing a greater amount of oxygen than normal to diffuse into the bloodstream of the patient. Hyperbaric chamber therapy is used to treat a variety of medical problems, such as wound and graft healing, anaerobic bacterial infections, and carbon monoxide poisoning. Exposure to and poisoning by carbon monoxide is difficult to reverse, because hemoglobin’s affinity for carbon monoxide is much stronger than its affinity for oxygen, causing carbon monoxide to replace oxygen in the blood. Hyperbaric chamber therapy can treat carbon monoxide poisoning, because the increased atmospheric pressure causes more oxygen to diffuse into the bloodstream. At this increased pressure and increased concentration of oxygen, carbon monoxide is displaced from hemoglobin. Another example is the treatment of anaerobic bacterial infections, which are created by bacteria that cannot or prefer not to live in the presence of oxygen. An increase in blood and tissue levels of oxygen helps to kill the anaerobic bacteria that are responsible for the infection, as oxygen is toxic to anaerobic bacteria. For wounds and grafts, the chamber stimulates the healing process by increasing energy production needed for repair. Increasing oxygen transport allows cells to ramp up cellular respiration and thus ATP production, the energy needed to build new structures. Transport of Gases - Describe the principles of oxygen transport - Describe the structure of hemoglobin - Compare and contrast fetal and adult hemoglobin - Describe the principles of carbon dioxide transport The other major activity in the lungs is the process of respiration, the process of gas exchange. The function of respiration is to provide oxygen for use by body cells during cellular respiration and to eliminate carbon dioxide, a waste product of cellular respiration, from the body. In order for the exchange of oxygen and carbon dioxide to occur, both gases must be transported between the external and internal respiration sites. Although carbon dioxide is more soluble than oxygen in blood, both gases require a specialized transport system for the majority of the gas molecules to be moved between the lungs and other tissues. Oxygen Transport in the Blood Even though oxygen is transported via the blood, you may recall that oxygen is not very soluble in liquids. A small amount of oxygen does dissolve in the blood and is transported in the bloodstream, but it is only about 1.5% of the total amount. The majority of oxygen molecules are carried from the lungs to the body’s tissues by a specialized transport system, which relies on the erythrocyte—the red blood cell. Erythrocytes contain a metalloprotein, hemoglobin, which serves to bind oxygen molecules to the erythrocyte (Figure 22.25). Heme is the portion of hemoglobin that contains iron, and it is heme that binds oxygen. One hemoglobin molecule contains iron-containing Heme molecules, and because of this, each hemoglobin molecule is capable of carrying up to four molecules of oxygen. As oxygen diffuses across the respiratory membrane from the alveolus to the capillary, it also diffuses into the red blood cell and is bound by hemoglobin. The following reversible chemical reaction describes the production of the final product, oxyhemoglobin (Hb–O2), which is formed when oxygen binds to hemoglobin. Oxyhemoglobin is a bright red-colored molecule that contributes to the bright red color of oxygenated blood. Hb + O2↔Hb − O2Hb + O2↔Hb − O2 In this formula, Hb represents reduced hemoglobin, that is, hemoglobin that does not have oxygen bound to it. There are multiple factors involved in how readily heme binds to and dissociates from oxygen, which will be discussed in the subsequent sections. Figure 22.25 Erythrocyte and Hemoglobin Hemoglobin consists of four subunits, each of which contains one molecule of iron. Function of Hemoglobin Hemoglobin is composed of subunits, a protein structure that is referred to as a quaternary structure. Each of the four subunits that make up hemoglobin is arranged in a ring-like fashion, with an iron atom covalently bound to the heme in the center of each subunit. Binding of the first oxygen molecule causes a conformational change in hemoglobin that allows the second molecule of oxygen to bind more readily. As each molecule of oxygen is bound, it further facilitates the binding of the next molecule, until all four heme sites are occupied by oxygen. The opposite occurs as well: After the first oxygen molecule dissociates and is “dropped off” at the tissues, the next oxygen molecule dissociates more readily. When all four heme sites are occupied, the hemoglobin is said to be saturated. When one to three heme sites are occupied, the hemoglobin is said to be partially saturated. Therefore, when considering the blood as a whole, the percent of the available heme units that are bound to oxygen at a given time is called hemoglobin saturation. Hemoglobin saturation of 100 percent means that every heme unit in all of the erythrocytes of the body is bound to oxygen. In a healthy individual with normal hemoglobin levels, hemoglobin saturation generally ranges from 95 percent to 99 percent. Oxygen Dissociation from Hemoglobin Partial pressure is an important aspect of the binding of oxygen to and disassociation from heme. An oxygen–hemoglobin dissociation curve is a graph that describes the relationship of partial pressure to the binding of oxygen to heme and its subsequent dissociation from heme (Figure 22.26). Remember that gases travel from an area of higher partial pressure to an area of lower partial pressure. In addition, the affinity of an oxygen molecule for heme increases as more oxygen molecules are bound. Therefore, in the oxygen–hemoglobin saturation curve, as the partial pressure of oxygen increases, a proportionately greater number of oxygen molecules are bound by heme. Not surprisingly, the oxygen–hemoglobin saturation/dissociation curve also shows that the lower the partial pressure of oxygen, the fewer oxygen molecules are bound to heme. As a result, the partial pressure of oxygen plays a major role in determining the degree of binding of oxygen to heme at the site of the respiratory membrane, as well as the degree of dissociation of oxygen from heme at the site of body tissues. Figure 22.26 Oxygen-Hemoglobin Dissociation and Effects of pH and Temperature These three graphs show (a) the relationship between the partial pressure of oxygen and hemoglobin saturation, (b) the effect of pH on the oxygen–hemoglobin dissociation curve, and (c) the effect of temperature on the oxygen–hemoglobin dissociation curve. The mechanisms behind the oxygen–hemoglobin saturation/dissociation curve also serve as automatic control mechanisms that regulate how much oxygen is delivered to different tissues throughout the body. This is important because some tissues have a higher metabolic rate than others. Highly active tissues, such as muscle, rapidly use oxygen to produce ATP, lowering the partial pressure of oxygen in the tissue to about 20 mm Hg. The partial pressure of oxygen inside capillaries is about 100 mm Hg, so the difference between the two becomes quite high, about 80 mm Hg. As a result, a greater number of oxygen molecules dissociate from hemoglobin and enter the tissues. The reverse is true of tissues, such as adipose (body fat), which have lower metabolic rates. Because less oxygen is used by these cells, the partial pressure of oxygen within such tissues remains relatively high, resulting in fewer oxygen molecules dissociating from hemoglobin and entering the tissue interstitial fluid. Although venous blood is said to be deoxygenated, some oxygen is still bound to hemoglobin in its red blood cells. This provides an oxygen reserve that can be used when tissues suddenly demand more oxygen. Factors other than partial pressure also affect the oxygen–hemoglobin saturation/dissociation curve. For example, a higher temperature promotes hemoglobin and oxygen to dissociate faster, whereas a lower temperature inhibits dissociation (see Figure 22.26, middle). However, the human body tightly regulates temperature, so this factor may not affect gas exchange throughout the body. The exception to this is in highly active tissues, which may release a larger amount of energy than is given off as heat. As a result, oxygen readily dissociates from hemoglobin, which is a mechanism that helps to provide active tissues with more oxygen. Certain hormones, such as androgens, epinephrine, thyroid hormones, and growth hormone, can affect the oxygen–hemoglobin saturation/disassociation curve by stimulating the production of a compound called 2,3-bisphosphoglycerate (BPG) by erythrocytes. BPG is a byproduct of glycolysis. Because erythrocytes do not contain mitochondria, glycolysis is the sole method by which these cells produce ATP. BPG promotes the disassociation of oxygen from hemoglobin. Therefore, the greater the concentration of BPG, the more readily oxygen dissociates from hemoglobin, despite its partial pressure. The pH of the blood is another factor that influences the oxygen–hemoglobin saturation/dissociation curve (see Figure 22.26). The Bohr effect is a phenomenon that arises from the relationship between pH and oxygen’s affinity for hemoglobin: A lower, more acidic pH promotes oxygen dissociation from hemoglobin. In contrast, a higher, or more basic, pH inhibits oxygen dissociation from hemoglobin. The greater the amount of carbon dioxide in the blood, the more molecules that must be converted, which in turn generates hydrogen ions and thus lowers blood pH. Furthermore, blood pH may become more acidic when certain byproducts of cell metabolism, such as lactic acid, carbonic acid, and carbon dioxide, are released into the bloodstream. Hemoglobin of the Fetus The fetus has its own circulation with its own erythrocytes; however, it is dependent on the mother for oxygen. Blood is supplied to the fetus by way of the umbilical cord, which is connected to the placenta and separated from maternal blood by the chorion. The mechanism of gas exchange at the chorion is similar to gas exchange at the respiratory membrane. However, the partial pressure of oxygen is lower in the maternal blood in the placenta, at about 35 to 50 mm Hg, than it is in maternal arterial blood. The difference in partial pressures between maternal and fetal blood is not large, as the partial pressure of oxygen in fetal blood at the placenta is about 20 mm Hg. Therefore, there is not as much diffusion of oxygen into the fetal blood supply. The fetus’ hemoglobin overcomes this problem by having a greater affinity for oxygen than maternal hemoglobin (Figure 22.27). Both fetal and adult hemoglobin have four subunits, but two of the subunits of fetal hemoglobin have a different structure that causes fetal hemoglobin to have a greater affinity for oxygen than does adult hemoglobin. Figure 22.27 Oxygen-Hemoglobin Dissociation Curves in Fetus and AdultFetal hemoglobin has a greater affinity for oxygen than does adult hemoglobin. Carbon Dioxide Transport in the Blood Carbon dioxide is transported by three major mechanisms. The first mechanism of carbon dioxide transport is by blood plasma, as some carbon dioxide molecules dissolve in the blood. The second mechanism is transport in the form of bicarbonate (HCO3–), which also dissolves in plasma. The third mechanism of carbon dioxide transport is similar to the transport of oxygen by erythrocytes (Figure 22.28). Figure 22.28 Carbon Dioxide Transport Carbon dioxide is transported by three different methods: (a) in erythrocytes; (b) after forming carbonic acid (H2CO3 ), which is dissolved in plasma; (c) and in plasma. Dissolved Carbon Dioxide Although carbon dioxide is not considered to be highly soluble in blood, a small fraction—about 7 to 10 percent—of the carbon dioxide that diffuses into the blood from the tissues dissolves in plasma. The dissolved carbon dioxide then travels in the bloodstream and when the blood reaches the pulmonary capillaries, the dissolved carbon dioxide diffuses across the respiratory membrane into the alveoli, where it is then exhaled during pulmonary ventilation. Bicarbonate Buffer A large fraction—about 70 percent—of the carbon dioxide molecules that diffuse into the blood is transported to the lungs as bicarbonate. Most bicarbonate is produced in erythrocytes after carbon dioxide diffuses into the capillaries, and subsequently into red blood cells. Carbonic anhydrase (CA) causes carbon dioxide and water to form carbonic acid (H2CO3), which dissociates into two ions: bicarbonate (HCO3–) and hydrogen (H+). The following formula depicts this reaction: CO2 + H2O CA↔ H2CO3↔H+ + HCO3−CO2 + H2O CA↔ H2CO3↔H+ + HCO3− Bicarbonate tends to build up in the erythrocytes, so that there is a greater concentration of bicarbonate in the erythrocytes than in the surrounding blood plasma. As a result, some of the bicarbonate will leave the erythrocytes and move down its concentration gradient into the plasma in exchange for chloride (Cl–) ions. This phenomenon is referred to as the chloride shift and occurs because by exchanging one negative ion for another negative ion, neither the electrical charge of the erythrocytes nor that of the blood is altered. At the pulmonary capillaries, the chemical reaction that produced bicarbonate (shown above) is reversed, and carbon dioxide and water are the products. Much of the bicarbonate in the plasma re-enters the erythrocytes in exchange for chloride ions. Hydrogen ions and bicarbonate ions join to form carbonic acid, which is converted into carbon dioxide and water by carbonic anhydrase. Carbon dioxide diffuses out of the erythrocytes and into the plasma, where it can further diffuse across the respiratory membrane into the alveoli to be exhaled during pulmonary ventilation. Carbaminohemoglobin About 20 percent of carbon dioxide is bound by hemoglobin and is transported to the lungs. Carbon dioxide does not bind to iron as oxygen does; instead, carbon dioxide binds amino acid moieties on the globin portions of hemoglobin to form carbaminohemoglobin, which forms when hemoglobin and carbon dioxide bind. When hemoglobin is not transporting oxygen, it tends to have a bluish-purple tone to it, creating the darker maroon color typical of deoxygenated blood. The following formula depicts this reversible reaction: CO2 + Hb↔HbCO2CO2 + Hb↔HbCO2 Similar to the transport of oxygen by heme, the binding and dissociation of carbon dioxide to and from hemoglobin is dependent on the partial pressure of carbon dioxide. Because carbon dioxide is released from the lungs, blood that leaves the lungs and reaches body tissues has a lower partial pressure of carbon dioxide than is found in the tissues. As a result, carbon dioxide leaves the tissues because of its higher partial pressure, enters the blood, and then moves into red blood cells, binding to hemoglobin. In contrast, in the pulmonary capillaries, the partial pressure of carbon dioxide is high compared to within the alveoli. As a result, carbon dioxide dissociates readily from hemoglobin and diffuses across the respiratory membrane into the air. In addition to the partial pressure of carbon dioxide, the oxygen saturation of hemoglobin and the partial pressure of oxygen in the blood also influence the affinity of hemoglobin for carbon dioxide. The Haldane effect is a phenomenon that arises from the relationship between the partial pressure of oxygen and the affinity of hemoglobin for carbon dioxide. Hemoglobin that is saturated with oxygen does not readily bind carbon dioxide. However, when oxygen is not bound to heme and the partial pressure of oxygen is low, hemoglobin readily binds to carbon dioxide. INTERACTIVE LINK Watch this video to see the transport of oxygen from the lungs to the tissues. Why is oxygenated blood bright red, whereas deoxygenated blood tends to be more of a purple color? Modifications in Respiratory Functions - Define the terms hyperpnea and hyperventilation - Describe the effect of exercise on the respiratory system - Describe the effect of high altitude on the respiratory system - Discuss the process of acclimatization At rest, the respiratory system performs its functions at a constant, rhythmic pace, as regulated by the respiratory centers of the brain. At this pace, ventilation provides sufficient oxygen to all the tissues of the body. However, there are times that the respiratory system must alter the pace of its functions in order to accommodate the oxygen demands of the body. Hyperpnea Hyperpnea is an increased depth and rate of ventilation to meet an increase in oxygen demand as might be seen in exercise or disease, particularly diseases that target the respiratory or digestive tracts. This does not significantly alter blood oxygen or carbon dioxide levels, but merely increases the depth and rate of ventilation to meet the demand of the cells. In contrast, hyperventilationis an increased ventilation rate that is independent of the cellular oxygen needs and leads to abnormally low blood carbon dioxide levels and high (alkaline) blood pH. Interestingly, exercise does not cause hyperpnea as one might think. Muscles that perform work during exercise do increase their demand for oxygen, stimulating an increase in ventilation. However, hyperpnea during exercise appears to occur before a drop in oxygen levels within the muscles can occur. Therefore, hyperpnea must be driven by other mechanisms, either instead of or in addition to a drop in oxygen levels. The exact mechanisms behind exercise hyperpnea are not well understood, and some hypotheses are somewhat controversial. However, in addition to low oxygen, high carbon dioxide, and low pH levels, there appears to be a complex interplay of factors related to the nervous system and the respiratory centers of the brain. First, a conscious decision to partake in exercise, or another form of physical exertion, results in a psychological stimulus that may trigger the respiratory centers of the brain to increase ventilation. In addition, the respiratory centers of the brain may be stimulated through the activation of motor neurons that innervate muscle groups that are involved in the physical activity. Finally, physical exertion stimulates proprioceptors, which are receptors located within the muscles, joints, and tendons, which sense movement and stretching; proprioceptors thus create a stimulus that may also trigger the respiratory centers of the brain. These neural factors are consistent with the sudden increase in ventilation that is observed immediately as exercise begins. Because the respiratory centers are stimulated by psychological, motor neuron, and proprioceptor inputs throughout exercise, the fact that there is also a sudden decrease in ventilation immediately after the exercise ends when these neural stimuli cease, further supports the idea that they are involved in triggering the changes of ventilation. High Altitude Effects An increase in altitude results in a decrease in atmospheric pressure. Although the proportion of oxygen relative to gases in the atmosphere remains at 21 percent, its partial pressure decreases (Table 22.4). As a result, it is more difficult for a body to achieve the same level of oxygen saturation at high altitude than at low altitude, due to lower atmospheric pressure. In fact, hemoglobin saturation is lower at high altitudes compared to hemoglobin saturation at sea level. For example, hemoglobin saturation is about 67 percent at 19,000 feet above sea level, whereas it reaches about 98 percent at sea level. Partial Pressure of Oxygen at Different Altitudes \| Example location \| Altitude (feet above sea level) \| Atmospheric pressure (mm Hg) \| Partial pressure of oxygen (mm Hg) \| \|---\|---\|---\|---\| \| New York City, New York \| 0 \| 760 \| 159 \| \| Boulder, Colorado \| 5000 \| 632 \| 133 \| \| Aspen, Colorado \| 8000 \| 565 \| 118 \| \| Pike’s Peak, Colorado \| 14,000 \| 447 \| 94 \| \| Denali (Mt. McKinley), Alaska \| 20,000 \| 350 \| 73 \| \| Mt. Everest, Tibet \| 29,000 \| 260 \| 54 \| Table 22.4 As you recall, partial pressure is extremely important in determining how much gas can cross the respiratory membrane and enter the blood of the pulmonary capillaries. A lower partial pressure of oxygen means that there is a smaller difference in partial pressures between the alveoli and the blood, so less oxygen crosses the respiratory membrane. As a result, fewer oxygen molecules are bound by hemoglobin. Despite this, the tissues of the body still receive a sufficient amount of oxygen during rest at high altitudes. This is due to two major mechanisms. First, the number of oxygen molecules that enter the tissue from the blood is nearly equal between sea level and high altitudes. At sea level, hemoglobin saturation is higher, but only a quarter of the oxygen molecules are actually released into the tissue. At high altitudes, a greater proportion of molecules of oxygen are released into the tissues. Secondly, at high altitudes, a greater amount of BPG is produced by erythrocytes, which enhances the dissociation of oxygen from hemoglobin. Physical exertion, such as skiing or hiking, can lead to altitude sickness due to the low amount of oxygen reserves in the blood at high altitudes. At sea level, there is a large amount of oxygen reserve in venous blood (even though venous blood is thought of as “deoxygenated”) from which the muscles can draw during physical exertion. Because the oxygen saturation is much lower at higher altitudes, this venous reserve is small, resulting in pathological symptoms of low blood oxygen levels. You may have heard that it is important to drink more water when traveling at higher altitudes than you are accustomed to. This is because your body will increase micturition (urination) at high altitudes to counteract the effects of lower oxygen levels. By removing fluids, blood plasma levels drop but not the total number of erythrocytes. In this way, the overall concentration of erythrocytes in the blood increases, which helps tissues obtain the oxygen they need. Acute mountain sickness (AMS), or altitude sickness, is a condition that results from acute exposure to high altitudes due to a low partial pressure of oxygen at high altitudes. AMS typically can occur at 2400 meters (8000 feet) above sea level. AMS is a result of low blood oxygen levels, as the body has acute difficulty adjusting to the low partial pressure of oxygen. In serious cases, AMS can cause pulmonary or cerebral edema. Symptoms of AMS include nausea, vomiting, fatigue, lightheadedness, drowsiness, feeling disoriented, increased pulse, and nosebleeds. The only treatment for AMS is descending to a lower altitude; however, pharmacologic treatments and supplemental oxygen can improve symptoms. AMS can be prevented by slowly ascending to the desired altitude, allowing the body to acclimate, as well as maintaining proper hydration. Acclimatization Especially in situations where the ascent occurs too quickly, traveling to areas of high altitude can cause AMS. Acclimatization is the process of adjustment that the respiratory system makes due to chronic exposure to a high altitude. Over a period of time, the body adjusts to accommodate the lower partial pressure of oxygen. The low partial pressure of oxygen at high altitudes results in a lower oxygen saturation level of hemoglobin in the blood. In turn, the tissue levels of oxygen are also lower. As a result, the kidneys are stimulated to produce the hormone erythropoietin (EPO), which stimulates the production of erythrocytes, resulting in a greater number of circulating erythrocytes in an individual at a high altitude over a long period. With more red blood cells, there is more hemoglobin to help transport the available oxygen. Even though there is low saturation of each hemoglobin molecule, there will be more hemoglobin present, and therefore more oxygen in the blood. Over time, this allows the person to partake in physical exertion Embryonic Development of the Respiratory System - Create a timeline of the phases of respiratory development in the fetus - Propose reasons for fetal breathing movements - Explain how the lungs become inflated after birth Development of the respiratory system begins early in the fetus. It is a complex process that includes many structures, most of which arise from the endoderm. Towards the end of development, the fetus can be observed making breathing movements. Until birth, however, the mother provides all of the oxygen to the fetus as well as removes all of the fetal carbon dioxide via the placenta. Time Line The development of the respiratory system begins at about week 4 of gestation. By week 28, enough alveoli have matured that a baby born prematurely at this time can usually breathe on its own. The respiratory system, however, is not fully developed until early childhood, when a full complement of mature alveoli is present. Weeks 4–7 Respiratory development in the embryo begins around week 4. Ectodermal tissue from the anterior head region invaginates posteriorly to form olfactory pits, which fuse with endodermal tissue of the developing pharynx. An olfactory pit is one of a pair of structures that will enlarge to become the nasal cavity. At about this same time, the lung bud forms. The lung bud is a dome-shaped structure composed of tissue that bulges from the foregut. The foregut is endoderm just inferior to the pharyngeal pouches. The laryngotracheal bud is a structure that forms from the longitudinal extension of the lung bud as development progresses. The portion of this structure nearest the pharynx becomes the trachea, whereas the distal end becomes more bulbous, forming bronchial buds. A bronchial bud is one of a pair of structures that will eventually become the bronchi and all other lower respiratory structures (Figure 22.29). Figure 22.29 Development of the Lower Respiratory System Weeks 7–16 Bronchial buds continue to branch as development progresses until all of the segmental bronchi have been formed. Beginning around week 13, the lumens of the bronchi begin to expand in diameter. By week 16, respiratory bronchioles form. The fetus now has all major lung structures involved in the airway. Weeks 16–24 Once the respiratory bronchioles form, further development includes extensive vascularization, or the development of the blood vessels, as well as the formation of alveolar ducts and alveolar precursors. At about week 19, the respiratory bronchioles have formed. In addition, cells lining the respiratory structures begin to differentiate to form type I and type II pneumocytes. Once type II cells have differentiated, they begin to secrete small amounts of pulmonary surfactant. Around week 20, fetal breathing movements may begin. Weeks 24–Term Major growth and maturation of the respiratory system occurs from week 24 until term. More alveolar precursors develop, and larger amounts of pulmonary surfactant are produced. Surfactant levels are not generally adequate to create effective lung compliance until about the eighth month of pregnancy. The respiratory system continues to expand, and the surfaces that will form the respiratory membrane develop further. At this point, pulmonary capillaries have formed and continue to expand, creating a large surface area for gas exchange. The major milestone of respiratory development occurs at around week 28, when sufficient alveolar precursors have matured so that a baby born prematurely at this time can usually breathe on its own. However, alveoli continue to develop and mature into childhood. A full complement of functional alveoli does not appear until around 8 years of age. Fetal “Breathing” Although the function of fetal breathing movements is not entirely clear, they can be observed starting at 20–21 weeks of development. Fetal breathing movements involve muscle contractions that cause the inhalation of amniotic fluid and exhalation of the same fluid, with pulmonary surfactant and mucus. Fetal breathing movements are not continuous and may include periods of frequent movements and periods of no movements. Maternal factors can influence the frequency of breathing movements. For example, high blood glucose levels, called hyperglycemia, can boost the number of breathing movements. Conversely, low blood glucose levels, called hypoglycemia, can reduce the number of fetal breathing movements. Tobacco use is also known to lower fetal breathing rates. Fetal breathing may help tone the muscles in preparation for breathing movements once the fetus is born. It may also help the alveoli to form and mature. Fetal breathing movements are considered a sign of robust health. Birth Prior to birth, the lungs are filled with amniotic fluid, mucus, and surfactant. As the fetus is squeezed through the birth canal, the fetal thoracic cavity is compressed, expelling much of this fluid. Some fluid remains, however, but is rapidly absorbed by the body shortly after birth. The first inhalation occurs within 10 seconds after birth and not only serves as the first inspiration, but also acts to inflate the lungs. Pulmonary surfactant is critical for inflation to occur, as it reduces the surface tension of the alveoli. Preterm birth around 26 weeks frequently results in severe respiratory distress, although with current medical advancements, some babies may survive. Prior to 26 weeks, sufficient pulmonary surfactant is not produced, and the surfaces for gas exchange have not formed adequately; therefore, survival is low. DISORDERS OF THE... Respiratory System: Respiratory Distress Syndrome Respiratory distress syndrome (RDS) primarily occurs in infants born prematurely. Up to 50 percent of infants born between 26 and 28 weeks and fewer than 30 percent of infants born between 30 and 31 weeks develop RDS. RDS results from insufficient production of pulmonary surfactant, thereby preventing the lungs from properly inflating at birth. A small amount of pulmonary surfactant is produced beginning at around 20 weeks; however, this is not sufficient for inflation of the lungs. As a result, dyspnea occurs and gas exchange cannot be performed properly. Blood oxygen levels are low, whereas blood carbon dioxide levels and pH are high. The primary cause of RDS is premature birth, which may be due to a variety of known or unknown causes. Other risk factors include gestational diabetes, cesarean delivery, second-born twins, and family history of RDS. The presence of RDS can lead to other serious disorders, such as septicemia (infection of the blood) or pulmonary hemorrhage. Therefore, it is important that RDS is immediately recognized and treated to prevent death and reduce the risk of developing other disorders. Medical advances have resulted in an improved ability to treat RDS and support the infant until proper lung development can occur. At the time of delivery, treatment may include resuscitation and intubation if the infant does not breathe on his or her own. These infants would need to be placed on a ventilator to mechanically assist with the breathing process. If spontaneous breathing occurs, application of nasal continuous positive airway pressure (CPAP) may be required. In addition, pulmonary surfactant is typically administered. Death due to RDS has been reduced by 50 percent due to the introduction of pulmonary surfactant therapy. Other therapies may include corticosteroids, supplemental oxygen, and assisted ventilation. Supportive therapies, such as temperature regulation, nutritional support, and antibiotics, may be administered to the premature infant as well. Key Terms - acclimatization - process of adjustment that the respiratory system makes due to chronic exposure to high altitudes - acute mountain sickness (AMS) - condition that occurs a result of acute exposure to high altitude due to a low partial pressure of oxygen - ala - (plural = alae) small, flaring structure of a nostril that forms the lateral side of the nares - alar cartilage - cartilage that supports the apex of the nose and helps shape the nares; it is connected to the septal cartilage and connective tissue of the alae - alveolar dead space - air space within alveoli that are unable to participate in gas exchange - alveolar duct - small tube that leads from the terminal bronchiole to the respiratory bronchiole and is the point of attachment for alveoli - alveolar macrophage - immune system cell of the alveolus that removes debris and pathogens - alveolar pore - opening that allows airflow between neighboring alveoli - alveolar sac - cluster of alveoli - alveolus - small, grape-like sac that performs gas exchange in the lungs - anatomical dead space - air space present in the airway that never reaches the alveoli and therefore never participates in gas exchange - apex - tip of the external nose - apneustic center - network of neurons within the pons that stimulate the neurons in the dorsal respiratory group; controls the depth of inspiration - atmospheric pressure - amount of force that is exerted by gases in the air surrounding any given surface - Bohr effect - relationship between blood pH and oxygen dissociation from hemoglobin - Boyle’s law - relationship between volume and pressure as described by the formula: P1V1 = P2V2 - bridge - portion of the external nose that lies in the area of the nasal bones - bronchial bud - structure in the developing embryo that forms when the laryngotracheal bud extends and branches to form two bulbous structures - bronchial tree - collective name for the multiple branches of the bronchi and bronchioles of the respiratory system - bronchiole - branch of bronchi that are 1 mm or less in diameter and terminate at alveolar sacs - bronchoconstriction - decrease in the size of the bronchiole due to contraction of the muscular wall - bronchodilation - increase in the size of the bronchiole due to contraction of the muscular wall - bronchus - tube connected to the trachea that branches into many subsidiaries and provides a passageway for air to enter and leave the lungs - carbaminohemoglobin - bound form of hemoglobin and carbon dioxide - carbonic anhydrase (CA) - enzyme that catalyzes the reaction that causes carbon dioxide and water to form carbonic acid - cardiac notch - indentation on the surface of the left lung that allows space for the heart - central chemoreceptor - one of the specialized receptors that are located in the brain that sense changes in hydrogen ion, oxygen, or carbon dioxide concentrations in the brain - chloride shift - facilitated diffusion that exchanges bicarbonate (HCO3–) with chloride (Cl–) ions - conducting zone - region of the respiratory system that includes the organs and structures that provide passageways for air and are not directly involved in gas exchange - cricoid cartilage - portion of the larynx composed of a ring of cartilage with a wide posterior region and a thinner anterior region; attached to the esophagus - Dalton’s law - statement of the principle that a specific gas type in a mixture exerts its own pressure, as if that specific gas type was not part of a mixture of gases - dorsal respiratory group (DRG) - region of the medulla oblongata that stimulates the contraction of the diaphragm and intercostal muscles to induce inspiration - dorsum nasi - intermediate portion of the external nose that connects the bridge to the apex and is supported by the nasal bone - epiglottis - leaf-shaped piece of elastic cartilage that is a portion of the larynx that swings to close the trachea during swallowing - expiration - (also, exhalation) process that causes the air to leave the lungs - expiratory reserve volume (ERV) - amount of air that can be forcefully exhaled after a normal tidal exhalation - external nose - region of the nose that is easily visible to others - external respiration - gas exchange that occurs in the alveoli - fauces - portion of the posterior oral cavity that connects the oral cavity to the oropharynx - fibroelastic membrane - specialized membrane that connects the ends of the C-shape cartilage in the trachea; contains smooth muscle fibers - forced breathing - (also, hyperpnea) mode of breathing that occurs during exercise or by active thought that requires muscle contraction for both inspiration and expiration - foregut - endoderm of the embryo towards the head region - functional residual capacity (FRC) - sum of ERV and RV, which is the amount of air that remains in the lungs after a tidal expiration - glottis - opening between the vocal folds through which air passes when producing speech - Haldane effect - relationship between the partial pressure of oxygen and the affinity of hemoglobin for carbon dioxide - Henry’s law - statement of the principle that the concentration of gas in a liquid is directly proportional to the solubility and partial pressure of that gas - hilum - concave structure on the mediastinal surface of the lungs where blood vessels, lymphatic vessels, nerves, and a bronchus enter the lung - hyperpnea - increased rate and depth of ventilation due to an increase in oxygen demand that does not significantly alter blood oxygen or carbon dioxide levels - hyperventilation - increased ventilation rate that leads to abnormally low blood carbon dioxide levels and high (alkaline) blood pH - inspiration - (also, inhalation) process that causes air to enter the lungs - inspiratory capacity (IC) - sum of the TV and IRV, which is the amount of air that can maximally be inhaled past a tidal expiration - inspiratory reserve volume (IRV) - amount of air that enters the lungs due to deep inhalation past the tidal volume - internal respiration - gas exchange that occurs at the level of body tissues - intra-alveolar pressure - (intrapulmonary pressure) pressure of the air within the alveoli - intrapleural pressure - pressure of the air within the pleural cavity - laryngeal prominence - region where the two lamina of the thyroid cartilage join, forming a protrusion known as “Adam’s apple” - laryngopharynx - portion of the pharynx bordered by the oropharynx superiorly and esophagus and trachea inferiorly; serves as a route for both air and food - laryngotracheal - bud forms from the lung bud, has a tracheal end and bulbous bronchial buds at the distal end - larynx - cartilaginous structure that produces the voice, prevents food and beverages from entering the trachea, and regulates the volume of air that enters and leaves the lungs - lingual tonsil - lymphoid tissue located at the base of the tongue - lung - organ of the respiratory system that performs gas exchange - lung bud - median dome that forms from the endoderm of the foregut - meatus - one of three recesses (superior, middle, and inferior) in the nasal cavity attached to the conchae that increase the surface area of the nasal cavity - naris - (plural = nares) opening of the nostrils - nasal bone - bone of the skull that lies under the root and bridge of the nose and is connected to the frontal and maxillary bones - nasal septum - wall composed of bone and cartilage that separates the left and right nasal cavities - nasopharynx - portion of the pharynx flanked by the conchae and oropharynx that serves as an airway - olfactory pit - invaginated ectodermal tissue in the anterior portion of the head region of an embryo that will form the nasal cavity - oropharynx - portion of the pharynx flanked by the nasopharynx, oral cavity, and laryngopharynx that is a passageway for both air and food - oxygen–hemoglobin dissociation curve - graph that describes the relationship of partial pressure to the binding and disassociation of oxygen to and from heme - oxyhemoglobin - (Hb–O2) bound form of hemoglobin and oxygen - palatine tonsil - one of the paired structures composed of lymphoid tissue located anterior to the uvula at the roof of isthmus of the fauces - paranasal sinus - one of the cavities within the skull that is connected to the conchae that serve to warm and humidify incoming air, produce mucus, and lighten the weight of the skull; consists of frontal, maxillary, sphenoidal, and ethmoidal sinuses - parietal pleura - outermost layer of the pleura that connects to the thoracic wall, mediastinum, and diaphragm - partial pressure - force exerted by each gas in a mixture of gases - peripheral chemoreceptor - one of the specialized receptors located in the aortic arch and carotid arteries that sense changes in pH, carbon dioxide, or oxygen blood levels - pharyngeal tonsil - structure composed of lymphoid tissue located in the nasopharynx - pharynx - region of the conducting zone that forms a tube of skeletal muscle lined with respiratory epithelium; located between the nasal conchae and the esophagus and trachea - philtrum - concave surface of the face that connects the apex of the nose to the top lip - pleural cavity - space between the visceral and parietal pleurae - pleural fluid - substance that acts as a lubricant for the visceral and parietal layers of the pleura during the movement of breathing - pneumotaxic center - network of neurons within the pons that inhibit the activity of the neurons in the dorsal respiratory group; controls rate of breathing - pulmonary artery - artery that arises from the pulmonary trunk and carries deoxygenated, arterial blood to the alveoli - pulmonary plexus - network of autonomic nervous system fibers found near the hilum of the lung - pulmonary surfactant - substance composed of phospholipids and proteins that reduces the surface tension of the alveoli; made by type II alveolar cells - pulmonary ventilation - exchange of gases between the lungs and the atmosphere; breathing - quiet breathing - (also, eupnea) mode of breathing that occurs at rest and does not require the cognitive thought of the individual - residual volume (RV) - amount of air that remains in the lungs after maximum exhalation - respiratory bronchiole - specific type of bronchiole that leads to alveolar sacs - respiratory cycle - one sequence of inspiration and expiration - respiratory epithelium - ciliated lining of much of the conducting zone that is specialized to remove debris and pathogens, and produce mucus - respiratory membrane - alveolar and capillary wall together, which form an air-blood barrier that facilitates the simple diffusion of gases - respiratory rate - total number of breaths taken each minute - respiratory volume - varying amounts of air within the lung at a given time - respiratory zone - includes structures of the respiratory system that are directly involved in gas exchange - root - region of the external nose between the eyebrows - thoracic wall compliance - ability of the thoracic wall to stretch while under pressure - thyroid cartilage - largest piece of cartilage that makes up the larynx and consists of two lamina - tidal volume (TV) - amount of air that normally enters the lungs during quiet breathing - total dead space - sum of the anatomical dead space and alveolar dead space - total lung capacity (TLC) - total amount of air that can be held in the lungs; sum of TV, ERV, IRV, and RV - total pressure - sum of all the partial pressures of a gaseous mixture - trachea - tube composed of cartilaginous rings and supporting tissue that connects the lung bronchi and the larynx; provides a route for air to enter and exit the lung - trachealis muscle - smooth muscle located in the fibroelastic membrane of the trachea - transpulmonary pressure - pressure difference between the intrapleural and intra-alveolar pressures - true vocal cord - one of the pair of folded, white membranes that have a free inner edge that oscillates as air passes through to produce sound - type I alveolar cell - squamous epithelial cells that are the major cell type in the alveolar wall; highly permeable to gases - type II alveolar cell - cuboidal epithelial cells that are the minor cell type in the alveolar wall; secrete pulmonary surfactant - ventilation - movement of air into and out of the lungs; consists of inspiration and expiration - ventral respiratory group (VRG) - region of the medulla oblongata that stimulates the contraction of the accessory muscles involved in respiration to induce forced inspiration and expiration - vestibular fold - part of the folded region of the glottis composed of mucous membrane; supports the epiglottis during swallowing - visceral pleura - innermost layer of the pleura that is superficial to the lungs and extends into the lung fissures - vital capacity (VC) - sum of TV, ERV, and IRV, which is all the volumes that participate in gas exchange Chapter Review 22.1 Organs and Structures of the Respiratory System The respiratory system is responsible for obtaining oxygen and getting rid of carbon dioxide, and aiding in speech production and in sensing odors. From a functional perspective, the respiratory system can be divided into two major areas: the conducting zone and the respiratory zone. The conducting zone consists of all of the structures that provide passageways for air to travel into and out of the lungs: the nasal cavity, pharynx, trachea, bronchi, and most bronchioles. The nasal passages contain the conchae and meatuses that expand the surface area of the cavity, which helps to warm and humidify incoming air, while removing debris and pathogens. The pharynx is composed of three major sections: the nasopharynx, which is continuous with the nasal cavity; the oropharynx, which borders the nasopharynx and the oral cavity; and the laryngopharynx, which borders the oropharynx, trachea, and esophagus. The respiratory zone includes the structures of the lung that are directly involved in gas exchange: the terminal bronchioles and alveoli. The lining of the conducting zone is composed mostly of pseudostratified ciliated columnar epithelium with goblet cells. The mucus traps pathogens and debris, whereas beating cilia move the mucus superiorly toward the throat, where it is swallowed. As the bronchioles become smaller and smaller, and nearer the alveoli, the epithelium thins and is simple squamous epithelium in the alveoli. The endothelium of the surrounding capillaries, together with the alveolar epithelium, forms the respiratory membrane. This is a blood-air barrier through which gas exchange occurs by simple diffusion. 22.2 The Lungs The lungs are the major organs of the respiratory system and are responsible for performing gas exchange. The lungs are paired and separated into lobes; The left lung consists of two lobes, whereas the right lung consists of three lobes. Blood circulation is very important, as blood is required to transport oxygen from the lungs to other tissues throughout the body. The function of the pulmonary circulation is to aid in gas exchange. The pulmonary artery provides deoxygenated blood to the capillaries that form respiratory membranes with the alveoli, and the pulmonary veins return newly oxygenated blood to the heart for further transport throughout the body. The lungs are innervated by the parasympathetic and sympathetic nervous systems, which coordinate the bronchodilation and bronchoconstriction of the airways. The lungs are enclosed by the pleura, a membrane that is composed of visceral and parietal pleural layers. The space between these two layers is called the pleural cavity. The mesothelial cells of the pleural membrane create pleural fluid, which serves as both a lubricant (to reduce friction during breathing) and as an adhesive to adhere the lungs to the thoracic wall (to facilitate movement of the lungs during ventilation). 22.3 The Process of Breathing Pulmonary ventilation is the process of breathing, which is driven by pressure differences between the lungs and the atmosphere. Atmospheric pressure is the force exerted by gases present in the atmosphere. The force exerted by gases within the alveoli is called intra-alveolar (intrapulmonary) pressure, whereas the force exerted by gases in the pleural cavity is called intrapleural pressure. Typically, intrapleural pressure is lower, or negative to, intra-alveolar pressure. The difference in pressure between intrapleural and intra-alveolar pressures is called transpulmonary pressure. In addition, intra-alveolar pressure will equalize with the atmospheric pressure. Pressure is determined by the volume of the space occupied by a gas and is influenced by resistance. Air flows when a pressure gradient is created, from a space of higher pressure to a space of lower pressure. Boyle’s law describes the relationship between volume and pressure. A gas is at lower pressure in a larger volume because the gas molecules have more space to in which to move. The same quantity of gas in a smaller volume results in gas molecules crowding together, producing increased pressure. Resistance is created by inelastic surfaces, as well as the diameter of the airways. Resistance reduces the flow of gases. The surface tension of the alveoli also influences pressure, as it opposes the expansion of the alveoli. However, pulmonary surfactant helps to reduce the surface tension so that the alveoli do not collapse during expiration. The ability of the lungs to stretch, called lung compliance, also plays a role in gas flow. The more the lungs can stretch, the greater the potential volume of the lungs. The greater the volume of the lungs, the lower the air pressure within the lungs. Pulmonary ventilation consists of the process of inspiration (or inhalation), where air enters the lungs, and expiration (or exhalation), where air leaves the lungs. During inspiration, the diaphragm and external intercostal muscles contract, causing the rib cage to expand and move outward, and expanding the thoracic cavity and lung volume. This creates a lower pressure within the lung than that of the atmosphere, causing air to be drawn into the lungs. During expiration, the diaphragm and intercostals relax, causing the thorax and lungs to recoil. The air pressure within the lungs increases to above the pressure of the atmosphere, causing air to be forced out of the lungs. However, during forced exhalation, the internal intercostals and abdominal muscles may be involved in forcing air out of the lungs. Respiratory volume describes the amount of air in a given space within the lungs, or which can be moved by the lung, and is dependent on a variety of factors. Tidal volume refers to the amount of air that enters the lungs during quiet breathing, whereas inspiratory reserve volume is the amount of air that enters the lungs when a person inhales past the tidal volume. Expiratory reserve volume is the extra amount of air that can leave with forceful expiration, following tidal expiration. Residual volume is the amount of air that is left in the lungs after expelling the expiratory reserve volume. Respiratory capacity is the combination of two or more volumes. Anatomical dead space refers to the air within the respiratory structures that never participates in gas exchange, because it does not reach functional alveoli. Respiratory rate is the number of breaths taken per minute, which may change during certain diseases or conditions. Both respiratory rate and depth are controlled by the respiratory centers of the brain, which are stimulated by factors such as chemical and pH changes in the blood. These changes are sensed by central chemoreceptors, which are located in the brain, and peripheral chemoreceptors, which are located in the aortic arch and carotid arteries. A rise in carbon dioxide or a decline in oxygen levels in the blood stimulates an increase in respiratory rate and depth. 22.4 Gas Exchange The behavior of gases can be explained by the principles of Dalton’s law and Henry’s law, both of which describe aspects of gas exchange. Dalton’s law states that each specific gas in a mixture of gases exerts force (its partial pressure) independently of the other gases in the mixture. Henry’s law states that the amount of a specific gas that dissolves in a liquid is a function of its partial pressure. The greater the partial pressure of a gas, the more of that gas will dissolve in a liquid, as the gas moves toward equilibrium. Gas molecules move down a pressure gradient; in other words, gas moves from a region of high pressure to a region of low pressure. The partial pressure of oxygen is high in the alveoli and low in the blood of the pulmonary capillaries. As a result, oxygen diffuses across the respiratory membrane from the alveoli into the blood. In contrast, the partial pressure of carbon dioxide is high in the pulmonary capillaries and low in the alveoli. Therefore, carbon dioxide diffuses across the respiratory membrane from the blood into the alveoli. The amount of oxygen and carbon dioxide that diffuses across the respiratory membrane is similar. Ventilation is the process that moves air into and out of the alveoli, and perfusion affects the flow of blood in the capillaries. Both are important in gas exchange, as ventilation must be sufficient to create a high partial pressure of oxygen in the alveoli. If ventilation is insufficient and the partial pressure of oxygen drops in the alveolar air, the capillary is constricted and blood flow is redirected to alveoli with sufficient ventilation. External respiration refers to gas exchange that occurs in the alveoli, whereas internal respiration refers to gas exchange that occurs in the tissue. Both are driven by partial pressure differences. 22.5 Transport of Gases Oxygen is primarily transported through the blood by erythrocytes. These cells contain a metalloprotein called hemoglobin, which is composed of four subunits with a ring-like structure. Each subunit contains one atom of iron bound to a molecule of heme. Heme binds oxygen so that each hemoglobin molecule can bind up to four oxygen molecules. When all of the heme units in the blood are bound to oxygen, hemoglobin is considered to be saturated. Hemoglobin is partially saturated when only some heme units are bound to oxygen. An oxygen–hemoglobin saturation/dissociation curve is a common way to depict the relationship of how easily oxygen binds to or dissociates from hemoglobin as a function of the partial pressure of oxygen. As the partial pressure of oxygen increases, the more readily hemoglobin binds to oxygen. At the same time, once one molecule of oxygen is bound by hemoglobin, additional oxygen molecules more readily bind to hemoglobin. Other factors such as temperature, pH, the partial pressure of carbon dioxide, and the concentration of 2,3-bisphosphoglycerate can enhance or inhibit the binding of hemoglobin and oxygen as well. Fetal hemoglobin has a different structure than adult hemoglobin, which results in fetal hemoglobin having a greater affinity for oxygen than adult hemoglobin. Carbon dioxide is transported in blood by three different mechanisms: as dissolved carbon dioxide, as bicarbonate, or as carbaminohemoglobin. A small portion of carbon dioxide remains. The largest amount of transported carbon dioxide is as bicarbonate, formed in erythrocytes. For this conversion, carbon dioxide is combined with water with the aid of an enzyme called carbonic anhydrase. This combination forms carbonic acid, which spontaneously dissociates into bicarbonate and hydrogen ions. As bicarbonate builds up in erythrocytes, it is moved across the membrane into the plasma in exchange for chloride ions by a mechanism called the chloride shift. At the pulmonary capillaries, bicarbonate re-enters erythrocytes in exchange for chloride ions, and the reaction with carbonic anhydrase is reversed, recreating carbon dioxide and water. Carbon dioxide then diffuses out of the erythrocyte and across the respiratory membrane into the air. An intermediate amount of carbon dioxide binds directly to hemoglobin to form carbaminohemoglobin. The partial pressures of carbon dioxide and oxygen, as well as the oxygen saturation of hemoglobin, influence how readily hemoglobin binds carbon dioxide. The less saturated hemoglobin is and the lower the partial pressure of oxygen in the blood is, the more readily hemoglobin binds to carbon dioxide. This is an example of the Haldane effect. 22.6 Modifications in Respiratory Functions Normally, the respiratory centers of the brain maintain a consistent, rhythmic breathing cycle. However, in certain cases, the respiratory system must adjust to situational changes in order to supply the body with sufficient oxygen. For example, exercise results in increased ventilation, and chronic exposure to a high altitude results in a greater number of circulating erythrocytes. Hyperpnea, an increase in the rate and depth of ventilation, appears to be a function of three neural mechanisms that include a psychological stimulus, motor neuron activation of skeletal muscles, and the activation of proprioceptors in the muscles, joints, and tendons. As a result, hyperpnea related to exercise is initiated when exercise begins, as opposed to when tissue oxygen demand actually increases. In contrast, acute exposure to a high altitude, particularly during times of physical exertion, does result in low blood and tissue levels of oxygen. This change is caused by a low partial pressure of oxygen in the air, because the atmospheric pressure at high altitudes is lower than the atmospheric pressure at sea level. This can lead to a condition called acute mountain sickness (AMS) with symptoms that include headaches, disorientation, fatigue, nausea, and lightheadedness. Over a long period of time, a person’s body will adjust to the high altitude, a process called acclimatization. During acclimatization, the low tissue levels of oxygen will cause the kidneys to produce greater amounts of the hormone erythropoietin, which stimulates the production of erythrocytes. Increased levels of circulating erythrocytes provide an increased amount of hemoglobin that helps supply an individual with more oxygen, preventing the symptoms of AMS. 22.7 Embryonic Development of the Respiratory System The development of the respiratory system in the fetus begins at about 4 weeks and continues into childhood. Ectodermal tissue in the anterior portion of the head region invaginates posteriorly, forming olfactory pits, which ultimately fuse with endodermal tissue of the early pharynx. At about this same time, an protrusion of endodermal tissue extends anteriorly from the foregut, producing a lung bud, which continues to elongate until it forms the laryngotracheal bud. The proximal portion of this structure will mature into the trachea, whereas the bulbous end will branch to form two bronchial buds. These buds then branch repeatedly, so that at about week 16, all major airway structures are present. Development progresses after week 16 as respiratory bronchioles and alveolar ducts form, and extensive vascularization occurs. Alveolar type I cells also begin to take shape. Type II pulmonary cells develop and begin to produce small amounts of surfactant. As the fetus grows, the respiratory system continues to expand as more alveoli develop and more surfactant is produced. Beginning at about week 36 and lasting into childhood, alveolar precursors mature to become fully functional alveoli. At birth, compression of the thoracic cavity forces much of the fluid in the lungs to be expelled. The first inhalation inflates the lungs. Fetal breathing movements begin around week 20 or 21, and occur when contractions of the respiratory muscles cause the fetus to inhale and exhale amniotic fluid. These movements continue until birth and may help to tone the muscles in preparation for breathing after birth and are a sign of good health. Interactive Link Questions Visit this site to learn more about what happens during an asthma attack. What are the three changes that occur inside the airways during an asthma attack? 2.Watch this video to learn more about lung volumes and spirometers. Explain how spirometry test results can be used to diagnose respiratory diseases or determine the effectiveness of disease treatment. 3.Watch this video to see the transport of oxygen from the lungs to the tissues. Why is oxygenated blood bright red, whereas deoxygenated blood tends to be more of a purple color? Review Questions Which of the following anatomical structures is not part of the conducting zone? - pharynx - nasal cavity - alveoli - bronchi What is the function of the conchae in the nasal cavity? - increase surface area - exchange gases - maintain surface tension - maintain air pressure The fauces connects which of the following structures to the oropharynx? - nasopharynx - laryngopharynx - nasal cavity - oral cavity Which of the following are structural features of the trachea? - C-shaped cartilage - smooth muscle fibers - cilia - all of the above Which of the following structures is not part of the bronchial tree? - alveoli - bronchi - terminal bronchioles - respiratory bronchioles What is the role of alveolar macrophages? - to secrete pulmonary surfactant - to secrete antimicrobial proteins - to remove pathogens and debris - to facilitate gas exchange Which of the following structures separates the lung into lobes? - mediastinum - fissure - root - pleura A section of the lung that receives its own tertiary bronchus is called the ________. - bronchopulmonary segment - pulmonary lobule - interpulmonary segment - respiratory segment The ________ circulation picks up oxygen for cellular use and drops off carbon dioxide for removal from the body. - pulmonary - interlobular - respiratory - bronchial The pleura that surrounds the lungs consists of two layers, the ________. - visceral and parietal pleurae. - mediastinum and parietal pleurae. - visceral and mediastinum pleurae. - none of the above Which of the following processes does atmospheric pressure play a role in? - pulmonary ventilation - production of pulmonary surfactant - resistance - surface tension A decrease in volume leads to a(n) ________ pressure. - decrease in - equalization of - increase in - zero The pressure difference between the intra-alveolar and intrapleural pressures is called ________. - atmospheric pressure - pulmonary pressure - negative pressure - transpulmonary pressure Gas flow decreases as ________ increases. - resistance - pressure - airway diameter - friction Contraction of the external intercostal muscles causes which of the following to occur? - The diaphragm moves downward. - The rib cage is compressed. - The thoracic cavity volume decreases. - The ribs and sternum move upward. Which of the following prevents the alveoli from collapsing? - residual volume - tidal volume - expiratory reserve volume - inspiratory reserve volume Gas moves from an area of ________ partial pressure to an area of ________ partial pressure. - low; high - low; low - high; high - high; low When ventilation is not sufficient, which of the following occurs? - The capillary constricts. - The capillary dilates. - The partial pressure of oxygen in the affected alveolus increases. - The bronchioles dilate. Gas exchange that occurs at the level of the tissues is called ________. - external respiration - interpulmonary respiration - internal respiration - pulmonary ventilation The partial pressure of carbon dioxide is 45 mm Hg in the blood and 40 mm Hg in the alveoli. What happens to the carbon dioxide? - It diffuses into the blood. - It diffuses into the alveoli. - The gradient is too small for carbon dioxide to diffuse. - It decomposes into carbon and oxygen. Oxyhemoglobin forms by a chemical reaction between which of the following? - hemoglobin and carbon dioxide - carbonic anhydrase and carbon dioxide - hemoglobin and oxygen - carbonic anhydrase and oxygen Which of the following factors play a role in the oxygen–hemoglobin saturation/dissociation curve? - temperature - pH - BPG - all of the above Which of the following occurs during the chloride shift? - Chloride is removed from the erythrocyte. - Chloride is exchanged for bicarbonate. - Bicarbonate is removed from the erythrocyte. - Bicarbonate is removed from the blood. A low partial pressure of oxygen promotes hemoglobin binding to carbon dioxide. This is an example of the ________. - Haldane effect - Bohr effect - Dalton’s law - Henry’s law Increased ventilation that results in an increase in blood pH is called ________. - hyperventilation - hyperpnea - acclimatization - apnea Exercise can trigger symptoms of AMS due to which of the following? - low partial pressure of oxygen - low atmospheric pressure - abnormal neural signals - small venous reserve of oxygen Which of the following stimulates the production of erythrocytes? - AMS - high blood levels of carbon dioxide - low atmospheric pressure - erythropoietin The olfactory pits form from which of the following? - mesoderm - cartilage - ectoderm - endoderm A full complement of mature alveoli are present by ________. - early childhood, around 8 years of age - birth - 37 weeks - 16 weeks If a baby is born prematurely before type II cells produce sufficient pulmonary surfactant, which of the following might you expect? - difficulty expressing fluid - difficulty inflating the lungs - difficulty with pulmonary capillary flow - no difficulty as type I cells can provide enough surfactant for normal breathing When do fetal breathing movements begin? - around week 20 - around week 37 - around week 16 - after birth What happens to the fluid that remains in the lungs after birth? - It reduces the surface tension of the alveoli. - It is expelled shortly after birth. - It is absorbed shortly after birth. - It lubricates the pleurae. Critical Thinking Questions Describe the three regions of the pharynx and their functions. 37.If a person sustains an injury to the epiglottis, what would be the physiological result? 38.Compare and contrast the conducting and respiratory zones. 39.Compare and contrast the right and left lungs. 40.Why are the pleurae not damaged during normal breathing? 41.Describe what is meant by the term “lung compliance.” 42.Outline the steps involved in quiet breathing. 43.What is respiratory rate and how is it controlled? 44.Compare and contrast Dalton’s law and Henry’s law. 45.A smoker develops damage to several alveoli that then can no longer function. How does this affect gas exchange? 46.Compare and contrast adult hemoglobin and fetal hemoglobin. 47.Describe the relationship between the partial pressure of oxygen and the binding of oxygen to hemoglobin. 48.Describe three ways in which carbon dioxide can be transported. 49.Describe the neural factors involved in increasing ventilation during exercise. 50.What is the major mechanism that results in acclimatization? 51.During what timeframe does a fetus have enough mature structures to breathe on its own if born prematurely? Describe the other structures that develop during this phase. 52.Describe fetal breathing movements and their purpose.	oercommons	2025-03-18T00:35:14.168585	10/14/2019	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/58770/overview", "title": "Anatomy and Physiology, Energy, Maintenance, and Environmental Exchange, The Respiratory System", "author": null }
https://oercommons.org/courseware/lesson/73501/overview	Figure 1.13 Directional Terms (no labels, no lines) Overview This image is of Fig.1.13 in section 1.6 of OpenStax's Anatomy and Physiology. I stripped-down all labels and lines to make this a testable image. 1.6 Anatomical Terminology - Directional Terms This image is of Fig.1.13 in section 1.6 of OpenStax's Anatomy and Physiology. I stripped-down all labels and lines to make this a testable image.	oercommons	2025-03-18T00:35:14.197918	Diagram/Illustration	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/73501/overview", "title": "Figure 1.13 Directional Terms (no labels, no lines)", "author": "Assessment" }
https://oercommons.org/courseware/lesson/114943/overview	Maximizing Instructional Time in the Classroom Strategies for Teachers to Maximize Student Learning Time Strategy: Teaching Classroom Routines by The Classroom Check-In The Environment: Schedules and Routines We Drastically Underestimate the Importance of Brain Breaks Schedules & Routines in the Classroom Overview In this resource, you will learn what routines are and how to establish them in your daily schedule, how to decide how much time you spend on a section of your day to increase instructional time, and the importance of including brain breaks throughout the day. Overview In this resource, you will learn what routines are and how to establish them in your daily schedule, how to decide how much time you spend on a section of your day to increase instructional time, and the importance of including brain breaks throughout the day. Sections in this Resource Overview Establishing Classroom Routines How to Allot Time Appropriately The Importance of Including "Brain Breaks" Conclusion: How This Applies to Educators Bibliography \| Establishing Classroom Routines As we all know, children are best behaved and enjoy their environment when participating in consistent daily routines. If implemented correctly, routines can "reduce disruptive behavior, therefore maximizing the time spent on instruction," (The Classroom Check-Up, n.d.). Routines should be found throughout all times, from the start of school, in between lessons and activities, and to the end of the school day. Below is a video by Edutopia that explains the importance of implementing routines in your classroom and discusses how you can continue to improve those routines throughout your teaching career. Many different types of routines can be implemented throughout the day, such as how students will get to their seats, how they will know what supplies they need, or what they need to do upon entering the classroom. Routines also include the procedures used during transitions between activities or classes. According to the Australian Education Research Organisation (2023b), the best steps to take in teaching routines to students are as follows: - Introduce the routine and briefly detail your expectations (why and what). - Model and describe the routine to your students by demonstrating the expected behaviours (I do). - Provide an opportunity for students to practise the routine with teacher support (we do). Practise the routine until everyone can do it the best they can, acknowledging students who are getting it and supporting those who are not. - Students complete the routine independently (you do), removing scaffolding from the teacher, as appropriate, and transferring ownership to students. - Reinforce and maintain the routine consistently through acknowledgment, praise, and practice. Below is a video posted by The Classroom Nook that reviews these steps on establishing and teaching routines in your classroom. The Classroom Check-Up (n.d.) also recommends using "visual prompts of the classroom routines" that are always available for students as a reminder of classroom expectations. Additionally, be sure to keep "the steps... developmentally appropriate" for the level you are teaching by having your routines include as few steps as possible. For more information, you can visit this site by clicking this link. Below are some examples of visual prompts for classroom routines. These can be created digitally and printed or created by hand on poster board. One recommendation that the Australian Education Research Organisation (2023a) has to ensure that routines are taught and executed most effectively is by "scripting and rehearsing without students present", "practise with students present", and/or "invite a colleague to observe your entrance routine in action." I also recommend checking out this section of the IRIS Center's module titled "Create a Structured Classroom" discussing types of routine at both the primary and secondary levels. OER Commons Use "Classroom Management Resources: User Guide" Australian Education Research Organisation is licensed under CC BY 4.0 How to Allot Time Appropriately The amount of time we spend on each activity or portion of the day matters—we have to get the timing version of Goldilocks and the Three Bears conundrum. Allowing too much time for a single activity will cause your students to lose focus, which leads to disruptive behaviors and can become a safety concern. Allowing too little time will lead to transitional chaos and, more than likely, your students will not gain anything from the activity. So how do you determine that perfect balance of just enough time? Below is a video by Let's Teach that introduces the "Ten Plus Two Teaching Strategy". This strategy ensures that students are engaged in the lesson by taking a two-minute discussion break after ten minutes of lecturing. Another great online resource from The Virtual Lab discusses schedules and routines, including the amount of time found to be developmentally appropriate for school-aged children. You can visit the resource using this link here. The hardest thing about allotting time for each aspect of your daily schedule is sticking to the time allotted. One recommendation is to have a visual reminder for both you and your students of the daily schedule and the times they are meant to happen. Below is an example of a classroom schedule and the times each activity or section of class should begin. As we will discuss in the next section of this resource, taking time to allow children to decompress is often forgotten in our daily schedule. Ultimately, however, children need time to take a break from constant working to better achieve their academic and personal goals. Included in this section (see resources) are a couple of links to some other outside resources that were not directly discussed in this section but contain great information on improving instructional time. The Importance of Including "Brain Breaks" Most adults think that when students are in school, their only job is to learn. While students do have to learn, we need to make sure that we are taking appropriate steps to make sure that students are taken care of mentally. Not only do brain breaks help students retain information, but it also allows them to recharge their brains (Terada, 2022). Adding brain breaks into your classroom schedule doesn’t mean taking up time from other things. Brain breaks can be quick and still effective. You can find videos on YouTube to play for the students to follow along. These videos can have anything from jumping, stretching, or dancing. All of these movements are going to get your students moving and active for a few minutes. Here are some examples of brain breaks that can be used in the classroom: When is it a good time to have a brain break? Before going to sit on the rug/carpet After quiet time or independent work After learning new information or a new concept Conclusion: How This Applies to Educators Creating, establishing, and maintaining classroom schedules and routines can greatly impact your classroom environment. Ultimately, having a consistent schedule will keep your students safe and keep your classroom from bursting into complete chaos! In this resource, we discussed the following topics: - What a routine is and how it impacts your overall classroom schedule - How to establish routines with demonstrations and practice - Methods of maintaining consistency of routines using visual reminders - How to determine how much time to spend on an activity - The importance of including brain breaks throughout the day - Examples of classroom-friendly brain break videos - When your students may need an emergency brain break One of the biggest reasons a teacher's classroom management may not be working is the lack of a consistent routine that students have had the opportunity to learn and implement, as well as a lack of visual reminders of those routines. Students also tend to get "antsy" after sitting in class, and allowing them to participate in brain breaks will increase the likeliness of disruptive behaviors during instruction. Bibliography Australian Education Research Organisation. (2023a). Classroom management practice guide: Entrance routine. OER Commons. Retrieved from https://oercommons.org/courses/classroom-management-resources-user-guide. Australian Education Research Organisation. (2023b). Teaching routines: Their role in classroom management. Australian Education Research Organisation. Retrieved from https://www.edresearch.edu.au/summaries-explainers/explainers/teaching-routines-their-role-classroom-management. Terada, Y. (2022). We drastically underestimate the importance of brain breaks. Edutopia. Retrieved in April 2024 from https://www.edutopia.org/article/we-drastically-underestimate-importance-brain-breaks/. The Classroom Check-Up. (n.d.). Strategy: Teaching classroom routines. The Classroom Check-Up. Retrieved in April 2024 from https://classroomcheckup.org/teaching-classroom-routines/.	oercommons	2025-03-18T00:35:14.232795	Module	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/114943/overview", "title": "Schedules & Routines in the Classroom", "author": "Higher Education" }
https://oercommons.org/courseware/lesson/114768/overview	the Councelor the Homemaker the Scientist the Technologist SDG 11: Concrete Jungle to Urban Oasis Lesson Plan Overview This is an engaging and interactive lesson plan designed to deepen students' understanding of the Sustainable Development Goals (SDGs), with a special focus on SDG 11: Sustainable Cities and Communities. This lesson combines a podcast, interactive gameplay, and reflective exercises to offer students a comprehensive view of global sustainability efforts and their part in these initiatives. Intro Introduction for Teachers: Sustainable Development Goals (SDG) Lesson Plan This lesson plan is designed to deepen students' understanding of the Sustainable Development Goals (SDGs), with a special focus on SDG 11: Sustainable Cities and Communities. This lesson combines multimedia learning, interactive gameplay, and reflective exercises to offer students a comprehensive view of global sustainability efforts and SS part in these initiatives. Learning Outcomes: By the end of this lesson, students will be able to: - Explain the importance and objectives of the Sustainable Development Goals, particularly SDG 11. - Identify challenges and solutions related to making cities and communities more inclusive, safe, resilient, and sustainable. - Reflect on their own experiences and propose actionable ideas that contribute to these goals. Lesson Flow: Podcast Listening: The lesson begins with a podcast that introduces the SDGs, providing real-world context and highlighting the significance of global collaboration in achieving these goals. This will set the stage for the topic and engage students with compelling storytelling. The podcast component of this lesson can be assigned as homework for a flipped classroom approach, allowing students to familiarize themselves with the SDGs at home and use class time for more interactive discussions and activities. Escape Room Game: Following the podcast, students will participate in an online escape room game centered around SDG 11. The game is divided into five rooms, each focusing on a key aspect of SDG 11: inclusivity, accessibility, safety, resilience, and sustainability. Through interactive challenges guided by characters, students will encounter real-life, relatable scenarios that illustrate the complexities of sustainable urban development. Students may need help in rooms with multiple-letter escape codes (from multiple-choice answers). Ensure you closely observe and offer support if they show signs of frustration, keeping the experience enjoyable and stress-free! Wrap-Up Task: After completing the game, students will engage in a wrap-up session to consolidate their learning. They will reflect on their learnings, discuss in groups, and brainstorm actionable steps they can take within their communities. This task encourages critical thinking and empowers students to envision their role in making a difference. Preparation: - Preview the podcast and the online escape room game to familiarize yourself with the content and technical requirements. - Prepare discussion questions and materials needed for the wrap-up task. - Consider how to facilitate group discussions and presentations in your classroom setting, whether in-person or online. This lesson plan is designed to be flexible and adaptable to various classroom settings and student groups. It aims to not only educate students on important global issues but also inspire them to connect these ideas to their environment and become proactive contributors to a more sustainable and equitable world. Hey! Welcome to the lesson. Let's start with a little discussion. Discuss in mini-groups, then present your ideas to the class: - What’s one thing you love about living in a city or community? - What are some challenges you think people face when living in cities? - If you were mayor for a day, what would you change in your city? Part 1: Podcast The podcast introduces the SDG 11 and its multiple aspects. Use it as a warmer to introduce the topic. https://soundcloud.com/katerina-astafeva-170940210/sdg11-podcast?utm_source=clipboard&utm_campaign=wtshare&utm_medium=widget&utm_content=https%253A%252F%252Fsoundcloud.com%252Fkaterina-astafeva-170940210%252Fsdg11-podcast After you can use some of these comprehension questions to check understanding. - What are the Sustainable Development Goals (SDGs)? - What is the main focus of SDG 11 discussed in the podcast? - Besides planting trees and recycling, what other aspects are important for sustainable cities? - How does Copenhagen aim to become carbon neutral by 2025? - What is one benefit of vertical gardens mentioned in the podcast? - What are some ways regular people can help achieve SDG 11 in their communities? - According to the podcast, what are two ways individuals can reduce their carbon footprint? - Besides reducing waste, what other action is mentioned in the podcast that can contribute to a more sustainable lifestyle? or add your own! We will start this class by listening to the podcast. It will introduce the topic of SDGs and SDG11. What doest SDG stand for? What aspects of SDG11 will you hear? Take notes while you're listening. Part 2: The Escape Room Game Overview The game is an online escape room designed to both spread awareness and educate on Sustainable Development Goal (SDG) 11, featuring five rooms centered on the goal's key aspects: inclusivity, accessibility, safety, resilience, and sustainability. Within each room, players encounter a character who introduces them to the theme and guides them through real-life, relatable challenges. These challenges are created to connect players closely to the topic, enhancing their understanding and engagement. To progress, players must solve 2-3 of these challenges per room, which, upon completion, reward them with a key to escape the room and advance to the next. This interactive approach aims to deeply educate players on addressing various components of SDG 11 in an immersive and engaging environment. Now you will jump into an online escape room game, all about Sustainable Development Goal (SDG) 11, aiming to make our cities and communities better for everyone! In this adventure, you'll explore five different rooms, each focusing on making places more inclusive, accessible, safe, resilient, and sustainable—key parts of SDG 11. The characters in each room will guide you through real-world issues. Solve the puzzles in each room to find keys that unlock the door to escape! How to play the game Topic and Characters - Inclusive (Assigned to Claus Christensen, the Councelor (social worker)): - Claus is an experienced social worker who is dedicated to fostering inclusivity in the city. He has a strong background in community development and a passion for helping marginalized groups. - Accessible (Assigned to Hasan Hukka, the Homemaker): - Hasan Hukka, as a homemaker and a father of 4, understands the importance of accessibility for families. He is dedicated to making sure that public spaces, transportation, and facilities are accessible to people of all ages, including parents with young children. - Safe (Assigned to Anttoni Aalto, the Architect): - Anttoni Aalto, the sustainable architect, prioritizes safety in urban design. He focuses on creating secure and resilient infrastructure, including buildings and public spaces, to protect residents from environmental hazards and ensure their safety. - Resilient (Assigned to Tara Törmä, the Technologist): - Tara Törmä, the tech innovator, specializes in smart city solutions that enhance the city's resilience. She develops technologies and systems that can withstand and recover from environmental challenges and crises. - Sustainable (Assigned to Sari Salmi, the Scientist): - Sari Salmi, the sustainability scientist, is deeply committed to the sustainability aspect of SDG 11. She works tirelessly to promote eco-friendly living, reduce pollution, and implement sustainable practices throughout the city. Attached: personas' portraits - Sari Salmi, the sustainability scientist, is deeply committed to the sustainability aspect of SDG 11. She works tirelessly to promote eco-friendly living, reduce pollution, and implement sustainable practices throughout the city. Room 1: Safety Task 1: Environmental Hazard Identification - Description: Players identify and mitigate potential environmental hazards in a virtual cityscape, such as pollution sources, unsafe water, and areas prone to landslides or flooding. - Key: number of hotspots - The first part of the code: 8 Task 2: CyberSecure Challenge: Safe vs. Unsafe Actions in CyberSafe City - Description: Players identify potential CyberSecurity hazards - Key: The second part of the code: UUSSU Mark receives an email from his bank asking for his account details. - Unsafe: This could be a phishing attempt. Banks typically do not request personal account details via email. Sara posts her family vacation photos on social media while still on vacation. - Unsafe: Sharing real-time location details can make your home a target for burglary. It’s safer to post after returning home. Nina sets up two-factor authentication (2FA) for her online banking account. - Safe: Enabling 2FA adds an extra layer of security, making it harder for unauthorized users to gain access to her account. Lucy downloads the city’s official app to pay for parking and local transit. - Safe: Using official city apps for payments is generally secure, as they are likely to have proper security measures in place. Carlos uses an open Wi-Fi network at the public library to access his personal emails. - Unsafe: Accessing sensitive information over an unsecured network can expose data to cybercriminals. </aside> Room 2: Accessibility Task 1: Braille Code Breaker - Description: Players are presented with words written in Braille. Using a provided Braille alphabet guide (link attached), they must decode the sentences. The guide is hidden in a separate hot spot. - Key: The first part of the code: 30 https://twoblindbrothers.com/pages/braille Task 2: Urban accessibility - Description: Players are presented with a detailed and intricate picture of an urban environment. This environment is bustling with activity and includes various elements like buildings, streets, public transportation, parks, and sidewalks. The task is to scrutinize the picture and identify all the problems related to accessibility. - Key: The number of problems they find is the number or the code. 6. - The second part of the code: the number of problems you find! 6: - 1. the elevator not working 2. the pit is open 3. the mud puddle - 3. the ramp is blocked 5. littered crossroads 6. the street light not working. Room 3: Inclusivity Task 2: Diverse Culture Quiz - Description: Players answer questions about various cultures represented in a virtual city, promoting cultural awareness. - Key: Correct answers reveal a series of digits forming the key code. - The first part CABAA - What is a common practice when greeting someone in many Middle Eastern countries? A A firm handshake. B A bow. C A light kiss on the cheek. D Avoiding eye contact. - During the month of Ramadan, many Muslims: A Fast from dawn until sunset. B Give up using technology. C Avoid speaking. D Fast every alternate day. - In many East Asian cultures, it's considered respectful to: A Make direct eye contact when speaking. B Bow slightly when greeting. C Speak loudly to show enthusiasm. D Address people by their first names. - When invited to someone's home for dinner in many Western cultures, it's polite to: A Bring a small gift, like wine or flowers. B Offer to take off your shoes. C Arrive exactly on time. D Greet the host with a hug. - In many Indian households, it's customary to: *\A Eat food with your hands. B Refuse food on the first offer. C Bring your own utensils. D Start eating before the host. </aside> Task 2: Multilingual Puzzle - Description: listen to a speaker and match to a country - Key: First letters of countries names - The second part of the code: FSISPC - France - Spain - Iran - Sri Lanka - Pakistan - China Room 4: Resilience Theme Overview: This room will focus on various aspects of urban safety, including crime prevention, disaster readiness, and safe public spaces. Task 1: Climate Change Effects - Description: Matching exercise - climate change aspect - every day effect. - Key: A successful plan reveals a digital key embedded in the plan's virtual document. - THE FIRST PART OF THE KEY: "rainfall" sysnonym in the task, all CAPS. PRECIPITATION Match Climate Change Effects: Increased Heat Waves Ice Caps Melting Oceans Getting Acidic Rising Sea Levels Disruption of Habitats and Loss of Biodiversity Disappearing Changing Precipitation Patterns More Frequent Severe Storms with Houses get damaged more and sometimes no electricity. Not enough fresh water to drink or use in farms. More floods near the sea. Homes and places people live can get damaged. Less nature to enjoy and visit. Sometimes too much or too little water for plants and daily use. People can get sick from the heat. It costs more to keep homes cool. Fewer fish to catch and eat. Task 2: Community Resilience Building - Description: memory style game to match people - Key: JAMES Building a Community, connect people who can help each other! THE FIRST PART OF THE KEY: NAME OF THE PERSON WHO CAN HELP SHOPHIE, ALL CAPS William, an aspiring chef, needs someone to taste and critique his culinary creations. Sarah is a single mother who needs help with cooking as she works during the day. Rebecca is a new immigrant who needs help learning the local language to communicate effectively. Elena, a language enthusiast, is willing to teach newcomers and improve their language skills. Javier is a struggling small business owner who needs advice on how to grow his company. Emma, an experienced entrepreneur, is available to mentor and guide on business endeavors. Sophie is visually impaired and needs help to read her mail and with essential paperwork. James, a veteran, seeks companionship and someone to talk to regularly. Olivia, a high school student, needs tutoring in math to improve her grades. Mark, a retired teacher, is eager to share his knowledge by volunteering as a tutor. Room 5: Sustainability Task 1: Eco-Friendly Objects Scavenger Hunt - Description: Players must locate and collect all eco-friendly objects. Each found object provides a clue or a part of a code that, when all are combined, reveals the location of the final key to "escape" the room. - Key: collect particular items to make the key word: green - The third part of the code: locate all eco-friendly objects, collect letters, make a word out of the letters - Solar-Powered Lantern - Clue: "I harness the sun's rays to light up the night." - Sustainability Principle: Renewable energy usage. - Bamboo Utensil Set - Clue: "I grow quickly and leave a gentle footprint." - Sustainability Principle: Sustainable material use. - Reusable Water Bottle - Clue: "I keep you hydrated without adding to plastic waste." - Sustainability Principle: Reducing plastic pollution. - Compost Bin - Clue: "I turn your waste into garden gold." - Sustainability Principle: Waste reduction and composting. - Bicycle - Clue: "I offer a clean and healthy way to travel." - Sustainability Principle: Eco-friendly transportation. - Energy-Efficient LED Bulb - Clue: "I shine bright while conserving energy." - Sustainability Principle: Energy efficiency. - Rainwater Harvesting System - Clue: "I catch what falls from the sky for your use." - Sustainability Principle: Water conservation. - Seed Packets of Native Plants - Clue: "I bring local flora back to your garden." - Sustainability Principle: Biodiversity and native planting. - Thrift Store Clothing Item - Clue: "I'm a fashionable choice that's also kind to the Earth." - Sustainability Principle: Sustainable fashion and reducing textile waste. </aside> Task 2: Recycling Sorting Quest - Description: Players sort virtual waste into correct recycling, compost, and trash categories, emphasizing the importance of proper waste management. - Key: Correct sorting unlocks a recycling bin where the key is hidden. - The second number for the key: go Players are presented with a variety of virtual waste items. The task is to sort these items into the correct categories: recycling, compost, and trash. List of Objects and Correct Categories - Glass Bottle - Correct Category: Recycling - Banana Peel - Correct Category: Compost - Plastic Shopping Bag - Correct Category: Trash - Aluminum Can - Correct Category: Recycling - Paper Newspaper - Correct Category: Recycling - Styrofoam Cup - Correct Category: Trash - Broken Ceramic Plate - Correct Category: Trash - Food Scraps - Correct Category: Compost - Plastic Water Bottle - Correct Category: Recycling - Cardboard Box - Correct Category: Recycling </aside> - Correct Category: Recycling Task 3: Sustainable Lifestyle Quiz - Description: Players answer questions about sustainable living practices, learning about energy conservation, water usage, and waste reduction. - Key: Correct answers open a digital book on sustainability, where the key is bookmarked. - The first part of the code: Your letters for correct answers in the order the questions appeared, e.g. ABCAB DBABB Q: If you were a superhero trying to save water, what would be your superpower? - A: Shoot lasers from your eyes to clean dishes. - B: Fly to bring rain clouds to dry areas. - C: Turn wine into water. - D: Take lightning-fast showers. Correct Answer: D - Take lightning-fast showers. Q: What's a sustainable way to enjoy music? A: Listen to bird songs instead of MP3s. B: Use a solar-powered music player. C: Only sing songs about recycling. D: Play air guitar to save electricity. Correct Answer: B - Use a solar-powered music player. Q: Which practice contributes most to reducing waste? A: Buying products with minimal packaging. B: Choosing disposable over reusable items. C: Shopping for new clothes every season. D: Using single-use plastic bags. Correct Answer: A - Buying products with minimal packaging. Q: How can you make your wardrobe more sustainable? A: Wear clothes inside out for a new look. B: Host a clothes-swapping party with friends. C: Use old shirts as superhero capes. D: Only wear clothes on Tuesdays. Correct Answer: B - Host a clothes-swapping party with friends. Q: How can you fight 'vampire energy' at home? A: Dress up like garlic. B: Unplug appliances when not in use. C: Only use electronics at night. D: Invite a vampire over to discuss energy use. Correct Answer: B - Unplug appliances when not in use. How to Play the Escape Room Game on ThingLink Welcome to the Game, all about making cities better! Here’s a quick guide on how to play: Starting the Game: Click on the link provided by your teacher to open the game. You’ll land on the ThingLink interface, where our escape room adventure begins. Navigating the Rooms: You’ll find yourself in the first of five rooms. Look around by clicking and dragging your mouse, or using your finger on touch devices. Meeting Characters: In each room, you’ll meet a virtual character. They'll introduce you to the room’s theme and give you your first challenge. To interact with characters or objects, just click on the icons that pop up as you explore. They might be hidden, so look carefully! Solving Challenges: Each room has 2-3 puzzles or challenges based on real-life scenarios. Read the instructions carefully, and use your smarts to solve them. Remember, sometimes, you’ll need to find clues hidden in the room! Collecting Keys: After solving all challenges in a room, you’ll receive a virtual key. This key unlocks the door to the next room. Click on the door to move forward. Progressing Through the Game: Repeat the process in each room. Remember, each room builds on the last, so use what you learn as you go. Finishing the Game: Once you’ve solved all the rooms’ challenges and collected all the keys, you’ve completed the game! Great job on navigating through all the puzzles and learning more about how to make our world a better place. Reflect and Share: Think about what you’ve learned and discuss it with your classmates or friends. What was the most interesting thing you found out? Wrap Up After your students complete the online escape room game focused on SDGs and SDG 11, guide them through a reflective and creative wrap-up session to consolidate their learning, encourage critical thinking, and inspire actionable ideas. Here's how you can facilitate it: Arrange a class discussion or ask students to form small groups to talk about their experiences with the game (SS questions). Encourage them to share challenges they found interesting and what they learned about SDGs and SDG 11. Ask students to brainstorm additional strategies or actions that could contribute to achieving SDG 11, emphasizing inclusivity, safety, resilience, and sustainability in cities and communities. Encourage them to think about changes they could advocate for or implement in their local area. Extension: Ask students to come up with a small, actionable plan on how they can apply what they've learned to make a difference in their community or school. This could be a project proposal, an awareness campaign, or a personal commitment to certain sustainable practices. Congratulations! You have solved all the puzzles! Now that you've seen some solutions and ideas in action through the game: What are some key things you learned about SDGs and specifically SDG 11 during this adventure? How do they connect to real-life situations and problems you're aware of? How can you apply what you've learned from this game to make a positive impact on your local environment or community? Can you think of additional ideas or actions that could help achieve SDG 11? Consider what changes could be made in your own community or school to support these goals.How do you think you can encourage others to work towards these goals too?	oercommons	2025-03-18T00:35:14.291400	Lesson	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/114768/overview", "title": "SDG 11: Concrete Jungle to Urban Oasis Lesson Plan", "author": "Interactive" }
https://oercommons.org/courseware/lesson/74991/overview	Diversity and Cultural Competency Overview Diversity: the art of thinking independently together. —Malcolm Forbes, entrepreneur, founder of Forbes magazine LEARNING OBJECTIVES By the end of this section, you will be able to: - Define diversity and identify many aspects of diversity - Differentiate between surface diversity and deep diversity, and explain the relationship between the two - Define and apply principles of cultural competency - Explore the positive effects of diversity in an educational setting Diversity and it's impact Introduction Cultural diversity is found everywhere in college, in the workplace, in life. It should be respected, appreciated, and celebrated. To be successful as a college student, it is critical that you understand and can describe your own diverse background and how it impacts your view of the world. Being self-aware allows you to identify what makes you who you are while recognizing the differences that exist between you, other students, your professors, and all the members of your community. This section will discuss the factors that make up a person’s culture and how one can effectively communicate and work with people who may be different. Diversity: the art of thinking independently together. —Malcolm Forbes, entrepreneur, founder of Forbes magazine What Is Diversity? There are few words in the English language that have more diverse interpretations than diversity. What does diversity mean? Better yet—what does diversity mean to you? And what does it mean to your best friend, your teacher, your parents, your religious leader, or the person standing behind you in a grocery store? For each of us, diversity has unique meaning. Below are a few of the many definitions offered by college students at a 2010 conference on the topic of diversity. Which of these definitions rings out to you as most accurate and thoughtful? Which definitions could use some embellishment or clarification, in your opinion? Diversity is a group of people who are different in the same place. Diversity to me is the ability for differences to coexist together, with some type of mutual understanding or acceptance present. Acceptance of different viewpoints is key. Tolerance of thought, ideas, people with differing viewpoints, backgrounds, and life experiences. Anything that sets one individual apart from another. People with different opinions, backgrounds (degrees and social experience), religious beliefs, political beliefs, sexual orientations, heritage, and life experience. Dissimilar Having a multitude of people from different backgrounds and cultures together in the same environment working for the same goals. Difference in students’ background, especially race and gender. Differences in characteristics of humans. Diversity is a satisfying mix of ideas, cultures, races, genders, economic statuses and other characteristics necessary for promoting growth and learning among a group. Diversity is the immersion and comprehensive integration of various cultures, experiences, and people. Heterogeneity brings about opportunities to share, learn and grow from the journeys of others. Without it, limitations arise and knowledge is gained in the absence of understanding. Diversity is not tolerance for difference but inclusion of those who are not the majority. It should not be measured as a count or a fraction—that is somehow demeaning. Success at maintaining diversity would be when we no longer ask if we are diverse enough, because it has become the norm, not remarkable.[1] Diversity means different things to people, and it can be understood differently in different environments. In the context of your college experience, diversity generally refers to people around you who differ by race, culture, ethnicity, religion, socioeconomic status, sexual orientation, abilities, opinions, political views, and in other ways. When it comes to diversity on the college campus, we also think about how groups interact with one another, given their differences (even if they are just perceived differences.) How do diverse populations experience and explore their relationships? “More and more organizations define diversity really broadly,” says Eric Peterson, who works on diversity issues for the Society for Human Resource Management (SHRM). “Really, it’s any way any group of people can differ significantly from another group of people—appearance, sexual orientation, veteran status, your level in the organization. It has moved far beyond the legally protected categories that we’ve always looked at.”[2] Surface Diversity and Deep Diversity Surface diversity and deep diversity are categories of personal attributes—or differences in attributes—that people perceive to exist between people or groups of people. Surface-level diversity refers to differences you can generally observe in others, like ethnicity, race, gender, age, culture, language, disability, etc. You can quickly and easily observe these features in a person. And people often do just that, making subtle judgments at the same time, which can lead to bias or discrimination. For example, if a teacher believes that older students perform better than younger students, she may give slightly higher grades to the older students than the younger students. This bias is based on a perception of the attribute of age, which is surface-level diversity. Deep-level diversity, on the other hand, reflects differences that are less visible, like personality, attitude, beliefs, and values. These attributes are generally communicated verbally and non-verbally, so they are not easily noticeable or measurable. You may not detect deep-level diversity in a classmate, for example, until you get to know him or her, at which point you may find that you are either comfortable with these deeper character levels, or perhaps not. But once you gain this deeper level of awareness, you may focus less on surface diversity. For example, at the beginning of a term, a classmate belonging to a minority ethnic group whose native language is not English (surface diversity) may be treated differently by fellow classmates in another ethnic group. But as the term gets underway, classmates begin discovering the person’s values and beliefs (deep-level diversity), which they find they are comfortable with. The surface-level attributes of language and perhaps skin color become more “transparent” (less noticeable) as comfort is gained with deep-level attributes. The following video is a quick summary of the differences between surface-level and deep-level diversity. As we’ll use the term here, diversity refers to the great variety of human characteristics—ways that we are different even as we are all human and share more similarities than differences. These differences are an essential part of what enriches humanity. Aspects of diversity may be cultural, biological, or personal in nature. Diversity generally involves things that may significantly affect some people’s perceptions of others—not just any way people happen to be different. For example, having different tastes in music, movies, or books is not what we usually refer to as diversity. When discussing diversity, it is often difficult to avoid seeming to generalize about different types of people—and such generalizations can seem similar to dangerous stereotypes. The following descriptions are meant only to suggest that individuals are different from other individuals in many possible ways and that we can all learn things from people whose ideas, beliefs, attitudes, values, backgrounds, experiences, and behaviors are different from our own. This is a primary reason college admissions departments frequently seek diversity in the student body. Following are various aspects of diversity: - Race: Race refers to what we generally think of as biological differences and is often defined by what some think of as skin color. Such perceptions are often at least as much social as they are biological. - Ethnicity: Ethnicity is a cultural distinction that is different from race. Ethnic groups share a common identity and a perceived cultural heritage that often involves shared ways of speaking and behaving, religion, traditions, and other traits. The term “ethnic” also refers to such a group that is a minority within the larger society. Race and ethnicity are sometimes interrelated but not automatically so. - Cultural background: Culture, like ethnicity, refers to shared characteristics, language, beliefs, behaviors, and identity. We are all influenced by our culture to some extent. While ethnic groups are typically smaller groups within a larger society, the larger society itself is often called the “dominant culture.” The term is often used rather loosely to refer to any group with identifiable shared characteristics. - Educational background: Colleges do not use a cookie-cutter approach to admit only students with identical academic skills. A diversity of educational background helps ensure a free flow of ideas and challenges those who might become set in their ways. - Geography: People from different places within the United States or the world often have a range of differences in ideas, attitudes, and behaviors. - Socioeconomic background: People’s identities are influenced by how they grow up, and part of that background involves socioeconomic factors. Socioeconomic diversity can contribute to a wide variety of ideas and attitudes. - Gender roles: Women hold virtually all professional and social roles, including those once dominated by men, and men have taken on many roles, such as raising a child, that were formerly occupied mostly by women. These changing roles have brought diverse new ideas and attitudes to college campuses. - Gender identity: Gender identity is one’s personal experience of one’s own gender. Gender identity can correlate with the sex at birth – male or female, or can differ from it completely: males may identify as female or vice versa, or a person may identify as a third gender or as falling somewhere along the continuum between male and female. - Age: While younger students attending college immediately after high school are generally within the same age range, older students returning to school bring a diversity of age. Because they often have broader life experiences, many older students bring different ideas and attitudes to the campus. - Sexual orientation: Gays and lesbians make up a significant percentage of people in American society and students on college campuses. Exposure to this diversity helps others overcome stereotypes and become more accepting of human differences. - Religion: For many people, religion is not just a Sunday morning practice but a larger spiritual force that infuses their lives. Religion helps shape different ways of thinking and behaving. - Political views: A diversity of political views helps broaden the level of discourse on campuses concerning current events and the roles of government and leadership at all levels. - Physical ability: Some students have athletic talents. Some students have physical disabilities. Physical differences among students bring yet another kind of diversity to colleges—a diversity that both widens opportunities for a college education and also helps all students better understand how people relate to the world in physical as well as intellectual ways. Cultural Competency As a college student, you are likely to find yourself in diverse classrooms, organizations, and – eventually – workplaces. It is important to prepare yourself to be able to adapt to diverse environments. Cultural competency can be defined as the ability to recognize and adapt to cultural differences and similarities. It involves “(a) the cultivation of deep cultural self-awareness and understanding (i.e., how one’s own beliefs, values, perceptions, interpretations, judgments, and behaviors are influenced by one’s cultural community or communities) and (b) increased cultural other-understanding (i.e., comprehension of the different ways people from other cultural groups make sense of and respond to the presence of cultural differences).”1 In other words, cultural competency requires you to be aware of your own cultural practices, values, and experiences, and to be able to read, interpret, and respond to those of others. Such awareness will help you successfully navigate the cultural differences you will encounter in diverse environments. Cultural competency is critical to working and building relationships with people from different cultures; it is so critical, in fact, that it is now one of the most highly desired skills in the modern workforce.2 We don’t automatically understand differences among people and celebrate the value of those differences. Cultural competency is a skill that you can learn and improve upon over time and with practice. What actions can you take to build your cultural competency skills? KEY TAKEAWAYS - Diversity refers to a great variety of human characteristics and ways in which people differ. - Surface-level diversity refers to characteristics you can easily observe, while deep-level diversity refers to attributes that are not visible and must be communicated in order to understand. - Cultural competency is the ability to recognize and adapt to cultural differences and similarities. - Diverse environments expose you to new perspectives and can help deepen your learning. - Bennett, J. M. (2015). "Intercultural Competence Development." The SAGE Encyclopedia of Intercultural Competence. Thousand Oaks, CA: SAGE Publications, Inc. - Bennett, J. M. (2015). "Intercultural Competence Development." The SAGE Encyclopedia of Intercultural Competence. Thousand Oaks, CA: SAGE Publications, Inc. - "10 Reasons Why We Need Diversity on College Campuses." Center for American Progress. 2016. Web. 2 Feb 2016. LICENSES AND ATTRIBUTIONS LICENSES AND ATTRIBUTIONS CC LICENSED CONTENT, ORIGINAL - Diversity and Cultural Competency. Authored by: Laura Lucas. Provided by: Austin Community College. License: CC BY: Attribution CC LICENSED CONTENT, SPECIFIC ATTRIBUTION - Chapter cover image. Authored by: maxlkt. Provided by: Pixabay. Located at: https://pixabay.com/en/hand-united-hands-united-together-1917895/. License: CC0: No Rights Reserved - Gender Identity. Provided by: Wikipedia. Located at: https://en.wikipedia.org/wiki/Gender_identity. License: CC BY-SA: Attribution-ShareAlike - 9.2 Living with Diversity. Provided by: University of Minnesota Libraries. Located at: http://open.lib.umn.edu/collegesuccess/chapter/9-2-living-with-diversity/. License: CC BY-NC-SA: Attribution-NonCommercial-ShareAlike ALL RIGHTS RESERVED CONTENT - Cultural Competency at Rutgers University Behavioral Health Care. Provided by: UBHC Production Studio. Located at: https://www.youtube.com/watch?v=c-h1ZuRXBpg. License: All Rights Reserved. License Terms: Standard YouTube License LUMEN LEARNING AUTHORED CONTENT - Diversity and Accessibility. Located at: https://courses.lumenlearning.com/collegesuccess-lumen/chapter/diversity-and-accessibility/. License: CC BY: Attribution	oercommons	2025-03-18T00:35:14.388549	Gail Sabo	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/74991/overview", "title": "Diversity and Cultural Competency", "author": "Unit of Study" }
https://oercommons.org/courseware/lesson/117688/overview	Education Standards Digital Citizenship Power Point Digital Citizenship Overview This is a lesson on the topic of Digital Citizenship. Digital Citizenship-Instructions Everyone needs to have enough information and knowlegde about Digital Citizenship to be safe. This is a short overview on the topic of Digital Citizenship. This lesson contains information about Digital Citizenship. Please view the information in this lesson. Digital Citizenship-Video Digital Citizenship-Power Point Please view this presentation. Digital Citizenship-Article Please read this article.	oercommons	2025-03-18T00:35:14.412522	07/08/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/117688/overview", "title": "Digital Citizenship", "author": "Joy Whitlow" }
https://oercommons.org/courseware/lesson/117004/overview	Education Standards Nature Scavenger Hunt (2) Nature Scavenger Hunt Overview Embark on an educational adventure through the fascinating world of mathematics with our math-themed nature scavenger hunt lesson plan. Students will explore the outdoors, engaging in activities that integrate mathematical concepts such as shapes, patterns, and measurements found in nature. This interactive experience not only enhances their understanding of math but also cultivates a deeper appreciation for the natural environment. Through hands-on exploration and problem-solving, students will discover the beauty of mathematics all around them, making learning both enriching and enjoyable. Introduction Subjects: • Math • Nature Time: 15-30 minutes Skills: •Basic Math Operations • C• Data collection • Measurement • Teamwork Learning Objective/Goal: - Students will make observations about nature and make connections with math topics - Students can do basic calculations such as multiplication and addition - Students will be able to measure objects they find in nature Materials Needed: - Scavenger Hunt Worksheet (linked below) - Outdoor space in nature (Trees, plants, bushes must be present) - Pen or Pencil - A ruler or a way to measure items - Optional: a prize for the person/group that finishes first Background Background: This scavenger hunt is designed to take place on school grounds where students can have a break from the classroom, while still practicing their math skills. It can be easily modified based on location, duration (adding or taking away tasks) and students' current level. Activity Introduction (5 minutes): - Read over the scavenger hunt tasks and modify them to fit the needs/requirements at your school or location. - Consider making an answer key beforehand. - Introduce the scavenger hunt, potential prize, and any rules or bounds students must follow. - Split into each group and decide a start and stopping point and time. During the Scavenger hunt (15 minutes): - Have the students (not volunteers if using) record the answers on the 3rd page of the worksheet in the correct box. - Remind students of the time and to complete every box periodically. Reflection/Debrief (5 minutes): - When everyone returns to the ending point ask the students how it went. - Compare student answers (between each other or with an answer key). - Go over any hard challenges or skills they struggled with - Give out incentives/awards. - Interview volunteer supervisors on how the activity went. Extra Tips for Students: - Make sure the data collected is accurate. - If working in groups have one person do the task and the other record the answer on the worksheet. - It may help to find a folder or hard object to bear down on when writing answers. Tips for Teachers: - Make sure there is a way to keep an eye on or monitor all students - this may include having a volunteer supervise each group or stay in a closed area - Encourage students to bring water bottles if it is hot outside. - Decide how accurate answers must be for students to earn rewards. Extensions: - Add more items/tasks for the students to complete. - Change the environment to be both indoors and outdoors. - Turn the questions into riddles the students must solve.	oercommons	2025-03-18T00:35:14.442518	Annabel Lee	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/117004/overview", "title": "Nature Scavenger Hunt", "author": "Lesson Plan" }
https://oercommons.org/courseware/lesson/87946/overview	Japan Overview Japan - An Introduction During the nineteenth century Japan was one of a number of traditional societies in Africa and Asia confronted with the military power of the industrialized and imperial powers of the West. These powers, including China, the Ottoman empire, and the Russian empire, each struggled to respond to the economic and military challenges presented by these Western powers. Learning Objectives - Explain the reactions to Western ideas and foreign aggression in Tokugawa Japan in the nineteenth century, particularly within the context of the responses of other tradition, preindustrial societies to impositions by the industrialized West. - Identify the main reforms and their significance during the Meiji Restoration, including within the context of other conservative and traditional societies’ efforts to modernize during the nineteenth century. - Explain the emergence of Japan as a world power by the early 20th century, including within the context of the emergence of other world powers. Key Terms / Key Concepts Tokugawa shogunate: the last feudal Japanese military government, ruling from 1603 to 1867, the end of which paved the way for the Meiji Restoration and the modernization of Japan From the late sixteenth century until 1868 Japan had a feudal political structure and was ruled by a military government that resisted change. This government, the Tokugawa Shogunate, was the third of three feudal shogunates that had ruled Japan from the twelfth century. Toward the end preventing changes that would endanger traditional Japanese culture and society the Tokugawa Shogunate had banned Christianity, outlawed firearms, criminalized any violations and even disrespect of the nation’s hierarchical structure, and ignored the growing role of merchants in the economy, as well as the developing urban culture in cities such as Edo (Tokyo). The Tokugawa also required respect for the emperor as a divine presence, only recognized the indigenous religion of Shintoism, and continued to embrace the traditional weapons and tactics of warfare. During the nineteenth century Japan had to determine how to respond to the power of the new industrialized imperial powers, as did other traditional African and Asian societies, such as the Zulu in southern Africa, China in east Asia, Russia in Eurasia, and the Ottoman empire in Africa and Eurasia. Of these traditional societies, Japan’s response was the most successful. After being confronted with foreign powers and enduring a civil war over how to respond, Japan by the late nineteenth century had embarked on a path of selective modernization and Westernization that would propel the nation into the ranks of the major world powers by the First World War. Among traditional Asian societies which attempted to modernize during the nineteenth and early twentieth centuries, including China and the Ottoman and Russian empires, Japan came closest to matching the Western imperial powers. However, facing discrimination and hostility from established Western industrialized imperial powers in reaction to Japanese imperial accomplishments, particularly in wars against China and Russia, Japan became alienated from them. Following the First World War authoritarian, militaristic, and nationally chauvinistic Japanese leaders exploited this feeling of alienation and took the Japanese empire down a self-destructive path that ultimately led to its dissolution. Meiji Restoration While China struggled with modernization during the nineteenth and first half of the twentieth century, Japan embraced it with the Meiji Restoration. As a result, within half a century, Japan had evolved from a conservative, preindustrial society cut off from the outside world, to a modern, industrializing world power that had taken control of its own destiny. At the forefront of the Meiji Restoration was the new Japanese government, a combination of Japanese tradition, along with institutions and practices adapted from Western national governments, based on principles of representative and responsible government. The first principle of the new government, a part of Japanese tradition, was that the emperor and his ministers were at the center of the government, and that initiative lay with them. This principle defined the course of the Meiji Restoration and Japanese modernization. Learning Objectives - Explain the reactions to Western ideas and foreign aggression in Tokugawa Japan in the nineteenth century, particularly within the context of the responses of other tradition, preindustrial societies to impositions by the industrialized West. - Identify the main reforms and their significance during the Meiji Restoration, including within the context of other conservative and traditional societies’ efforts to modernize during the nineteenth century. - Explain the emergence of Japan as a world power by the early 20th century, including within the context of the emergence of other world powers. Key Terms / Key Concepts Tokugawa shogunate: the last feudal Japanese military government, ruling from 1603 to 1867, the end of which paved the way for the Meiji Restoration and the modernization of Japan Iwakura Mission: 1871-3 Japanese diplomatic mission to the United States and Europe toward the end of furthering Japanese modernization zaibatsu: industrial and financial business conglomerates in the Empire of Japan, emerging as part of the Meiji Restoration, and becoming influential players in Japan until the end of World War II 1890 Constitution - Japanese constitution promulgated as part of the Meiji Restoration, which provided for a conservative national government with select republican features and responsibility of government ministers to the emperor Bakumatsu The Tokugawa Shogunate came to an end during a period known as the Bakumatsu from 1853 to 1867, also known as the last years of the Edo period, when the Tokugawa shogunate ended. During this period Japan ended its isolationist foreign policy known as sakoku and changed from a feudal Tokugawa shogunate to the pre-modern empire of the Meiji government. In this transition from the Tokugawa Shogunate to the Meiji government pro-imperial nationalists called ishin shishi, who sought to end the Tokugawa Shogunate, triumphed over pro-Tokugawa forces, including elite shinsengumi swordsmen. Although these two groups were the most visible powers, many other factions attempted to use the chaos of Bakumatsu to seize power. There were two other main driving forces for dissent: growing resentment among outside feudal lords and growing anti-western sentiment following the arrival of Matthew C. Perry and the resulting end of isolationism. The feudal lords fought against Tokugawa forces at the Battle of Sekigahara in 1600 and had from that point on been excluded permanently from all powerful positions within the shogunate. The anti-Western sentiment was often expressed in the phrase sonnō jōi, or “revere the Emperor, expel the barbarians.” During the last years of the Bakumatsu, the Tokugawa Shogunate took strong measures to try to reassert its dominance, although its involvement with modernization and foreign powers made it a target of anti-Western sentiment throughout the country. The Shogunate sent naval students to study in Western schools for several years, starting a tradition of foreign-educated future leaders. By the end of the Tokugawa shogunate in 1868, the Japanese navy already possessed eight western-style steam warships. In 1867 France established a military mission in Japan to help modernize the Shogunate armies. Japan sent a delegation to and participated in the 1867 World Fair in Paris. Tokugawa Yoshinobu took over the position of shogun at the time of massive turmoil. The opening of Japan to uncontrolled foreign trade brought massive economic instability. While some entrepreneurs prospered, many others went bankrupt. Unemployment and inflation rose. Coincidentally, major famines increased the price of food drastically. Incidents occurred between brash foreigners, qualified as “the scum of the earth” by a contemporary diplomat, and the Japanese. Boshin War The last step in the demise of the Tokugawa Shogunate was the 1868-9 Boshin War, a civil war between factions in support of a more rapid of modernization through the Meiji Emperor and factions that favored a slower more conservative pace through the Tokugawa Shogunate. The last Tokugawa Shogun, Yoshinobu, accepted that the end of the shogunate was inevitable and imminent. By 1869 pro-Meiji forces, including the Chōshū, Satsuma, and Tosa domains, as well as court officials, had triumphed over pro-Tokugawa forces. While the triumph of pro-Meiji forces ended the Tokugawa Shogunate, the last uprising against the Meiji Restoration, the Satsuma Rebellion did not occur until 1877. The defeat of the Satsuma Rebellion marked the end of organized efforts to restore the Tokugawa Shogunate. The Meiji Restoration and the resultant modernization of Japan influenced Japanese self-identity with respect to its Asian neighbors, as Japan became the first Asian state to modernize based on the European model, replacing the traditional Confucian hierarchical order that persisted previously under a dominant China with one based on modernity. Meiji Restoration The fall of Edo in 1868 marked the end of the Tokugawa shogunate, and a new era was proclaimed: Meiji. The first reform was the proclamation of the Charter Oath in 1868, a general statement of the aims of the Meiji leaders to boost morale and win financial support for the new government. Its main provisions included the establishment of assemblies, the involvement of all classes in carrying out state affairs, the revocation of class restrictions on employment, the introduction of the “just laws of nature,” and the search for international expertise to strengthen the foundations of imperial rule. Implicit in the Charter Oath was an end to exclusive political rule by the bakufu (a shogun’s direct administration including officers) and a move toward more democratic participation in government. To implement the Charter Oath, a short-lived constitution was drawn up in 1868. Besides providing for a new Council of State, legislative bodies, and systems of ranks for nobles and officials, it limited office tenure to four years, allowed public balloting, provided for a new taxation system, and ordered new local administrative rules. The Meiji government assured the foreign powers that it would follow the old treaties negotiated by the bakufu and announced that it would act in accordance with international law. Mutsuhito, who was to reign until 1912, selected a new reign title—Meiji, or Enlightened Rule—to mark the beginning of a new era in Japanese history. To further dramatize the new order, the capital was relocated from Kyoto, where it had been situated since 794, to Tokyo (Eastern Capital), the new name for Edo. In a move critical for the consolidation of the new regime, most daimyōs voluntarily surrendered their land and census records to the emperor in the abolition of the han (feudal domain) system, symbolizing that the land and people were under the emperor’s jurisdiction. Confirmed in their hereditary positions, the feudal lords became governors and the central government assumed their administrative expenses and paid samurai stipends. The han were replaced with prefectures in 1871 and authority continued to flow to the national government. Officials from the favored former han, such as Satsuma, Chōshū, Tosa, and Hizen, staffed the new ministries. Formerly old court nobles and lower-ranking but more radical samurai became a new ruling class. New Imperial Government After the Meiji restoration, the leaders of the samurai who overthrew the Tokugawa shogunate had no clear agenda or pre-developed plan on how to run Japan. Immediately after the resignation of Tokugawa Yoshinobu in 1867, with no official centralized government, the country was a collection of largely semi-independent feudal domains (the han system), held together by the prestige of the Imperial Court and the military strength of the Satchō Alliance (military alliance between the feudal domains of Satsuma and Chōshū formed in 1866 to combine their efforts to restore Imperial rule). In 1868, with the outcome of the Boshin War still uncertain, the new Meiji government summoned delegates from all of the domains to Kyoto to establish a provisional consultative national assembly. The Charter Oath was promulgated, in which Emperor Meiji set out the broad general outlines for Japan’s development and modernization. The same year, an administrative code known as Seitaisho was decreed to establish the new administrative basis for the Meiji government. It was a mixture of western concepts, such as division of powers and a revival of ancient Japanese structures of bureaucracy. Centralization: Abolition of Han System In 1869, the central government led by Ōkubo Toshimichi of Satsuma felt strong enough to effect centralization. After merging the armies of Satsuma and Chōshū into a combined force, Ōkubo and Kido Takayoshi convinced the feudal lords (daimyō) of Satsuma—Chōshū, Hizen, and Tosa—to surrender their domains to the emperor. Other daimyō were forced to do the same and all were reappointed as governors to their respective domains, now treated as sub-divisions of the central government. In 1871, Ōkubo and several other leaders held a secret meeting and decided to completely abolish the han domains. Eventually, all of the ex-daimyō were summoned to the emperor, who issued a decree converting the domains to prefectures headed by a bureaucratic appointee from the central government. The daimyō were generously pensioned into retirement and their castles became the local administrative centers for the central government. By the end of 1871, Japan was a fully centralized state. The transition was made gradually to avoid disruption to the lives of the common people and outbreaks of resistance or violence. The central government absorbed all of the debts and obligations of the domains and many former officials found new employment with the central government. In 1871, after the han domains were abolished, the central government supported the creation of consultative assemblies at the town, village, and county levels. The membership of the prefectural assemblies was drawn from these local assemblies. As the local assemblies only had the power of debate and not legislation, they provided an important safety valve without the ability to challenge the authority of the central government. The Meiji Constitution The Meiji Constitution, proclaimed in 1889, enacted in 1890, and known as the 1890 Constitution, established a mixed constitutional and absolute monarchy, with the emperor as head of state and the prime minister as head of government, creating tensions between opposing groups favoring a democratic or authoritarian government. Prior to the Meiji Restoration, Japan had no written constitution, and the idea of one became a subject of heated debate. The conservative Meiji oligarchy viewed anything resembling democracy or republicanism with suspicion. The Freedom and People’s Rights Movement demanded the immediate establishment of an elected national assembly and the promulgation of a constitution. In 1881, Itō Hirobumi was appointed to chair a government bureau to research various forms of constitutional government and in 1882, Itō led an overseas mission to observe and study various systems first-hand. The United States Constitution was rejected as too liberal. The French and Spanish models were rejected as tending toward despotism. The Reichstag and legal structures of the German Empire, particularly that of Prussia, proved to be of the most interest to the Constitutional Study Mission. Influence was also drawn from the British Westminster system, although it was considered being unwieldy and granting too much power to Parliament. The Council of State was replaced in 1885 with a cabinet headed by Itō as Prime Minister. The draft committee included Japanese officials along with a number of foreign advisers, in particular some German legal scholars. The central issue was the balance between sovereignty vested in the person of the emperor and an elected representative legislature with powers that would limit or restrict the power of the sovereign. The final version, drafted without public debate, was submitted to Emperor Meiji in 1888. The new constitution was promulgated by Emperor Meiji on February 11, 1889 (the National Foundation Day of Japan in 660 BC), coming into effect in 1890. The first National Diet of Japan, a new representative assembly, convened on the day the Meiji Constitution came into force. The organizational structure of the Diet reflected both Prussian and British influences, most notably in the inclusion of the House of Representatives as the lower house and the House of Peers as the upper house. The second chapter of the constitution, detailing the rights of citizens, bore a resemblance to similar articles in both European and North American constitutions of the day. The Meiji Constitution established clear limits on the power of the executive branch and the emperor. It also created an independent judiciary. Civil rights and civil liberties were guaranteed, although in many cases they were subject to limitation by law. Unlike its modern successor, the Meiji Constitution was founded on the principle that sovereignty resided in person of the emperor, by virtue of his divine ancestry “unbroken for ages eternal,” rather than in the people. The emperor had the right to exercise executive authority and to appoint and dismiss all government officials. He also had the sole rights to declare war, make peace, conclude treaties, dissolve the lower house of Diet, and issue Imperial ordinances in place of laws when the Diet was not in session. Most importantly, command over the Imperial Japanese Army and Imperial Japanese Navy was directly held by the emperor and not the Diet. The Cabinet consisted of Ministers of State who answered to the emperor rather than the Diet. The Privy Council, an advisory council to the Emperor of Japan, was also established. Not mentioned in the Constitution were the genrō, an inner circle of advisers to the emperor, who wielded considerable influence. The Privy Council consisted of a chairman, a vice chairman (non-voting), 12 (later expanded to 24) councilors, a chief secretary, and three additional secretaries. All privy councilors were appointed by the emperor for life, on the advice of the prime minister and the cabinet. In addition to the 24 voting privy counselors, the prime minister and the other ministers of state were ex officio members of the council. The Meiji Constitution was ambiguous in wording and in many places self-contradictory. The leaders of the government and the political parties were left to interpret whether the Meiji Constitution could be used to justify authoritarian or liberal-democratic rule. It was the struggle between these tendencies that dominated the government of the Empire of Japan. Following Japan’s defeat in World War II, the Meiji Constitution was replaced by a new document, the postwar Constitution of Japan. This document—officially an amendment to the Meiji Constitution—replaced imperial rule with a form of Western-style liberal democracy. Japan’s Industrial Revolution The rapid industrialization of Japan during the Meiji period resulted from a carefully engineered transfer of Western technology, modernization trends, and education led by the government in partnership with the private sector. Iwakura Mission The Industrial Revolution in Japan began about 1870 when Meiji period leaders decided to catch up with the West. In 1871, a group of Japanese statesmen and scholars known as the Iwakura Mission embarked upon a voyage across Europe and the United States. The mission is the most well-known and possibly most significant in terms of its impact on the modernization of Japan after a long period of isolation from the West. It was first proposed by the influential Dutch missionary and engineer Guido Verbeck, based to some degree on the model of the Grand Embassy of Peter I. The aim of the mission was threefold: to gain recognition for the newly reinstated imperial dynasty under the emperor Meiji, to begin preliminary renegotiation of the unequal treaties with the dominant world powers, and to explore modern Western industrial, political, military, and educational systems and structures. The mission was named after and headed by Iwakura Tomomi in the role of extraordinary and plenipotentiary ambassador, assisted by four vice-ambassadors. It also included a number of administrators and scholars, totaling 48 people. In addition to the mission staff, about 53 students and attendants joined. Several students were left behind to complete their education in the foreign countries, including five young women who stayed in the United States. Of the initial goals of the mission, the aim of revision of the unequal treaties was not achieved, prolonging the mission by almost four months but also impressing the importance of the second goal on its members. The attempts to negotiate new treaties under better conditions with the foreign governments led to criticism that members of the mission were attempting to go beyond the mandate set by the Japanese government. The missionaries were nonetheless impressed by industrial modernization in America and Europe and the tour provided them with a strong impetus to lead similar modernization initiatives. Industrialization in Japan Japan’s Industrial Revolution first appeared in textiles, including cotton and especially silk, traditionally made in home workshops in rural areas. By the 1890s, Japanese textiles dominated the home markets and competed successfully with British products in China and India. Japanese shippers competed with European traders to carry these goods across Asia and even in Europe. As in the West, the textile mills employed mainly women, half of them younger than age 20. They were sent by and gave their wages to their fathers. Japan largely skipped water power and moved straight to steam-powered mills, which were more productive. That in turn created a demand for coal. To promote industrialization, the government decided that while it should help private business to allocate resources and to plan, the private sector was best equipped to stimulate economic growth. The greatest role of government was to help provide the economic conditions in which business could flourish. In the early Meiji period, the government-built factories and shipyards were sold to entrepreneurs at a fraction of their values. Many of these businesses grew rapidly into larger conglomerates. The government emerged as chief promoter of private enterprise, enacting a series of pro-business policies. The government also provided infrastructure, : building railroads, improving roads, and inaugurating a land reform program to prepare the country for further development. Social Changes Important social changes supported by the government also fueled industrialization. One of the biggest economic impacts of the period was the end of the feudal system. With a relatively loose social structure, the Japanese were able to advance through the ranks of society more easily than before by inventing and selling their own wares. The Japanese people also now had greater access to education. The Meiji period leaders inaugurated a new Western-based education system for all young people, sent thousands of students to the United States and Europe, and hired more than 3,000 Westerners to teach modern science, mathematics, technology, and foreign languages in Japan. With a more educated population, Japan’s industrial sector grew significantly. Tsuda Umeko, who left Japan to study in the US at the age of 7, returned to Japan in 1900 and founded Tsuda College. It remains one of the most prestigious women’s institutes of higher education in Japan. Although Tsuda strongly desired social reform for women, she did not advocate feminist values and opposed the women’s suffrage movement. Her activities were based on her philosophy that education should focus on developing individual intelligence and personality. Government vs. Private Sector The government initially was involved in economic modernization, providing a number of “model factories” to facilitate the transition to the modern period. Economic reforms included a unified modern currency based on the yen, banking, commercial and tax laws, stock exchanges, and a communications network. Establishment of a modern institutional framework conducive to an advanced capitalist economy took time, but it was completed by the 1890s. By this time, the government had largely relinquished direct control of the modernization process, primarily for budgetary reasons. From the onset, the Meiji rulers embraced the concept of a market economy and adopted British and North American forms of free enterprise capitalism. The private sector—in a nation with an abundance of aggressive entrepreneurs—welcomed such change. Hand in hand, industrial and financial business conglomerates known as zaibatsu and government guided the nation, borrowing technology from the West. Many of the former feudal lords, whose pensions had been paid in a lump sum, benefited greatly through investments they made in emerging industries. Those who had been informally involved in foreign trade before the Meiji Restoration also flourished. Old firms that clung to their traditional ways failed in the new business environment. After the first twenty years of the Meiji period, the industrial economy expanded rapidly with inputs of advanced Western technology and large private investments. Implementing the Western ideal of capitalism into the development of technology and applying it to their military helped make Japan into both a militaristic and economic powerhouse by the beginning of the 20th century. Stimulated by wars and through cautious economic planning, Japan emerged from World War I as a major industrial nation. Japan gradually took control of much of Asia’s market for manufactured goods. The economic structure became very mercantilistic, importing raw materials and exporting finished products—a reflection of Japan’s relative poverty in raw materials. Consequences The phenomenal industrial growth sparked rapid urbanization. The proportion of the population working in agriculture shrank from 75 percent in 1872 to 50 percent by 1920. Japan enjoyed solid economic growth during the Meiji period and most people lived longer and healthier lives. The population rose from 34 million in 1872 to 52 million in 1915. Like in other rapidly industrializing countries, poor working conditions in factories led to growing labor unrest, and many workers and intellectuals came to embrace socialist ideas. The Meiji government responded with harsh suppression of dissent. Radical socialists plotted to assassinate the Emperor in the High Treason Incident of 1910, after which the Tokkō secret police force was established to root out left-wing agitators. The government also introduced social legislation in 1911, setting maximum work hours and a minimum age for employment. Taken together the changes in Japan in the Meiji period propelled the country into the ranks of the modern nations of the world, and the great powers. Emergence of Japan as a World Power As part of the Meiji Restoration, Japan emerged as a world power, with the acquisition of territories in northeast Asia and the western Pacific. This emergence included the formulation and pursuit of a new set of national goals as a world power, a reorientation of Japanese foreign policy, changes in relationships with imperial rivals and other world powers, and the modernization of Japanese military and naval forces. By the beginning of the First World War Japan’s development as a world power, along with discriminatory treatment by Russia and the European powers, would lay some of the foundations for Japanese participation as an Axis Power in the Second World War. Learning Objectives - Identify the main reforms and their significance during the Meiji Restoration, including within the context of other conservative and traditional societies’ efforts to modernize during the nineteenth century. - Explain the emergence of Japan as a world power by the early 20th century, including within the context of the emergence of other world powers. Key Terms / Key Concepts Treaty of Kanagawa: 1854 treaty imposed by the U.S. on the Tokugawa Shogunate, which, along with similar treaties imposed by various European powers, paved the way for the transition from the Tokugawa Shogunate to the Meiji Restoration Anglo-Japanese Treaty of Alliance: 1902 treaty between Japan and the United Kingdom that marked British recognition of Japan’s emergence as a world power First Sino-Japanese War: 1894-5 war between China and Japan, primarily about influence over Korea, that Japan won, as part of its emergence as a world power Treaty of Shimonoseki: 1895 treaty between Japan and China on Japanese terms, reflecting Japan's emergence as a regional power Triple Intervention: a diplomatic intervention by Russia, Germany, and France in 1895 reversing a number of terms in the Treaty of Shimonoseki, toward the end of discounting Japan's emergence as a regional power Russo-Japanese War: 1904-5 war between Russia and Japan, primarily about influence over Korea and Manchuria, that Japan won, as part of its emergence as a world power Battle of Tsushima Strait - concluding naval battle of the Russo-Japanese War fought between the Japanese and Russian Pacific fleets on 27-28 May 1905 in the strait between Japan and Korea, in which the Japanese fleet sunk 21 Russian ships and captured five others, leading to peace on Japanese terms 1905 Treaty of Portsmouth - treaty that ended the Russo-Japanese War on Japanese terms in northeastern Asia and reflected Japan's growing strength as a world power Japanese Militarization The modernization of the Japanese military during the Meiji period was a response to the growing presence and threat of Western colonial powers. It followed Western European military models, ending the centuries-long dominance of the samurai class. Meiji Militarization Efforts In 1853 Commodore Matthew Perry inadvertently set off a chain of events leading to the Meiji Restoration and the rise of Japan as a world power with the visit of a U.S. naval squadron to Tokyo Bay. One of the purposes of his expedition was to open diplomatic relations with Japan. After Commodore Perry forced the signing of the Treaty of Kanagawa the next year, Japanese elites concluded that they needed to modernize the Japanese military and navy or risk further coercion from Western powers. The Tokugawa shogunate did not officially share this point of view, which was one factor in its downfall. But it was not until the beginning of the Meiji Era in 1868 that the Japanese government begin to modernize the military and the navy. Modernization of the Japanese military and navy included technological modernization, the use of new industrial manufacturing capabilities, and the democratization of the army and the navy. Toward these ends in 1868, the Japanese government established the Tokyo Arsenal, in which small arms and associated ammunition were developed and manufactured. Also in 1868, Masujiro Omura established Japan’s first military academy in Kyoto. In 1870, another arsenal opened in Osaka. At that site, machine guns and ammunition were produced, and four gunpowder facilities were opened. Under the new Meiji government, Omura—regarded today as the father of the modern Japanese army—was appointed to a post equivalent to vice minister of war. He was tasked with the creation of a national army along western lines and sought to introduce conscription and military training for commoners, rather than rely on a hereditary feudal force. He also strongly supported the abolition of the han system (feudal domains) and with it the numerous private armies maintained by the feudal lords, which he considered a drain on resources and a potential threat to security. Omura faced opposition from many of his peers, including most conservative samurai, who saw his ideas on modernizing and reforming the Japanese military as too radical, ending not only the livelihood of thousands of samurai but also their privileged position in society. In 1869, a group of ex-samurai assassinated Omura. When the Emperor Meiji assumed all the powers of state, he ordered the formation of Imperial Guard to protect himself, the Japanese imperial family, and their properties. In 1867, the Imperial Guard was formed from loyal retainers and former samurai. This unit would go on to form the nucleus of the new Imperial Japanese Army. By the 1870s the Imperial Guard, which had been organized and trained along French military lines, consisted of 12,000 officers and men. In 1873, the Conscription Law was passed, requiring every able-bodied male Japanese citizen, regardless of class, to serve a mandatory term of three years with the first reserves and two additional years with the second reserves. This monumental law, signifying the beginning of the end for the samurai class, initially met resistance from both the peasants and warriors. The peasant class interpreted the term used for military service—ketsu-eki (blood tax)—literally and attempted to avoid service by any means necessary, including self-mutilation, and protesting. The Conscription Law was also a method of social control, placing the unruly samurai class back into their roles as warriors. The Meiji Restoration initially caused dissent among the samurai class and the conscription system was a way of stabilizing that dissent. The samurai were generally resentful of the new, western-style military and at first refused to stand in formation with the lowly peasant class. Some of the samurai, more disgruntled than the others, formed pockets of resistance to circumvent the mandatory military service. Many committed self-mutilation or openly rebelled. The law also allowed the military to educate the enlisted, providing opportunities for both basic (e.g., learning how to read) and advanced education, as well as career advancement. The government realized that an educated soldier could be a more productive member of society, and education was seen as a path to the advancement of the state. Military service also required a medical examination. Those unable to pass the exam were sent back to their families. While there was no material penalty for failing the exam, the practice created a division between those able to serve the country and those who were not. The latter were often marginalized by society. In conjunction with the new law, the Japanese government began modeling their ground forces after the French military, and the new Japanese army used the same rank structure as the French. The French government contributed substantially to the training of Japanese officers. Many were employed at the military academy in Kyoto and many more were feverishly translating French field manuals for use in the Japanese ranks. End of the Samurai Class An imperial rescript of 1882 called for unquestioning loyalty to the emperor by the new armed forces and asserted that commands from superior officers were equivalent to commands from the emperor himself. Thenceforth, the military existed in an intimate and privileged relationship with the imperial institution. Top-ranking military leaders were given direct access to the emperor and the authority to transmit his pronouncements directly to the troops. The sympathetic relationship between conscripts and officers, particularly junior officers who were drawn mostly from the peasantry, tended to bring the military closer to the people, and contribute to the militarization of Japanese society from the Meiji Restoration to the Second World War. In time, most people came to look for guidance in national matters from military commanders rather than from political leaders. From the Meiji Restoration to the 1931 Japanese invasion of Manchuria Japanese military leaders gradually came to disregard then usurp the civilian government. An early such instance occurred in 1871 when a Ryukyuan ship shipwrecked on Taiwan, and the crew was massacred. In 1874, using the incident as a pretext, Japan sent a military expedition to Taiwan meant to assert its claims to the Ryukyu Islands. The expedition featured the first instance of the Japanese military ignoring the orders of the civilian government, as the expedition set sail after being ordered to postpone. At home, the decisive test for the new army came in 1877 when Saigō Takamori led the Satsuma Rebellion—the last samurai rebellion. Its name comes from Satsuma Domain, which became home to unemployed samurai after military reforms rendered their status increasingly obsolete. Kumamoto castle was the site of the first major engagement when garrisoned forces fired on Saigō’s army, as they attempted to force their way into the castle. Two days later, Saigō’s rebels, while attempting to block a mountain pass, encountered advanced elements of the national army en route to reinforce Kumamoto castle. After a short battle, both sides withdrew to reconstitute their forces. A few weeks later the national army engaged Saigō’s rebels in a frontal assault at what now is called the Battle of Tabaruzuka. During this eight-day battle, Saigō’s nearly 10,000-strong army battled hand-to-hand with the equally matched national army. Both sides suffered nearly 4,000 casualties. Due to conscription, however, the Japanese army was able to reconstitute its forces, while Saigō’s was not. Later, forces loyal to the emperor broke through rebel lines and managed to end the siege on Kumamoto castle after 54 days. Saigō’s troops fled north and were pursued by the national army. The national army caught up with Saigō at Mt. Enodake. Saigō’s army was outnumbered seven-to-one, prompting a mass surrender of many samurai. The rebellion ended following the final engagement with Imperial forces, which resulted in the deaths of the remaining 40 samurai including Saigō, who was honorably beheaded by his retainer after suffering a fatal bullet wound. The national army’s victory validated the modernization of the Japanese army and ended the era of the samurai. Financially, crushing the Satsuma Rebellion cost the government greatly, forcing Japan off the gold standard and causing the government to print paper currency. The rebellion also effectively ended the samurai class, along with the concept of an explicit warrior caste in this new Japanese society, as the new Imperial Japanese Army built of conscripts without regard to social class had proven itself in battle. Foreign Policy in the Meiji Period Meiji Japan’s foreign policy was defined from the outset by the vision of gaining recognition as not only a major Asian power, but also a major world power in an international order dominated by the West. Toward the end of achieving this vision the principal foreign policy goals of the Meiji period (1868 – 1912) included securing the integrity and independence of Japan against Western domination and winning equal status with the leading nations of the West by reversing the unequal treaties they forced on Japan. Because fear of Western military power was the chief concern for the Meiji leaders, their highest priority was building up the military. With such power Japan would be able to wrest the respect of the Western powers and achieve equal status with them in the international community, even if the Western powers did not explicitly admit such status. The unequal treaties first imposed on Japan by the Western Powers when they forcefully reopened Japan symbolized Japan’s unequal status during the 1850s, before the Meiji Restoration. The treaties were objectionable to the Japanese not only because they imposed low fixed tariffs on foreign imports, and thus handicapped domestic industries, but also because their provisions gave a virtual monopoly of external trade to foreigners and granted extraterritorial status to foreign nationals in Japan, exempting them from Japanese jurisdiction and placing Japan in the inferior category of nations incapable of determining their own laws. Many of the social and institutional reforms of the Meiji period were designed to remove the stigma of backwardness and inferiority represented by the unequal treaties, and a major task of Meiji diplomacy was to press for the revision of the treaties. Overseas Expansion The Meiji government used the newly created military to extend Japanese power overseas. Meiji leaders believed national security depended on territorial expansion and not merely a strong defense. In 1873 and 1874, friction came about between China and Japan over Taiwan, particularly when the Japanese launched the previously referenced punitive expedition into Taiwan after several Okinawans were killed by Taiwanese aborigines. Later, after Japan’s victory in the First Sino-Japanese War (1894 – 95), the peace treaty ceded the island to Japan. The Japanese realized that its home islands could only support a limited resource base and hoped that Taiwan, with its fertile farmlands, would provide additional resources for further imperial expansion. By 1905, Taiwan was producing significant amounts of rice and sugar. Perhaps more importantly, Japan gained enormous prestige by being the first non-Western country to operate a modern colony, in which Japan installed a police state. The Korean Peninsula, a strategically located feature critical to the defense of the Japanese archipelago, occupied Japan’s attention in the late nineteenth century. Earlier tension over Korea had been settled temporarily through the Japan–Korea Treaty of 1876, which opened Korean ports to Japan, as well as through the Tianjin Convention in 1885, which provided for the removal from Korea of both Chinese and Japanese troops sent to support contending factions in the Korean court. In effect, the convention made Korea a co-protectorate of China and Japan at a time when Russian, British, and American interests in the peninsula were also increasing. As a result of their intensifying competition over Korea, China and Japan went to war in 1894, a conflict that came to be known as the First Sino-Japanese War. After nine months of fighting, China and Japan agreed to a cease-fire and initiated peace talks. The resulting Treaty of Shimonoseki provided for the recognition of Korean independence, the cessation of Korean tribute to China, a 200 million tael indemnity to Korea from China (the equivalent in 1895 of $150 million US), the opening of Chang Jiang (Yangtze River) ports to Japanese trade, and the cession to Japan of Taiwan, the Penghu Islands, and the Liaodong Peninsula. It also assured Japanese rights to engage in industrial enterprises in China. Ironically, a decade after the Treaty of Shimonoseki forced China to recognize Korean independence, Japan, in the wake of the Russo-Japanese War, effectively forced Korea to sign the Eulsa Protective Treaty, which made it a protectorate of Japan. In 1910, Korea was formally annexed to the Japanese empire, beginning a period of Japanese colonial rule of Korea that would not end until 1945. Western Response Immediately after the terms of the treaty became public, Russia—with its own designs on and sphere of influence in China—expressed concern about the Japanese acquisition of the Liaodong Peninsula and the possible impact of the terms of the treaty on the stability of China, not to mention Russian interests in northeast Asia. Russia persuaded France and Germany to apply diplomatic pressure on Japan for return of the territory to China in exchange for a larger indemnity (Triple Intervention). Threatened with a tripartite naval attack by these three powers in Korean waters, Japan decided to give back Liaodong in return for a larger indemnity from China. Russia moved to fill the void by securing from China a 25-year lease of Dalian (Dairen in Japanese, also known as Port Arthur) and rights to the South Manchurian Railway Company, a semi-official Japanese company, to construct a railroad. Russia also wanted to lease more Manchurian territory, and although Japan was loath to confront Russia over this issue, it did move to use Korea as a bargaining chip. Japan would recognize Russian leaseholds in southern Manchuria if Russia would leave Korean affairs to Japan. The Russians only agreed not to impede the work of Japanese advisers in Korea, but Japan was able to use diplomatic initiatives to keep Russia from leasing Korean territory in 1899. At the same time, Japan was able to wrest a concession from China that the coastal areas of Fujian Province, across the strait from Taiwan, were within Japan’s sphere of influence and could not be leased to other powers. Japan also succeeded in attracting a Western ally to its cause. Japan and Britain, both of whom wanted to keep Russia out of Manchuria, signed the Anglo-Japanese Alliance Treaty in 1902, which stayed in effect until 1921 when the two signed the Four Power Treaty on Insular Possessions, taking effect in 1923. The British recognized Japanese interests in Korea and assured Japan they would remain neutral in case of a Russo-Japanese war but would become more actively involved if another power (an allusion to France) entered the war as a Russian ally. In the face of this joint threat, Russia became more conciliatory toward Japan and agreed to withdraw its troops from Manchuria in 1903. The new balance of power in Korea favored Japan and allowed Britain to concentrate its interests elsewhere in Asia. Hence, the Japanese government moved to gain influence over Korean banks, opened its own financial institutions in Korea, and began constructing railroads and obstructing Russian and French undertakings on the peninsula In response to the alliance, Russia sought to form alliances with France and Germany, which Germany declined. In 1902, a mutual pact was signed between France and Russia, which would have unrelated repercussions for Germany in the First World War. China and the United States strongly opposed the alliance. Nevertheless, the nature of the Anglo-Japanese alliance meant that France was unable to come to Russia’s aid in the Russo-Japanese War of 1904, as this would mean war with Britain. Russo-Japanese War When Russia failed to withdraw its troops from Manchuria by an appointed date, Japan issued a protest. Russia replied that it would agree to a partition of Korea at the 39th parallel, with a Japanese sphere to the south and a neutral zone to the north; however, Manchuria was to be outside Japan’s sphere, and Russia would not guarantee the evacuation of its troops. The Russo-Japanese War broke out in 1904 with Japanese surprise attacks on Russian warships at Dalian and Chemulpo (in Korea, now called Incheon). With tremendous loss of life on both sides, the Japanese won a series of land battles and then decisively defeated Russia’s Baltic Sea Fleet (renamed the Second Pacific Squadron) at the Battle of Tsushima Strait in 1905. At a U.S.-mediated peace conference in Portsmouth, New Hampshire, Japanese and Russian representatives negotiated the 1905 Treaty of Portsmouth, marked by terms favorable to Japanese imperial interests in northeast Asia. Russia acknowledged Japan’s paramount interests in Korea and agreed to avoid “military measures” in Manchuria and Korea. Both sides agreed to restore the occupied areas to China and evacuate Manchuria, except for the Guandong Territory (a leasehold on the Liaodong Peninsula). Russia transferred its lease on Dalian and adjacent territories and railroads to Japan, ceded the southern half of Sakhalin to Japan, and granted Japan fishing rights in the Sea of Okhotsk and the Bering Sea. This treaty, which implicitly recognized Japan’s limited victory in this war, was another grudging acknowledgement of Japan’s emergence as a world power and a major power in northeast Asia. From the Meiji Restoration in 1868 to the beginning of the First World War, Japan expanded into a major regional empire in east Asia, acquiring a succession of territories and fighting two successful limited wars against the Chinese and the Russian empires for territories and influence across east Asia and the western Pacific Ocean. Victories over China and Russia, an alliance with Britain, and annexation of Korea marked Japan’s emergence as a world power, but not the recognition of this emergence by the imperial powers of Europe, the United States, or Russia. Regardless of this slight, or, in part, because of it, Meiji Japan went on to become a leader in East Asia and a highly respected military power among the most influential countries in the world. Primary Source: Mitsuhito, Emperor of Japan Letter from Meiji Emperor to U.S. President Grant In 1871, the fledgling Meiji government dispatched a mission of almost fifty high officials and scholars to travel around the world, including extended tours of the United States, Western Europe, Scandinavia, and Russia. The Iwakura Mission (named after its leader, Iwakura Tomomi, 1825-1883) spent almost two years studying the political, economic, social, legal, and educational systems of the developed world as potential models for the modernization of Japan. The leaders of the mission also attempted to begin the renegotiation of the "unequal treaties" — the exploitative diplomatic and economic agreements imposed by the Western powers on Japan in the 1850s, although governments in America and Europe were not yet willing to relax any of their privileges in Japan. This letter from the Emperor Meiji (Mutsuhito, 1852-1912; r. 1867-1912) was presented to U.S. President Ulysses S. Grant (1822-1885) when the Iwakura Mission visited Washington, D.C. “Letter from Meiji Emperor to U.S. President Grant” [Abridged] Mitsuhito, Emperor of Japan (1871) Mitsuhito, Emperor of Japan, etc., to the President of the United States of America, our good brother and faithful friend, greeting: Mr. President: Whereas since our accession by the blessing of heaven to the sacred throne on which our ancestors reigned from time immemorial, we have not dispatched any embassy to the Courts and Governments of friendly countries. We have thought fit to select our trusted and honored minister, Iwakura Tomomi, the Junior Prime Minister (udaijin), as Ambassador Extraordinary … and invested [him] with full powers to proceed to the Government of the United States, as well as to other Governments, in order to declare our cordial friendship, and to place the peaceful relations between our respective nations on a firmer and broader basis. The period for revising the treaties now existing between ourselves and the United States is less than one year distant. We expect and intend to reform and improve the same so as to stand upon a similar footing with the most enlightened nations, and to attain the full development of public rights and interest. The civilization and institutions of Japan are so different from those of other countries that we cannot expect to reach the declared end at once. It is our purpose to select from the various institutions prevailing among enlightened nations such as are best suited to our present conditions, and adapt them in gradual reforms and improvements of our policy and customs so as to be upon an equality with them. With this object we desire to fully disclose to the United States Government the constitution of affairs in our Empire, and to consult upon the means of giving greater efficiency to our institutions at present and in the future, and as soon as the said Embassy returns home we will consider the revision of the treaties and accomplish what we have expected and intended.… Your affectionate brother and friend, Signed Mutsuhito CountersignedSanjō Sanetomi, Prime Minister From Asia for Educators, Weatherhead East Asian Institute, Columbia University This text was adopted from the official translation as reproduced in The New York Times, March 15, 1872. Attributions Images courtesy of Wikipedia Commons and Metropolitan Museum of Art Title Image - Illustration of a Steam Locomotive Running on the Takanawa Railroad in Tokyo (Tōkyō takanawa tetsudō jōkisha sōkō no zu). Attribution: Utagawa Kuniteru, Public domain, via Metropolitan Museum of Art. Provided by: Metropolitan Museum of Art. Location: https://www.metmuseum.org/art/collection/search/55340. License: Creative Commons Zero v1.0 Universal. Boundless World History "From the Edo Period to Meiji Restoration in Japan" Adapted from https://courses.lumenlearning.com/boundless-worldhistory/chapter/from-the-edo-period-to-meiji-restoration-in-japan/ CC LICENSED CONTENT, SHARED PREVIOUSLY - Curation and Revision. Provided by: Boundless.com. License: CC BY-SA: Attribution-ShareAlike CC LICENSED CONTENT, SPECIFIC ATTRIBUTION - Terakoya. Provided by: Wikipedia. License: CC BY-SA: Attribution-ShareAlike - History of Japan. Provided by: Wikipedia. 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Located at: https://commons.wikimedia.org/wiki/File:%E3%80%8A%E9%A9%AC%E5%85%B3%E6%9D%A1%E7%BA%A6%E3%80%8B%E7%AD%BE%E5%AD%97%E6%97%B6%E7%9A%84%E6%83%85%E6%99%AF.jpg. License: Public Domain: No Known Copyright - Punch_Anglo-Japanese_Alliance.jpg. Provided by: Wikipedia. License: Public Domain: No Known Copyright	oercommons	2025-03-18T00:35:14.512449	Neil Greenwood	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/87946/overview", "title": "Statewide Dual Credit World History, European Imperialism and Crises 1871-1919 CE, Chapter 11: Reactions, Japan", "author": "Anna McCollum" }
https://oercommons.org/courseware/lesson/72629/overview	Biological Explanations and Interventions Video Biological Explanations and Interventions for Psychological Disorders: An Introduction Overview An introductory video for biological explanations of and interventions for psychological disorders. This may be a helpful tool to introduce students to biological causes and biological treatments (medicinal and non-medicinal) related to psychological disorders. Suitable for Introductory Psychology, Abnormal Psychology, and other courses that introduce basic knowledge of these topics. Runtime: 18:08 An introductory video for biological explanations of and interventions for psychological disorders. This may be a helpful tool to introduce students to biological causes and biological treatments (medicinal and non-medicinal) related to psychological disorders. Suitable for Introductory Psychology, Abnormal Psychology, and other courses that introduce basic knowledge of these topics. Runtime: 18:08	oercommons	2025-03-18T00:35:14.535090	09/16/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/72629/overview", "title": "Biological Explanations and Interventions for Psychological Disorders: An Introduction", "author": "Michael Mallott" }
https://oercommons.org/courseware/lesson/94231/overview	The Emotional Robot Overview introducing or practicing emotions and recognition Can’t express his/her feelings This Emotional Robot is easy to make and it is a craft to engage with your little one. You’ll have about +/- 15 Minutes of crafting plus endless hours of coloring, play and storytelling with your little one. Have your little one help you with coloring and attaching the flaps to the robot page. It makes the child easier to express his feelings Print off the Emotional Robot Bundle Pack, cut out the flaps, pre-fold the flaps a little and attach them to the robot printable. Color and chat about emotions! In different situations ask the child about his/her feeling and make him/her color it. Activity materials Depends on the no. of students \| the Emotional Robot with Flaps Printable Pack \| Depends on the no. of students \| scissors \| Depends on the no. of students \| tape or glue \| Depends on the no. of students \| coloring&pens \|	oercommons	2025-03-18T00:35:14.549021	Activity/Lab	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/94231/overview", "title": "The Emotional Robot", "author": "Special Education" }
https://oercommons.org/courseware/lesson/11007/overview	African American Civil Rights Aircraft American Decades: 1970s Annotation for Comparing Country Population Data Assessing Technology Integration: The RAT- Replacement, Amplification,and Transformation - Framework Building Resiliance: Getting Started (Scenario) Char Booth's USER Method "Content Curation: Finding the Needles in the Haystacks" by Christopher Lister Curriculum Curation Process: A Modified TPACK Disciplinary repositories "Diversity in Collection Development: An Interpretation of the Library Bill of Rights" (ALA 2014) Final Product: Components of an Annotated Source List Finding Background Information Goodbye SAMR, Hello RATL! Grant Wiggins' Understanding by Design How did the post-war economy, and themes of anxiety and consent impact consumption patterns in the 1950s? Infusing SAMR into Teaching and Learning Introduction to the SAMR Model LibGuides Community LucidChart Venn Diagram Template NoodleTools MLA Lite (free) OER Commons Planning Conversation Matrix Resources' Value to Learners T-Chart Template Technology's Value to Learners "The Trailblazers: The Art of Curation in the Information Forest" by Cathy Evans, Dorcas Hand, Robyn Martin, and David Wee TPACK Explained Venn Diagram Template Curriculum Curation Overview Collection development, a foundational component of the library program, is the formal, professional process of selecting, with the aid of appropriate evaluation tools and knowledge of the school, comprehensive and balanced materials to meet the diverse needs of the community. Rather than using a comprehensive and balanced acquisitions procedure, curriculum curation is a tightly targeted selection process to meet the knowledge and/or cognitive goals of instruction in service of student learning. Rather than generalized pointers to resources, curation will identify a specific section or element within each resource. Therefore, curriculum curation requires co-planning with faculty and using professional discernment, adding value to the chosen resources. Dialogue between librarian and instructor must be part of the curation process In order to surface student learning goals. Such negotiated curation shines a light on the expertise that each educator brings to the conversation about the thinking tasks and relevant experiences that will augment student learning. This module scaffolds and models curating an interdependent set of OER sources and tools to support the instructional core of a unit. Granite State Learning Outcomes 3. Demonstrate the ability to facilitate developmentally appropriate and challenging learning experiences based on the unique needs of each learner (and) make the discipline(s) accessible and meaningful for learners; 6. Design and implement instructional strategies that engage students’ interests and develop their ability to: inquire; think both critically and creatively; and ethically gain and share knowledge; 15. Complete a narrative reflection on the course and personal growth. AASL Competencies AASL Standard 1.2 a: Implement the principles of effective teaching and learning that contribute to an active, inquiry-based approach to learning. AASL Standard 1.2 b: Make use of a variety of instructional strategies and assessment tools to design and develop digital-age learning experiences and assessments in partnership with classroom teachers and other educators. AASL Standard 1.3 a: Model, share, and promote effective principles of teaching and learning as collaborative partners with other educators. AASL Standard 1.4 c: Integrate the use of technologies as a means for effective and creative teaching and to support P-12 students' conceptual understanding, critical thinking and creative processes. PSEL Standard 4 a: Implement coherent systems of curriculum, instruction, and assessment that promote the mission, vision, and core values of the school, embody high expectations for student learning, align with academic standards, and are culturally responsive. PSEL Standard 4 e: Promote the effective use of technology in the service of teaching and learning. Distinguishing Curation from Collection Development Collection development is the professional function of building content and technology resources based on the needs of the school community, the school's ascribed mission and standards, as well as knowledge of the strengths and gaps in the current collection. While curation is described as "adding value" to a set of online resources, educators often conflate the goals of curation with those of collection development. This initial task will ask students to examine this misconception and begin to explore how and why these concepts are different. Collection development is the professional function of building content and technology resources based on the needs of the school community, the school's ascribed mission and standards, as well as knowledge of the strengths and gaps in the current collection. A foundational component of the library program, the goal of a selection process is to choose, with the aid of evaluation tools and a broad knowledge of the school, comprehensive and balanced materials representing diverse points of view for the school community's needs and interests. Begin exploring the role of curriculum curator by reading "Diversity in Collection Development," an interpretation of the The Library Bill of Rights (ALA), "The Trailblazers" (2015), an exploration of the curation process authored by four school librarians and an IT teacher's reflection for a grad class on his evolving insights about effective digital "Content Curation." Drawing and journaling are two methods of exploring and documenting one's understanding of a concept. By blending linguistic information with a nonlinguistic representation in a graphic organizer, your students are prompted to transform their evolving understanding through analysis, evaluation and higher-order thinking. If students are given a choice of representations, they will experience inquiry at self-selected levels of proficiency. The class will need a landing page or another public space so that they can read, view and respond to their peers' individual comparisons of curriculum curation and collection development. Draw on the readings and your own professional practices to document your current understanding of the differences between collection development and curation. Sketch, journal or select a graphic organizer to record what you identify as the key attributes of each concept. For example, you can use a Venn Diagram to visually list the overlaps and distinctions between these two concepts. Or you can use a T-chart to categorizes facets in parallel columns. While private journaling can result in personal growth, public journaling and visual documentation prompt reflective writers to recognize that a learning community can be an important source of growth and emerging insights - rather than a space for finalizing ideas or displaying polished products. Your own commitment to transparent self-analysis and risk-taking sets the stage for shared learning in the classroom and for life. "Wondering is about entertaining and exploring possibilities. It is about hope and faith. It can also be about questioning and doubt..." (Jamie McKenzie) Upload your draft drawing to the designated class sharing-space provided by your instructor so that you and your peers can share emerging insights. Here is a suggested process for peer reviewing a graphic. After viewing these drafts, use the class's public journaling space to respond to these questions: - What do you wonder about curation now? - What behaviors or actions might you question? Planning Resource Curation This task and framework can be grounded in a school curation project using OER resources or the scenario created to stand-in for an actual project. - An advantage of using actual school work is that students can turn to this learning community for advice and then test ideas within the real-world of their schools. - An advantage of using the climate change scenario to stand-in for a real-world project is that the learning community you build for the class can develop common content knowledge and evaluate the same topical sources as they explore the process of curation. You and your students will need a shared space to brainstorm initial questions for the instructor. In preparation for their co-curation meeting with an instructor, each student will select questions from the brainstormed list to add to their "Planning Conversation" template. This rough draft will be refined further before meeting with the instructor. Ultimately the questions will help them precisely identify the goals and clarify the structure of a curricular project. Either (a) identify a school project that involves curating OER resources or (b) use the scenario on climate change below. a. School project: You will work with a specific teacher about learning goals in preparation for curating a set of resources. So that your peers can understand your situation, compose an initial narrative description similar to the scenario below (b) and share it with the class. b. Scenario: A teacher is beginning an action-research project in which student groups with diverse abilities identify a climate problem and then plan, implement and monitor a practical, doable solution. The action-research process is described at the U.S. Climate Resilience Toolkit website where information has been gathered from across U.S. federal government agencies. The website's goal is to help communities and businesses understand actual climate problems, anticipate their risks and options, and identify more "resilient" responses to climate events. Your first step is to understand something about the topic. If you are using the scenario, view "Building Resiliance: Getting Started" and then explore the website in order to understand how resilience will frame the actions students will choose. If you are working on a school-related project (a), use "Finding Background Information" to acquire basic content knowledge and definitions of important disciplinary terms. Add to the class's brainstormed list of questions that you might want to ask your teacher. If you have trouble beginning to brainstorm, start with journalistic question stems like Who...? What...? Where...? When...? and Why...? A Canadian elementary school teacher describes the "added value" of curation in this way: More than merely collecting content on a specific subject; to curate is to make sense of the information we consume online. Strong curation involves carefully selecting content and evaluating it for a specific purpose, topic, or subject. It also involves making decisions about what is and is not useful to deepening understanding of the subject. Content deemed useful can then be customized and personalized, by the curator, by adding ones professional experience to enhance it before sharing that curated content with one’s learning network. Curating is a higher-level thinking skill. In order to curate content that is useful for others the content needs to be synthesized, evaluated, and interpreted before being disseminated. Well curated topics and subjects help to inform and allow learning to happen at faster rates. Planning for curation depends on explicitly identifying learning goals, taught through what instructional process and with what learners. To prepare for a fruitful dialogue with an instructor, this next task uses a matrix, (another graphic organizer) to begin to frame relevant and specific questions at potential entry points. The statement that "students will do an action-research project" does not, in itself, define the kind of learning that is going to happen. One teacher might identify the learning goal of an action-research project as "understanding different trade-offs" while another might want students to "collaboratively learn to solve problems" and a third might emphasize "confident public speaking." Therefore curriculum curation requires conversation with the instructor. To prepare for a negotiated process of co-curation, you will brainstorm questions to help the teacher clearly explain his/her learning goals and instructional orientation, so that you can pinpoint both salient and essential resources. Rather than one set of curated resources, it is likely that you will develop a sequence of curated sets built progressively in response to learning and teaching needs. These may be outlined by the teacher initially but, in practice, may be revised as the unit progresses. A curator’s open-mindedness is a mental shift for most school librarians. Ask questions that will clarify the scope and goals of the teacher’s assignment. Use the "Planning Conversation Matrix" to add and revise questions from the class's brainstormed list in preparation for your meeting with an instructor. A Landscape Scan Professionally librarians are trained in a discipline-neutral information literacy process. However, without content-area background, curated sets of resources may lack an appropriate disciplinary focus. For example, the C3 Framework (66-67), identifies how disciplinary "Ways of Knowing" affect the kinds of data sources that are used by political scientists, economists, geographers and historians below. This step suggests that curators use a landscape scan as a strategy to develop a working bibliography of key sources to bring to the co-curation conversation. All investigations begin by developing background. Whether we are guiding students through an "Immerse phase" or doing scientific research that results in "small modifications of prior knowledge," we are operating under the premise that background frames and fortifies new learning. Initially you developed content background. Your landscape scan will help you locate the hubs and experts that will jump-start the pinpointing of key sources and expert knowledge centers from which you will extract elements to curate for the topic: - LibGuides is a hub of pathfinder-creating experts - around 120,000 librarians from 70+ countries - who are aggregating resources for instructors in over 5000 institutions of different types. - OER Commons is a hub of curriculum experts and instructors at all levels who are developing high-quality open-education resources to meet the needs of teachers and learners. - Discipline-specific repositories are hubs of scholarly work and data within a particular subject. Browse these hubs and bookmark potential experts, resources and tools that you will consider for a working bibliography. Scenario: Many STEM teachers identify time and lack of expertise as barriers to finding media-rich, current and curriculum-linked resources for their curricula (Mardis). One curator uses OER to search the high-school level-resources on glaciers. To see what other librarians are identifying as useful, s/he uses terms like "environmental studies," "Earth Sciences" and "glaciers" to narrow down to relevant curricular pathfinders in LibGuides, a community of multi-type librarians. S/he contacts several curators to ask practical questions about how successful certain approaches have been in their own instruction. From them s/he develops a pool of high-quality hubs and experts that seem to fit the teacher’s learning goals. A working annotated bibliography is a highly specialized type of organizer that acts as a rough-draft for a curated set. It provides a low-stakes platform on which co-curators can discuss and evaluate potential sources. Weed and organize your bookmarks into several working bibliographies, noting why they might be useful in the annotations. You will share these rough draft organizers with your instructional partner. In STEM disciplines your working bibiliographies might support such varied goals as: - Conceptual understanding For example, these sources define and explain the concept of "food sustainability." - Data analysis For example, these sources point to data sources for global poverty and tools for analyzing the data. - Rhetorical analysis For example, this text set by one author who has published his scientific research study in three formats for different audiences. In our scenario, the Toolkit website is a perfect hub because the teacher plans to use its problem-solving process and resources. The site contains a wealth of tools and topics directly related to the project. However, since it has been designed for an adult audience, you will need to pinpoint and scaffold: - content within these sources - directions about using these tools that will enable high school students to participate effectively in the cognitively-rich tasks that the teacher plans to assign. To create and save an annotated MLA Works Cited rough draft list of tools and resources, register for a free NoodleTools MLA Lite account. Rough-Drafting Resources for a Curated Set Distinguishing between just-in-case collection and just-in-time curation is challenging; one always wants to "hedge the bet" by adding a few extra sources. By using a matrix to explicitly align the resources with the instruction or learning goals, the curator can become more rigorous, more willing to reject Google-search knowledge in favor of deeply-targeted, essential resources. While a Google search will aggregate “best guess” relevant resources that “match” a topic, you will target essential resources for specific learning goals contextualized by the teacher's needs and the students' diverse strengths. Less is more. Use a matrix (another type of organizer) to help you cull and evaluate resources. It requires that you identify the teaching and learning criteria that guide your selection. As you add resources, specify the exact learning and instructional goals that they meet. To do this: - Copy the "Resources' Value to Learners" to your own account. - Use the first column of the matrix to identify each teaching or learning goal stated clearly and succintly. - Add a resource by replacing the green placeholder at the top. - Match it to the goal, explaining why in the corresponding matrix cell. Why it is relevant, essential and unique? Acquisition of both knowledge and cognitive process goals are often intertwined, so document both and explain how they will interact. It is time for your students to return to their initial comparison of curation vs. collection development in order to document new understandings. The act of taking notes on notes - in this case, perhaps also revising a sketch - encourages metacognitive awareness and can raise new questions. Rather than erasing their first draft, suggest that they use a new color so that the diagram and words become a visible record of learning. Return to your initial comparison of collection development vs. curation. Using a different color, revise your rough draft diagram (do not erase your first ideas) to reflect your new learning. Upload your draft or drawing to your class space so that your peers can view your emerging insights. After viewing your peers' draft ideas, use your journaling space to respond to this prompt: - What do you wonder about curation now? - What behaviors or actions might you question - and why? Rough-Drafting Technology for a Curated Set A number of models have emerged from educational practice to help teachers select a technology they will use with students. Ostensibly each model's goal is to deepen engagement and amplify learning through technology. However, as this blogger points out, none have been validated in research studies and only some consider the interaction betwen teaching, learning and technology. Rather than favoring one, offer these models as thought-starters and ask curators to organize and frame a process that fits their thinking, instruction and learning within the context of their project. This task continues to characterize graphic organizers as thinking tools rather than forms to complete. Our goal is to have learners recognize that co-curation involves thinking independently as well as interdependenly. Before you include technology as part of a curated set, identify what benefits might accrue from its use. Just as you have done previously with resources, ask yourself why and how they contribute to learning goals. Educators have created a number of frames or models to help teachers decide which technology tool they want to use. While SAMR is the most popular model, various others (RAT, TPACK, IOI) have their own loyal supporters. Their value is in scaffolding your thinking about technology selection. After you familiarize yourself with these models, read "Infusing SAMR into Teaching and Learning" by Aaron Davis, a secondary school English / Humanities teacher and ICT integrator in Melbourne, who weighs the strengths and weaknesses of various models. Your task is to either select and modify one of these models or develop your own hybrid model to guide your curation choices. Return again to the collaborative learning community to draw, share and reflect - identifying the new understandings that have emerged - this time by creating your own graphic organizer to model a curator's thinking process. On what basis does the curator justify particular technologies? In the readings for Task 1, Christopher Lister included a process model of curation practice but it omitted teaching and learning goals. In contrast, the student's graphic organizer should merge a curation thinking process with learning and instructional goals. In an accompanying "Purpose Statement" your curators will explain their thinking map. How do they use linguistic information and a nonlinguistic representation to expose differences between collection development and curation? A thinking map is a graphic organizer which visualizes a thought process (Hyerle). From your reading and professional practices, develop a thinking map that explains your process for technology curation. The map should: - use learning goals as curation criteria - model a dynamic curation process If you are inspired by one of the existing models, modify it to reflect your unique situation and original thinking. One example variation is a revision of TPACK called "Curriculum Curation Process: A Modified TPACK." A second example, "Technology's Value to Learners," retools the resources matrix you used earlier to address technology curation. Your organizer must consider the dynamic relationship between: - the knowledge and cognitive process goals for learners - the teacher's instructional strategies In an accompanying "Purpose Statement," explain why and how this graphic organizer captures the concept of your curation process. How does curation of technology differ from assigning a technology tool? What is the added value? Share your diagram and statement with your learning community. Respond to the diagrams and purpose statements that others post. Moving from Rough-Draft Aggregations to a Curated Set It makes sense that experts spend more time on problem-definition than problem-solving. It's foolish to try to solve a problem you don't understand or work toward a solution which doesn't match your goals. In How to Solve It, George Pólya, a mathematician known for an elegantly simple problem-solving framework, says that understanding the problem is the first step toward solving it. Indeed, when one is able to develop an accurate, complex representation of a problem, creative solutions are more likely to occur. The curator's previous planning has been devoted to defining the problem and developing the necessary background which will be further refined during a co-curation dialogue with an instructor. It is time to listen with respect and empathy to the teacher's characterization of the project, ask thoughtful questions, wrestle with trade-offs and revise working drafts in order to create a curated set of essential and unique resources. Co-curation involves a shift from being expert to actively seeking to understand your partner’s expertise and goals. Rather than immediately presenting a teacher with your “best guess” resources, initiate an exploratory conversation, listen with empathy and ask questions in order to gain insights about gaps in knowledge and the teacher’s own learning affinities and capabilities (Abilock, Growing Schools 352) as well as the goals of the assignment. As you discuss the unit, use your draft Planning Conversation matrix as a transparent roadmap and revise it in coversation with the instructor. By seeking to understand deeply before you curate, you are assured of targeting what's essential to student learning rather than just what’s relevant to a particular unit or lesson. Scenario: The librarian decides to test his/her own understanding of the scope of a project by running choices by the teacher. (Q#1) S/he emails the teacher with a pointer to an inventory of glaciers and asks if the students will need to learn how to select their own glaciers. The teacher thanks her for the pointer but responds by attaching a list of the most important glaciers s/he’s already identified - each student will choose one to research. Q #2. In the same e-mail s/he points to an article describing field work on glaciers and asks if students need to understand how glacial mass is measured. The teacher confirms that this is a key concept for students to understand about glacial melting During the co-curation discussion s/he provides the instructor with a rough draft bibliography along with clarifying questions. Included are several tools and simulations that would help students learn about glacial mass change (factual knowledge), evaluate data about their glaciers (cognitive processes) and communicate their findings to the class (procedural knowledge). Asking knowledge questions Q #3. The librarian asks how students will learn factual information about glacial mass. To prompt the teacher’s thinking s/he shows a definition source which has an overview explanation of how the length and thickness of glaciers are measured. Written by the USGS’ Glaciology Project, this source describes how glaciers respond to climate changes (conceptual knowledge) and how scientists use glaciers to both predict and prepare for climate change impacts (procedural knowledge). Q #4. As a follow up question, the librarian wonders if the teacher would like students to learn how to read the charts and graphs the students will encounter in this source and others (procedural knowledge). If so, the librarian could add several online tools to help students develop data literacy skills. Many of the sources the librarian has reviewed display data visually, such as these visual explanations of glacial mass balance. Asking cognitive process questions Q #5. The librarian shows the teacher a discussion of the significance of glacial mass research. S/he wonders if this could serve as a model for students’ own synthesis of the evidence of change for their own glacier. Q #6. The librarian is aware of the many opportunities to teach data literacy in STEM curation. S/he has found two key data sets about glaciers and wonders if students would find these useful in gathering evidence they need: The Arctic Sea Ice Thickness Maps Data from The Centre for Polar Observation and Modelling (CPOM) is a source of near-real-time current data from comparing satellite radar signals that bounce off ice vs. water which, when used with ice concentration and other types of data, can produce accurate thickness measurements. She refers to a Nature News article that explains the process by which satellites are used to measure glaciers. The second source, the Glacier Mass Balance Data, is an archive of historical downloadable data which could be used in computations. Data for the period from 1945-2003 has been compiled and published by the National Snow and Ice Data Center (NSIDC), an organization which supports research about the cryosphere. Ask product and audience questions. Q7. The librarian wonders to whom students will be presenting their results and if students will need help using a particular technology (procedural knowledge). As an example, s/he shows the teacher a lesson plan which ends with students creating Google Earth tours to explore “key characteristics and visible changes” in individual glaciers. Negotiate curation The teacher considers the librarian’s choices (Q#3 & Q #4) and realizes that s/he will need to help students understand and discuss glacial mass in class prior to their research. However, s/he asks that the librarian include both sources in the curated list just in case students need to refer to them during their research. The teacher asks the librarian to introduce both data sources (Q #6) to students. Having explored these sources already, the librarian proposes that s/he do a minilesson in which s/he describes their content, explains how they are used and, finally, helps students locate data for their own glaciers (factual and procedural knowledge). S/he adds that this information will also be included in her curated set. In response the teacher realizes that it would be helpful to find software that would aggregate and compare (cognitive process) the students’ data from all the glaciers. So s/he asks the librarian to investigate what online options would allow students to view each others’ work. The librarian makes a note to check out online tools for collaboration. Addressing product and audience (Q #5 & Q #7), the science teacher tells the librarian that s/he’d like to hold off teaching Google Earth or any other presentation of information until s/he sees how long students spend on the first part of the process. S/he wants students to use the information they gather from this exploratory research to pivot toward action research, Step 5 in the Toolkit. Once the curator and instructor have met and agreed on what students have to know and learn to do - and how instruction will scaffold that learning - then it is time to turn the rough-drafted source list into a curated set with annotations that explain how and why the sources or tools are useful. This process can be used iteratively throughout a long-term project or at a high leverage / high impact entry point in the curriculum. Many technologies are billed as "curation tools" but only a few can scaffold the curation needs defined in this module. However, it is useful for your students to determine this themselves by exploring tools and seeing how others curate or aggregate resources. Once you meet with the instructor, it is time to turn your rough-drafted source list into a curated set with annotations. Below are four different approaches to curation - but others exist. Which are loosely-organized aggregations and which are curated sets? There are an overwhelming number of technologies billed as "curation tools." Browse them. What are their strengths and flaws? Share your ideas on the class discussion board. Your students have done the intellectual "heavy lifting" for successful curation. They spent significant time building knowledge, evaluating options and understanding the instructor's goals. Now they should be able to rather quickly turn a few sources into a curated set in a format they select. If the school does not have access to a particular curation tool, the student can mock-up the curated set in a word processing document that can be shared with others or even as an annotated source list in a free NoodleTools MLA Lite account. Accompanying the curated set will be the final revision of their evolving curation graphic organizer and the planning document they used to co-curate resources with an instructor. There should be time for their work to be explained, discussed and honored within your learning community. You have done the intellectual "heavy lifting" that allows you to create a tightly targeted selection of resources to meet the knowledge and/or cognitive goals of instruction in service of student learning. Your final annotations will add significant value based on your thoughtful work and will support the instructional core of a unit. This checklist will remind you of the substance of these annotations and help your peers review your curated work: - Identify the learning goal. - Succinctly describe the purpose of each resource. - Explain why it is useful for the goal. - Include tips or cautions to help students navigate or use the resource. - Organize the curated set in a useful way for learners. You may choose to present your curated set in any curation tool, do a mock-up in a word processing document that can be shared with others, or even revise your annotated source list in a free NoodleTools MLA Lite account. You will share your curated set anong with a final revision of the curation graphic organizer and the planning document you developed for the co-curation dialogue with an instructor. Your instructor will provide time for you to explain your work, celebrate the work of others, and discuss your insights about curation with your learning community. Finalize and Submit Your students have done the intellectual "heavy lifting" of becoming successful curators. They spent significant time building knowledge, evaluating options and understanding the instructor's goals. Now they should be able to rather quickly turn a few sources into a curated set in a format of choice. If the school does not have access to a particular curation tool, the student can mock-up the curated set in a word processing document or even as an annotated source list in a free NoodleTools MLA Lite account. They will share with their peers: - their curated set - the final revision of their evolving curation graphic organizer - the planning document they used to co-curate resources with an instructor. They should have an opportunity to explain, discuss, evaluate and honor their work and that of their peers in your learning community. You have done the intellectual "heavy lifting" that allows you to create a tightly targeted selection of resources to meet the knowledge and cognitive goals of instruction in service of student learning. Your final annotations will add significant value because they are grounded in your thoughtful preparation and are uniquely suited to amplify the instructional core of a unit or project. An annotation for one source in this list and the "Components of an Annotated Source List" (both in the resources below) review the substance of these annotations which: - identify the learning goal - succinctly summarize the resource's content or tool's purpose - explain why the resource is useful for the goal - include tips or cautions that will help students navigate or use the resource. You may choose to present your curated set in any tool that allows for annotation and organization. Alternatively you can mock-up your set in a word processing document, or even revise your annotated source list in your free NoodleTools MLA Lite account. If you have created multiple sets, organize them in a useful way for learners. Now share: - your curated set - a final revision of the curation graphic organizer - the planning document developed during a co-curation dialogue Your instructor will provide time for you to explain your work, celebrate the work of others, and discuss your insights about curation with your learning community. Reflect to Synthesize Reflection enables synthesis and transfer. Leave time for this last journal entry because it will go to the heart of their learning. To reflect on your experience and your learning, use this visible thinking routine “I used to think...but now I think..." to identify how your thinking has evolved. Then respond to these questions in your journal: - How has your understanding of curriculum collaboration changed? What significance does this have for your teaching? - How does it fit with your operational model for instructional design? See Booth and Wiggins examples below or use your own. - What concerns do you have about this role? How strongly do you feel about these concerns and how might you go about resolving them? - What questions remain about the curation process itself? What steps might you take to investigate answers to them? - What changes do you anticipate making in your future teaching? Who might you call upon to support your learning?	oercommons	2025-03-18T00:35:14.627333	10/11/2016	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/11007/overview", "title": "Curriculum Curation", "author": "Debbie Abilock" }
https://oercommons.org/courseware/lesson/64453/overview	Grade 9-12 STEM Learning Resources Overview Resources for grade 9-12 STEM STEM Resources STEM Works: STEM-Works provides resource for teachers, mentors, parents, STEM professionals, volunteers, and everyone passionate about getting children eager to learn about science, technology, engineering, and math. Career Exploration: This site has compiled a list of career exploration activities and resources categorized by grade level. Oregon Connections: Oregon Connections is the next generation, web-based tool that makes it easy for industry professionals to connect with K-20 educators. Professionals can share their skills and expertise to bring real world, authentic learning opportunities to all our students helping to create the next generation of innovators. Photo by Jonathan Auh on Unsplash	oercommons	2025-03-18T00:35:14.643226	Engineering	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/64453/overview", "title": "Grade 9-12 STEM Learning Resources", "author": "Electronic Technology" }
https://oercommons.org/courseware/lesson/105463/overview	Spiral Curriculum Overview This document explains the meaning, definitions, principles, values, origin, and features of Spiral curriculum. This document also contains content of How to design a curriculum using Spiral approach also explaining its advantages and disadvantages. This document is very helpful for teachers in designing the curriculum based on increasing level of difficulty and concept. Spiral Curriculum: Meaning and Definitions Objectives - Learner will understand the meaning of spiral curriculum. - Learner will know about the key principles of spiral curriculum. - Learner will be able to describe the approaches of spiral curriculum. SPIRAL CURRICULUM Introduction: A spiral curriculum refers to an educational method that involves revisiting and building upon previously learned topics, subjects, or themes throughout a student's academic journey. This approach, originally proposed by Jerome Bruner in 1960, goes beyond mere repetition of information. Instead, it focuses on deepening the understanding of concepts with each subsequent encounter. According to Bruner's cognitive theory, any subject can be taught to children at any stage of development in an intellectually meaningful manner. In the spiral curriculum, the same educational topics are revisited regularly, allowing students to acquire a more profound knowledge of the subject each time. This approach offers several advantages, such as reinforcing information over time and leveraging prior knowledge to facilitate future learning. The spiral method is commonly employed in teaching and textbooks. Initially, students grasp the fundamental facts of a subject without delving into intricate details. As learning progresses, more complex details are introduced while continually reinforcing the basics. This repetition aids in solidifying the foundational knowledge in long-term memory. This principle bears resemblance to the spiral curriculum. Definitions Year \| Author \| Definition \| 1972 \| Kabara \| “The spiral curriculum approach is usually alien to departmental teaching. Departmental course offerings to medical students are different and less holistic. Because the student’s exposure to any discipline by a department is a one-shot affair, faculty feel justified to teach all in one dose. The method outlined above obviates this classical approach.” \| 1999 \| Harden and Stamper \| “Spiral Curriculum involves an iterative revisiting of topics, subjects or themes throughout the course.” \| 2005 \| Lohani et al. \| “Bruner advocates that a curriculum as it develops should revisit the basic ideas repeatedly, building upon them until the student has grasped the full formal apparatus that goes with them” \| 2007 \| Howard \| “In the curriculum fundamental ideas, once identified, should be constantly revisited and reexamined so that understanding deepens over time” \| Principles, Values, Origin and Features of Spiral Curriculum SPIRAL CURRICULUM Principles The spiral approach in education is guided by three principles, which are as follows: Recurring Engagement: Students are encouraged to revisit the same topic multiple times throughout their academic journey. Deepening Understanding: Each time the topic is revisited, the focus is on acquiring a more profound comprehension and exploring increased complexity. Utilizing Prior Knowledge: Students' existing knowledge and understanding of the topic are leveraged when it is revisited, enabling them to build a strong foundation rather than starting a new. Grade 3 \| Grade 4 \| Grade 5 \| Grade 6 \| Characteristics of Living Things Parts and Functions of Living Things Interaction of Living Things with the Environment. \| Humans: Major Organs of The Body Care for them Diseases Animals, Plants Terrestrial Aquatic Life Cycles Interactions: Beneficial Harmful \| Stages of Growth and Development Development of Secondary Sex Differences in modes of reproduction in Human, Animals, Plants. Flowering plants Non flowering Plants \| Human Body System Musculoskeletal system Digestive System Circulatory System Humans, of Animals and Plants Respiratory system Characteristics of Vertebrates and Invertebrates\ Economic Importance Caring for animals. \| Features • Revisiting Topics: Throughout a course, students have multiple opportunities to revisit various topics, themes, or subjects. They may return to specific areas like the cardiovascular system or medical ethics, as well as generalizable skills such as communication or management. Jerome Bruner (1960) proposed the term "spiral curriculum" and suggested that such a curriculum should be organized around significant societal issues, principles, and values that demand ongoing attention from its members. • Increasing Complexity: The topics covered in the curriculum are addressed in progressively challenging levels. Each time a topic is revisited, new objectives are introduced, providing fresh learning opportunities that contribute to the overall goals. During each visit, students can acquire new knowledge or skills related to the theme, explore advanced applications of previously covered areas, and enhance their proficiency through practical experience. • Building on Previous Learning: New information or skills introduced in the curriculum are explicitly connected to prior learning, establishing a link between current and past phases of the spiral. Preexisting knowledge serves as a prerequisite for subsequent learning. According to Dowding (1993), this sequential approach creates connections between lessons as students progress upward in their studies. The introduction of new knowledge and skills reinforces what has already been learned and becomes intertwined with previously acquired information. By gradually introducing concepts in the initial stages, students are not overwhelmed by the subject matter. • Increasing Competence: With each revisit, students' competence and mastery of the subject matter grow until they achieve the final overall objectives. The progressive improvement in competence can be assessed through appropriate evaluation methods. Values of Spiral Curriculum: The value of a spiral curriculum can be attributed to several factors: • Reinforcement: Continuous exposure to previously learned topics or subjects helps reinforce knowledge. In traditional curricula, students often forget topics covered earlier, but in a spiral curriculum, students regularly revisit and review previously learned subjects. • Progression from Simple to Complex: The spiral curriculum introduces topics in a controlled manner, ensuring that students are not overwhelmed and can grasp the subject matter. As they progress, students build upon their prior knowledge, deepening their understanding of the topics. • Integration: The traditional approach of dividing the curriculum into separate courses and departments limits integration. However, a spiral curriculum breaks down these barriers and promotes integration among different subjects, fostering a holistic view of education. • Continuity: A spiral curriculum maintains continuity and vertical integration throughout the different stages of learning. Concepts and competencies acquired in the early years serve as a foundation for later stages, highlighting the relevance of basic sciences to teachers and students. • Logical Sequence: The scope and sequence of topics are carefully considered in a spiral curriculum. This approach brings order to the complexity of medical education by ensuring a logical progression of subjects. • Higher-Level Objectives: A spiral curriculum encourages students to move beyond simple factual recall and apply their knowledge and skills. For example, understanding thyroid hormone synthesis in the early phases of the curriculum can be applied to later phases when studying thyroid disorders and managing patients with thyroid disease. • Flexibility: The spiral curriculum offers flexibility, allowing students to directly transfer to the next level of a medical course if they have mastered the initial level in a science-based course. This flexibility accommodates individual learning needs and preferences. Origins Of The Approach The spiral curriculum teaching strategy was originally formulated by Jerome Bruner, a cognitive theorist, in 1960. Although many teachers intuitively employed this method, Bruner documented its approach and highlighted its significant value for curriculum designers and student learning. In his own words, Bruner observed: "I noticed that successful attempts to teach well-structured bodies of knowledge, such as mathematics, physical sciences, and even history, often followed a metamorphic spiral pattern. Initially, a set of ideas or operations would be introduced in a simple and intuitive manner. Once students grasped these concepts at a basic level, they would then revisit and reconstruct them in a more formal or operational manner. This process involved making connections with other knowledge, advancing to a higher level of formality and operational rigor, and achieving a broader understanding and abstraction. Eventually, students would master the interconnectedness and structure of a vast body of knowledge..." (Bruner, 1960) In essence, Bruner recognized the effectiveness of the spiral curriculum in facilitating the acquisition and mastery of complex knowledge by progressively building upon foundational concepts. Principles, Values, Origin and Features of Spiral Curriculum SPIRAL CURRICULUM Principles The spiral approach in education is guided by three principles, which are as follows: Recurring Engagement: Students are encouraged to revisit the same topic multiple times throughout their academic journey. Deepening Understanding: Each time the topic is revisited, the focus is on acquiring a more profound comprehension and exploring increased complexity. Utilizing Prior Knowledge: Students' existing knowledge and understanding of the topic are leveraged when it is revisited, enabling them to build a strong foundation rather than starting a new. Grade 3 \| Grade 4 \| Grade 5 \| Grade 6 \| Characteristics of Living Things Parts and Functions of Living Things Interaction of Living Things with the Environment. \| Humans: Major Organs of The Body Care for them Diseases Animals, Plants Terrestrial Aquatic Life Cycles Interactions: Beneficial Harmful \| Stages of Growth and Development Development of Secondary Sex Differences in modes of reproduction in Human, Animals, Plants. Flowering plants Non flowering Plants \| Human Body System Musculoskeletal system Digestive System Circulatory System Humans, of Animals and Plants Respiratory system Characteristics of Vertebrates and Invertebrates\ Economic Importance Caring for animals. \| Features • Revisiting Topics: Throughout a course, students have multiple opportunities to revisit various topics, themes, or subjects. They may return to specific areas like the cardiovascular system or medical ethics, as well as generalizable skills such as communication or management. Jerome Bruner (1960) proposed the term "spiral curriculum" and suggested that such a curriculum should be organized around significant societal issues, principles, and values that demand ongoing attention from its members. • Increasing Complexity: The topics covered in the curriculum are addressed in progressively challenging levels. Each time a topic is revisited, new objectives are introduced, providing fresh learning opportunities that contribute to the overall goals. During each visit, students can acquire new knowledge or skills related to the theme, explore advanced applications of previously covered areas, and enhance their proficiency through practical experience. • Building on Previous Learning: New information or skills introduced in the curriculum are explicitly connected to prior learning, establishing a link between current and past phases of the spiral. Preexisting knowledge serves as a prerequisite for subsequent learning. According to Dowding (1993), this sequential approach creates connections between lessons as students progress upward in their studies. The introduction of new knowledge and skills reinforces what has already been learned and becomes intertwined with previously acquired information. By gradually introducing concepts in the initial stages, students are not overwhelmed by the subject matter. • Increasing Competence: With each revisit, students' competence and mastery of the subject matter grow until they achieve the final overall objectives. The progressive improvement in competence can be assessed through appropriate evaluation methods. Values of Spiral Curriculum: The value of a spiral curriculum can be attributed to several factors: • Reinforcement: Continuous exposure to previously learned topics or subjects helps reinforce knowledge. In traditional curricula, students often forget topics covered earlier, but in a spiral curriculum, students regularly revisit and review previously learned subjects. • Progression from Simple to Complex: The spiral curriculum introduces topics in a controlled manner, ensuring that students are not overwhelmed and can grasp the subject matter. As they progress, students build upon their prior knowledge, deepening their understanding of the topics. • Integration: The traditional approach of dividing the curriculum into separate courses and departments limits integration. However, a spiral curriculum breaks down these barriers and promotes integration among different subjects, fostering a holistic view of education. • Continuity: A spiral curriculum maintains continuity and vertical integration throughout the different stages of learning. Concepts and competencies acquired in the early years serve as a foundation for later stages, highlighting the relevance of basic sciences to teachers and students. • Logical Sequence: The scope and sequence of topics are carefully considered in a spiral curriculum. This approach brings order to the complexity of medical education by ensuring a logical progression of subjects. • Higher-Level Objectives: A spiral curriculum encourages students to move beyond simple factual recall and apply their knowledge and skills. For example, understanding thyroid hormone synthesis in the early phases of the curriculum can be applied to later phases when studying thyroid disorders and managing patients with thyroid disease. • Flexibility: The spiral curriculum offers flexibility, allowing students to directly transfer to the next level of a medical course if they have mastered the initial level in a science-based course. This flexibility accommodates individual learning needs and preferences. Origins Of The Approach The spiral curriculum teaching strategy was originally formulated by Jerome Bruner, a cognitive theorist, in 1960. Although many teachers intuitively employed this method, Bruner documented its approach and highlighted its significant value for curriculum designers and student learning. In his own words, Bruner observed: "I noticed that successful attempts to teach well-structured bodies of knowledge, such as mathematics, physical sciences, and even history, often followed a metamorphic spiral pattern. Initially, a set of ideas or operations would be introduced in a simple and intuitive manner. Once students grasped these concepts at a basic level, they would then revisit and reconstruct them in a more formal or operational manner. This process involved making connections with other knowledge, advancing to a higher level of formality and operational rigor, and achieving a broader understanding and abstraction. Eventually, students would master the interconnectedness and structure of a vast body of knowledge..." (Bruner, 1960) In essence, Bruner recognized the effectiveness of the spiral curriculum in facilitating the acquisition and mastery of complex knowledge by progressively building upon foundational concepts.	oercommons	2025-03-18T00:35:14.743317	06/16/2023	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/105463/overview", "title": "Spiral Curriculum", "author": "Gagandeep Kaur" }
https://oercommons.org/courseware/lesson/85906/overview	Open Access Chapters from Copyright Conversations: Rights Literacy in a Digital World Overview This is an edited volume of chapters from copyright experts around the globe explaining complex copyright issues in a clear, concise way. The majority of the chapters are licensed CC-BY. Open Access Chapters from Copyright Conversations: Rights Literacy in a Digital World Table of Contents iii Foreword by Kenneth D. Crews - COPYRIGHT LIBRARIANS’ ROLE & ADVOCACY Chapter 1. “Kids These Days”… May Know More About Copyright Than You Nancy Sims Chapter 2. Copyright Law’s Role in Advocacy and Education for Open Access Policies on Campus Colin Lukens, Shannon Kipphut-Smith, and Kyle K. Courtney Chapter 3. Fear and Fair Use: Addressing the Affective Domain Sara R. Benson Chapter 4. The Origins and Future of Fair Use/Fair Dealing Week: Why Should Libraries, Museums, and Other Cultural Institutions Participate? Kyle K. Courtney and Krista L. Cox Chapter 5. An Exercise in Contradiction? The Role of Academic Copyright Librarians Mélanie Brunet and Amanda Wakaruk Sarah A. Norris, Barbara Tierney, and Lily Dubach II. EDUCATION Allison Nowicki Estell Chapter 8. "Information Has Value" and Beyond: Copyright Education within and around the Framework Gesina A. Phillips Chapter 9. An Active Learning Approach to Teaching Copyright Essentials Melina Thiede and Jennifer Zerkee Chapter 10. Online Classrooms: Is the TEACH Act Enough? Carla S. Myers Melanie T. Kowalski and Lisa A. Macklin Andrea L. Schuler Roger Gillis - RESEARCH AND POLICY Chapter 14. Copyright Essentials and Information Policy (Policy Implications for Copyright Law) Carrie Russell Alexandra Kohn Rina Elster Pantalony Rachael G. Samberg and Cody Hennesy Chapter 18. Whose Stuff is it Anyway? Adopting Strategies for US Orphan Works Pia M. Hunter IV. INTERNATIONAL ISSUES Chapter 19. The International Copyright Regime – Just Enough to Make You Cringe Bing Wang Chapter 20. From Fair Dealing to Fair Use: How Universities Have Adapted to the Changing Copyright Landscape in Canada Mark Swartz, Ann Ludbrook, Stephen Spong, and Graeme Slaght Chapter 21. Interlibrary Loan and Copyright in Italy: A Case Study of Bocconi University Library Anna Vaglio	oercommons	2025-03-18T00:35:14.770976	Sara Benson	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/85906/overview", "title": "Open Access Chapters from Copyright Conversations: Rights Literacy in a Digital World", "author": "Reading" }
https://oercommons.org/courseware/lesson/96130/overview	The Origins of the Cold War, 1945–1949 United-States-History-II-1621223637 Cold War Overview Overview This unit leads students to create an overview of the Cold War, from 1945-1991. Students will work in groups of four, reading and researching the texts and web address provided. They will develop a timeline of the unit followed by generating Quizlet flashcards. The teacher will include Quizlet Live as a formative assessment by using links to each groups’ Quizlets for Quizlet live games. Cold War Overview Cover Image: "Cold War 01, Introduction" by The National Infantry Museum and Soldier Center is licensed under CC BY 2.0. © 2010 The National Infantry Museum and Soldier Center. Website Reading - The Origins of the Cold War, 1945–1949 © 2019 National Endowment for the Humanities. Except where otherwise noted this work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Textbook - Bay College - HIST 212 - U.S. History 1865 to Present Unit 10 The Cold War P. 290-324 © 2017 Bay College and Content Creators. Except where otherwise noted this work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Textbook - United States History II Unit 12 The Cold War P. 501-541 © 2021 Yvonne Frear, San Jacinto College. Except where otherwise noted this work is licensed under the Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. By the middle of June, 1941, the Soviet Union was forced to fight Nazi Germany when Hitler invaded Soviet territory. He openly violated the non-aggression pact signed by Joseph Stalin and himself. As the Soviets turned the tide against Hitler in the east, Stalin and the Soviets made alliances with Britain and the US. Hope arose that this alliance would last beyond the war. By the time Berlin fell, however, signs existed that the Soviets were also willing to break agreements. This unit leads students to create an overview of the Cold War, from 1945-1991. Students will work in groups of four, reading and researching the texts and web addresses provided. They will develop a timeline of the unit followed by generating Quizlet flashcards. The teacher will include Quizlet Live as a formative assessment by using links to each groups’ Quizlets for Quizlet live games. Objectives: -Analyze the motives for and outcomes of the Yalta and Potsdam Agreements. -Analyze the origins of the strategy of containment and evaluate its implementation. -Evaluate the arguments forwarded by supporters and critics of the containment policy. -Explain the origins of the Truman Doctrine and how it fits into the strategy of containment. -Explain the origins of the Marshall Plan and how it fits into the strategy of containment. -Analyze the reasons for implementing the Berlin Airlift and evaluate the outcomes. -Evaluate the role of international alliances at the outset of the Cold War. -Explain the differences between capitalism and communism. -Analyze the strategies both Americans and the Soviets used. -Evaluate the effectiveness of each US President’s Cold War strategies. -Assess the results of the arms race. -Evaluate the necessity of the Space Race. -Define McCarthyism. -Explain decolonization. -Assess the causes of the Soviet Union’s collapse.	oercommons	2025-03-18T00:35:14.794251	Textbook	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/96130/overview", "title": "Cold War Overview", "author": "Reading" }
https://oercommons.org/courseware/lesson/74104/overview	HS+ U.S. History, Art and English (2020) Overview This theme-based English course integrates reading, writing, listening, speaking, and critical thinking skills around assignments and activities focusing on US History and Art. This competency-based class allows students to work at their own pace, exit at a level appropriate to demonstrated skills and knowledge, and earn high school credits in English, US History, Art, and/or electives. About this Course This theme-based English course integrates reading, writing, listening, speaking, and critical thinking skills around assignments and activities focusing on US History and Art. Topics include: - Group Identity Through Music - Exploring The US Constitution - Exploring the History of Resistance and Civil Rights Movements through Music with Particular Emphasis on Native Americans, African Americans, Latin Americans, Asian Americans, and Women. This competency-based class allows students to work at their own pace, exit at a level appropriate to demonstrated skills and knowledge, and earn high school credits in English, US History, Art, and/or electives. Culturally Responsive Approach This course was intentionally developed to align with the Washington State Board for Community and Technical College’s vision, mission, values and strategic plan. The Culturally Responsive Scorecard, developed by NYU Steinhardt, was a guiding document in the development of this course. Sincere efforts were made to develop culturally responsive curriculum that is inclusive of all students, with particular emphasis on highlighting the histories, experiences, and strengths of historically underserved populations. Faculty planning to teach this course should review modules thoroughly prior to presenting material to students. The HS+ Instructor Resource Guide provides resources and strategies that may be a useful starting place for faculty to address gaps in knowledge and confidence. Course Outcomes - Understand the link between people and music - Explore the uses of music within acts of resistance - Understand the difference between primary and secondary sources - Explore the Big Six ideas within the Constitution - Cite and understand specific events, legislation, and court decisions that affected various ethnic and racial groups throughout United States history - Compare forms of communication - Understand the evolution of the feminist movement - Revise and edit your reflections for each module. - Develop and Present Reflection and Mixtape Project with original artwork - Identify different aspects of an essay and their purpose - Engage in a drafting process that results in a five-paragraph essay College and Career Readiness Standards Throughout the course students demonstrate the following: Reading - Reading anchor standard 2: Determine central ideas or themes of a text and analyze their development; summarize the key supporting details and ideas. - Reading anchor standard 9: Analyze how two or more texts address similar themes or topics in order to build knowledge or to compare the approaches the authors take. - Reading anchor standard 10: Read and comprehend complex literary and informational texts independently and proficiently. Writing - Writing Anchor Standard 1: Write arguments to support claims in an analysis of substantive topics or texts, using valid reasoning and relevant and sufficient evidence. - Writing anchor standard 5: Develop and strengthen writing as needed by planning, revising, editing, rewriting, or trying a new approach. - Writing anchor standard 6: Use technology, including the Internet, to produce and publish writing and to interact and collaborate with others. - Writing anchor standard 8: Gather relevant information from multiple print and digital sources, assess the credibility and accuracy of each source, and integrate the information while avoiding plagiarism. Speaking and Listening Speaking and Listening anchor standard 3: Evaluate a speaker’s point of view, reasoning, and use of evidence and rhetoric.	oercommons	2025-03-18T00:35:14.810783	Full Course	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/74104/overview", "title": "HS+ U.S. History, Art and English (2020)", "author": "U.S. History" }
https://oercommons.org/courseware/lesson/113951/overview	Introduction to American Literature Iroquois Creation Story Jamestown-Yorktown Foundation - Phillis Wheatley On the Equality of the Sexes The Raven Audio The Scarlet Letter by Nathaniel Hawthorne The Scarlet Letter full audio book with rolling text The Tell-Tale Heart Audio The World on the Turtle's Back performed by Samuel Larsen Women's History Organization - Phillis Wheatley American Literature Beginnings to Present Overview This is a open educational resource material for American Literature: Beginnings through 1865 and American Literature: 1865 to present. Attributions American Literature Beginning to Present © 2024 by Alexa Chiefari, Betsy Ralph-Tollefson is licensed under CC BY-SA 4.0 Introduction: Beginnings to 1865 American Literature Beginnings to 1865 Why Study Literature? - We can easily communicate facts, but what is really important is experience. Literature helps to give full experiences to understand a story. - Literature captures experiences. For example, a memoir about a person does a lot more for the reader than reading a biography online about the person. - Any piece of literature is a product of the time. Therefore, reading literature of a certain period will help us to understand that period of history, including the values and cultures of the time. We will read diverse perspectives to get a better understanding of a variety of perspectives from American history. - Humans love stories. Literature frames stories that will sell us more than just bald facts, but helps us to understand human experiences at a deeper level. - Telling stories is communicating more than just the story. They provide a lesson or a purpose to the reader. - Literature is a map. It is a map that one person has written for another. They are hoping to communicate their view of the universe and world around them. While this cannot portray everything, it does provide the reader with an outlook for a situation that they do not have experience with. What do we mean when we say “American Literature”? - It takes place in the United States of America. - The author is American. - Themes, ideas, values, experiences, and purposes that represent American (United States) identity - United States history influences the material Thoughts and Considerations for Readings: - Where and when is the text from? - Who wrote it? (identity) - Why did they write the text? What is the purpose? What story needed to be told? - What is the experience of reading? What is the goal of the author for the reader think or feel? - Is the meaning deeper than the content? If so, what is it? - What sources influenced this text? - What phrases, passages, selections seem to stick or linger in your mind? - What symbols and themes occur in what you’re reading? Are there reoccurring themes throughout various readings? What are they? - In what ways is the text valuable? If it is not valuable to you, it must be valuable to others, so who is it? Literary Terms Literary Terms Alliteration- the repetition of the same sound at the start of a series of words in succession whose purpose is to provide an audible pulse that gives a piece of writing a lulling, lyrical, and/or emotive effect. Rhyme-repetition of syllables, most often at the end of the line. Most often used as a device in poetry Motif-a repeated pattern, an image, sound, word, or symbol that comes back again and again within a particular story. Tone-the attitude of a character, narrator, author, or speaker towards a given subject Mood- the physical atmosphere that provokes a reader’s emotions Narrator –fictional construct through which a story is told Foreshadowing- hints, suggestions or warnings about events to come that are dropped or planted to build anticipation or suspense. Symbolism –the use of objects, characters, or elements that represent deeper ideas, themes, or emotions Characterization- The representation of the traits, motives, and psychology of a character in a story Plot -The linear order of events that make up a story, including exposition, rising action, climax, falling action, and resolution (definition in Foreshadowing video) Setting-a time and/or place in which a story is told. Point of view-The audience’s perspective on the events of the narrative. This is determined by the storyteller. Most common third person and first person. Imagery-descriptive language that appeals to the senses. Metaphor - comparison between two things otherwise unrelated, the qualities are figuratively carried over to the other. Theme - central, unifying idea in a story. Theme addresses bigger issues that emerge as the characters pursue their goals. Addresses deeper questions like identity, philosophy, or morality. Protagonist - the main character, the character that drives the action that is central to the plot or conflict. Antagonist- The character or force that opposes the main character creating conflict and other obstacles. Satire- the art of making something or someone look ridiculous, raising laughter in order to embarrass, humble, or discredit its targets. Irony –when someone says something or does something that departs from what they (or we) expect them to say or do. Three main types in literature: verbal, dramatic, and situational irony Conflict-thwarted, endangered, or opposing desire. Creates tension, launches the plot, and it evokes the themes of a story. Oregon State Guide To English Literary Terms, Oregon State, The Oregon State Guide to English Literary Terms \| Oregon State University, CC BY 4.0 Characteristics of Different Types of Literature POETRY: Literary work that has an intense and specific focus on the use of the rhythmic and aesthetic qualities of language to evoke meaning, express feeling, or share experience. Characteristics of Poetry: Written in verse and often employs various forms of meter, rhyme, and stanza structures. The language utilized favors concise word choice and vivid imagery. Other literary devices commonly used include symbolism, simile, metaphors, and personification, which leaves each work open to varied interpretations. Poems can be written in a variety of styles including sonnets, haikus, free verse, and more. DRAMA: Literary work intended for performance, which includes plays, scripts, and dialogues. Characteristics of Drama: Dramas have a more immediate and focused structure, divided into acts and scenes. Designed for performance, the narrative is conveyed through dialogue and stage direction, limiting the depth of description. The visual and auditory emphasis is on character interaction. The purpose of dramas is to entertain, provoke thought, and evoke emotions. They are categorized into genres like tragedy, melodrama, and comedy. SATIRE/COMEDY: Comedy is a broad genre with the purpose of entertaining and amusing. Satire is a type of comedy. Satire is a genre of literary work that uses humor, exaggeration, irony, and other devices to critique and expose societal follies. Comedy is a broad genre with the purpose to entertain and amuse. Characteristics of Satire: Satire targets specific aspects of society or human behavior to critique. Satire employs sarcasm, wit, and irony to get to the point and often layers a social message or moral message under the humor. Satire can be found in various forms of literary work such as novels, plays, poems, and essays. FICTION: Narrative works of literature that are created from a writer’s imagination Characteristics of Fiction: Fiction features invented characters, settings, and plots that may or may not reflect reality. Allows authors to explore themes, ideas, and emotions through invented stories and because of this it may incorporate elements of realism or surrealism. It can encompass every type of genre such as historical fiction, science fiction, fantasy, mystery, romance, and others. NONFICTION: Factual writing based on research, observation, or personal experience that presents information or account of real people, events, or phenomena. Characteristics of NonFiction: The purpose is to inform, educate, or persuade the reader about real-world subjects. It takes the form such as biographies, memoirs, essays, histories, news articles, or other journalistic writing. Requires accuracy, credibility, and truthfulness. Common features include artifactual evidence, citations, and references to support claims. 2. Pre-Colonial 1500-1599 The literary work in the period spanning from 1500 to 1599, primarily consists of the indigenous oral traditions of the Indigenous people that inhabited the land before European colonization. Indigenous people shared stories, songs, and ceremonial speeches orally from one generation to the next. This oral tradition was central to the preservation and transmission of cultural values, beliefs, and knowledge within indigenous communities. This was the beginning The oral works of the Indigenous people often recounted the experiences of their ancestors, including migration patterns, battles, treaties, and interactions with other tribal nations. These oral histories served as a means of preserving tribal identity and collective memory. Another common theme was the role nature played in their lives. They reflected a deep connection to the natural world, portraying animals, plants, and landscapes as sacred and imbued with spiritual significance. Many stories and songs celebrated the interdependence between humans and the environment, emphasizing the importance of living in harmony with nature. Literary work at this time was closely intertwined with rituals and ceremonies, such as rites of passage, seasonal celebrations, and religious ceremonies. These rituals often incorporated storytelling, songs, chants, and dances as integral components of cultural and spiritual expression. Different tribes and nations across the continent developing their own unique oral literature, languages, and storytelling techniques. Each indigenous culture had its rich tapestry of myths, legends, and oral traditions that reflected its distinct cultural heritage. Creation & Trickster Stories Creation Story Haudenosaunee (Iroquois) In the great past, deep water covered all the earth. The air was filled with birds, and great monsters were in possession of the waters when a beautiful woman was seen by them falling from the sky. Then huge ducks gathered in council and resolved to meet this wonderful creature and break the force of her fall. So they arose, and, with pinion overlapping pinion, unitedly received the dusky burden. Then the monsters of the deep also gathered in council to decide which should hold this celestial being and protect her from the terrors of the water, but none was able except a giant tortoise, who volunteered to endure this lasting weight upon his back. There she was gently placed, while he, constantly increasing in size, soon became a large island. Twin boys were after a time brought forth by the woman—one the spirit of good, who made all good things, and caused the maize, fruit, and tobacco to grow; the other the spirit of evil, who created the weeds and all vermin. Ever the world was increasing in size, although occasional quakings were felt, caused by the efforts of the monster tortoise to stretch out, or by the contraction of his muscles. After the lapse of ages from the time of his general creation Ta‑rhuⁿ‑hiă‑wăh‑kuⁿ, the Sky Holder, resolved upon a special creation of a race which should surpass all others in beauty, strength, and bravery; so from the bosom of the great island, where they had previously subsisted upon moles, Ta‑rhuⁿ‑hiă‑wăh‑kuⁿ brought out the six pairs, which were destined to become the greatest of all people. The Tuscaroras tell us that the first pair were left near a great river, now called the Mohawk. The second family were directed to make their home by the side of a big stone. Their descendants have been termed the Oneidas. Another pair were left on a high hill, and have ever been called the Onondagas. Thus each pair was left with careful instructions in different parts of what is now known as the State of New York, except the Tuscaroras, who were taken up the Roanoke River into North Carolina, where Ta‑rhuⁿ‑hiă‑wăh‑kuⁿ also took up his abode, teaching them many useful arts before his departure. This, say they, accounts for the superiority of the Tuscaroras. But each of the six tribes will tell you that his own was the favored one with whom Sky Holder made his terrestrial home, while the Onondagas claim that their possession of the council fire prove them to have been the chosen people. Later, as the numerous families became scattered over the State, some lived in localities where the bear was the principal game, and were called from that circumstance the clan of the Bear. Others lived where the beavers were trapped, and they were called the Beaver clan. For similar reasons the Snipe, Deer, Wolf, Tortoise, and Eel clans received their appellations. How the World Was Made (Cherokee) The earth is a great floating island in a sea of water. At each of the four corners there is a cord hanging down from the sky. The sky is of solid rock. When the world grows old and worn out, the cords will break, and then the earth will sink down into the ocean. Everything will be water again. All the people will be dead. The Indians are much afraid of this. In the long time ago, when everything was all water, all the animals lived up above in Galun’lati, beyond the stone arch that made the sky. But it was very much crowded. All the animals wanted more room. The animals began to wonder what was below the water and at last Beaver’s grandchild, little Water Beetle, offered to go and find out. Water Beetle darted in every direction over the surface of the water, but it could find no place to rest. There was no land at all. Then Water Beetle dived to the bottom of the water and brought up some soft mud. This began to grow and to spread out on every side until it became the island which we call the earth. Afterwards this earth was fastened to the sky with four cords, but no one remembers who did this. At first the earth was flat and soft and wet. The animals were anxious to get down, and they sent out different birds to see if it was yet dry, but there was no place to alight; so the birds came back to Galun’lati. Then at last it seemed to be time again, so they sent out Buzzard; they told him to go and make ready for them. This was the Great Buzzard, the father of all the buzzards we see now. He flew all over the earth, low down near the ground, and it was still soft. When he reached the Cherokee country, he was very tired; his wings began to flap and strike the ground. Wherever they struck the earth there was a valley; whenever the wings turned upwards again, there was a mountain. When the animals above saw this, they were afraid that the whole world would be mountains, so they called him back, but the Cherokee country remains full of mountains to this day. [This was the original home, in North Carolina.] When the earth was dry and the animals came down, it was still dark. Therefore they got the sun and set it in a track to go every day across the island from east to west, just overhead. It was too hot this way. Red Crawfish had his shell scorched a bright red, so that his meat was spoiled. Therefore the Cherokees do not eat it. Then the medicine men raised the sun a handsbreadth in the air, but it was still too hot. They raised it another time; and then another time; at last they had raised it seven handsbreadths so that it was just under the sky arch. Then it was right and they left it so. That is why the medicine men called the high place “the seventh height.” Every day the sun goes along under this arch on the under side; it returns at night on the upper side of the arch to its starting place. There is another world under this earth. It is like this one in every way. The animals, the plants, and the people are the same, but the seasons are different. The streams that come down from the mountains are the trails by which we reach this underworld. The springs at their head are the doorways by which we enter it. But in order to enter the other world, one must fast and then go to the water, and have one of the underground people for a guide. We know that the seasons in the underground world are different, because the water in the spring is always warmer in winter than the air in this world; and in summer the water is cooler. We do not know who made the first plants and animals. But when they were first made, they were told to watch and keep awake for seven nights. This is the way young men do now when they fast and pray to their medicine. They tried to do this. The first night, nearly all the animals stayed awake. The next night several of them dropped asleep. The third night still more went to sleep. At last, on the seventh night, only the owl, the panther, and one or two more were still awake. Therefore, to these were given the power to see in the dark, to go about as if it were day, and to kill and eat the birds and animals which must sleep during the night. Even some of the trees went to sleep. Only the cedar, the pine, the spruce, the holly, and the laurel were awake all seven nights. Therefore they are always green. They are also sacred trees. But to the other trees it was said, “Because you did not stay awake, therefore you shall lose your hair every winter.” After the plants and the animals, men began to come to the earth. At first there was only one man and one woman. He hit her with a fish. In seven days a little child came down to the earth. So people came to the earth. They came so rapidly that for a time it seemed as though the earth could not hold them all. Reference "Native American Stories". American Literature 1600-1865. Lumen Learning. n.d. https://courses.lumenlearning.com/suny-empire-amliterature/ These two Native American creation stories are among thousands of accounts for the origins of the world. The Salinan and Cherokee, from what we now call California and the American southeast respectively, both exhibit the common Native American tendency to locate spiritual power in the natural world. For both Native Americans and Europeans, the collision of two continents challenged old ideas and created new ones as well. Salinan Indian Creation Story When the world was finished, there were as yet no people, but the Bald Eagle was the chief of the animals. He saw the world was incomplete and decided to make some human beings. So he took some clay and modeled the figure of a man and laid him on the ground. At first he was very small but grew rapidly until he reached normal size. But as yet he had no life; he was still asleep. Then the Bald Eagle stood and admired his work. “It is impossible,” said he, “that he should be left alone; he must have a mate.” So he pulled out a feather and laid it beside the sleeping man. Then he left them and went off a short distance, for he knew that a woman was being formed from the feather. But the man was still asleep and did not know what was happening. When the Bald Eagle decided that the woman was about completed, he returned, awoke the man by flapping his wings over him and flew away. The man opened his eyes and stared at the woman. “What does this mean?” he asked. “I thought I was alone!” Then the Bald Eagle returned and said with a smile, “I see you have a mate! Have you had intercourse with her?” “No,” replied the man, for he and the woman knew nothing about each other. Then the Bald Eagle called to Coyote who happened to be going by and said to him, “Do you see that woman?” Try her first!” Coyote was quite willing and complied, but immediately afterwards lay down and died. The Bald Eagle went away and left Coyote dead, but presently returned and revived him. “How did it work?” said the Bald Eagle. “Pretty well, but it nearly kills a man!” replied Coyote. “Will you try it again?” said the Bald Eagle. Coyote agreed, and tried again, and this time survived. Then the Bald Eagle turned to the man and said, “She is all right now; you and she are to live together.” Source: John Alden Mason, The Ethnology of the Salinan Indians (Berkeley: 1912), 191-192. Available through the Internet Archive Cherokee Indian Creation Story The earth is a great island floating in a sea of water, and suspended at each of the four cardinal points by a cord hanging down from the sky vault, which is of solid rock. When the world grows old and worn out, the people will die and the cords will break and let the earth sink down into the ocean, and all will be water again. The Indians are afraid of this. When all was water, the animals were above in Gälûñ’lätï, beyond the arch; but it was very much crowded, and they were wanting more room. They wondered what was below the water, and at last Dâyuni’sï, “Beaver’s Grandchild,” the little Water-beetle, offered to go and see if it could learn. It darted in every direction over the surface of the water, but could find no firm place to rest. Then it dived to the bottom and came up with some soft mud, which began to grow and spread on every side until it became the island which we call the earth. It was afterward fastened to the sky with four cords, but no one remembers who did this. At first the earth was flat and very soft and wet. The animals were anxious to get down, and sent out different birds to see if it was yet dry, but they found no place to alight and came back again to Gälûñ’lätï. At last it seemed to be time, and they sent out the Buzzard and told him to go and make ready for them. This was the Great Buzzard, the father of all the buzzards we see now. He flew all over the earth, low down near the ground, and it was still soft. When he reached the Cherokee country, he was very tired, and his wings began to flap and strike the ground, and wherever they struck the earth there was a valley, and where they turned up again there was a mountain. When the animals above saw this, they were afraid that the whole world would be mountains, so they called him back, but the Cherokee country remains full of mountains to this day. When the earth was dry and the animals came down, it was still dark, so they got the sun and set it in a track to go every day across the island from east to west, just overhead. It was too hot this way, and Tsiska’gïlï’, the Red Crawfish, had his shell scorched a bright red, so that his meat was spoiled; and the Cherokee do not eat it. The conjurers put the sun another hand-breadth higher in the air, but it was still too hot. They raised it another time, and another, until it was seven handbreadths high and just under the sky arch. Then it was right, and they left it so. This is why the conjurers call the highest place Gûlkwâ’gine Di’gälûñ’lätiyûñ’, “the seventh height,” because it is seven hand-breadths above the earth. Every day the sun goes along under this arch, and returns at night on the upper side to the starting place. There is another world under this, and it is like ours in everything–animals, plants, and people–save that the seasons are different. The streams that come down from the mountains are the trails by which we reach this underworld, and the springs at their heads are the doorways by which we enter, it, but to do this one must fast and, go to water and have one of the underground people for a guide. We know that the seasons in the underworld are different from ours, because the water in the springs is always warmer in winter and cooler in summer than the outer air. When the animals and plants were first made–we do not know by whom–they were told to watch and keep awake for seven nights, just as young men now fast and keep awake when they pray to their medicine. They tried to do this, and nearly all were awake through the first night, but the next night several dropped off to sleep, and the third night others were asleep, and then others, until, on the seventh night, of all the animals only the owl, the panther, and one or two more were still awake. To these were given the power to see and to go about in the dark, and to make prey of the birds and animals which must sleep at night. Of the trees only the cedar, the pine, the spruce, the holly, and the laurel were awake to the end, and to them it was given to be always green and to be greatest for medicine, but to the others it was said: “Because you have not endured to the end you shall lose your, hair every winter.” Men came after the animals and plants. At first there were only a brother and sister until he struck her with a fish and told her to multiply, and so it was. In seven days a child was born to her, and thereafter every seven days another, and they increased very fast until there was danger that the world could not keep them. Then it was made that a woman should have only one child in a year, and it has been so ever since. Source: W. Powell, Nineteenth Annual Report of the Bureau of American Ethnology to the Secretary of the Smithsonian Institution, 1897-1898, Part I (Washington: 1900), 239-240. 3. Colonial 1600-1829 Coming to America The literary period of Colonial America, spanning from roughly 1600 to 1829, is marked by the development of literature in the English colonies established in North America. Religion played a central role in the lives of the early colonists, and religious literature was a dominant genre during the Colonial period. Puritan writers produced sermons, theological treatises, and devotional writings that emphasized themes of sin, salvation, divine providence, and the importance of leading a moral life. Narratives depicted accounts of exploration and settlement, describing the challenges and hardships faced by early settlers and encounters with the Indigenous people. Cultural encounters, survival, and identity were other common themes to emerge from Colonial writers. Poetry and prose flourished in Colonial America, encompassing a wide range of styles, themes, and subjects. While much of the literature of this period was influenced by European literary traditions, Colonial writers also drew inspiration from their experiences in the New World, exploring themes such as nature, landscape, and the American wilderness. Colonial America was home to a diverse population of settlers from different ethnic, religious, and cultural backgrounds. As a result, Colonial literature reflects the cultural diversity of the early American colonies, incorporating elements of English, Dutch, French, Spanish, African, and Native American literary traditions. The Colonial period was also marked by political upheaval and debates over issues such as colonial governance, taxation, and independence from British rule. Political pamphlets and tracts were widely circulated, expressing various political viewpoints and advocating for colonial rights and liberties. Personal writings and public documents provided accounts of significant events, figures, and developments in the colonies, shaping early understandings of American history and identity. Overall, the literary time of Colonial America from 1600 to 1829 laid the groundwork for the development of American literature, providing insights into the experiences, values, and aspirations of the early settlers who helped shape the course of American history. Notable writers during this period that left a lasting impact on literature and culture include Anne Bradstreet, Benjamin Franklin, Thomas Paine, Phillis Wheatley, Washington Irving, and James Fenimore Cooper. Jonathan Edwards Jonathan Edwards (1703–1758) was a preeminent theologian and philosopher in British American Puritanism, central to the Great Awakening religious revival, and a pioneer of the 19th-century Protestant missionary movement. Raised in a devout environment, he entered Yale College at 13 and became a pastor in Northampton, Massachusetts. Edwards is known for his deep introspection on divine sovereignty and predestination, contributing significantly to Christian philosophy. His works, including "Sinners in the Hands of an Angry God," played a critical role in shaping early American religious thought. "Sinners in the Hands of an Angry God" by Jonathan Edwards, Abridged Version Sinners in the Hands of An Angry God, abridged version Jonathan Edwards There is no want of power in God to cast wicked men into hell at any moment. Men's hands cannot be strong when God rises up. The strongest have no power to resist him, nor can any deliver out of his hands So that it is not because God is unmindful of their wickedness, and does not resent it, that he does not let loose his hand and cut them off. God is not altogether such one as themselves, though they may imagine him to be so. The wrath of God burns against them, their damnation does not slumber; the pit is prepared, the fire is made ready, the furnace is now hot, ready to receive them; the flames do now rage and glow. The glittering sword is whet and held over them, and the pit hath opened its mouth under them. So that, thus it is that natural men are held in the hand of God, over the pit of hell; they have deserved the fiery pit, and are already sentenced to it; and God is dreadfully provoked, his anger is as great towards them as to those that are actually suffering the executions of the fierceness of his wrath in hell, and they have done nothing in the least to appease or abate that anger, neither is God in the least bound by any promise to hold them up one moment; the devil is waiting for them, hell is gaping for them, the flames gather and flash about them, and would fain lay hold on them, and swallow them up; the fire bent up in their hearts is struggling to break out: and they have no interest in any Mediator, there are no means within reach that can be any security to them. In short, they have no refuge, nothing to take hold of; all that preserves them every moment is the mere arbitrary will and uncovenanted, unobligated forbearance of an incensed God. You probably are not sensible of this; you find you are kept out of hell, but do not see the hand of God in it; but look at other things, such as the good state of your bodily constitution, your care of your own life, and the means you use for your preservation. But indeed these things are nothing; if God should withdraw his hand, they would avail no more to keep you from falling, than the thin air to hold up a person that is suspended in it. Your wickedness makes you as it were heavy as lead, and to tend downwards with great weight and pressure towards hell; and if God should let you go, you would immediately sink and swiftly descend and plunge into the bottomless gulf, and your healthy constitution, and your care and prudence, and best contrivance, and all your righteousness, would have no more influence to uphold you and keep you out of hell than a spider's web would have to stop a fallen rock. There are black clouds of God's wrath now hanging directly over your heads, full of the dreadful storm, and big with thunder; and were it not for the restraining hand of God, it would immediately burst forth upon you. The sovereign pleasure of God, for the present, stays his rough wind; otherwise, it would come with fury, and your destruction would come like a whirlwind, and you would be like the chaff of the summer threshing floor. The wrath of God is like great waters that are damned for the present; they increase more and more, and rise higher and higher, till an outlet is given; and the longer the stream is stopped, the more rapid and mighty is its course, when once it is let loose. It is true, that judgment against your evil works has not been executed hitherto; the floods of God's vengeance have been withheld; but your guilt in the meantime is constantly increasing, and you are every day treasuring up more wrath; the waters are constantly rising, and waxing more and more mighty; and there is nothing but the mere pleasure of God, that holds the waters back, that are unwilling to be stopped, and press hard to go forward. If God should only withdraw his hand from the flood-gate, it would immediately fly open, and the fiery floods of the fierceness and wrath of God would rush forth with inconceivable fury, and would come upon you with omnipotent power; and if your strength were ten thousand times greater than it is, yea, ten thousand times greater than the strength of the stoutest, sturdiest devil in hell, it would be nothing to withstand or endure it. The bow of God's wrath is bent, and the arrow made ready on the string, and justice bends the arrow at your heart, and strains the bow, and it is nothing but the mere pleasure of God, and that of an angry God, without any promise or obligation at all, that keeps the arrow one moment from being made drunk with your blood. Thus all you that never passed under a great change of heart, by the mighty power of the Spirit of God upon your souls; all you that were never born again, and made new creatures, and raised from being dead in sin, to a state of new, and before altogether inexperienced light and life, are in the hands of an angry God. However, you may have reformed your life in many things, and may have had religious affections, and may keep up a form of religion in your families and closets, and in the house of God, it is nothing but his mere pleasure that keeps you from being this moment swallowed up in everlasting destruction. However unconvinced you may now be of the truth of what you hear, by and by you will be fully convinced of it. Those that are gone from being in the like circumstances with you, see that it was so with them; for destruction came suddenly upon most of them; when they expected nothing of it, and while they were saying Peace and safety: now they see, that those things on which they depended for peace and safety, were nothing but thin air and empty shadows. The God that holds you over the pit of hell, much as one holds a spider, or some loathsome insect over the fire, abhors you, and is dreadfully provoked: his wrath towards you burns like a fire; he looks upon you as worthy of nothing else, but to be cast into the fire; he is of purer eyes than to bear to have you in his sight; you are ten thousand times more abominable in his eyes than the most hateful venomous serpent is in ours. You have offended him infinitely more than ever a stubborn rebel did his prince, and yet it is nothing but his hand that holds you from falling into the fire every moment. It is to be ascribed to nothing else, that you did not go to hell the last night; that you suffered to awake again in this world after you closed your eyes to sleep. And there is no other reason to be given, why you have not dropped into hell since you arose in the morning, but that God's hand has held you up. There is no other reason to be given why you have not gone to hell, since you have sat here in the house of God, provoking his pure eyes by your sinful wicked manner of attending his solemn worship. Yea, there is nothing else that is to be given as a reason why you do not this very moment drop down into hell. O sinner! Consider the fearful danger you are in: it is a great furnace of wrath, a wide and bottomless pit, full of the fire of wrath, that you are held over in the hand of that God, whose wrath is provoked and incensed as much against you, as against many of the damned in hell. You hang by a slender thread, with the flames of divine wrath flashing about it, and ready every moment to singe it, and burn it asunder; and you have no interest in any Mediator, and nothing to lay hold of to save yourself, nothing to keep off the flames of wrath, nothing of your own, nothing that you ever have done, nothing that you can do, to induce God to spare you one moment. And consider here more particularly, It is everlasting wrath. It would be dreadful to suffer this fierceness and wrath of Almighty God one moment, but you must suffer it to all eternity. There will be no end to this exquisite horrible misery. When you look forward, you shall see a long forever, a boundless duration before you, which will swallow up your thoughts, and amaze your soul; and you will absolutely despair of ever having any deliverance, any end, any mitigation, any rest at all. So, that your punishment will indeed be infinite. Oh, who can express what the state of a soul in such circumstances is! All that we can say about it, gives but a very feeble, faint representation of it; it is inexpressible and inconceivable: For "who knows the power of God's anger?" And now you have an extraordinary opportunity, a day wherein Christ has thrown the door of mercy wide open, and stands in calling and crying with a loud voice to poor sinners; a day wherein many are flocking to him, and pressing into the kingdom of God. And you, children, who are unconverted, do not you know that you are going down to hell, to bear the dreadful wrath of that God, who is now angry with you every day and every night? Will you be content to be the children of the devil, when so many other children in the land are converted and become the holy and happy children of the King of kings? And let every one that is yet of Christ, and hanging over the pit of hell, whether they be old men and women, or middle-aged, or young people, or little children, now hearken to the loud calls of God's word and providence. "Haste and escape for your lives, look not behind you, escape to the mountain, lest you be consumed." Anne Bradstreet Anne Bradstreet (1612–1672) was the first notable American poet and the first woman to be published in Colonial America. Her work, often deeply personal and reflective, navigated the complexities of life as a Puritan woman, touching on themes of love, faith, and domesticity. Despite living in a male-dominated society, Bradstreet's voice emerged with eloquence and insight, earning her a place in American literary history. Her legacy continues to inspire as a pioneering figure for female writers in the New World. "To My Dear and Loving Husband" by Anne Bradstreet (attached as PDF) AnneBPhillisWPoetry_5XlfMdD.pdf (oercommons.s3.amazonaws.com) Phyllis Wheatley Phillis Wheatley Peters, born around 1753 in Gambia and brought to America as an enslaved child, emerged as the first African American woman to publish a book of poems. Educated by the Wheatley family, her literary talent flourished early, leading to the publication of her work in 1773 with endorsements from prominent figures. Wheatley's poetry, celebrated for its elegance and expression of religious and moral themes, played a pivotal role in challenging contemporary perceptions of African American intellect and capability. Despite her contributions, Wheatley faced hardships, including failed attempts to publish further and personal losses, leading to her death in 1784. Her legacy endures in scholarly study and institutional honors. For more details, you can visit the full article on the National Women's History Museum's website here. "On Being Brought from Africa to America" by Phyllis Wheatley (same PDF as Anne Bradstreet poem) AnneBPhillisWPoetry_5XlfMdD.pdf (oercommons.s3.amazonaws.com) Judith Sargent Murray Judith Sargent Murray (1751-1820) was a significant figure in early American literature, an advocate for women's equality, and a proponent of women's education and the right to control their earnings. Her influential essay, "On the Equality of the Sexes," predates Mary Wollstonecraft's similar works. Facing financial difficulties and personal loss, including the death of her first husband, Murray's writings supported her family and contributed to the early discourse on women's rights. Her efforts laid foundational ideas for the education of women and the concept of "Republican Motherhood," advocating that educated women were essential to the nation's success. For more detailed information, visit the full article at the National Women's History Museum here. "Equality of the Sexes" by Judith Sargent Murray (attached as PDF) Anne Bradstreet, Judith Sargent Murray, Jonathan Edwards, and Phyllis Wheatley: authors are published under the public domain license. Romantic, Gothic Literature 1820-1849 During this time, writers explored themes of individualism, nature, emotion, and the supernatural, while also grappling with the social and political issues of the day. In the United States, Romanticism flourished during the 1820s, with writers celebrating the beauty of nature, the power of imagination, and the importance of individual freedom and expression. American Romantic literature often reflected the country's growing sense of national identity and explored themes of exploration, frontier life, and the American wilderness. To do this, authors tapped into folklore and mythology to explore history and identity. These writers also often rebelled against societal norms, expressing priority in individualism and their ideals. The exploration and advancement of themes of passion, romantic idealism and love as a transcendent force that could overcome social barriers and conventions is a tenet of Romanticism. Writing featured descriptive and figurative writing meant to evoke strong and passionate emotions. Authors that exemplified these literary styles that of Romanticism include: Washington Irving, James Fennimore Cooper, William Cullen Bryant, and Henry Wadsworth Longfellow. Another trend in literature that evolved in the late 18th century and remained popular through the 1820s was Gothic literature. Hallmarks of Gothic literature include its dark, mysterious, settings, characters, and themes of madness, terror, and the supernatural. Gothic literature relied heavily on mystery and suspense to engage readers, with writers often weaving complex and convoluted plots filled with unexpected twists and turns supported by the supernatural and fear of the unknown. Themes delved into the darker side of human nature and the workings of the brain including forbidden relationships, longing, obsessive behaviors, and psychological turmoil. Authors that exemplify Gothic literature include Edgar Allen Poe, Nathaniel Hawthorne, and Charles Brockedn Brown. Edgar Allan Poe Edgar Allan Poe (1809–1849) was an American writer known for his contributions to Romanticism and Gothic literature. His life was marked by tragedy, including the loss of his parents at a young age, struggles with financial instability, and the death of his wife, Virginia. These experiences influenced his macabre and often melancholic writing style. Romanticism, a movement emphasizing emotion and individualism, is evident in Poe's celebration of the imaginative and the supernatural. His works often explore the complexities of the human mind and emotions, aligning with Romantic ideals of exploring the self and the transcendent. Poe's Gothic literature, characterized by its use of horror, decay, and the grotesque, is exemplified in stories like "The Tell-Tale Heart" and "The Fall of the House of Usher." These works showcase his mastery of creating tension and psychological depth, making him a central figure in both Romantic and Gothic literary traditions. "The Raven" by Edgar Allan Poe Once upon a midnight dreary, while I pondered, weak and weary, Over many a quaint and curious volume of forgotten lore— While I nodded, nearly napping, suddenly there came a tapping, As of some one gently rapping, rapping at my chamber door. “’Tis some visitor,” I muttered, “tapping at my chamber door— Only this and nothing more.” Ah, distinctly I remember it was in the bleak December; And each separate dying ember wrought its ghost upon the floor. Eagerly I wished the morrow;—vainly I had sought to borrow From my books surcease of sorrow—sorrow for the lost Lenore— For the rare and radiant maiden whom the angels name Lenore— Nameless here for evermore. And the silken, sad, uncertain rustling of each purple curtain Thrilled me—filled me with fantastic terrors never felt before; So that now, to still the beating of my heart, I stood repeating “’Tis some visitor entreating entrance at my chamber door— Some late visitor entreating entrance at my chamber door;— This it is and nothing more.” Presently my soul grew stronger; hesitating then no longer, “Sir,” said I, “or Madam, truly your forgiveness I implore; But the fact is I was napping, and so gently you came rapping, And so faintly you came tapping, tapping at my chamber door, That I scarce was sure I heard you”—here I opened wide the door;— Darkness there and nothing more. Deep into that darkness peering, long I stood there wondering, fearing, Doubting, dreaming dreams no mortal ever dared to dream before; But the silence was unbroken, and the stillness gave no token, And the only word there spoken was the whispered word, “Lenore?” This I whispered, and an echo murmured back the word, “Lenore!”— Merely this and nothing more. Back into the chamber turning, all my soul within me burning, Soon again I heard a tapping somewhat louder than before. “Surely,” said I, “surely that is something at my window lattice; Let me see, then, what thereat is, and this mystery explore— Let my heart be still a moment and this mystery explore;— ’Tis the wind and nothing more!” Open here I flung the shutter, when, with many a flirt and flutter, In there stepped a stately Raven of the saintly days of yore; Not the least obeisance made he; not a minute stopped or stayed he; But, with mien of lord or lady, perched above my chamber door— Perched upon a bust of Pallas just above my chamber door— Perched, and sat, and nothing more. Then this ebony bird beguiling my sad fancy into smiling, By the grave and stern decorum of the countenance it wore, “Though thy crest be shorn and shaven, thou,” I said, “art sure no craven, Ghastly grim and ancient Raven wandering from the Nightly shore— Tell me what thy lordly name is on the Night’s Plutonian shore!” Quoth the Raven “Nevermore.” Much I marvelled this ungainly fowl to hear discourse so plainly, Though its answer little meaning—little relevancy bore; For we cannot help agreeing that no living human being Ever yet was blessed with seeing bird above his chamber door— Bird or beast upon the sculptured bust above his chamber door, With such name as “Nevermore.” But the Raven, sitting lonely on the placid bust, spoke only That one word, as if his soul in that one word he did outpour. Nothing farther then he uttered—not a feather then he fluttered— Till I scarcely more than muttered “Other friends have flown before— On the morrow he will leave me, as my Hopes have flown before.” Then the bird said “Nevermore.” Startled at the stillness broken by reply so aptly spoken, “Doubtless,” said I, “what it utters is its only stock and store Caught from some unhappy master whom unmerciful Disaster Followed fast and followed faster till his songs one burden bore— Till the dirges of his Hope that melancholy burden bore Of ‘Never—nevermore’.” But the Raven still beguiling all my fancy into smiling, Straight I wheeled a cushioned seat in front of bird, and bust and door; Then, upon the velvet sinking, I betook myself to linking Fancy unto fancy, thinking what this ominous bird of yore— What this grim, ungainly, ghastly, gaunt, and ominous bird of yore Meant in croaking “Nevermore.” This I sat engaged in guessing, but no syllable expressing To the fowl whose fiery eyes now burned into my bosom’s core; This and more I sat divining, with my head at ease reclining On the cushion’s velvet lining that the lamp-light gloated o’er, But whose velvet-violet lining with the lamp-light gloating o’er, She shall press, ah, nevermore! Then, methought, the air grew denser, perfumed from an unseen censer Swung by Seraphim whose foot-falls tinkled on the tufted floor. “Wretch,” I cried, “thy God hath lent thee—by these angels he hath sent thee Respite—respite and nepenthe from thy memories of Lenore; Quaff, oh quaff this kind nepenthe and forget this lost Lenore!” Quoth the Raven “Nevermore.” “Prophet!” said I, “thing of evil!—prophet still, if bird or devil!— Whether Tempter sent, or whether tempest tossed thee here ashore, Desolate yet all undaunted, on this desert land enchanted— On this home by Horror haunted—tell me truly, I implore— Is there—is there balm in Gilead?—tell me—tell me, I implore!” Quoth the Raven “Nevermore.” “Prophet!” said I, “thing of evil!—prophet still, if bird or devil! By that Heaven that bends above us—by that God we both adore— Tell this soul with sorrow laden if, within the distant Aidenn, It shall clasp a sainted maiden whom the angels name Lenore— Clasp a rare and radiant maiden whom the angels name Lenore.” Quoth the Raven “Nevermore.” “Be that word our sign of parting, bird or fiend!” I shrieked, upstarting— “Get thee back into the tempest and the Night’s Plutonian shore! Leave no black plume as a token of that lie thy soul hath spoken! Leave my loneliness unbroken!—quit the bust above my door! Take thy beak from out my heart, and take thy form from off my door!” Quoth the Raven “Nevermore.” And the Raven, never flitting, still is sitting, still is sitting On the pallid bust of Pallas just above my chamber door; And his eyes have all the seeming of a demon’s that is dreaming, And the lamp-light o’er him streaming throws his shadow on the floor; And my soul from out that shadow that lies floating on the floor Shall be lifted—nevermore! "The Tell-Tale Heart" by Edgar Allan Poe True! — nervous — very, very dreadfully nervous I had been and am; but why will you say that I am mad? The disease had sharpened my senses — not destroyed — not dulled them. Above all was the sense of hearing acute. I heard all things in the heaven and in the earth. I heard many things in hell. How, then, am I mad? Hearken! and observe how healthily — how calmly I can tell you the whole story. It is impossible to say how first the idea entered my brain; but once conceived, it haunted me day and night. Object there was none. Passion there was none. I loved the old man. He had never wronged me. He had never given me insult. For his gold I had no desire. I think it was his eye! yes, it was this! One of his eyes resembled that of a vulture — a pale blue eye, with a film over it. Whenever it fell upon me, my blood ran cold; and so by degrees — very gradually — I made up my mind to take the life of the old man, and thus rid myself of the eye forever. Now this is the point. You fancy me mad. Madmen know nothing. But you should have seen me. You should have seen how wisely I proceeded — with what caution — with what foresight — with what dissimulation I went to work! I was never kinder to the old man than during the whole week before I killed him. And every night, about midnight, I turned the latch of his door and opened it — oh, so gently! And then, when I had made an opening sufficient for my head, I put in a dark lantern, all closed, closed, so that no light shone out, and then I thrust in my head. Oh, you would have laughed to see how cunningly I thrust it in! I moved it slowly — very, very slowly, so that I might not disturb the old man’s sleep. It took me an hour to place my whole head within the opening so far that I could see him as he lay upon his bed. Ha! — would a madman have been so wise as this? And then, when my head was well in the room, I undid the lantern cautiously — oh, so cautiously — cautiously (for the hinges creaked) — I undid it just so much that a single thin ray fell upon the vulture eye. And this I did for seven long nights — every night just at midnight — but I found the eye always closed; and so it was impossible to do the work; for it was not the old man who vexed me, but his Evil Eye. And every morning, when the day broke, I went boldly into the chamber, and spoke courageously to him, calling him by name in a hearty tone, and inquiring how he had passed the night. So you see he would have been a very profound old man, indeed, to suspect that every night, just at twelve, I looked in upon him while he slept. Upon the eighth night I was more than usually cautious in opening the door. A watch’s minute hand moves more quickly than did mine. Never before that night had I felt the extent of my own powers — of my sagacity. I could scarcely contain my feelings of triumph. To think that there I was, opening the door, little by little, and he not even to dream of my secret deeds or thoughts. I fairly chuckled at the idea; and perhaps he heard me; for he moved on the bed suddenly, as if startled. Now you may think that I drew back — but no. His room was as black as pitch with the thick darkness, (for the shutters were close fastened, through fear of robbers,) and so I knew that he could not see the opening of the door, and I kept pushing it on steadily, steadily. I had my head in, and was about to open the lantern, when my thumb slipped upon the tin fastening, and the old man sprang up in the bed, crying out — “Who’s there?” I kept quite still and said nothing. For a whole hour I did not move a muscle, and in the meantime I did not hear him lie down. He was still sitting up in the bed listening; — just as I have done, night after night, hearkening to the death watches in the wall. Presently I heard a slight groan, and I knew it was the groan of mortal terror. It was not a groan of pain or of grief — oh, no! — it was the low stifled sound that arises from the bottom of the soul when overcharged with awe. I knew the sound well. Many a night, just at midnight, when all the world slept, it has welled up from my own bosom, deepening, with its dreadful echo, the terrors that distracted me. I say I knew it well. I knew what the old man felt, and pitied him, although I chuckled at heart. I knew that he had been lying awake ever since the first slight noise, when he had turned in the bed. His fears had been ever since growing upon him. He had been trying to fancy them causeless, but could not. He had been saying to himself — “It is nothing but the wind in the chimney — it is only a mouse crossing the floor,” or “it is merely a cricket which has made a single chirp.” Yes, he has been trying to comfort himself with these suppositions: but he had found all in vain. All in vain; because Death, in approaching him had stalked with his black shadow before him, and enveloped the victim. And it was the mournful influence of the unperceived shadow that caused him to feel — although he neither saw nor heard — to feel the presence of my head within the room. When I had waited a long time, very patiently, without hearing him lie down, I resolved to open a little — a very, very little crevice in the lantern. So I opened it — you cannot imagine how stealthily, stealthily — until, at length a single dim ray, like the thread of the spider, shot from out the crevice and fell upon the vulture eye. It was open — wide, wide open — and I grew furious as I gazed upon it. I saw it with perfect distinctness — all a dull blue, with a hideous veil over it that chilled the very marrow in my bones; but I could see nothing else of the old man’s face or person: for I had directed the ray as if by instinct, precisely upon the damned spot. And now have I not told you that what you mistake for madness is but over acuteness of the senses? — now, I say, there came to my ears a low, dull, quick sound, such as a watch makes when enveloped in cotton. I knew that sound well, too. It was the beating of the old man’s heart. It increased my fury, as the beating of a drum stimulates the soldier into courage. But even yet I refrained and kept still. I scarcely breathed. I held the lantern motionless. I tried how steadily I could maintain the ray upon the eye. Meantime the hellish tattoo of the heart increased. It grew quicker and quicker, and louder and louder every instant. The old man’s terror must have been extreme! It grew louder, I say, louder every moment! — do you mark me well? I have told you that I am nervous: so I am. And now at the dead hour of the night, amid the dreadful silence of that old house, so strange a noise as this excited me to uncontrollable terror. Yet, for some minutes longer I refrained and stood still. But the beating grew louder, louder! I thought the heart must burst. And now a new anxiety seized me — the sound would be heard by a neighbor! The old man’s hour had come! With a loud yell, I threw open the lantern and leaped into the room. He shrieked once — once only. In an instant I dragged him to the floor, and pulled the heavy bed over him. I then smiled gaily, to find the deed so far done. But, for many minutes, the heart beat on with a muffled sound. This, however, did not vex me; it would not be heard through the wall. At length it ceased. The old man was dead. I removed the bed and examined the corpse. Yes, he was stone, stone dead. I placed my hand upon the heart and held it there many minutes. There was no pulsation. He was stone dead. His eye would trouble me no more. If still you think me mad, you will think so no longer when I describe the wise precautions I took for the concealment of the body. The night waned, and I worked hastily, but in silence. First of all I dismembered the corpse. I cut off the head and the arms and the legs. I then took up three planks from the flooring of the chamber, and deposited all between the scantlings. I then replaced the boards so cleverly, so cunningly, that no human eye — not even his — could have detected any thing wrong. There was nothing to wash out — no stain of any kind — no blood-spot whatever. I had been too wary for that. A tub had caught all — ha! ha! When I had made an end of these labors, it was four o ‘clock — still dark as midnight. As the bell sounded the hour, there came a knocking at the street door. I went down to open it with a light heart, — for what had I now to fear? There entered three men, who introduced themselves, with perfect suavity, as officers of the police. A shriek had been heard by a neighbor during the night; suspicion of foul play had been aroused; information had been lodged at the police office, and they (the officers) had been deputed to search the premises. I smiled, — for what had I to fear? I bade the gentlemen welcome. The shriek, I said, was my own in a dream. The old man, I mentioned, was absent in the country. I took my visitors all over the house. I bade them search — search well. I led them, at length, to his chamber. I showed them his treasures, secure, undisturbed. In the enthusiasm of my confidence, I brought chairs into the room, and desired them here to rest from their fatigues, while I myself, in the wild audacity of my perfect triumph, placed my own seat upon the very spot beneath which reposed the corpse of the victim. The officers were satisfied. My manner had convinced them. I was singularly at ease. They sat, and while I answered cheerily, they chatted of familiar things. But, ere long, I felt myself getting pale and wished them gone. My head ached, and I fancied a ringing in my ears: but still they sat and still chatted. The ringing became more distinct: — it continued and became more distinct: I talked more freely to get rid of the feeling: but it continued and gained definitiveness — until, at length, I found that the noise was not within my ears. No doubt I now grew very pale; — but I talked more fluently, and with a heightened voice. Yet the sound increased — and what could I do? It was a low, dull, quick sound — much such a sound as a watch makes when enveloped in cotton. I gasped for breath — and yet the officers heard it not. I talked more quickly — more vehemently; but the noise steadily increased. I arose and argued about trifles, in a high key and with violent gesticulations; but the noise steadily increased. Why would they not be gone? I paced the floor to and fro with heavy strides, as if excited to fury by the observations of the men — but the noise steadily increased. Oh God! what could I do? I foamed — I raved — I swore! I swung the chair upon which I had been sitting, and grated it upon the boards, but the noise arose over all and continually increased. It grew louder — louder — louder! And still the men chatted pleasantly, and smiled. Was it possible they heard not? Almighty God! — no, no! They heard! — they suspected! — they knew! — they were making a mockery of my horror! — this I thought, and this I think. But anything was better than this agony! Anything was more tolerable than this derision! I could bear those hypocritical smiles no longer! I felt that I must scream or die! — and now — again! — hark! louder! louder! louder! louder! — “Villains!” I shrieked, “dissemble no more! I admit the deed! — tear up the planks! — here, here! — it is the beating of his hideous heart!" Edgar Allan Poe: author is published under the public domain license. Transcendentalism 1830-1865 Transcendentalism (1830-1865) “True American Voice Emerges” Transcendentalism was a literary, philosophical, and cultural movement that emerged in the United States during the mid-19th century, roughly 1830-1860. It was born out of New England and was heavily influenced by Romanticism and European philosophers, such as Immanual Kant and Johann Wolfgang von Goethe of Germany. The notion of rugged individualism as an American value grew from this movement due to the emphasis on individualism, self-reliance, non-conformity, and dissent Transcendentalists encouraged individuals to trust their instincts and judgments, rather than conforming to societal expectations and external authorities. They were often critical of organized religion, government, and social hierarchy. Instead, they sought solace in nature and incorporated elements of spirituality and mysticism in favor of direct, personal experience with the divine. They believed nature as a source of spiritual insight, often advocating for a return to nature as a means of finding spiritual fulfillment and connection. Social movements they were actively involved with included education reform, women’s rights, and abolitionism. Prominent writers of the time include Ralph Waldo Emerson, Henry David Thoreau, Margaret Fuller, Frederick Douglass, and Walt Whitman. Author Biography: Nathanial Hawthorne Nathaniel Hawthorne was an American novelist and short story writer. He was born in 1804 in Salem, Massachusetts. His ancestors include John Hathorne, the only judge involved in the Salem witch trials who never repented of his actions. He graduated from Bowdoin College in 1825. He worked at the Boston Custom House and joined Brook Farm, a transcendentalist community, before marrying Sophia Peabody in 1842. Much of Hawthorne’s writing centres on New England, with many of his works featuring moral metaphors with an anti-Puritan inspiration. His themes often centre on the inherent evil and sin of humanity, and his works often have moral messages and deep psychological complexity. Hawthorne’s works belong to Romanticism or, more specifically, Dark Romanticism, cautionary tales that suggest that guilt, sin, and evil are the most inherent natural qualities of humanity. Many of his works are inspired by Puritan New England, combining historical romance loaded with symbolism and deep psychological themes, bordering on surrealism. His depictions of the past are a version of historical fiction used only as a vehicle to express common themes of ancestral sin, guilt, and retribution. His later writings also reflect his negative view of the transcendentalism movement. Hawthorne was predominantly a short story writer in his early career. Upon publishing the collection Twice-Told Tales, however, he noted, “I do not think much of them,” and he expected little response from the public. His four major novels were written between 1850 and 1860: The Scarlet Letter (1850), The House of the Seven Gables (1851), The Blithedale Romance (1852), and The Marble Faun: Or, The Romance of Monte Beni (1860). Hawthorne died on May 19, 1864, and was survived by his wife and their three children. The Scarlet Letter. 1850. Nathaniel Hawthorne. The Project Gutenburg. Author work also found in the public domain. Introduction: 1865-Present Introduction: 1865-Present Realism 1865-1910 Realism - 1865-1910, Post Civil War Realism as a literary movement emerged in the mid-19th century as a reaction against the highly stylized and idealized art of Romanticism, aiming to depict everyday activities and experiences as they are. This period, particularly from 1865 to 1910, was marked by significant socio-economic changes that influenced the development of Realism in literature. The end of the American Civil War in 1865 marked the beginning of Reconstruction in the United States, a period of significant social and political upheaval. In Europe and the Americas, the industrial revolution was transforming societies, shifting populations from rural to urban areas, and creating new social classes and tensions. This era also saw the expansion of empires, colonization, and the early stages of globalization, as well as scientific advancements and increasing secularism challenging traditional beliefs and structures. Realist writers sought to portray life with a new level of accuracy and detail, focusing on ordinary people and everyday situations. They delved into the complexities of human behavior and societal issues, often highlighting the struggles of the middle and lower classes. This movement was a shift away from the emphasis on emotion and individual heroism of the Romantic era, towards a focus on society and the conditions of life for its members. Authors that exemplify the Realism movement of offering insight into American society and culture during a time of profound change and transformation include Mark Twain, Henry James, Edith Warton, Kate Chopin, Stephen Crane, Willa Cather, and Ambrose Bierce. Modernism 1910-1945 Modernism is the literary period that roughly spans 1910-1945. This period of significant experimentation, innovation, and upheaval in literature, was marked by a break from traditional writing and social forms and conventions. Modernist writers sought to capture the complexities and uncertainties of the modern world, exploring themes of alienation, fragmentation, identity, and the search for meaning in a rapidly changing society. Modernist literature reflects experimentation with style, form, and type of writing such as different narrative structures, language, and style use, such as non-linear storytelling, stream of consciousness, and fragmented narratives. Realism and transcendental writers wrote through a more objective lens while writers during the modernism movement took up the subjective and symbolic perspectives of the reality of the characters they created. Writers turned inward and explored the inner lives of characters, the subconscious mind, and the complexities of human perception, memory, and identity. Modernist writers experienced great changes in the early 20th century including World War I, the Industrial Revolution, urbanization, the fight for Women’s Rights (that is still going on today), and other social changes. Because of these major societal changes, many works of Modernist literature reflect existential angst, alienation, and disillusionment. Symbolism, allegory, and allusion are literary conventions used to convey deeper meaning and themes. Symbols and motifs were commonly used to explore complex ideas and evoke emotional responses from readers. Popular Modernist authors include James Joyce, T.S. Elliot, Virginia Woolf, F. Scott Fitzgerald, Ernest Hemingway, and Katherine Mansfield. Contemporary 1946-present The literary time of contemporary writing spans from 1946 to the present day and encompasses a diverse array of styles, themes, and voices. Writers during this time have played a significant role in pushing the boundaries of literary expression, challenging norms, and exploring alternative perspectives as it relates to reality, identity, and society. It reflects the ever-evolving nature of literature and the dynamic cultural, social, and technological changes that have shaped the world since the end of World War II. Contemporary literature embraces diversity and inclusivity, featuring voices from a range of backgrounds, cultures, and perspectives. Many modern works transcend national boundaries exploring migration and cultural exchange themes while engaging with global issues and perspectives. Writers delve into the intersectionality of identity, examining how race, gender, class, sexuality, and other factors which shape individual lives and perspectives. This leads authors to grapple with pressing social and political issues of the day, including social justice, human rights, technology, and the impacts of globalization. Writers use their platforms to raise awareness, provoke thought, and inspire change. Some popular writers have even fallen out of public favor due to limited personal beliefs that they have shared publicly about identity, gender, and human rights. Not only have contemporary writers taken up the topic of technology and how our human experience is impacted by technology, but writers also experiment with new technology to reach audiences in new ways. They’ve experimented with form and structure, incorporating multimedia, hybrid genres, and interactive storytelling. Digital technology has opened up new possibilities for storytelling, allowing writers to explore innovative ways of engaging with readers. Contemporary American literature resonates with readers today by offering insights into the human experience, sparking dialogue on pressing issues, and providing a mirror to society’s triumphs, challenges, and aspirations. Popular Contemporary authors include Arthur Miller, Ralph Ellison, Toni Morrison, Kurt Vonnegut, Don DiLillo, Jesmyn Ward, and Chimamanda Ngozi Adichie. Alice Walker © Virginia DeBolt is licensed under a CC BY-SA (Attribution ShareAlike) license	oercommons	2025-03-18T00:35:14.910778	Textbook	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/113951/overview", "title": "American Literature Beginnings to Present", "author": "Reading" }
https://oercommons.org/courseware/lesson/123186/overview	Demonstration of the Open Author Tool Overview This resource is part of the OERizona Advanced Course. This section explores the tools that support the creation of new OER. In this section, the user can see a sample demonstration on how to use the Open Author tool that is built into OER Commons. OER Creation Goals Open Educational Resources (OER) are often created in collaboration with others. As you prepare to author an OER, consider the following groups for collaboration - Faculty peers who can bring new viewpoints about the content area. - Faculty colleagues who can bring new instructional design ideas and technology support. - Students who can be co-creators that bring authenticity and diverse experiences Earlier in the Coursework, we examined the Arizona Quality Review Rubric. We are also including it here for your review to support guiding your content creation. Demonstration of OER Authoring Tools (Joanna to insert video of Open Author tool)	oercommons	2025-03-18T00:35:14.930874	12/18/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/123186/overview", "title": "OERizona Advanced OER Skills, Author a Starter OER, Demonstration of the Open Author Tool", "author": null }
https://oercommons.org/courseware/lesson/123185/overview	OER Authoring Tools on OER Commons Overview This resource is part of the OERizona Advanced Coursework and supports OERizona faculty across Arizona in using tools to create OER. Using the Open Author Tool on OER Commons As faculty prepare to create OER, they should consider each of the following steps: - Who is my audience and what are their needs? - Does an OER for this topic already exist and can it be remixed? - What is my timeline for creating this OER? - Who can collaborate with me to support this OER Creation? - What tool do I want to use to author the OER? - What license do I plan to use? - What do I need to get started? When you consider question five from above, you may choose to use the Open Author tool on OER Commons. This tool was designed to help faculty organize their OER into sections that are easy to navigate, easy to remix and are accessibility compliant. Below are some key features of the Open Author Tool: - Open Author allows you to organize your content into sections that can be navigated within a single resource or built into a full course shell. - The authoring tool is designed with accessibility principles, so it includes an accessibility checker, requires Alt Text for images and uses Styles to create reading order for screenreaders. - Open Author allows you to embed a variety of multi-media including videos, mathematical equations, images with Alt Text and tables. - Resources authored on OER Commons get tagged with key metadata that makes it easy for other faculty to find and adopt your OER. - Open Author supports authors in selecting an Creative Commons license and includes that license on the description page of the resource. - Any remixes that are made of a resource authored on OER Commons will generate an email to the original author notifying them that a remix was made of their resource. See the next section for a demonstration of using Open Author.	oercommons	2025-03-18T00:35:14.944782	12/18/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/123185/overview", "title": "OERizona Advanced OER Skills, Author a Starter OER, OER Authoring Tools on OER Commons", "author": null }
https://oercommons.org/courseware/lesson/124718/overview	Assessment - Aspirin & Equilibrium Assessment Key - Aspirin & Equilibrium Lesson Plan Outline - Aspirin & Equilibrium Powerpoint - Aspirin & Equilibrium Aspirin & Equilibrium Lesson Plan Overview Welcome. Our goal is to design high school chemistry lesson plans that integrate fundamental organic chemisty concepts. These lessons aim to bridge the gap between introductory chemistry and organic chemistry, giving students a head start in understanding molecular structures, reactions, and more, in a way that is engaging and accessible. By connecting these core ideas with hands-on experiments, real-world applucations, and interactive learning tools, students will be better equipped to understand the relevance of organic chemistry in everyday life and future scientific studies. For additional organic chemistry lesson plans, view the following:O-Chem Lesson Plans Folder Overview Welcome Our goal is to design high school chemistry lesson plans that integrate fundamental organic chemisty concepts. These lessons aim to bridge the gap between introductory chemistry and organic chemistry, giving students a head start in understanding molecular structures, reactions, and more, in a way that is engaging and accessible. By connecting these core ideas with hands-on experiments, real-world applucations, and interactive learning tools, students will be better equipped to understand the relevance of organic chemistry in everyday life and future scientific studies. For additional organic chemistry lesson plans, view the following: Feedback We value your feedback and would like to know how to make our lesson plans more engaging, accessible, and clear. Please take the following survey for this lesson plan, Aspirin & Equilibrium, by using the following link: Aspirin & Equilibrium Lesson Plan Aspirin & Equilibrium Brief Lesson Description: \| \| Standard (from Utah SEEd Standards): Standard CHEM.3.7 \| \| Specific Learning Outcomes for This Lesson: \| \| Estimated Time Requirements: \|	oercommons	2025-03-18T00:35:14.968875	Lesson Plan	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/124718/overview", "title": "Aspirin & Equilibrium Lesson Plan", "author": "Lesson" }
https://oercommons.org/courseware/lesson/123180/overview	Demonstration of OER Remixing Tools Overview This resource is part of the OERizona Advanced Course. This section explores the tools of OER Remixing that support iteration of OER. In this section, the user can see a sample demonstration on how to use the Remix tools that are built into OER Commons. OER Remixing Goals Many Open Educational Resources (OER) are designed to be dynamic resources that can be revised and remixed to increase accuracy, relevancy, and localization. - Look at the license of the OER to determine if the resource can be revised or remixed and shared. The terms of the license will guide the remixing process. - Giving conspicuous and thorough attribution is a key part of the Open Education community. OER Remixing can take place in many different editing platforms. You may choose to use the Open Author tool provided on the OER Commons platform. This allows the original author to be notified when the remix is published, and it also keeps the related resources connected via a "Version History" tool. See below for a demonstration of Remixing using the Open Author tool. Using the Remix Tool To use the Remix tool that is built into OER Commons, follow the below steps. - Log in - ensure that you are logged into your account on OER Commons - Visit the original resource - The Remix button is a green rectangle with the word "Remix" and is available on the landing/description page of each resource and is also visible on the contents of the resource - Begin Remixing - Once you click the green Remix button, the Open Author tool will open a new copy of the resource. This copy is automatically saved in your "My Items" part of your profile. It will remain in "Draft" mode until you click "Publish" inside the resource editing page. - Rename Your Version - Nomenclature of OER is extremely important to discoverability. Take time to rename your resource and then choose the "Save" button at the top. The platform will save your work occasionally as you add sections, but it's highly recommended that you save your work. - Add Co-Authors - You can add other faculty as co-authors as long as they have an OER Commons account. Use the "View & Manage Authors" option at the top left of the editing pane. - Make your edits - As you make edits, be sure to run the Accessibility Checker and include proper citation and attribution. You may choose to add a Section for attributions. - Add Metadata - The Green "Next" button at the top of the editing window will take you to a page for adding metadata for your resource to align it to keywords and other criteria that help users search for and find your resource. - Publish - When you are finished with the resource and ready to publish. Now you can celebrate! (Joanna to insert video here)	oercommons	2025-03-18T00:35:14.983351	Lesson	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/123180/overview", "title": "OERizona Advanced OER Skills, Revise and Remix OER, Demonstration of OER Remixing Tools", "author": null }
https://oercommons.org/courseware/lesson/123184/overview	Authoring for the OERizona Hub Overview This resource is part of the OERizona Advanced Course. This section supports the user in exploring the OERizona Hub for considerations about creating new OER. Exploring and Practicing The OERIzona Hub was created to support faculty from across Arizona as they adopt, adapt and create OER. The Hub includes collections of OER that have been vetted by Arizona faculty, and these collections serve as a valuable place for looking both for inspiration and for a place to remix. Many of these resources were created using the Open Textbooks for Rural Arizona Publishing Template. Let's take a moment to explore some of the existing resources so that as you can gain inspiration for your own creation process. (insert video of Megan C describing the Arizona collection)	oercommons	2025-03-18T00:35:14.996341	12/18/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/123184/overview", "title": "OERizona Advanced OER Skills, Author a Starter OER, Authoring for the OERizona Hub", "author": "Megan Crossfield" }
https://oercommons.org/courseware/lesson/123178/overview	OERizona Collection and Remixing Overview This resource is an overview of the OERiszona Collection of resources that can be remixed to increase usage across Arizona. Exploring and Practicing The OERizona Collections are a source of high-quality, vetted OER that are ready for implementation in courses across Arizona. These resources often include a link to an OER Textbook, a link to a Canvas Course Shell and a link to a Thin Common Cartridge for use outside of Canvas. An example that is included in the English and Writing Collection is from Yavapai College Professor Laura Cline. This English102 College Composition Course in Open Author includes the course desription, a link to the course in Canvas, and the dowloadable Course Common Cartrdge. As you examine these OER or use them, you will adapt it to your classroom. We encourage you to keep track of the supplemental materials that you use, the iterations that you make to the materials and the supports that you create for students so that you can share those with the broader OER community. To share these, you can just choose the "Remix" button on the resource and a copy of the original is made, thus allowing you to add and edit, guided by your own teaching experiences. Once you publish, the resources will be linked together so that faculty who find the original will also see your iteration and those who find your iteration will be able to find the original. This remixing genuinely grows the OER community, especially with respect to the specific needs of Arizona. (Insert video of [Micah Weedman]?)	oercommons	2025-03-18T00:35:15.009504	12/18/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/123178/overview", "title": "OERizona Advanced OER Skills, Revise and Remix OER, OERizona Collection and Remixing", "author": "Megan Crossfield" }
https://oercommons.org/courseware/lesson/122067/overview	Reviewing OER Commons and the OERizona Hub Overview This resource is an overview of the OER Commons platform and the OERizona network and Hub. Exploring and Practicing As faculty use, remix and share Open Educational Resources (OER), the opportunity exists to build collaborative and generative communities. Faculty often find that while they start by using OER for one reason, becoming part of a community helps them more effectively and creatively implement and engage with OER. Below are some reasons for being part of the larger OER Community: - Finding larger numbers of OER - Curate OER into collections based on topics and theme - Evaluate OER to provide feedback and collaboration - Remix OER to increase accessibility, localization, and customizations - Create OER, especially in collaboration with diverse voices from your institution OER Commons is a global, digital repository for sharing OER and collaborating with other faculty. OER Commons has a search engine that uses metadata and analytics to help users refine their OER searches. Also on the OER Commons platform are Hubs and Groups for collaborative discussions and resource sharing. Follow the below steps to join the OER Commons community: - Visit OERCommons.org - Choose Sign In/Register at the top right of the webpage - Create and confirm your account - Explore the collaborative Groups, especially the groups on the OERizona Hub OERizona is the _______(Megan C to add content here)_________	oercommons	2025-03-18T00:35:15.023224	11/21/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/122067/overview", "title": "OERizona Advanced OER Skills, Evaluating OER, Reviewing OER Commons and the OERizona Hub", "author": "Megan Crossfield" }
https://oercommons.org/courseware/lesson/66256/overview	Federal Constitution of the United Mexican States (1824) Overview Federal Constitution of the United Mexican States (1824) Learning Objective By the end of this section, you will be able to: - Understand the Federal Constitution of the United Mexican States (1824)’s role in Texas history Introduction This section discusses the Federal Constitution of the United Mexican States (1824)’s role in Texas history. Federal Constitution of the United Mexican States of 1824 Constitutional government in Texas began with the Mexican Federal Constitution of 1824, which, to some degree, was patterned after the United States Constitution but resembled more the Spanish Constitution of 1812. Congress was made the final interpreter of the document; the Catholic religion was made the state faith; and the church was supported by the public treasury. The president and vice president were elected for four-year terms by the legislative bodies of the states, the lower house of Congress to elect in case of a tie or lack of a majority. There were numerous limitations on the powers of the president. The Congress was composed of two houses meeting annually from January 1 to April 15. The president could prolong the regular session for an additional thirty days and could call extra sessions. Deputies in the lower house served two years, while senators were selected by their state legislatures for four- year terms. The judicial power was vested in a Supreme Court and superior courts of departments and districts. The Supreme Court was composed of eleven judges and the attorney general. There was no particular effort to define the rights of the states in the confederacy. They were required to separate executive, legislative, and judicial functions in their individual constitutions, which were to be in harmony with the national constitution, but local affairs were independent of the general government. Link to Learning More information on the Federal Constitution of the United Mexican States (1824) may be found at the Texas Constitutions 1824-1876 project of the Tarlton Law Library, Jamail Center for Legal Research at the University of Texas School of Law, the University of Texas at Austin. The project includes digitized images and searchable text versions of the constitutions. References and Further Reading Federal Constitution of the United Mexican States (1824) may be found at the Texas Constitutions 1824-1876 project of the Tarlton Law Library, Jamail Center for Legal Research at the University of Texas School of Law, the University of Texas at Austin. Licenses and Attribution CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: Kris S. Seago. License: CC BY: Attribution	oercommons	2025-03-18T00:35:15.044050	05/05/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66256/overview", "title": "Texas Government 2.0, The Texas State Constitution and the American Federal System, Federal Constitution of the United Mexican States (1824)", "author": "Kris Seago" }
https://oercommons.org/courseware/lesson/108017/overview	Education Standards Circle Format Self-assessment Community _ Cognition - Advanced High Circle Format Self-assessment Culture _ Connection - Advanced High WL Self Assessment Circles - Advanced High Overview Research shows that engaging students in self-assessment positively impacts language learning, motivation, and learner autonomy. To help World Language Educators accomplish this, the Nebraska Department of Education invited experienced world language teachers across the state to create student-friendly assessments in the form of can-do statements in the summer of 2023. This document is a student-friendly self-assessment activity for Advanced Low world language learners created based on the 2019 Nebraska World Language Standards. The language use described in all can-do statements is meant for the target language, except for the second for standard 3.1 and the first for standard 4.2. It is recommended that world language teachers engage students with this document three times in an academic year: pre-course, mid-course, and post-course. Engaging students with this self-assessment activity will help students see growth over time and hopefully attribute growth to effective learning practices. Please feel free to contact chrystal.liu@nebraska.gov for any questions or concerns. Description Research shows that engaging students in self-assessment positively impacts language learning, motivation, and learner autonomy. To help World Language Educators accomplish this, the Nebraska Department of Education invited experienced world language teachers across the state to create student-friendly assessments in the form of can-do statements in the summer of 2023. This document is a student-friendly self-assessment for activity Advanced-High world language learners created based on the 2019 Nebraska World Language Standards. The language use described in all can-do statements is meant for the target language, except for the second for standard 3.1 and the first for standard 4.2. It is recommended that word language teachers engage students with this document three times in an academic year: pre-course, mid-course, and post-course. Engaging students with this self-assessment activity will help students see growth over time and hopefully attribute growth to effective learning practices. Please feel free to contact chrystal.liu@nebraska.gov for any questions or concerns.	oercommons	2025-03-18T00:35:15.075888	Dorann Avey	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/108017/overview", "title": "WL Self Assessment Circles - Advanced High", "author": "Chrystal Liu" }
https://oercommons.org/courseware/lesson/112856/overview	Introduction to Computers Overview This course is an introduction for non-computer science students. Instead, this course is a gentler, lighter survey course without delving too much into technical details. It will also examine computers from the perspective on how they influence society. What Is a Computer? A computer is an "electronic box" that you put some "stuff" in, the box does "stuff" with it, and then the box has some way of showing the world what it has done. You are using a computer right now! The stuff you put into a computer is called data, and gets into the computer using the input. Data is simply a form of information. You can put data into a computer from your keyboard, a mouse, a trackpad, a camera, an infrared sensor; anything that will give the computer more information about the world around it. Based on what information the computer has received, it can decide to do stuff with it. Input – Data which a computer receives via some input component. Processing – What the computer does with the data is known as processing. A computer will process information differently based on what kind of data it has gotten. Program – the computer processes the data we have put in it, in some way - by following a set of instructions: the program. Once the computer has done some processing, there should be a way to show the world what it has done. Another way to think about a program is if you gave a recipe to a friend, you tell them the instructions and the instructions make the output of the program (or recipe) Output – This is usually done through a screen, but can also be done with a speaker, LEDs, a laser, a robotic arm; all of these are called outputs. A basic computer consists of three major components: input/output, the processor, and memory. Input and output provide a way to interact with a computer: - Keyboard - Mouse - Trackpad or touchpad - Display - Power Button - Microphone - Camera The processor, or Central Processing Unit (CPU), is the part that does the processing. The CPU can be said to manipulate data: - Encryption and Decryption (This makes your data secure.) - Math - Logic The memory gives your computer a place to store information that it might need in order to process data well. The processor can be told to use the memory by specifying it as the input or output. Some things that might be stored in memory might be: - Photos from a Camera (A camera is an input) - A Program - A Text Document - An Executable Document	oercommons	2025-03-18T00:35:15.101658	02/15/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/112856/overview", "title": "Introduction to Computers", "author": "V.N. Battu" }
https://oercommons.org/courseware/lesson/95193/overview	Black Americans as Activists in Tennessee Overview This activity was produced in conjunction with The Library of Congress and the TPS at the Metropolitan State University of Denver. This activity allows learners to examine and listen to first-hand accounts and primary sources images of history during the Civil Right time period. This activity will allow learners to develop empathy and understanding of: - why someone might feel they should protest or stand up for their beliefs. - how we can interact and respect others who may be different or have experiences we cannot fully understand. Activity Plan for Elementary/Middle School Grades 3-8 Crossroads of History Activity Plan Template Non-classroom setting or this could be used in the classroom as well Activity Title \| Black Americans as Activists in Tennessee \| Instructional Level \| Elementary/Middle 3-8 \| Target Audience \| Youth Grades 3-8 \| TPS Western Region Location \| Tennessee (Participant is outside the western region) \| Duration of Time or Lesson \| This could be one lesson or broken up into multiple days. \| \| \| Overarching question: Why do Black Americans choose to be Activists? \| Social Justice Standard: 9. Learners will respond to diversity by building empathy, respect, understanding, and connection. \| \| \| The four corners debate strategy will be used to examine a primary source image 1:Civil rights march on Washington, D.C. / [MST]. \| Library of Congress (loc.gov) Label the room with four corner signs Corner 1: strongly agree, Corner 2 agree, Corner 3 disagree, Corner 4 strongly disagree This activity will allow youth of all ethnicities to respond privately and in a group setting about the Black American activist community. The final step in the activity will allow learners to respond with their choice of writing, drawing, or composing a song or poem about the image and what it allows us to observe about the Black American activist community. \| Library of Congress Teacher Resources \| Image 1: Civil rights march on Washington, D.C. / [MST]. \| Library of Congress (loc.gov) Constructing Compelling Questions Processes, Rules, and Laws \| Introductory Text/ Program justification (Describe the marginalized people whose stories and history within your community you will be teaching about through these activities, and why their stories must be shared at this point in history.) \| Often, we see groups of people protesting or standing up for what they believe in and often we can wonder why they would do this and wish they were not inconveniencing others by sharing their beliefs. In my area, we often see groups of African American or black community leaders standing up for what they believe in such as the Black Lives Matter movement. This activity will allow learners to understand why someone might feel they should protest or stand up for their beliefs. Learners will learn how we can interact and respect others who may be different or have experiences we cannot fully understand. The African American or black population is the largest marginalized community in Tennessee. These activities focus on learning why this community becomes activists for change. Key Vocabulary: Activist-someone that calls or takes action for change Non-violent march or protest- when a group of people gathers to show their beliefs to others \| \| \| Materials needed: (What supplies do you need to do this activity with your learners?) \| Primary Source Images are large on a screen or a printed paper to learners to observe individually or in small groups. Feeling Chart displayed on a Project for everyone to see or print out for each table to see. Chart Paper with Markers or pens to Post questions throughout for discussions. Sign labels for each of the four corners of the room. Corner 1: strongly agree, Corner 2 agree, Corner 3 disagree, Corner 4 strongly disagree \| Technology: (What technology will you need to complete this activity?) \| Projector with the large primary source image displayed for learners. A computer and speakers to play the video recording in the entry task. \| Consumables & Copies: (What materials do you need to provide for learners to use during this activity that can not be reused during another cohort?) \| If a projector is not available, print multiple copies of the primary source image on paper. Learners will need to divide a paper into four equal squares labeled just as the room is labeled. Corner (Square) 1: strongly agree, Corner 2 (Square) agree, Corner 3 (Square) disagree, Corner 4 (Square) strongly disagree \| Library of Congress Primary Source links (Attach links here to documents, videos, any materials from research that you will be sharing with learners during this program.) \| Video or Audio Recording: Martha Prescod Norman Noonan oral history interview conducted by John Dittmer in Cockeysville, Maryland, 2013 March 18. \| Library of Congress (loc.gov) Listen to the video from 4:34 until 10:43 Citations: Noonan, Martha P., Interviewee, John Dittmer, and U.S Civil Rights History Project. Martha Prescod Norman Noonan oral history interview conducted by John Dittmer in Cockeysville, Maryland. 2013. Video. Retrieved from the Library of Congress, <www.loc.gov/item/2015669179/>. Image 1: Trikosko, Marion S, photographer. Civil rights march on Washington, D.C. / MST. Photograph. Retrieved from the Library of Congress, <www.loc.gov/item/2003673960/>. Image 2: Leffler, Warren K, and Warren K Leffler, photographer. ANTI-WAR DEMONSTRATION. 14th St. March to Justice Dept. May 4. Photograph. Retrieved from the Library of Congress, <www.loc.gov/item/2017646302/>. Image 3: Harris & Ewing, Washington, D.C. Women marching in national suffrage demonstration in Washington, D.C., May 9. May 9. Photograph. Retrieved from the Library of Congress, <www.loc.gov/item/mnwp000268/>. \| Entry Activity/Task 20 minutes \| Listen and respond to Martha’s Early Childhood Experiences The group leader will play the video allowing learners to listen the first time starting at 4:34 and listening until 10:43 The group leader will then pass out a paper and allow learners to write or draw any key details or items they hear as the recording is played for a second time to capture key details of Martha’s early childhood experiences. Group leader then asks learners how the video recording made them feel and find the image that best represents Their feeling on this feelings chart (displayed for all to see on a project or a printout at each table) after watching to the video. Learners will write the face of the feeling they feel after watching the video. If learners would like to share their feelings and why to encourage them to do so with a partner. it is expected learners will feel angry, sad, surprised, and scared about the experiences Martha shares. The group leader then allows learners to find connections or non-connection to what they heard on the recording such as questions in an open discussion. The group leader shares that sometimes it is hard for us to understand how different groups of people feel because we have had different experiences. Even though we might not understand what it feels like to be that person or that group of people like Martha we can all practice respect when others are sharing their opinions and beliefs by listening and being respectful. Key Learning- Often a person’s actions or beliefs are formed by previous experiences or family values. Such as Martha’s parents were Activists and stood up for what they believed in and Martha experienced hatred firsthand as a child. Post the definition of an Activist- someone that calls or takes action for change. The group leader reads this definition aloud for learners and shows the next few images to learners. (give learners time to process images without talking for one minute each) These people are protesting war in this image 2: ANTI-WAR DEMONSTRATION. 14th St. March to Justice Dept. - digital file from original item \| Library of Congress (loc.gov) These women are celebrating suffrage (right to vote for women) in Washington, DC in image 3: [Women marching in national suffrage demonstration in Washington, D.C., May 9, 1914.] \| Library of Congress (loc.gov) The group leader explains that as you can see any group of people can protest or be activists showing their beliefs. Let learners break up into a pair of two learners to discuss this question: Why would Martha have been an Activist in her life? \| Focused Activity/Task 30 minutes \| Observe and Understand Now we are going to look at some primary source images and see if we disagree or agree with statements about them and think about what might be happening in each one. Group leader displays Image one: Civil rights march on Washington, D.C. / [MST]. - digital file from original \| Library of Congress (loc.gov) Learners choose the square of their response and record the statement in the correct square for Corner (Square) 1: strongly agree, Corner 2 (Square) agree, Corner 3 (Square) disagree, Corner 4 (Square) strongly disagree Learners choose the square of their response and record the statement in the correct square for Corner (Square) 1: strongly agree, Corner 2 (Square) agree, Corner 3 (Square) disagree, Corner 4 (Square) strongly disagree Learners choose the square of their response and record the statement in the correct square for Corner (Square) 1: strongly agree, Corner 2 (Square) agree, Corner 3 (Square) disagree, Corner 4 (Square) strongly disagree After learners have recorded private answers now allow them to go to the classroom corner that has been labeled as you continue to have the image displayed on the projector or paper in each corner. Once learners go to the corner allow them to discuss with other group members and why they chose to agree or disagree and allow learners to share out if they like with the group. Learners may also change their minds and choose a different corner. Group leader explains the history behind the image of the primary source that this image comes from a 1963 Civil Rights march in Washington, DC when black Americans were speaking up for fair hiring practices and fair voting rights for black Americans. This event was concluded by Martin Luther King Jr. giving his well-known “I have a Dream” speech. \| Conclusion Activity/Task 30-50 minutes (Descriptions and details of what activities you will provide for your learners to present to them the primary source materials from the LOC.) \| Sharing Learning about Activists Group Leader: Today we have learned about how groups of people have different experiences which cause them to stand up for something they believe in becoming Activists. When you see a group of people gather at a protest or for a rally think about what may have caused them to feel strong enough to share their beliefs with others. Learners will now choose to create a poem, song, or drawing sharing their learning about groups of people with different experiences becoming activists. The group leader goes back to the video recording of Martha and plays the video starting at 28:50 to see what Martha did when she was older in college and how she planned to help the Black Americans in a Southern community, Albany, Georgia, and Greenwood Mississippi. Note tread with care Some leaders may choose to restart the video at 38:02 to skip some sensitive topics. Listen to the video to learn how Martha worked with Black Americans to work for equal voting rights for Black Americans. Stop the recording at 46:34. After learners finish the activity allow learners to go back to the feelings chart and identify how they feel now about Martha from the video and her becoming an activist. \| Assessment of Student Learning (How will you determine if your learners have completed the activity? How will you determine if your learners have used the primary sources from LOC to understand the history of the marginalized people that are your activity focus?) \| Youth learning will be assessed by observing how learners indicate on the feelings chart they feel about learning about a black American Activist. Learners should mark one feeling at the beginning of the lesson and progress to a positive feeling toward the end of the lesson and feel a sense of empowerment to be an activist for beliefs. Youth learning will also be assessed by the final product the student expresses in the form of a narrative story, poem, song, or drawing. Learners will demonstrate learning about those that choose to be activists in their community. The expression will show how one’s past experiences lead to the role of an activist. \| Student Learning Accommodations & Modifications (How will you adapt your activity plans for learners who are differently abled? Will you provide alternate paths to activity completion? Aid or peer support?) \| Group Leader will read all statements aloud to accommodate for student reading levels. Learners will express themselves privately and through peer and group discussions. Learners should not be expected to share publicly as this could be better for learners to internalize and they may want to keep thoughts private. When viewing the video transcript (found below the video) may be provided for learners that may find it easier to follow a transcript. The leader could highlight parts used in the video for learners. Learners have the choice to produce the product of their choice depending on their strengths. \| Multicultural Considerations (What specific considerations should be made for any other community program leader who might teach this activity in the future? Are there specific facts that should be noted while researching? Specific books that should be included? Please note your recommendations here.) \| *Caution: Note during the video at 31:24 Martha describes the conditions and how a girl had been raped and died by white Americans depending on the age group and leader’s discretion. If you would like to tread with care start the video at 38:02 depending on the age range and experiences of your youth. Group leaders should listen to the full video recording before using this lesson to be aware of the background and vocabulary used. \|	oercommons	2025-03-18T00:35:15.142315	U.S. History	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/95193/overview", "title": "Black Americans as Activists in Tennessee", "author": "Ethnic Studies" }
https://oercommons.org/courseware/lesson/82016/overview	- - Choice Board - Washington Office of Superintendent of Public Instruction - wa-early-learning - wa-families - wa-math - wa-supporting-youngest-learners - License: - Creative Commons Attribution - Language: - English - Media Formats: - Text/HTML Education Standards Learning Domain: Operations and Algebraic Thinking Standard: Relate counting to addition and subtraction using strategies, such as, by counting on and back. Learning Domain: Counting and Cardinality Standard: Understand the relationship between numbers and quantities; connect counting to cardinality. Learning Domain: Geometry Standard: Compose two-dimensional shapes (rectangles, squares, trapezoids, triangles, half-circles, and quarter-circles) or three-dimensional shapes (cubes, right rectangular prisms, right circular cones, and right circular cylinders) to create a composite shape, and compose new shapes from the composite shape. (Students do not need to learn formal names such as "right rectangular prism."ť) Learning Domain: Geometry Standard: Partition circles and rectangles into two and four equal shares, describe the shares using the words halves, fourths, and quarters, and use the phrases half of, fourth of, and quarter of. Describe the whole as two of, or four of the shares. Understand for these examples that decomposing into more equal shares creates smaller shares. Learning Domain: Measurement and Data Standard: Organize, represent, and interpret data with up to three categories; ask and answer questions about the total number of data points, how many in each category, and how many more or less are in one category than in another. Learning Domain: Operations and Algebraic Thinking Standard: Relate counting to addition and subtraction (e.g., by counting on 2 to add 2). Learning Domain: Operations and Algebraic Thinking Standard: Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 - 4 = 13 - 3 - 1 = 10 - 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 - 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13). Learning Domain: Counting and Cardinality Standard: Understand the relationship between numbers and quantities; connect counting to cardinality. Learning Domain: Counting and Cardinality Standard: Count to answer how many?ť questions about as many as 20 things arranged in a line, a rectangular array, or a circle, or as many as 10 things in a scattered configuration; given a number from 1-20, count out that many objects. Learning Domain: Geometry Standard: Analyze and compare two- and three-dimensional shapes, in different sizes and orientations, using informal language to describe their similarities, differences, parts (e.g., number of sides and vertices/"corners"ť) and other attributes (e.g., having sides of equal length). Learning Domain: Geometry Standard: Model shapes in the world by building shapes from components (e.g., sticks and clay balls) and drawing shapes. Learning Domain: Geometry Standard: Compose simple shapes to form larger shapes. For example, "can you join these two triangles with full sides touching to make a rectangle?"ť Learning Domain: Measurement and Data Standard: Describe measurable attributes of objects, such as length or weight. Describe several measurable attributes of a single object. Learning Domain: Measurement and Data Standard: Directly compare two objects with a measurable attribute in common, to see which object has "more of"ť/"less of"ť the attribute, and describe the difference. For example, directly compare the heights of two children and describe one child as taller/shorter. Learning Domain: Measurement and Data Standard: Classify objects into given categories; count the numbers of objects in each category and sort the categories by count. (Limit category counts to be less than or equal to 10.) Learning Domain: Operations and Algebraic Thinking Standard: Represent addition and subtraction with objects, fingers, mental images, drawings (drawings need not show details, but should show the mathematics in the problem), sounds (e.g., claps), acting out situations, verbal explanations, expressions, or equations. Cluster: Count to tell the number of objects Standard: Understand the relationship between numbers and quantities; connect counting to cardinality. Cluster: Count to tell the number of objects Standard: Count to answer “how many?” questions about as many as 20 things arranged in a line, a rectangular array, or a circle, or as many as 10 things in a scattered configuration; given a number from 1-20, count out that many objects. Cluster: Understand addition as putting together and adding to, and understand subtraction as taking apart and taking from Standard: Represent addition and subtraction with objects, fingers, mental images, drawings (drawings need not show details, but should show the mathematics in the problem), sounds (e.g., claps), acting out situations, verbal explanations, expressions, or equations. Cluster: Describe and compare measurable attributes Standard: Describe measurable attributes of objects, such as length or weight. Describe several measurable attributes of a single object. Cluster: Describe and compare measurable attributes Standard: Directly compare two objects with a measurable attribute in common, to see which object has “more of”/“less of” the attribute, and describe the difference. For example, directly compare the heights of two children and describe one child as taller/shorter. Cluster: Classify objects and count the number of objects in each category Standard: Classify objects into given categories; count the numbers of objects in each category and sort the categories by count. (Limit category counts to be less than or equal to 10.) Cluster: Analyze, compare, create, and compose shapes Standard: Analyze and compare two- and three-dimensional shapes, in different sizes and orientations, using informal language to describe their similarities, differences, parts (e.g., number of sides and vertices/“corners”) and other attributes (e.g., having sides of equal length). Cluster: Analyze, compare, create, and compose shapes Standard: Model shapes in the world by building shapes from components (e.g., sticks and clay balls) and drawing shapes. Cluster: Analyze, compare, create, and compose shapes Standard: Compose simple shapes to form larger shapes. For example, "can you join these two triangles with full sides touching to make a rectangle?” Cluster: Add and subtract within 20 Standard: Relate counting to addition and subtraction (e.g., by counting on 2 to add 2). Cluster: Add and subtract within 21 Standard: Add and subtract within 20, demonstrating fluency for addition and subtraction within 10. Use strategies such as counting on; making ten (e.g., 8 + 6 = 8 + 2 + 4 = 10 + 4 = 14); decomposing a number leading to a ten (e.g., 13 – 4 = 13 – 3 – 1 = 10 – 1 = 9); using the relationship between addition and subtraction (e.g., knowing that 8 + 4 = 12, one knows 12 – 8 = 4); and creating equivalent but easier or known sums (e.g., adding 6 + 7 by creating the known equivalent 6 + 6 + 1 = 12 + 1 = 13). Cluster: Represent and interpret data Standard: Organize, represent, and interpret data with up to three categories; ask and answer questions about the total number of data points, how many in each category, and how many more or less are in one category than in another. Cluster: Reason with shapes and their attributes Standard: Compose two-dimensional shapes (rectangles, squares, trapezoids, triangles, half-circles, and quarter-circles) or three-dimensional shapes (cubes, right rectangular prisms, right circular cones, and right circular cylinders) to create a composite shape, and compose new shapes from the composite shape. (Students do not need to learn formal names such as “right rectangular prism.”) Cluster: Reason with shapes and their attributes Standard: Partition circles and rectangles into two and four equal shares, describe the shares using the words halves, fourths, and quarters, and use the phrases half of, fourth of, and quarter of. Describe the whole as two of, or four of the shares. Understand for these examples that decomposing into more equal shares creates smaller shares. Math Choice Board PreK – 1st Grade Summer Edition Overview Explore the Mathematics Student Choice Boards for PreK – 1st grade created by the Washington Office of Superintendent of Public Instruction. Math Choice Board PreK – 1st Grade Summer Edition Explore the OSPI-created Choice Boards for PreK – 1st grade. So often we get locked into the idea that math has to be taught by sitting down at a table and completing worksheets. We want to challenge that idea by providing you with some choice boards. These grids are filled with fun activities you can do at home while playing with your kids. We like choice boards because they give children choice while still setting specific parameters designed to encourage developmentally appropriate math skills. We have set up the choice boards by grade bands. Each column focuses on a different math concept, and the activities dive deeper into the skill as you work your way down the board. This gives you the freedom to enter the board at a place that best suits your child, and provides additional activities to continue working on the skill.	oercommons	2025-03-18T00:35:15.204209	06/04/2021	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/82016/overview", "title": "Math Choice Board PreK – 1st Grade Summer Edition", "author": "Washington OSPI Mathematics Department" }
https://oercommons.org/courseware/lesson/68130/overview	Education Standards Grade K Science Framework (pdf) Resource 1: Anchor Phenomena Resource 1: Distance Learning Assignment Resource 2: The Great Trash Bash Read Aloud Resource 3: Recycling Center Field Trip Assignment Resource 3: Virtual Field Trip Resource 4 Alternate: Betsy's Kindergarten Adventure Resource 4: Junk Necklaces Resource 5: Sort the Recycling Resource 6: Printable Download Sort the Recycling Resource 7: Lending the Earth a Helping Hand Resource 8: Opinion Writing How Can We Help the Earth? Kindergarten - Elementary Science and Integrated Subjects: Tackling Trash Overview Elementary Science and Integrated Subjects is a statewide Clime Time collaboration among ESD 123, ESD 105, and the Office of Superintendent of Public Instruction. Development of the resources is in response to a need for research- based science lessons for elementary teachers that are integrated with English language arts, mathematics and other subjects such as social studies. The template for Elementary integration can serve as an organized, coherent and research-based roadmap for teachers in the development of their own NGSS aligned science lessons. Lessons can also be useful for classrooms that have no adopted curriculum as well as to serve as enhancements for current science curriculum. Introduction: Standards, Phenomena, Big Ideas, and Routines Washington State Learning Standards Elementary Science and Integrated Subjects are designed to be an example of how to develop a coherent lesson or suite of lessons that integrate other content areas such as English Language Arts, Mathematics and other subjects into science learning for students. The examples provide teachers with ways to think about all standards, identify anchoring phenomena, and plan for coherence in science and integrated subjects learning. Kindergarten Disciplinary Core Ideas include PS2, PS3, LS1, ESS2, ESS3 For ESS3, students are expected to develop an understanding of: - things that people do can affect the world around them - people can develop solutions to the impacts they make that reduce their impact - what plants and animals (including humans) need to survive The Crosscutting Concepts are called out as organizing concepts for these disciplinary core ideas. Crosscutting Concepts: - patterns; - cause and effect; - systems and system models; Students are expected to use the practices to demonstrate understanding of the core ideas. Science and Engineering Practices: - asking questions - developing and using models - analyzing and interpreting data - planning and carrying out investigations - designing and communicate solutions - engaging in argument from evidence - obtaining, evaluating and communicating information Performance Expectation(s) Identify Performance Expectation(s) from Next Generation Science Standards that will be your focus (Climate Science related PEs preferred but not mandatory). Copy and paste below all the possible disciplinary core ideas and performance expectations that relate to your topic. K-ESS3-3 Communicate solutions that will reduce the impact of humans on the land, water, air, and/or other living things in the local environment. [Clarification Statement: Examples of human impact on the land could include cutting trees to produce paper and using resources to produce bottles. Examples of solutions could include reusing paper and recycling cans and bottles.] Science and Engineering Practices Which SEPs will be a focus for investigating this topic/phenomenon? Obtaining, Evaluating, and Communicating Information Obtaining, evaluating, and communicating information in K–2 builds on prior experiences and uses observations and texts to communicate new information K-ESS3-3 Communicate solutions with others in oral and/or written forms using models and/or drawings that provide detail about scientific ideas. Crosscutting Concepts Which Crosscutting Concepts will be a focus for investigating this topic/phenomenon? K-LS1-2 Patterns - Patterns in the natural and human designed world can be observed and used as evidence. K-ESS3-3 Cause and Effect - The shape and stability of structures of natural and designed objects are related to their function(s). English Language Arts (ELA) Standards How will I Integrate ELA Standards (which standard, what strategy…?) RI.K.1 - With prompting and support, ask and answer questions about key details in a text. RI.K.3 - With prompting and support, describe the connection between two individuals, events, ideas or pieces of information in a text. W.K.2 - Use a combination of drawing, dictating, and writing to compose informative/explanatory texts in which they name what they are writing about and supply some information about the topic. W.K.6 - With guidance and support from adults, explore a variety of digital tools to produce and publish writing, including in collaboration with peers W.K.8 - Recall information from experiences or gather information from print and digital sources; take brief notes on sources and sort evidence into provided categories. K.L.1d - I can use these question words: who, what, where, when, why and how. K.SL.1 - Participate in Collaborative conversations with diverse partners about kindergarten topics and texts with peers and adults in small and larger groups. K.SL.3 - Ask and answer questions in order to seek help, get information, or clarify something that is not understood. Mathematics Standards How will I Integrate Mathematics Standards? K.CC. 6 - Identify whether the number of objects in one group is greater than, less than, or equal to the number of objects in another group, e.g., by using matching and counting strategies. K.MD.3 - Classify objects into given categories; count the number of objects in each category and sort the categories by count. Social Studies Standards SSS1.K.1 - State and clarify one’s point of view. SSS1.K.3 - State own viewpoints on fairness and listen to the viewpoints of classmates and teacher. SSS1.K.4 - Retell a sequence of events that have happened over time. Computer Science Standards 1A-A-5-3 - Plan and create a design document to illustrate thoughts, ideas, and stories in a sequential (step-by-step) matter (e.g., story map, storyboard, sequential graphic organizer) Phenomena How does our trash affect our community? Phenomena Resources: Communicating in Scientific Ways \| OpenSciEd Big Ideas - Human impact on the environment - Everything humans do has an impact on something (cause and effect) Trash and waste are a part of everyday life. Waste can be found in the classroom, home, and community. However, trash doesn't disappear when you're done with it. It must move on to somewhere else. But you can help solve this problem. Open Sci Ed Routines \| Routine \| Description of Routine \| \|---\|---\| \| Anchoring Phenomenon Routine \| Develop curiosity to drive learning throughout the suite of lessons or unit based on a common experience of a phenomenon \| \| Navigation Routine \| Establish and reinforce the connections between what we have previously done in a unit, what we are about to do, what we will do in the future, and what our driving purpose is in the contexts of the suite of lessons or unit. \| \| Investigation Routine \| Use scientific practices to investigate and make sense of a phenomenon \| \| Putting Pieces Together Routine \| Take the pieces of ideas we have developed across multiple lessons and figure out how they can be connected to account for the phenomenon we have been working on \| \| Problematizing Routine \| Evaluate the adequacy of our scientific ideas to explain and phenomenon in order to identify what we still need to understand. \| Lesson 1: What Is Trash? Lesson 1: What is Trash? Anchoring Phenomenon Routine Materials: - slide show Resource 1: National Geographic Kids “See How Animals Can Be Affected by Plastic” Slideshow: https://kids.nationalgeographic.com/explore/nature/kids-vs-plastic/ - Poster paper chart Nxmarkers What is Trash? or individual observation charts, - markers Preparation: - have link to slide show ready on computer - OR if using observation charts glue one slide show picture to each of several blank 8”x11” sheets of paper - Label chart paper with the title, “What is Trash?” Vocabulary: Trash, Garbage, Thrown Away Integration Points: - Look for integration points for English Language Arts and Mathematics within the procedures below. They will be noted in italics and dark blue. Procedures Procedure 1: Introduce the Phenomena: Display the slideshow for students. Resource 1: National Geographic Kids “See How Animals Can Be Affected by Plastic” Slideshow: https://kids.nationalgeographic.com/explore/nature/kids-vs-plastic/ Have students react to the photos. Create a class poster of Observations and Wonders. - This could alternatively be completed as a Project GLAD Observation Chart activity. - Place each picture individually on a separate piece of paper and post around the room. - Partner students in pairs and give each pair a different colored marker or crayon to use - Students move from picture to picture and observe the pictures. - Students take a few moments and draw or write ideas and questions. Digital/Distance Learning Suggestions Option 1: This could be broadcast to students as a Topic via Flipgrid or similar platform. The teacher could record a screenshare of a selection of the photos provided. Students will record their “noticings” and “wonderings” in their Flipgrid response. - Goal: Students should be guided to find PATTERNS from image to image. Students should begin to recognize that non-living objects in the environment affect the living things. - Result: Students were able to identify the trash and garbage as the pattern from image to image. They asked questions about the why and where of the garbage, especially as it related to the animals in each picture. Many also expressed concern about how people brought the trash and garbage into the animals’ environments. Option 2: Animals & Garbage Observation observe pictures of animals and garbage on a google slide and write what they notice. - Goal: For students to notice the excessive amount of trash that is surrounding the animals, which in turn begins the conversation about why there is that much, how it affects animals and humans, and how can we help (multiple days of course) - Result: Students did notice the trash, however in their answer they didn’t really address the amount of it. This wouldbe something to go back and visit and give some guiding questions to begin the conversation piece. Procedure 2: Gather students on the carpet, or in a group space or “scientist circle”- a common area where they can all sit and see/listen/discuss/share. Procedure 3: Teacher introduces the topic of garbage and trash. Review what students observed on the Observation Walk/slideshow pictures, discussing what types of non-living things were seen in the photos. Procedure 4: Tell students that we are going to look for patterns in the pictures. Patterns are similar things that we see in the various pictures. Procedure 5: What is trash? Have students draw/write to define what “trash” is. They should label their model as Trash or What is Trash? (This will be their initial model). W.K.2 - Use a combination of drawing, dictating, and writing to compose informative/explanatory texts Digital/Distance Learning Suggestions Option 1 Students can search Google Images to find pictures of what they feel trash is, then use a Google slide to create a poster. - Goal: The goal for this is to find out how students perceive trash in the real world. It also allows for them to use technology to search for pictures and add them to a poster. Ideally, I would create a slideshow in Google Slides and then show all the students the presentation and we could talk about what they noticed and what they wondered. This would be done during a Zoom meeting (or something similar). - Result: students were able to find pictures using the Google search function, then explain their thinking during our Zoom meeting. K.SL.1-Participate in Collaborative conversations with diverse partners about kindergarten topics and texts with peers and adults in small and larger groups. - Note: a teaching tutorial would have been helpful for students to watch before beginning this. Option 2 Students are given the prompt, What Is Trash? They then draw pictures on a paper and discuss it with family. They share their ideas and label the pictures to name items they have drawn. At the end, parents can send a photo through SeeSaw, Remind, or by using a Google Form. The teacher can collect the photos to create a collage of all submissions to then send out to the class showing everyone’s ideas. K.SL.1-Participate in Collaborative conversations with diverse partners about kindergarten topics and texts with peers and adults in small and larger groups. Description of Student Example (Option 2): The lesson was uploaded through digital learning activities. The first image shows the Google Forms prompt sent out the families. It provides the directions and a “turn-in” location for the photo once the child has finished. The second image is a collage of student submissions. Some families also chose to separately sent video of their child explaining the drawings and why they included certain items they consider, “trash.” Lesson 2: The Great Trash Bash (or other comparable choice) Lesson 2: Read-Aloud: The Great Trash Bash (or other choice) Investigation Routine Materials: - Resource 2:Read-Aloud of the book, The Great Trash Bash by Loreen Leedy YouTube Video Link: https://youtu.be/pvyeJ-YTeW0 (or other book choice on this topic with a similar theme) Preparation: - Pre-read the book or set up the YouTube link for use Vocabulary: Trash, recycle, bash Procedures Procedure 1: Call students to the back carpet, group space or “scientist circle”- a common area where they can all sit and see/listen/discuss/share. Read aloud The Great Trash Bash by Loreen Leedy pointing out patterns of behavior by the animal citizens in the first couple of pages. Ask students to find causes and effects such as “someone through a banana peel on the sidewalk and that made the mayor slip.” RI.K.1 - With prompting and support, ask and answer questions about key details in a text. Procedure 2: As the story is read, have students look for the problem and solution in the story. RI.K.3 - With prompting and support, describe the connection between two individuals, events, ideas or pieces of information in a text. Procedure 3: Discuss what students have observed and thought during the story. K.SL.1-Participate in Collaborative conversations with diverse partners about kindergarten topics and texts with peers and adults in small and larger groups. Digital/Distance Learning Suggestions Option 1 Use Flipgrid or other platform to prepare this as a Topic. Create a Topic Focus Video by using the YouTube link and Screencastify. Present and record the story. Upload to Flipgrid. Students will record a response to the story to talk about the major events in the story including the characters, setting, and the problem and solution. RL K.3- With prompting and support, describe the connection between two individuals, events, ideas or pieces of information in a text. Description of Student Examples (Option 1): The lesson was uploaded through digital learning activities. The image shows a screenshot of the Screencastify Video presented through a Flipgrid Topic. The read-aloud was presented through use of the YouTube link. Lesson 3: Virtual Field Trip Lesson 3: Virtual Field Trip Investigation Routine Materials: - Resource 3: YouTube Video Virtual Field Trip Learnings Preparation: - link to or download the YouTube video and check for audio, etc. Vocabulary: Field Trip, Recycle, Recycling Center, Sorting, Procedures Procedure 1: Provide the link Resource 3: YouTube Video Virtual Field Trip Learnings to the class through the classroom communication tool (SeeSaw, Google Classroom, Edmodo, etc.) Procedure 2: Students will watch the YouTube video and report back to the teacher. Use the following prompt options to gather a response from students. RL K.1-With prompting and support, ask and answer questions about key details in a text. - “What kinds of things can be recycled? - “What did you see at the Recycling Center?” - “Write one thing you saw on our field trip.” W K.8-Recall information from experiences, or gather information from print and digital sources Description of Student Examples: The lesson was uploaded through Google Classroom. Students responded to the prompts through Google Slides or Google Doc. The read-aloud was presented through use of the YouTube link. Lesson 4: Non-Trash Day Lesson 4: Non-Trash Day Investigation Routine Problematizing Routine Materials: - Recycling Bin, - Misc. Recyclable items (paper, cardboard, plastics, etc.-no organic or food waste) Preparation: - Gather your materials - Vocabulary: Recycle, Plastic, Paper Goods, Glass, Aluminum Procedures Procedure 1: Find a bin to use for recycled items. Place this in a convenient place for everyone to use. Procedure 2: Discuss what types of items should be collected. Have students Review what types of items were seen during the Virtual Field Trip. Look for students to say, paper, bottles and cans, and other items that could be recycled. (It may be important to note that food items may not be easily recycled because they are soiled.)K.SL.1-Participate in Collaborative conversations with diverse partners about kindergarten topics and texts with peers and adults in small and larger groups. Procedure 3: Collect recyclable items for one day and place these in the Recycling Bin. Procedure 4: At the end of the day, look over what was collected. Sort things by type and count the items in each category (example: 7 pieces of paper, 3 plastic lids, etc.) K.MD.3 - Classify objects into given categories; count the number of objects in each category and sort the categories by count. Procedure 5: Pose the question: Could these things be reused somehow? As students discuss the question Record ideas on a class poster.K.SL.1-Participate in Collaborative conversations with diverse partners about kindergarten topics and texts with peers and adults in small and larger groups. Procedure 6: Keep the recyclable items for the next activity. Digital/Distance Learning Suggestions Option 1 Betsy's Kindergarten Adventures: Happy Earth Day watch the video and answer the questions about trash/recycling and have students understand what recycling is and how they can do it in a variety of ways and places and the impact it has on our planet. K.SL.1-Participate in Collaborative conversations with diverse partners about kindergarten topics and texts with peers and adults in small and larger groups. The images are examples of student work from Google Classroom, where students first watched the video then answered questions. Lesson 5: Make a Junk Necklace Lesson 5: Make a Junk Necklace Putting the Pieces Together Routine Materials: - Items from Lesson 4, - scissors, - hole punch, - adult assistance, - string, yarn, or shoelace for necklace - Resource 4: Link for directions to make a recycled craft called, Junk Necklaces. This could be used after the No Trash Day Lesson.https://minimadthings.com/blogs/news/junk-necklaces Link for an alternate, distance learning assignment Betsy's Kindergarten Adventures: Happy Earth Day Preparation: - Gather all items needed - Cut string long enough to fit loosely around neck and be tied (about 14”) Vocabulary: Recycle, Reuse, Repurpose Procedures (Adult Help and Supervision is Needed) Procedure 1: Gather recycled items from Lesson 4. Procedure 2: Cut paper and cardboard into shapes and punch a hole in the middle or at one end. Procedure 3: Make holes in the middle of other items. Procedure 4: String the items together to make the necklace. - Hint: Cut straws could help space items along the necklace. Digital/Distance Learning Suggestions Option 1 Students and families are asked to take a photo or video of the finished necklace to share to a group page or submit through an online assignment portal. Description of Student Examples: The image shows examples of students and their completed Junk or Trash Necklaces, and a listing of some of the items students collected and used in their project. Videos were provided by parents including students’ explanation of what they created, what they used, and how they completed the project. Alternatively, some parents sent in photos of their students, items that were saved, along with text explaining their family project. Lesson 6: Sorting Out the Trash Lesson 6: Sorting out the Trash Putting the Pieces Together Routine Materials: - Google Slide Deck Sort the Recycling or Printable Sorting Worksheet Printable Download Sort the Recycling - glue if using the paper version - scissors Preparation: - download or link to the Google Slide Deck to be sure it functions - Gather all items needed - cut cards apart if using the paper version Vocabulary: Sort, Group, Classify, Plastic, Paper, Glass Procedures (Adult Help and Supervision is Needed) Procedure 1: Either use the printable or digital version of the sorting activity. Procedure 2: Provide a copy of the Sort the Recycling document to each student. See Resources 5 & 6 Procedure 3: Name each picture and discuss how each is made. Ask, “What is this made from?” Extend the discussion by asking students, “Can this be recycled? Why or why not?” K.SL.1-Participate in Collaborative conversations with diverse partners about kindergarten topics and texts with peers and adults in small and larger groups. Procedure 4: Students will manipulate the pictures (digital version) or cut to sort by type of material. Recycling categories include paper, plastic and cans. K.MD.3 - Classify objects into given categories; count the number of objects in each category and sort the categories by count. Digital/Distance Learning Suggestions Option 1 Use Google Classroom to assign the Google Slide Deck to each student. Students will sort the objects into the correct recycling bin. An extension in the classroom includes discussing the items that were sorted, students explaining why they chose to put it where they did, counting the items and recording the information on a graph, where students will answer questions (How many items were in the paper bin? How many more items were in the plastic bin than the paper bin?, etc) The image shows student work that was turned in using Google Slides (there was no graph for the distance learning piece). SSS1.K.1 State and clarify one’s point of view, K.MD.3 - Classify objects into given categories; count the number of objects in each category and sort the categories by count. Description of Student Examples: The sample below shows the printable version of the sorting activity. See Resource 6. Lesson 7: Lend the Earth a Helping Hand Lesson 7: Lend the Earth a Helping Hand Putting Pieces Together Routine Materials: - Resource 7: Lend the Earth a Helping Hand Preparation: - Create/assign the document on Google Slides and Google Classroom Vocabulary: recycle, helping, Earth Procedures (Adult Help and Supervision is Needed) Procedure 1: Assign the Google Slide to Google Classroom so each student has their own copy. Students will find a picture that represents how they want to help the Earth. Once the picture is chosen, they will explain how they are going to help the Earth. The second part consists of students writing a sentence about how their choice will help (defending their answer). This also is the assessment piece to determine if students understood the overall concept, and also allows for assessment of sentence writing. SSS1.K.1 State and clarify one’s point of view, W.K.2 - Use a combination of drawing, dictating, and writing to compose informative/explanatory texts in which they name what they are writing about and supply some information about the topic. Alternate Lesson 7: Lend the Earth a Helping Hand (Non-Digital) Materials: - Resource 8: Opinion Writing: How Can I Help the Earth?, - materials to support research Preparation: - Prepare printable, - gather books, phenomena photos, videos to support research Vocabulary: Recycle, helping, Earth, environment, living, non-living Procedures Procedure 1: Prepare the printable. Provide one for each student. Procedure 2: Have a class discussion to discuss the learning from this unit. Use the main question, “How do people change and effect the environment?” Refocus students on remembering how the non-living things in the phenomena photos changed the environment for the living things. Procedure 3: Continue discussion allowing students to brainstorm ideas to keep the environment safe from harm. Procedure 4: Provide a copy of the Graphic Organizer to each student. Procedure 5: Instruct students to draw and/or write to share their ideas about what the best way to help the earth would be. Procedure 6: Provide resources students can use for research to support their opinion and ideas. Allow students time to gather information. Procedure 7: Complete the graphic organizer. Procedure 8: Provide a copy of the writing page for each student. Encourage each to write their opinion and supporting reasons/facts, and to draw a picture to add key details. RL K.1-With prompting and support, ask and answer questions about key details in a text. Procedure 9: Encourage students to share their work with an audience. SL.K.4 Describe events and 6 speak audibly and express thoughts, feelings, and ideas clearly Appendix: Lesson Resources Appendix: Resource 1: Anchor Phenomena-National Geographic Kids “See How Animals Can Be Affected by Plastic” Slideshow: https://kids.nationalgeographic.com/explore/nature/kids-vs-plastic/ Link for the distance learning assignment What is Trash? Resource 2: Read-Aloud of the book, The Great Trash Bash by Loreen Leedy YouTube Video Link: https://www.youtube.com/watch?v=icaG_UrCkuk Resource 3: YouTube Video Link, Virtual Field Trip: Take a Field Trip to the Recycling Center, KidVision Pre-K https://youtu.be/-jAAux3g17k Link for the distance learning assignment Virtual Field Trip Learnings Resource 4: Link for directions to make a recycled craft called, Junk Necklaces. This could be used after the No Trash Day Lesson. https://minimadthings.com/blogs/news/junk-necklaces Link for an alternate, distance learning assignment Betsy's Kindergarten Adventures: Happy Earth Day Resource 5: Link for the digital recycling sort distance learning assignment Sort the Recycling Resource 6: Link to access the printable version of the sorting activity in Lesson 6. Printable Download of Sort the Recycling Resource 7: Link for the assessment that is done through distance learning Lend the Earth a Helping Hand Resource 8: Downloadable option for final project/Alternate Lesson 7. Opinion Writing: How Can We Help The Earth? Attribution and License Attribution NGSS Lead States. 2013. Next Generation Science Standards: For States, By States. Washington, DC: The National Academies Press \| Public License Common Core State Standards © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved \| Public License Screenshots of student work examples are used pursuant to fair use. License Except where otherwise noted, this work developed for ClimeTime is licensed under a Creative Commons Attribution License. All logos and trademarks are the property of their respective owners. Sections used under fair use doctrine (17 U.S.C. § 107) are marked. This resource may contain links to websites operated by third parties. These links are provided for your convenience only and do not constitute or imply any endorsement or monitoring. If this work is adapted, note the substantive changes and re-title, removing any ClimeTime logos. Provide the following attribution: This resource was adapted from Plants and Their Parts by ClimeTime and licensed under a Creative Commons Attribution 4.0 International License. Access the original work for free in the ClimeTime group on the OER Commons Washington Hub. This resource was made possible by funding from the ClimeTime initiative, a state-led network for climate science learning that helps teachers and their students understand climate science issues affecting Washington communities.	oercommons	2025-03-18T00:35:15.335588	Environmental Science	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/68130/overview", "title": "Kindergarten - Elementary Science and Integrated Subjects: Tackling Trash", "author": "Elementary Education" }
https://oercommons.org/courseware/lesson/98284/overview	Education Standards Storyline Online: Website Guidance Overview This guidance document describes Storyline Online, the SAG-AFTRA Foundation's free website featuring actors reading children’s books. Storyline Online Purpose of Website Storyline Online is the SAG-AFTRA Foundation’s free, award-winning, children’s literacy website. The site features famous actors reading children’s books alongside creatively produced illustrations. The videos are housed on YouTube by default but teachers can also choose to view them via SchoolTube. Site Navigation Strategy On the website, the library of books may be sorted by author, reader, title, run time, or publisher. Tiles with images and information about each book appear and users may click on them to select the option. Tips for Effective Implementation or Differentiation Stories have accompanying activity guides that are great resources for adults to help kids with reading comprehension issues, or to simply connect each story to a larger experience. Activities list potential connections to the ELA Common Core Standards as well as connections to other subject areas. A link to Barnes and Noble online is also provided if users wish to purchase the book. Comments Though not openly licensed, video content is available for free online access and activity guides may be downloaded for offline use. The Foundation is a nonprofit organization that relies entirely on gifts, grants and donations to fund Storyline Online and produce all of its videos. Attribution and License Attribution - Storyline Online is a program of the SAG-AFTRA Foundation. The rights and permissions for Storyline Online videos DO NOT extend to any other organization. Read FAQ - Storyline Online logo and screenshots copyright SAG-AFTRA Foundation. All rights reserved. Used pursuant to fair use. License Except where otherwise noted, this website guidance document by Washington Office of Superintendent of Public Instruction is licensed under a Creative Commons Attribution License. All logos and trademarks are the property of their respective owners. Sections used under fair use doctrine (17 U.S.C. § 107) are marked. This resource contain links to websites operated by third parties. These links are provided for your convenience only and do not constitute or imply any endorsement or monitoring by OSPI. Please confirm the license status of any third-party resources and understand their terms before use.	oercommons	2025-03-18T00:35:15.373341	Barbara Soots	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/98284/overview", "title": "Storyline Online: Website Guidance", "author": "Reading" }
https://oercommons.org/courseware/lesson/107494/overview	A. (Start Here First!) Introduction to Onboarding Resources Overview Welcome to the TIES therapist onboarding resource! These resources are available to help standardize school-based therapist training throughout the state of OR while also allowing individual school districts and ESDs to remix each resource to suit the needs of their region. By doing so, we aim to ensure continuity of training and services throughout the state. A. (Start Here First!) Introduction to Onboarding Resources Welcome to the TIES therapist onboarding resource! These resources are available to help standardize school-based therapist training throughout the state of OR while also allowing individual school districts and ESDs to remix each resource to suit the needs of their region. By doing so, we aim to ensure continuity of training and services throughout the state. Here are some tips on navigating this group: We have organized different elements of the onboarding process into 3 “buckets.” Each “bucket” contains related topics. Tags can be found at the bottom of each resource page; clicking on these will pull up more related topics to each resource Priority levels are tagged in each resource to clearly communicate where in the onboarding process each resource topic should be introduced Make sure to check the Resource Library in each resource for any downloadable content Note: Any text that is underlined, bolded, and italicized has a downloadable component available within that resource. (e.g., Service Summary (OT Services_Support) instead of Service Summary (OT Services_Support), Service Summary (OT Services_Support), or Service Summary (OT Services_Support)) If you want to create your own resource plan or remix an already existing resource please remember to do the following: Click the “remix” feature on the resource to create a copy of the resource that you can edit Do not link to any Google docs. The reason is to ensure that particular resource will still be available to others in the event the Google doc owner vacates their position. Instead, UPLOAD a copy (.doc AND .pdf files preferred) When using tags please add a hyphen then “TIES” to the end. This ensures only TIES resources appear if a user were to click on it. (e.g., Onboarding – TIES instead of Onboarding)	oercommons	2025-03-18T00:35:15.389138	08/07/2023	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/107494/overview", "title": "A. (Start Here First!) Introduction to Onboarding Resources", "author": "Nathaniel Baniqued" }
https://oercommons.org/courseware/lesson/64146/overview	Early Learning: Family Resource Suggestions Overview Resource suggestions for family leadership, voice, and engagement, including ideas to explore with your family learning with remote learning. Websites, Apps, and Read Alouds Resource Sites Message in a Backpack ™ \| National Association for the Education of Young Children (NAEYC) This is a column that appears in Teaching Young Children. Download printable documents with helpful tips for families to engage in learning activities with their children. Message in a Backpack ™ Recipes to Road Maps: Fun Ways to Learn from Everyday Information Message in a Backpack™ Fun Ways to Build Your Child’s Literacy Skills While Doing Laundry Together Mensaje en la mochila: Ayude a su hijo a aprender a ser responsable Message in a Backpack™ Helping Your Child Learn Responsibility Message in a Backpack™ Things Every Parent Should Know about Play رسالة في حقيبة الظهر (Message in a Backpack™) الفقاعات (Bubbles) 书包金点子 (Message in a Backpack ™) 泡泡 (Bubbles) PBS KIDS for Parents \| Public Broadasting Service Offers activities and tips you can use to help kids play and learn at home. Great Schools.org Website with worksheets, booklists, parenting cue cards and other free resources for parents Kinderart Lesson Library \| Kinderart Free art lesson plans that parents and teachers can use in their home and school classrooms. Fun and Free Educational Websites for Kids \| VeryWell Family Apps w/ Activities Appropriate Apps for Children \| Madison Public Library PBS KIDS Video app \| Public Broadcasting Service Available on mobile, tablet, and connected TV devices and offers on-demand educational videos, and a live stream of the PBS KIDS 24/7 channel. No subscription required. PBS KIDS Games app \| Public Broadcasting Service Nearly 200 educational games, which can be downloaded for offline play anytime, anywhere Online Storytime Events on Facebook Read Alouds Rosie Revere, Engineer \| Storytime from Space The Bad Seed \| HarperKids Storytime Anytime Authors reading their own books \| Kate Messner website Storyline Online \| Screen Actors Guild -American Federation of Television and Radio Artists Except where otherwise noted, this work by the Office of Superintendent of Public Instruction is licensed under a Creative Commons Attribution License. All logos and trademarks are property of their respective owners. This resource contains links to websites operated by third parties. These links are provided for your convenience only and do not constitute or imply any endorsement or monitoring by OSPI. Please confirm the license status of any third-party resources and understand their terms of use before reusing them. Family Voice - Natural Leaders This program serves as multi-cultural bridges between students, families, communities, and schools. The organization that runs the program is the Washington Alliance for Better Schools. It can be a way to use a combination of funds for building sustainable, family leaders. http://www.wabsalliance.org/community-leadership/natural-leaders/ - The Washington State Family and Community Engagement Trust and the Everett Community College have The Parent Leadership Training Institute (PLTI) The PLTI is a free, 11-week, 6-hours per week civic and community engagement course for parents and community members offered in partnership with Everett Community College, https://www.wafamilyengagement.org/ - Parent Academy — Mount Vernon School District The Mount Vernon School District is not only made up of wonderful, hard-working students, but also of amazing, dedicated parents. The district offers a six-week Bilingual/Migrant Parent Academy for parents to learn and understand the complex educational system. This program is offered in 4 different languages. Click here to learn more. Toolkits & Guides - Family Engagement Toolkit: Continuous Improvement Through an Equity Lens click here (California and WestEd), other state’s toolkits - The U.S. Department of Education (ED) Parent and Family Digital Guide English \| Spanish - The Dual Capacity-Building Framework for Family-School Partnerships (Version 2) - OSPI’s Multilingual Families Toolkit English \| Spanish - Hawaii's AFFECT five online modules, supports both preservice and in-service teachers to understand and use family engagement principles and strategies - Flamboyant Foundation Academic Partnering: Teacher \| School Leader Guides. - Seek common ground and the experts at Student Achievement Partners have created Family Guides to help parents, grandparents, caregivers, friends. - Build Initiative’s Family Engagement Toolkit Other Resources and grade levels - COVID-19: Evidence-Based Resources from the RELs and USDE click here (includes Early Learning and more). P-3 School Improvement Family and Community Partnerships Washington Superintendent of Public Instruction (OSPI) and Association of Educational Service Districts (AESD) publishes ideas for school improvement in the P-3 School Improvement Monthly Bite. The issue released January 2021 include content and data to equip school districts to engage in "authentic and transformational partnership with famiies and communities."	oercommons	2025-03-18T00:35:15.430549	Gretchen Stahr Breunig	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/64146/overview", "title": "Early Learning: Family Resource Suggestions", "author": "Barbara Soots" }
https://oercommons.org/courseware/lesson/106200/overview	SEL Preschool Activity Template Overview This is a template for an early childhood social/emotional activity plan. Lesson Template The purpose of this template is to provide a resource of recommended aspects for a preschool social/emotional skills activity guide. Each aspect is necessary and can be remixed to fit the standards or requirements of local early childhood guidelines. Attached is a PDF version that can be modified as well. Book Title: Age: Supplies: Texas PreK Guidelines: Learning Goals: Activity Instructions: Example Image:	oercommons	2025-03-18T00:35:15.451510	Leah Carruth	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/106200/overview", "title": "SEL Preschool Activity Template", "author": "Lesson Plan" }
https://oercommons.org/courseware/lesson/115820/overview	https://lor.instructure.com/resources/23d04730a7564b1c9acc94950b8e2d9c?shared ECE 260 - Child Guidance Overview Open Textbooks for Rural Arizona participants are invited to remix this template to share their courses, textbooks, and other OER material on our Hub. ECE 260- Child Guidance Course Description Relationship-based proactive strategies to promote pro-social development of young children (infants, toddlers, preschoolers, and early elementary children). Special focus on building relationships outside of conflict and sustaining relationships during conflicts, utilizing developmentally effective teaching and guidance approaches, and employing effective teacher-child communication balanced with nurturing guidance and supportive instruction. Particular emphasis on the interplay of attachment and self-regulation, along with a trauma-informed brain-based approach to interventions with persistent and challenging behaviors. This course requires 5 face-to-face observation hours in an early childhood setting. This course is cross-listed with ECE/PSY 260. Course Materials Textbook and other materials provided in Canvas. Access to the internet. Course Requirements This course requires 5 face-to-face observation hours in an early childhood setting. Course Content and Learning Outcomes Course Content - Relationship-based approach to conflicts - Proactive pro-social development and self-reliance strategies - Effective intentional teacher-child communication - Interplay of attachment and emotional regulation - Trauma-informed brain-based approach to challenging behaviors - Power of observation to recognize the child’s underlying need(s) - Positive strength-based guidance strategies Learning Outcomes - Describe the relationship-based approach of building on relationships outside of conflict and sustaining relationships during conflicts. - Explain proactive strategies to promote pro-social development and self-reliance with young children. - Discuss the importance of effective intentional teacher-child communication nurturing positive relationships, respectful interchanges and fostering mutual trust. - Analyze the interplay of attachment and emotional regulation, initiating with adult modeling emotional regulation and then facilitating the child’s emotional regulation. - Investigate the dynamic of a trauma-informed brain-based approach to understanding and addressing persistent and challenging behaviors. - Examine the power of observation to look beyond problem behavior and to recognize the underlying need(s) of the child. - Describe positive strength-based guidance strategies focusing on a child’s strengths and facilitating emotional growth from the inside out. - Devise a well-developed guidance plan based on an assigned case study of a child with persistent and challenging behavior. Early Childhood Program Outcomes PO #2: Articulate historical perspectives, as well as current trends, in the field of Early Childhood Education. PO #3: Apply relationship-based proactive strategies to promote pro-social development of young children, aged birth through 8 years. PO #5: Use formal and informal observation techniques to document the development and learning in young children PO #6: Provide opportunities and environments that support the physical, social, emotional, cognitive, language and creative development and learning in children birth-age eight. PO #8: Apply ethical and professional standards that emphasize reflective practices in working with young children, parents, other professionals and self.	oercommons	2025-03-18T00:35:15.473554	05/07/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/115820/overview", "title": "ECE 260 - Child Guidance", "author": "Tara O'Neill" }
https://oercommons.org/courseware/lesson/66244/overview	Introduction: Six Flags Over Texas Overview Six Flags Over Texas Chapter Learning Objective By the end of this chapter, you will be able to: - Summarize the social history of Texas and how it has shaped the political characteristics of the state's population Introduction: Six Flags Over Texas Texas has a rich and diverse history. Understanding that history helps explain why contemporary Texas is the way it is. This chapter explores a tiny piece of that history.	oercommons	2025-03-18T00:35:15.490231	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66244/overview", "title": "Texas Government 2.0, Introduction to Texas History and Politics", "author": null }
https://oercommons.org/courseware/lesson/66245/overview	Independence for Texas Overview Independence for Texas Learning Objective By the end of this section, you will be able to: - Describe the political culture of Texas and how it has developed over time Introduction American expansionists had desired the area of Spain’s empire we now call Texas for many years. After the 1819 Adams-Onís treaty established the boundary between Mexico and the United States, more American expansionists began to move into the northern portion of Mexico’s province of Coahuila y Texas. Following Mexico’s independence from Spain in 1821, American settlers immigrated to Texas in even larger numbers, intent on taking the land from the new and vulnerable Mexican nation in order to create a new American slave state. American Settlers Move to Texas After the 1819 Adams-Onís Treaty defined the U.S.-Mexico boundary, Spain began actively encouraging Americans to settle their northern province. Texas was sparsely settled, and the few Mexican farmers and ranchers who lived there were under constant threat of attack by hostile Indian tribes, especially the Comanche, who supplemented their hunting with raids in pursuit of horses and cattle. To increase the non-Indian population in Texas and provide a buffer zone between its hostile tribes and the rest of Mexico, Spain began to recruit empresarios. An empresario was someone who brought settlers to the region in exchange for generous grants of land. Moses Austin, a once-prosperous entrepreneur reduced to poverty by the Panic of 1819, requested permission to settle three hundred English-speaking American residents in Texas. Spain agreed on the condition that the resettled people convert to Roman Catholicism. On his deathbed in 1821, Austin asked his son Stephen to carry out his plans, and Mexico, which had won independence from Spain the same year, allowed Stephen to take control of his father’s grant. Like Spain, Mexico also wished to encourage settlement in the state of Coahuila y Texas and passed colonization laws to encourage immigration. Thousands of Americans, primarily from slave states, flocked to Texas and quickly came to outnumber the Tejanos, the Mexican residents of the region. The soil and climate offered good opportunities to expand slavery and the cotton kingdom. Land was plentiful and offered at generous terms. Unlike the U.S. government, Mexico allowed buyers to pay for their land in installments and did not require a minimum purchase. Furthermore, to many whites, it seemed not only their God-given right but also their patriotic duty to populate the lands beyond the Mississippi River, bringing with them American slavery, culture, laws, and political traditions. The Texas War for Independence Many Americans who migrated to Texas at the invitation of the Mexican government did not completely shed their identity or loyalty to the United States. They brought American traditions and expectations with them (including, for many, the right to own slaves). For instance, the majority of these new settlers were Protestant, and though they were not required to attend the Catholic mass, Mexico’s prohibition on the public practice of other religions upset them and they routinely ignored it. Accustomed to representative democracy, jury trials, and the defendant’s right to appear before a judge, the Anglo-American settlers in Texas also disliked the Mexican legal system, which provided for an initial hearing by an alcalde, an administrator who often combined the duties of mayor, judge, and law enforcement officer. The alcalde sent a written record of the proceeding to a judge in Saltillo, the state capital, who decided the outcome. Settlers also resented that at most two Texas representatives were allowed in the state legislature. Their greatest source of discontent, though, was the Mexican government’s 1829 abolition of slavery. Most American settlers were from southern states, and many had brought slaves with them. Mexico tried to accommodate them by maintaining the fiction that the slaves were indentured servants. But American slaveholders in Texas distrusted the Mexican government and wanted Texas to be a new U.S. slave state. The dislike of most for Roman Catholicism (the prevailing religion of Mexico) and a widely held belief in American racial superiority led them generally to regard Mexicans as dishonest, ignorant, and backward. Belief in their own superiority inspired some Texans to try to undermine the power of the Mexican government. When empresario Haden Edwards attempted to evict people who had settled his land grant before he gained title to it, the Mexican government nullified its agreement with him. Outraged, Edwards and a small party of men took prisoner the alcalde of Nacogdoches. The Mexican army marched to the town, and Edwards and his troops then declared the formation of the Republic of Fredonia between the Sabine and Rio Grande Rivers. To demonstrate loyalty to their adopted country, a force led by Stephen Austin hastened to Nacogdoches to support the Mexican army. Edwards’s revolt collapsed, and the revolutionaries fled Texas. The growing presence of American settlers in Texas, their reluctance to abide by Mexican law, and their desire for independence caused the Mexican government to grow wary. In 1830, it forbade future U.S. immigration and increased its military presence in Texas. Settlers continued to stream illegally across the long border; by 1835, after immigration resumed, there were twenty thousand Anglo-Americans in Texas. Fifty-five delegates from the Anglo-American settlements gathered in 1831 to demand the suspension of customs duties, the resumption of immigration from the United States, better protection from Indian tribes, the granting of promised land titles, and the creation of an independent state of Texas separate from Coahuila. Ordered to disband, the delegates reconvened in early April 1833 to write a constitution for an independent Texas. Surprisingly, General Antonio Lopez de Santa Anna, Mexico’s new president, agreed to all demands, except the call for statehood. Coahuila y Texas made provisions for jury trials, increased Texas’s representation in the state legislature, and removed restrictions on commerce. Texans’ hopes for independence were quashed in 1834, however, when Santa Anna dismissed the Mexican Congress and abolished all state governments, including that of Coahuila y Texas. In January 1835, reneging on earlier promises, he dispatched troops to the town of Anahuac to collect customs duties. Lawyer and soldier William B. Travis and a small force marched on Anahuac in June, and the fort surrendered. On October 2, Anglo-American forces met Mexican troops at the town of Gonzales; the Mexican troops fled and the Americans moved on to take San Antonio. Now more cautious, delegates to the Consultation of 1835 at San Felipe de Austin voted against declaring independence, instead drafting a statement, which became known as the Declaration of Causes, promising continued loyalty if Mexico returned to a constitutional form of government. They selected Henry Smith, leader of the Independence Party, as governor of Texas and placed Sam Houston, a former soldier who had been a congressman and governor of Tennessee, in charge of its small military force. The Consultation delegates met again in March 1836. They declared their independence from Mexico and drafted a constitution calling for an American-style judicial system and an elected president and legislature. Significantly, they also established that slavery would not be prohibited in Texas. Many wealthy Tejanos supported the push for independence, hoping for liberal governmental reforms and economic benefits. Remember the Alamo! Mexico had no intention of losing its northern province. Santa Anna and his army of four thousand had besieged San Antonio in February 1836. Hopelessly outnumbered, its two hundred defenders, under Travis, fought fiercely from their refuge in an old mission known as the Alamo. After ten days, however, the mission was taken and all but a few of the defenders were dead, including Travis and James Bowie, the famed frontiersman who was also a land speculator and slave trader. A few male survivors, possibly including the frontier legend and former Tennessee congressman Davy Crockett, were led outside the walls and executed. The few women and children inside the mission were allowed to leave with the only adult male survivor, a slave owned by Travis who was then freed by the Mexican Army. Terrified, they fled. Although hungry for revenge, the Texas forces under Sam Houston nevertheless withdrew across Texas, gathering recruits as they went. Coming upon Santa Anna’s encampment on the banks of San Jacinto River on April 21, 1836, they waited as the Mexican troops settled for an afternoon nap. Assured by Houston that “Victory is certain!” and told to “Trust in God and fear not!” the seven hundred men descended on a sleeping force nearly twice their number with cries of “Remember the Alamo!” Within fifteen minutes the Battle of San Jacinto was over. Approximately half the Mexican troops were killed, and the survivors, including Santa Anna, taken prisoner. Santa Anna grudgingly signed a peace treaty and was sent to Washington, where he met with President Andrew Jackson and, under pressure, agreed to recognize an independent Texas with the Rio Grande River as its southwestern border. By the time the agreement had been signed, however, Santa Anna had been removed from power in Mexico. For that reason, the Mexican Congress refused to be bound by Santa Anna’s promises and continued to insist that the renegade territory still belonged to Mexico. \| Visit the oﬃcial Alamo website to learn more about the battle of the Alamo and take a virtual tour of the old mission. \| The Lone Star Republic In September 1836, military hero Sam Houston was elected president of Texas, and, following the relentless logic of U.S. expansion, Texans voted in favor of annexation to the United States. This had been the dream of many settlers in Texas all along. They wanted to expand the United States west and saw Texas as the next logical step. Slaveholders there, such as Sam Houston, William B. Travis and James Bowie (the latter two of whom died at the Alamo), believed too in the destiny of slavery. Mindful of the vicious debates over Missouri that had led to talk of disunion and war, American politicians were reluctant to annex Texas or, indeed, even to recognize it as a sovereign nation. Annexation would almost certainly mean war with Mexico, and the admission of a state with a large slave population, though permissible under the Missouri Compromise, would bring the issue of slavery once again to the fore. Texas had no choice but to organize itself as the independent Lone Star Republic. To protect itself from Mexican attempts to reclaim it, Texas sought and received recognition from France, Great Britain, Belgium, and the Netherlands. The United States did not officially recognize Texas as an independent nation until March 1837, nearly a year after the final victory over the Mexican army at San Jacinto. Uncertainty about its future did not discourage Americans committed to expansion, especially slaveholders, from rushing to settle in the Lone Star Republic, however. Between 1836 and 1846, its population nearly tripled. By 1840, nearly twelve thousand enslaved Africans had been brought to Texas by American slaveholders. Many new settlers had suffered financial losses in the severe financial depression of 1837 and hoped for a new start in the new nation. According to folklore, across the United States, homes and farms were deserted overnight, and curious neighbors found notes reading only “GTT” (“Gone to Texas”). Many Europeans, especially Germans, also immigrated to Texas during this period. In keeping with the program of ethnic cleansing and white racial domination, as illustrated by the image at the beginning of this chapter, Americans in Texas generally treated both Tejano and Indian residents with utter contempt, eager to displace and dispossess them. Anglo- American leaders failed to return the support their Tejano neighbors had extended during the rebellion and repaid them by seizing their lands. In 1839, the republic’s militia attempted to drive out the Cherokee and Comanche. The impulse to expand did not lay dormant, and Anglo-American settlers and leaders in the newly formed Texas republic soon cast their gaze on the Mexican province of New Mexico as well. Repeating the tactics of earlier filibusters, a Texas force set out in 1841 intent on taking Santa Fe. Its members encountered an army of New Mexicans and were taken prisoner and sent to Mexico City. On Christmas Day, 1842, Texans avenged a Mexican assault on San Antonio by attacking the Mexican town of Mier. In August, another Texas army was sent to attack Santa Fe, but Mexican troops forced them to retreat. Clearly, hostilities between Texas and Mexico had not ended simply because Texas had declared its independence. Licenses and Attributions CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: Daniel M. Regalado. License: CC BY: Attribution CC LICENSED CONTENT, SHARED PREVIOUSLY U.S. History. Authored by: OpenStax. Provided by: OpenStax; Rice University. Located at: http://cnx.org/contents/a7ba2fb8-8925-4987- b182-5f4429d48daa@6.16 License: CC BY: Attribution. License Terms: Download for free at http://cnx.org/contents/a7ba2fb8-8925-4987-b182-5f4429d48daa@6.16.	oercommons	2025-03-18T00:35:15.522765	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66245/overview", "title": "Texas Government 2.0, Introduction to Texas History and Politics", "author": null }
https://oercommons.org/courseware/lesson/66246/overview	The Mexican-American War, 1846–1848 Overview The Mexican-American War, 1846–1848 Learning Objective By the end of this section, you will be able to: - Describe the influence the Mexican-American War had on Texas Introduction Tensions between the United States and Mexico rapidly deteriorated in the 1840s as American expansionists eagerly eyed Mexican land to the west, including the lush northern Mexican province of California. Indeed, in 1842, a U.S. naval fleet, incorrectly believing war had broken out, seized Monterey, California, a part of Mexico. Monterey was returned the next day, but the episode only added to the uneasiness with which Mexico viewed its northern neighbor. The forces of expansion, however, could not be contained, and American voters elected James Polk in 1844 because he promised to deliver more lands. President Polk fulfilled his promise by gaining Oregon and, most spectacularly, provoking a war with Mexico that ultimately fulfilled the wildest fantasies of expansionists. By 1848, the United States encompassed much of North America, a republic that stretched from the Atlantic to the Pacific. James K. Polk And The Triumph Of Expansion A fervent belief in expansion gripped the United States in the 1840s. In 1845, a New York newspaper editor, John O’Sullivan, introduced the concept of “manifest destiny” to describe the popular idea of the special role of the United States in overspreading the continent—the divine right and duty of white Americans to seize and settle the American West, thus spreading Protestant, democratic values. In this climate of opinion, voters in 1844 elected James K. Polk, a slaveholder from Tennessee, because he vowed to annex Texas as a new slave state and take Oregon. Annexing Oregon was an important objective for U.S. foreign policy because it appeared to be an area rich in commercial possibilities. Northerners favored U.S. control of Oregon because ports in the Pacific Northwest would be gateways for trade with Asia. Southerners hoped that, in exchange for their support of expansion into the northwest, northerners would not oppose plans for expansion into the southwest. President Polk—whose campaign slogan in 1844 had been “Fifty-four forty or fight!”—asserted the United States’ right to gain full control of what was known as Oregon Country, from its southern border at 42° latitude (the current boundary with California) to its northern border at 54° 40′ latitude. According to an 1818 agreement, Great Britain and the United States held joint ownership of this territory, but the 1827 Treaty of Joint Occupation opened the land to settlement by both countries. Realizing that the British were not willing to cede all claims to the territory, Polk proposed the land be divided at 49° latitude (the current border between Washington and Canada). The British, however, denied U.S. claims to land north of the Columbia River (Oregon’s current northern border). Indeed, the British foreign secretary refused even to relay Polk’s proposal to London. However, reports of the difficulty Great Britain would face defending Oregon in the event of a U.S. attack, combined with concerns over affairs at home and elsewhere in its empire, quickly changed the minds of the British, and in June 1846, Queen Victoria’s government agreed to a division at the forty-ninth parallel. In contrast to the diplomatic solution with Great Britain over Oregon, when it came to Mexico, Polk and the American people proved willing to use force to wrest more land for the United States. In keeping with voters’ expectations, President Polk set his sights on the Mexican state of California. After the mistaken capture of Monterey, negotiations about purchasing the port of San Francisco from Mexico broke off until September 1845. Then, following a revolt in California that left it divided in two, Polk attempted to purchase Upper California and New Mexico as well. These efforts went nowhere. The Mexican government, angered by U.S. actions, refused to recognize the independence of Texas. Finally, after nearly a decade of public clamoring for the annexation of Texas, in December 1845 Polk officially agreed to the annexation of the former Mexican state, making the Lone Star Republic an additional slave state. Incensed that the United States had annexed Texas, however, the Mexican government refused to discuss the matter of selling land to the United States. Indeed, Mexico refused even to acknowledge Polk’s emissary, John Slidell, who had been sent to Mexico City to negotiate. Not to be deterred, Polk encouraged Thomas O. Larkin, the U.S. consul in Monterey, to assist any American settlers and any Californios, the Mexican residents of the state, who wished to proclaim their independence from Mexico. By the end of 1845, having broken diplomatic ties with the United States over Texas and having grown alarmed by American actions in California, the Mexican government warily anticipated the next move. It did not have long to wait. War With Mexico, 1846–1848 Expansionistic fervor propelled the United States to war against Mexico in 1846. The United States had long argued that the Rio Grande was the border between Mexico and the United States, and at the end of the Texas war for independence Santa Anna had been pressured to agree. Mexico, however, refused to be bound by Santa Anna’s promises and insisted the border lay farther north, at the Nueces River. To set it at the Rio Grande would, in effect, allow the United States to control land it had never occupied. In Mexico’s eyes, therefore, President Polk violated its sovereign territory when he ordered U.S. troops into the disputed lands in 1846. From the Mexican perspective, it appeared the United States had invaded their nation. In January 1846, the U.S. force that was ordered to the banks of the Rio Grande to build a fort on the “American” side encountered a Mexican cavalry unit on patrol. Shots rang out, and sixteen U.S. soldiers were killed or wounded. Angrily declaring that Mexico “has invaded our territory and shed American blood upon American soil,” President Polk demanded the United States declare war on Mexico. On May 12, Congress obliged. The small but vocal antislavery faction decried the decision to go to war, arguing that Polk had deliberately provoked hostilities so the United States could annex more slave territory. Illinois representative Abraham Lincoln and other members of Congress issued the “Spot Resolutions” in which they demanded to know the precise spot on U.S. soil where American blood had been spilled. Many Whigs also denounced the war. Democrats, however, supported Polk’s decision, and volunteers for the army came forward in droves from every part of the country except New England, the seat of abolitionist activity. Enthusiasm for the war was aided by the widely held belief that Mexico was a weak, impoverished country and that the Mexican people, perceived as ignorant, lazy, and controlled by a corrupt Roman Catholic clergy, would be easy to defeat. U.S. military strategy had three main objectives: 1) Take control of northern Mexico, including New Mexico; 2) seize California; and 3) capture Mexico City. General Zachary Taylor and his Army of the Center were assigned to accomplish the first goal, and with superior weapons they soon captured the Mexican city of Monterrey. Taylor quickly became a hero in the eyes of the American people, and Polk appointed him commander of all U.S. forces. General Stephen Watts Kearny, commander of the Army of the West, accepted the surrender of Santa Fe, New Mexico, and moved on to take control of California, leaving Colonel Sterling Price in command. Despite Kearny’s assurances that New Mexicans need not fear for their lives or their property, and in fact the region’s residents rose in revolt in January 1847 in an effort to drive the Americans away. Although Price managed to put an end to the rebellion, tensions remained high. Kearny, meanwhile, arrived in California to find it already in American hands through the joint efforts of California settlers, U.S. naval commander John D. Sloat, and John C. Fremont, a former army captain and son-in-law of Missouri senator Thomas Benton. Sloat, at anchor off the coast of Mazatlan, learned that war had begun and quickly set sail for California. He seized the town of Monterey in July 1846, less than a month after a group of American settlers led by William B. Ide had taken control of Sonoma and declared California a republic. A week after the fall of Monterey, the navy took San Francisco with no resistance. Although some Californios staged a short-lived rebellion in September 1846, many others submitted to the U.S. takeover. Thus Kearny had little to do other than take command of California as its governor. Leading the Army of the South was General Winfield Scott. Both Taylor and Scott were potential competitors for the presidency, and believing—correctly—that whoever seized Mexico City would become a hero, Polk assigned Scott the campaign to avoid elevating the more popular Taylor, who was affectionately known as “Old Rough and Ready.” Scott captured Veracruz in March 1847, and moving in a northwesterly direction from there (much as Spanish conquistador Hernán Cortés had done in 1519), he slowly closed in on the capital. Every step of the way was a hard-fought victory, however, and Mexican soldiers and civilians both fought bravely to save their land from the American invaders. Mexico City’s defenders, including young military cadets, fought to the end. According to legend, cadet Juan Escutia’s last act was to save the Mexican flag, and he leapt from the city’s walls with it wrapped around his body. On September 14, 1847, Scott entered Mexico City’s central plaza; the city had fallen. While Polk and other expansionists called for “all Mexico,” the Mexican government and the United States negotiated for peace in 1848, resulting in the Treaty of Guadalupe Hidalgo. The Treaty of Guadalupe Hidalgo, signed in February 1848, was a triumph for American expansionism under which Mexico ceded nearly half its land to the United States. The Mexican Cession, as the conquest of land west of the Rio Grande was called, included the current states of California, New Mexico, Arizona, Nevada, Utah, and portions of Colorado and Wyoming. Mexico also recognized the Rio Grande as the border with the United States. Mexican citizens in the ceded territory were promised U.S. citizenship in the future when the territories they were living in became states. In exchange, the United States agreed to assume $3.35 million worth of Mexican debts owed to U.S. citizens, paid Mexico $15 million for the loss of its land, and promised to guard the residents of the Mexican Cession from Indian raids. Explore the U.S.-Mexican War at PBS to read about life in the Mexican and U.S. armies during the war and to learn more about the various battles. \| As extensive as the Mexican Cession was, some argued the United States should not be satisfied until it had taken all of Mexico. Many who were opposed to this idea were southerners who, while desiring the annexation of more slave territory, did not want to make Mexico’s large mestizo (people of mixed Indian and European ancestry) population part of the United States. Others did not want to absorb a large group of Roman Catholics. These expansionists could not accept the idea of new U.S. territory filled with mixed-race, Catholic populations. Licenses And Attributions CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: Daniel M. Regalado. License: CC BY: Attribution CC LICENSED CONTENT, SHARED PREVIOUSLY U.S. History. Authored by: OpenStax. Provided by: OpenStax; Rice University. Located at: http://cnx.org/contents/a7ba2fb8-8925-4987- b182-5f4429d48daa@6.16. License: CC BY: Attribution License Terms: Download for free at http://cnx.org/contents/a7ba2fb8-8925-4987-b182-5f4429d48daa@6.16.	oercommons	2025-03-18T00:35:15.550383	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66246/overview", "title": "Texas Government 2.0, Introduction to Texas History and Politics", "author": null }
https://oercommons.org/courseware/lesson/66247/overview	Texas in the American Civil War Overview Texas in the American Civil War Learning Objective By the end of this section, you will be able to: - Summarize the American Civil War's influence on Texas Introduction The U.S. state of Texas declared its secession from the United States of America on February 1, 1861, and joined the Confederate States on March 2, 1861, after it replaced its governor, Sam Houston, when he refused to take an oath of allegiance to the Confederacy. As with those of other States, the Declaration was not recognized by the United States government at Washington. Some Texan military units fought in the Civil War east of the Mississippi River, but Texas was most useful for supplying soldiers and horses for Confederate forces. Texas’ supply role lasted until mid-1863, after which time Union gunboats controlled the Mississippi River, making large transfers of men, horses or cattle impossible. Some cotton was sold in Mexico, but most of the crop became useless because of the Union naval blockade of Galveston, Houston, and other ports. Secession In the late winter of 1860, Texan counties sent delegates to a special convention to debate the merits of secession. The convention adopted an “Ordinance of Secession” by a vote of 166 to 8, which was ratified by a popular referendum on February 23. Separately from the Ordinance of Secession, which was considered a legal document, Texas also issued a declaration of causes spelling out the rationale for declaring secession. The document specifies several reasons for secession, including its solidarity with its “sister slave-holding States,” the U.S. government’s inability to prevent Indian attacks, slave-stealing raids, and other border-crossing acts of banditry. It accuses northern politicians and abolitionists of committing a variety of outrages upon Texans. The bulk of the document offers justifications for slavery saying that remaining a part of the United States would jeopardize the security of the two. The declaration includes this extract praising slavery, in which the Union itself is referred to as the “confederacy”: "We hold as undeniable truths that the governments of the various States, and of the confederacy itself, were established exclusively by the white race, for themselves and their posterity; that the African race had no agency in their establishment; that they were rightfully held and regarded as an inferior and dependent race, and in that condition only could their existence in this country be rendered beneficial or tolerable." — Texas Secession Convention, A Declaration of the Causes which Impel the State of Texas to Secede from the Federal Union, (February 1861). At this time, African Americans comprised 30 percent of the state’s population, and they were overwhelmingly enslaved. According to one Texan, keeping them enslaved was the primary goal of the state in joining the Confederacy: "Independence without slavery, would be valueless… The South without slavery would not be worth a mess of pottage." — Caleb Cutwell, letter to the Galveston Tri- Weekly, (February 22, 1865). Secession Convention and the Confederacy Following the election of Abraham Lincoln in 1860, public opinion in the cotton states of the Lower South (South Carolina through Texas) swung in favor of secession. By February 1861, the other six states of the sub-region had separately passed ordinances of secession. However, events in Texas were delayed, largely due to the resistance of Southern Unionist governor, Sam Houston. Unlike the other “cotton states”‘ chief executives, who took the initiative in secessionist efforts, Houston refused to call the Texas Legislature into special session to consider the question, relenting only when it became apparent citizens were prepared to act without him. In early December 1860, before South Carolina even seceded, a group of State officials published via newspaper a call for a statewide election of convention delegates on January 8, 1861. This election was highly irregular, even for the standards of the day. It often relied on voice vote at public meetings, although “viva voce” (voice) voting for popular elections had been used since at least March 1846, less than three months after statehood. Unionists were often discouraged from attending or chose not to participate. This resulted in lopsided representation of secessionists delegates. The election call had stipulated for the delegates to assemble in convention on January 28. Houston called the Legislature into session, hoping that the elected body would declare the unauthorized convention illegal. On January 21, 1861, the Legislature met in Austin and was addressed by Houston. Calling Lincoln’s election “unfortunate,” he nonetheless emphasized, in a reference to the upcoming meeting of the secession convention, it was no justification for “rash action.” However, the Texas Legislature voted the delegates’ expense money and supplies and—over Houston’s veto—made a pledge to uphold the legality of the Convention’s actions. The only stipulation was that the people of Texas have the final say in referendum. With gubernatorial forces routed, the Secession Convention convened on January 28 and, in the first order of business, voted to back the legislature 140–28 in that an ordinance of secession, if adopted, be submitted for statewide consideration. The following day, convention president Oran Roberts introduced a resolution suggesting Texas leave the Union. The ordinance was read on the floor the next day, citing the failures of the federal government to protect the lives and property of Texas citizens and accusing the Northern states of using the same as a weapon to “strike down the interests and prosperity” of the Southern people. After the grievances were listed, the ordinance repealed the one of July 4, 1845, in which Texas approved annexation by the United States and the Constitution of the United States, and revoked all powers of, obligations to, and allegiance to, the U.S. federal government and the U.S. Constitution. In the interests of historical significance and posterity, the ordinance was written to take effect on March 2, the date of Texas Declaration of Independence (and, coincidentally, Houston’s birthday). On February 1, members of the Legislature, and a huge crowd of private citizens, packed the House galleries and balcony to watch the final vote on the question of secession. Seventy “yea” votes were recorded before there was a single “nay.” One of the negative votes is enshrined in Texas history books. James Webb Throckmorton, from Collin County in North Texas, in response to the roar of hisses and boos and catcalls which greeted his decision, retorted, “When the rabble hiss, well may patriots tremble.” Appreciating his style, the crowd afforded him a grudging round of applause (like many Texans who initially opposed secession, Throckmorton accepted the result and served his state, rising to the rank of brigadier-general in the Confederate army). The final tally for secession was 166–7, a vote whose legality was upheld by the Texas Legislature on February 7. Other than in South Carolina, where the vote was unanimous, this was the highest percentage of any other state of the Lower South. On February 7, the Legislature ordered a referendum to be held on the ordinance under the direction of the convention. The decision was further affirmed on February 23 when a statewide referendum resulted in Texas voters approving the measure, 46,129 to 14,697. The last order of business was to appoint a delegation to represent Texas in Montgomery, Alabama, where their counterparts from the other six seceding states were meeting to form a new Confederacy. On March 4, the convention assembled again to formally declare Texas out of the Union and to approve the “Constitution of the Confederate States of America”, which had been drawn up by its “Provisional Congress” (as it turned out, Texas had already been admitted into the fold on March 1).In March, George Williamson, the Louisianan state commissioner, addressed the Texan secession convention, where he called upon Texas and the slave states of the U.S. to declare secession from the Union in order to continue the institution of slavery: "With the social balance wheel of slavery to regulate its machinery, we may fondly indulge the hope that our Southern government will be perpetual… Louisiana looks to the formation of a Southern confederacy to preserve the blessings of African slavery…" — George Williamson, speech to the Texan secession convention, (March 1861). Governor Sam Houston accepted secession but asserted that the Convention had no power to link the state with the new Southern Confederacy. Instead, he urged that Texas revert to its former status as an independent republic and stay neutral. Houston took his seat on March 16, the date state officials were scheduled to take an oath of allegiance to the Confederacy. He remained silent as his name was called out three times and, after failing to respond, the office of governor was declared vacant and Houston was deposed from office. Seizure of Federal Property and Arms After Texas passed its Ordinance of Secession, the state government appointed four men as “Commissioners of Public Safety” to negotiate with the federal government for the safe transfer of military installations and bases in Texas to the Confederates. Along with land baron Samuel A. Maverick and Thomas J. Devine, Dr. Philip N. Luckett met with U.S. Army General David E. Twiggs on February 8, 1861, to arrange the surrender of the federal property in San Antonio, including the military stores being housed in the old Alamo mission. As a result of the negotiations, Twiggs delivered his entire command and its associated Army property (10,000 rifled muskets) to the Confederacy, an act that brought cries of treason from Unionists throughout the state. Almost immediately, Twiggs was dismissed from the U.S. Army by President Buchanan for “treachery to the flag of his country.” Shortly afterwards, he accepted a commission as general in the Confederate Army but was so upset by being branded a traitor that he wrote a letter to Buchanan stating the intention to call upon him for a “personal interview” (then a common euphemism to fight a duel). Future Confederate general Robert E. Lee, then still a colonel in the U.S. Army, was in San Antonio at the time and when he heard the news of the surrender to Texas authorities, responded, “Has it come so soon as this?” Unionist Sentiment and Opposition to The Confederacy Despite the prevailing view of the vast majority of the state’s politicians and the delegates to the Secession Convention, there were a significant number of Texans who opposed secession. The referendum on the issue indicated that some 25% favored remaining in the Union at the time the question was originally considered. The largest concentration of anti-secession sentiment was among the German Texan population in the Texas Hill Country, and in some of the counties of North Texas. In the latter region, most of the residents were originally from states of the Upper South. Some of the leaders initially opposed to secession accepted the Confederate cause once the matter was decided, some withdrew from public life, others left the state, and a few even joined the Union army. Confederate conscription laws forced most men of military age into the Confederate army, regardless of their sentiment. However, at least 2000 Texans joined the Union rank. In October 1862, approximately 150 settlers in and around Cooke County on the Red River were arrested by the 11th Texas Cavalry led by Colonel William C. Young on the orders of Colonel James Bourland, Confederate Provost Marshal for northern Texas. A court was convened in Gainesville to try them for allegedly plotting to seize the arsenals at Sherman and Gainesville and to kill their Confederate neighbors, seize their property, and to cooperate with Union army forces poised to invade northern Texas from Arkansas and/or Indian Territory. Several of the settlers were hanged in what is now downtown Gainesville during the first week of October. Nineteen additional men were found guilty and hanged before the end of the month. A total of about forty Unionists were hanged in Gainesville, two were shot while trying to escape, and two more were hanged elsewhere after being turned over to a military tribunal. Under the primitive conditions on the Texas frontier during the Civil War, evidence against the accused was questionable, and the legal proceedings were highly imperfect. A granite monument in a small park marks the spot where the hangings took place. The Confederacy’s conscription act proved controversial, not only in Texas but all across the South. Despite the referendum result, some opponents argued that the war was being fought by poor people on behalf of a few wealthy slave owners. The Act exempted from the draft men who owned fifteen or more slaves. Draft resistance was widespread especially among Texans of German or Mexican descent; many of the latter went to Mexico. Potential draftees went into hiding, Confederate officials hunted them down, and many were shot or captured and forced into the army. Sam Houston Sam Houston was the premier Southern Unionist in Texas. While he argued for slave property rights and deplored the election of the Lincoln Administration, he considered secession unconstitutional and thought secession at that moment in time was a “rash action” that was certain to lead to a conflict favoring the industrial and populated North. He predicted: “Let me tell you what is coming. After the sacrifice of countless millions of treasure and hundreds of thousands of lives, you may win Southern independence if God be not against you, but I doubt it. I tell you that, while I believe with you in the doctrine of states rights, the North is determined to preserve this Union. They are not a fiery, impulsive people as you are, for they live in colder climates. But when they begin to move in a given direction, they move with the steady momentum and perseverance of a mighty avalanche; and what I fear is, they will overwhelm the South.” Houston rejected the actions of the Texas Secession Convention, believing it had overstepped its authority in becoming a member state of the newly formed Confederacy. He refused to take an oath of allegiance to the Confederacy and was deposed from office. In a speech he wrote, but did not deliver, he said: Fellow-Citizens, in the name of your rights and liberties, which I believe have been trampled upon, I refuse to take this oath. In the name of the nationality of Texas, which has been betrayed by the Convention, I refuse to take this oath. In the name of the Constitution of Texas, I refuse to take this oath. In the name of my own conscience and manhood, which this Convention would degrade by dragging me before it, to pander to the malice of my enemies, I refuse to take this oath. I deny the power of this Convention to speak for Texas….I protest….against all the acts and doings of this convention and I declare them null and void. After his ouster from the governor’s office, Houston maintained a low public profile until his death in July 1863. Before he died, Houston wrote a friend: “There comes a time a man’s section is his country…I stand with mine. I was a conservative citizen of the United States…I am now a conservative citizen of the Southern Confederacy.” Military Recruitment Over 70,000 Texans served in the Confederate army and Texas regiments fought in every major battle throughout the war. Some men were veterans of the Mexican–American War; a few had served in the earlier Texas Revolution. The state furnished the Confederacy with 45 regiments of cavalry, 23 regiments of infantry, 12 battalions of cavalry, 4 battalions of infantry, 5 regiments of heavy artillery, and 30 batteries of light artillery. The state maintained at its own expense some additional troops that were for home defense. These included 5 regiments and 4 battalions of cavalry, and 4 regiments and one battalion of infantry. In 1862 the Confederate Congress in Richmond, Virginia, passed a conscription law that ordered all men from 18 to 45 years of age to be placed into military service except ministers, state, city, county officers, and certain slave owners; all persons holding 20 slaves or more were exempt from Confederate conscription under the “Twenty Negro Law.” When the first companies of Texas soldiers reached Richmond, Virginia, Confederate President Jefferson Davis greeted them with the words: “Texans! The troops of other states have their reputations to gain, but the sons of the defenders of the Alamo have theirs to maintain. I am assured that you will be faithful to the trust.” “The Texas Brigade” (also known as “Hood’s Brigade”) was a unit composed of the 1st, 4th and 5th Texas infantry regiments augmented at times by the 18th Georgia Infantry and Hampton’s (South Carolina) Legion until they were permanently teamed with the 3rd Arkansas Infantry. Often serving as “shock troops” of General Robert E. Lee’s Army of Northern Virginia, the Texas Brigade was “always favorites” of General Lee and on more than one occasion Lee praised their fighting qualities, remarking that none had brought greater honor to their native state than “my Texans.” Hood’s men suffered severe casualties in a number of fights, most notably at the Battle of Antietam, where they faced off with Wisconsin’s Iron Brigade, and at Gettysburg, where they assaulted Houck’s Ridge and then Little Round Top. “Walker’s Greyhound Division” was a division composed of four brigades with Texan units; the only division in the Confederate States Army that maintained its single-state composition throughout the War. Formed in 1862 under command of Major General John George Walker it fought in the Western Theater and the Trans-Mississippi Department, and was considered an elite backbone of the army. Detached from the division in 1863, the 4th brigade fought at the Battle of Arkansas Post, where it became isolated and was forced to surrender. A new fourth brigade was added the division in 1865. Among the most famous mounted units were Terry’s Texas Rangers, a militia of former rangers and frontiersmen, many of whom later became peacekeepers in the Old West; and the 33rd Texas Cavalry Regiment of Colonel Santos Benavides, which guarded the Confederate cotton trade lines from Texas into northern Mexico. Over 2,000 Texas men joined the Union Army. Notable among them was future Texas governor Edmund J. Davis who initially commanded the Union Army’s 1st Texas Cavalry and rose to the rank of brigadier general. Texas’s relatively large German population around Austin County led by Paul Machemehl tried to remain neutral in the War but eventually left Confederate Texas for Mexico. East Texas gave the most support to secession, and the only East Texas counties in which significant numbers of people opposed secession were Angelina County, Fannin County, and Lamar County, although these counties supplied many men to Texas regiments, including the 9th Texas Infantry Regiment; the 1st Partisan Rangers; 3rd, 4th, 9th, 27th, and 29th Texas Cavalry; and the 9th Texas Field Battery. In 1862, Abraham Lincoln named a former United States Congressman, Andrew J. Hamilton, as the Military Governor of Texas. Hamilton held the title throughout the War. During the early stages of Reconstruction Hamilton was named as the first provisional civilian governor. For a time thereafter, active-duty U.S. Army officers served as military governors of Texas. Years into the war, one Confederate soldier from Texas gave his reasons for fighting for the Confederacy, stating that “we are fighting for our property”, whereas Union soldiers were fighting for the “flimsy and abstract idea that a negro is equal to an Anglo.” Civil War Battles In Texas Texas did not experience many significant battles. However, the Union mounted several attempts to capture the “Trans-Mississippi” regions of Texas and Louisiana from 1862 until the war’s end. With ports to the east captured or under blockade, Texas in particular became a blockade-running haven. Referred to as the “backdoor” of the Confederacy, Texas and western Louisiana continued to provide loads of harvested cotton that were transported overland to the Mexican border town of Matamoros, Tamaulipas and shipped to Europe in exchange for supplies. Determined to shut off this trade, the Union mounted several attacks, each of them unsuccessful. Texas Occupation The U.S. Navy blockaded the principal seaport, Galveston, for four years, and federal infantry occupied the city for three months in late 1862. Confederate troops under Gen. John B. Magruder recaptured the city on January 1, 1863 and it remained in Confederate hands until the end of the war. A few days later the Confederate raider CSS Alabama attacked and sank the USS Hatteras in a naval engagement off the coast of Galveston. A few other cities also fell to Union troops at times during the war, including Port Lavaca, Indianola, and Brownsville. Federal attempts to seize control of Laredo, Corpus Christi, and Sabine Pass failed. By the end of the war no territory but Brazos Island and El Paso was in Union hands. The California Column occupied the region around El Paso from 1862 to the end of the war. The most notable military battle in Texas during the war happened on September 8, 1863. At the Second Battle of Sabine Pass, a small garrison of 46 Confederates from the mostly-Irish Davis Guards under Lt. Richard W. Dowling, 1st Texas Heavy Artillery, defeated a much larger Union force from New Orleans under Gen. William B. Franklin. Skilled gunnery by Dowling’s troops disabled the lead ships in Franklin’s flotilla, prompting the remainder—4,000 men on 27 ships—to retreat back to New Orleans. This victory against such overwhelming odds resulted in the Confederate Congress passing a special resolution of recognition, and the only contemporary military decoration of the South, the Davis Guard Medal. CSA President Jefferson Davis stated, “Sabine Pass will stand, perhaps for all time, as the greatest military victory in the history of the world.” In 1864, many Texas forces, including a division under Camille de Polignac, a French prince and Confederate general, moved into Northwestern Louisiana to stall Union Maj. Gen. Nathaniel Banks’ Red River Campaign, which was intended to advance into Texas from its eastern border. Confederate forces halted the expedition at the Battle of Mansfield, just east of the Texas border. Union forces from Brazos Island launched the Brazos Santiago Expedition, leading to the last battle of the Civil War, the Battle of Palmito Ranch, fought in Texas on May 12, 1865, well after Robert E. Lee’s surrender on April 9, 1865, at Old Appomattox Court House, Virginia. Collapse of Confederate Authority In Texas In the spring of 1865, Texas contained over 60,000 soldiers of the Army of the Trans-Mississippi under General Edmund Kirby Smith. As garrison troops far removed from the main theaters of the war, morale had deteriorated to the point of frequent desertion and thievery. News of the surrender of Lee and other Confederate generals east of the Mississippi finally reached Texas around April. Local Confederate authorities had mixed opinions on their future course of action. Most senior military leaders vowed to press on with the war, including commanding general Kirby Smith. Many soldiers, however, greeted frequent speeches whose theme was “fight on, boys” with derision, or simply failed to attend them. The month of May brought increasing rates of desertion. News of Joseph E. Johnston’s and Richard Taylor’s surrenders confirmed that Texas, Louisiana, and Arkansas were now essentially alone to continue the Confederate cause. On May 14, troops in Galveston briefly mutinied, but were persuaded to remain under arms. However, morale continued to sink. Generals John B. Magruder and Kirby Smith (who had already corresponded with Union Maj. Gen. John Pope regarding surrender terms on May 9) no longer sought to rally their demoralized troops, but rather began discussing the distribution of Confederate government property. Magruder pleaded that the rapid disbanding of the army would prevent depredations by disgruntled soldiers against the civilian population. The haste to disband the army, combined with the pressing need to protect Confederate property from Union confiscation, created general mayhem. Soldiers began openly pillaging the Galveston quartermasters stores on May 21. Over the next few days, a mob demanded that a government warehouse be opened to them, and soldiers detained and plundered a train. Several hundred civilians sacked the blockade runner Lark when it docked on May 24, and troops sent to pacify the crowd soon joined in the plunder. On May 23, residents in Houston sacked the ordnance building and the clothing bureau. Riots continued in the city until May 26. Both government and private stores were raided extensively in Tyler, Marshall, Huntsville, Gonzales, Hempstead, La Grange, and Brownsville. In Navasota, a powder explosion cost eight lives and flattened twenty buildings. In Austin, the State Treasury was raided and $17,000 in gold was stolen. By May 27, half of the original confederate forces in Texas had deserted or been disbanded, and formal order had disappeared into lawlessness in many areas of Texas. The formal remnants of Kirby Smith’s army had finally disintegrated by the end of May. Upon his arrival in Houston from Shreveport, the general called a court of inquiry to investigate the “causes and manner of the disbandment of the troops in the District of Texas, New Mexico and Arizona.” The May 30 findings laid the blame primarily on the civilian population. Kirby Smith addressed his few remaining soldiers and condemned those that had fled for not struggling to the last and leaving him “a commander without an army– a General without troops.” On June 2, he formally surrendered what was left of the Army of the “Trans-Mississippi.” Restoration to The Union Federal troops did not arrive in Texas to restore order until June 19, 1865, when Union Maj. Gen. Gordon Granger and 2,000 Union soldiers arrived on Galveston Island to take possession of the state and enforce the new freedoms of former slaves. The Texas holiday Juneteenth commemorates this date. The Stars and Stripes were not raised over Austin until June 25. President Andrew Johnson appointed Union General Andrew J. Hamilton, a prominent politician before the war, as the provisional governor on June 17. He granted amnesty to ex-confederates if they promised to support the Union in the future, appointing some to office. On March 30, 1870, the United States Congress permitted Texas’ representatives to take their seat in Congress, although Texas did not meet all the formal requirements for readmission. Notable Civil War Leaders from Texas A number of notable leaders were associated with Texas during the Civil War. John Bell Hood gained fame as the commander of the Texas Brigade in the Army of Northern Virginia and played a prominent role as an army commander late in the war. “Sul” Ross was a significant leader in a number of “Trans-Mississippi” Confederate armies. Felix Huston Robertson was the only native Texan Confederate general. Capt. TJ Goree was one of Lt. General James Longstreet’s most trusted aides. John H. Reagan was an influential member of Jefferson Davis’s cabinet. Col. Santos Benavides was a Confederate colonel during the American Civil War. Benavides was the highest-ranking Tejano soldier to serve in the Confederate military. The office of Governor of Texas was in flux throughout the war, with several men in power at various times. Sam Houston was governor when Texas seceded from the United States, but refused to declare any loyalty to the new Confederacy. He was replaced by Lieutenant Governor Edward Clark. Clark filled the rest of Houston’s term in 1861, and narrowly lost re-election by just 124 votes to Francis Lubbock. During his tenure, Lubbock supported Confederate conscription, working to draft all able-bodied men, including resident aliens, into the Confederate army. When Lubbock’s term ended in 1863, he joined the military. Ardent secessionist Pendleton Murrah replaced him in office. Even after Robert E. Lee surrendered in 1865, Murrah encouraged Texans to continue the revolution, and he and several supporters fled to Mexico. Lingering Effects The effects of the American Civil War linger even after 150 years have passed. It’s not uncommon to see the Confederate flag (especially the “Confederate Battle Flag”) and there are dozens of statues, monuments, and schools named after Confederate leaders. The controversy over these elements rages today. References and Further Reading "A Declaration of the Causes which Impel the State of Texas to Secede from the Federal Union". Avalon Project. Yale Law School. 2008. Cutwell, Caleb (February 22, 1865). "Letter to the Galveston Tri- Weekly". Civil War Talk. Texas. Retrieved September 13, 2015. An Act to direct the mode of voting in all popular elections, approved March 19, 1846. Gammel, H.P.N., ed. (1898). The Laws of Texas, 1822- 1897. 2. University of North Texas. p. 1318. Buenger, Walter L. (March 8, 2011). "Secession Convention". Handbook of Texas Online. Texas State Historical Association. Buenger, Walter L. (March 8, 2011). "Secession Convention". Handbook of Texas Online. Texas State Historical Association. "An Ordinance: To dissolve the union between the State of Texas and the other States, united under the compact styled "The Constitution of the United States of America." Adopted in Convention, at Austin City, the first day of February, A.D. 1861." Narrative History of Texas Secession and Readmission to the Union. Austin. August 24, 2011. "An Ordinance: To dissolve the union between the State of Texas and the other States, united under the compact styled "The Constitution of the United States of America." Adopted in Convention, at Austin City, the first day of February, A.D. 1861." Narrative History of Texas Secession and Readmission to the Union. Austin. August 24, 2011. Minor, David (November 1, 2011). "Throckmorton, James Webb". Handbook of Texas Online. Texas State Historical Association. An Act to provide for submitting the Ordinance of Secession to a vote of the People, approved February 7, 1861. Gammel, H.P.N., ed. (1898). The Laws of Texas, 1822-1897. 5. University of North Texas. pp. 347–348. Winkler, E.W. (1861). Journal of the Secession Convention of Texas. Texas. Retrieved September 8, 2015. Roberts, O.M. (1899). Evans, Clement A., ed. Texas. Confederate Military History. XI. Atlanta, Georgia: Confederate Publishing Company. pp. 20–22. "General Twiggs and Buchanan". The New York Times. May 13, 1861. Freeman, Douglas S. (1934). "R. E. Lee, A Biography". Charles Scribner's Sons. Retrieved May 20, 2008. "Civil War". Texas Military Forces Museum. Retrieved November 5, 2015. Wooster, Ralph A. (March 4, 2011). "Civil War". Handbook of Texas Online. Texas State Historical Association. McGowen, Stanley S. (July 2000). "Battle or Massacre? The Incident on the Nueces, August 10, 1862". Southwestern Historical Quarterly. Texas State Historical Association. 104 (1): 64–86. JSTOR 30241669. Campbell, Randolph B. (2003). Gone to Texas: A History of the Lone Star State. New York: Oxford University Press. p. 265. ISBN 978-0-1998- 8138-3. "Lamar W. Henkins: German Freethinkers and the Massacre at the Nueces". The Rag Blog. August 15, 2012. Foner, Eric (March 1989). "The South's Inner Civil War: The more fiercely the Confederacy fought for its independence, the more bitterly divided it became. To fully understand the vast changes the war unleashed on the country, you must first understand the plight of the Southerners who didn't want secession". American Heritage. Vol. 40 no. American Heritage Publishing Company. p. 5. Archived from the original on January 3, 2015. Retrieved December 18, 2013. McCaslin, Richard B. (June 15, 2010). "Great Hanging at Gainesville". Handbook of Texas Online. Texas State Historical Association. Retrieved 22 November 2014. Texas in the Civil War: A Capsule History Archived August 20, 2006, at the Wayback Machine. Elliott, Claude (1947). "Union Sentiment in Texas 1861-1865". Southwestern Historical Quarterly. Texas State Historical Association. 50 (4): 449–477. JSTOR 30237490. Williams, Alfred Mason (1893). Sam Houston and the War of Independence in Texas. Houghton, Miﬄin and Company. p. 354. Haley, James l. (2004). Sam Houston. Norman: University of Oklahoma Press. pp. 390–391. ISBN 978-0-8061-5214-1. Houston, General (June 2, 1861). "Gen. Houston's Position". The New York Times. Retrieved July 11, 2011. Loewen, James W. (2007). Lies My Teacher Told Me: Everything Your American History Textbook Got Wrong. New York: The New Press. pp. 224–226. ISBN 978-1-56584-100-0. OCLC 29877812. Retrieved January 19, 2016. McComb, David G. (1989). Texas, a modern history. Austin: University of Texas Press. p. 72. ISBN 0-292-74665-2. McPherson, James M. (1997). For Cause and Comrades: Why Men Fought in the Civil War. New York City, New York: Oxford University Press, Inc. p. 117. ISBN 0-19-509-023-3. OCLC 34912692. Retrieved March 8, 2016. Clampitt, Brad R. (April 2005). "The Breakup: The Collapse of the Confederate Trans-Mississippi Army in Texas, 1865". Southwest Historical Quarterly. Texas State Historical Association. 108 (4). JSTOR 30240424. "An Act to admit the State of Texas to Representation in the Congress of the United States". Texas State Archives and Library Commission. Retrieved August 24, 2011. McComb, David G. (1989). Texas, a modern history. Austin: University of Texas Press. p. 72. ISBN 0-292-74665-2. McPherson, James M. (1997). For Cause and Comrades: Why Men Fought in the Civil War. New York City, New York: Oxford University Press, Inc. p. 117. ISBN 0-19-509-023-3. OCLC 34912692. Retrieved March 8, 2016. Clampitt, Brad R. (April 2005). "The Breakup: The Collapse of the Confederate Trans-Mississippi Army in Texas, 1865". Southwest Historical Quarterly. Texas State Historical Association. 108 (4). JSTOR 30240424. "An Act to admit the State of Texas to Representation in the Congress of the United States". Texas State Archives and Library Commission. Retrieved August 24, 2011. Licenses And Attributions CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: Kris S. Seago. License: CC BY: Attribution	oercommons	2025-03-18T00:35:15.590197	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66247/overview", "title": "Texas Government 2.0, Introduction to Texas History and Politics", "author": null }
https://oercommons.org/courseware/lesson/66248/overview	Reconstruction Overview Reconstruction Learning Objective By the end of this section/chapter, you will be able to: - Summarize the influence Reconstruction had on Texas Introduction The term Reconstruction has two applications: the first applies to the complete history of the entire country from 1865 to 1877 following the American Civil War; the second, to the attempted transformation of the 11 former Confederate states from 1863 to 1877, as directed by Congress, and the role of the Union states in that transformation. Reconstruction ended the remnants of Confederate secession and abolished slavery, making the newly freed slaves citizens with civil rights ostensibly guaranteed by three new constitutional amendments. As a former Confederate state, Texas underwent this transformation. Juneteenth During the American Civil War, Texas had joined the Confederate States. The Confederacy was defeated, and U.S. Army soldiers arrived in Texas on June 19, 1865 to take possession of the state, restore order, and enforce the emancipation of slaves. The date is now commemorated as the holiday Juneteenth. On June 25, troops raised the American flag in Austin, the state capital. Formerly enslaved people in Galveston rejoiced in the streets after the announcement, although in the years afterward many struggled to work through the changes against the resistance of whites. The following year, freedmenorganized the first of what became the annual celebration of Juneteenth in Texas.3 In some cities, African-Americans were barred from using public parks because of state-sponsored segregation of facilities. Across parts of Texas, freed people pooled their funds to purchase land to hold their celebrations, such as Houston's Emancipation Park, Mexia's Booker T. Washington Park, and Emancipation Park in Austin. Reconstruction in Texas U.S. President Andrew Johnson appointed Union General Andrew J. Hamilton, a prominent politician before the war, as the provisional governor on June 17. He granted amnesty to ex- Confederates if they promised to support the Union in the future, appointing some to office. Angry returning veterans seized state property and Texas went through a period of extensive violence and disorder. Most outrages took place in northern Texas and were committed by outlaws who had their headquarters in the Indian Territory and plundered and murdered without distinction of party. On March 30, 1870, the United States Congress readmitted Texas into the Union, although Texas did not meet all the formal requirements for readmission. Like other Southern states, by the late 1870s white Democrats regained control, often with a mix of intimidation and terrorism by paramilitary groups operating for the Democratic Party. They passed a new constitution in 1876 that segregated schools and established a poll tax to support them, but it was not originally required for voting. In 1901 the Democratic- dominated legislature imposed a poll tax as a requirement for voting, and succeeded in disfranchising most blacks. The number of voters decreased from 100,000 in the 1890s to 5,000 by 1906. References and Further Reading Stephenson, Mrs. Charles (Grace Murray). Emancipation Day Celebration band, June 19, 1900, photograph, June 19, 1900; Accessed August 25, 2019. University of North Texas Libraries, The Portal to Texas History, crediting Austin History Center, Austin Public Library. Clampit, Brad R. (April 2005). The Breakup: The Collapse of the Confederate Trans-Mississippi Army in Texas, 1865. Southwest Historical Quarterly. CVIII. "Juneteenth". Texas State Library and Archives Commission. Retrieved August 25, 2019. Gates, Henry Louis, Jr. "What Is Juneteenth?" The African Americans: Many Rivers to Cross. PBS. Originally posted on The Root. Retrieved August 25, 2019. Constitution of 1876. Handbook of Texas Online. Accessed August 25, 2019. W. Marvin Dulaney, "AFRICAN AMERICANS," Handbook of Texas Online, accessed February 22, 2014. Uploaded on June 9, 2010. Modified on June 20, 2013. Published by the Texas State Historical Association. Licenses And Attributions CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: Kris S. Seago. License: CC BY: Attribution	oercommons	2025-03-18T00:35:15.611996	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66248/overview", "title": "Texas Government 2.0, Introduction to Texas History and Politics", "author": null }
https://oercommons.org/courseware/lesson/66249/overview	Governor E.J. Davis Overview Governor E.J. Davis Learning Objective By the end of this chapter, you will be able to: - Summarize the role Governor E.J. Davis played in Texas history Introduction Edmund Jackson Davis (October 2, 1827 – February 24, 1883) was an American lawyer, soldier, and politician. He was a Southern Unionist and a general in the Union Army in the American Civil War. He also served for one term from 1870 to 1874 as the 14th Governor of Texas. Civil War Years In early 1861, Edmund Davis supported Governor Sam Houston in their mutual stand against secession. Davis also urged Robert E. Lee not to violate his oath of allegiance to the United States. Davis ran to become a delegate to the Secession Convention but was defeated. He thereafter refused to take an oath of allegiance to theConfederate States of America and was removed from his judgeship. He fled from Texas and took refuge in Union-occupied New Orleans, Louisiana. He next sailed to Washington, D.C., where President Abraham Lincoln issued him a colonel’s commission with the authority to recruit the 1st Texas Cavalry Regiment (Union). Davis recruited his regiment from Union men who had fled from Texas to Louisiana. The regiment would see considerable action during the remainder of the war. On November 10, 1864, President Lincoln appointed Davis as a brigadier general of volunteers. Lincoln did not submit Davis’s nomination to this grade to the U.S. Senate until December 12, 1864. The U.S. Senate confirmed the appointment on February 14, 1865. Davis was among those present when General Edmund Kirby Smith surrendered the Confederate forces in Texas on June 2, 1865. Davis was mustered out of the volunteers on August 24, 1865. Post War Following the end of the war, Davis became a member of the 1866 Texas Constitutional Convention. He supported the rights of freed slaves and urged the division of Texas into several Republican- controlled states. In 1869, he was narrowly elected governor against Andrew Jackson Hamilton, a Unionist Democrat. As a Radical Republican during Reconstruction, his term in office was controversial. On July 22, 1870, the Texas State Police came into being to combat crime statewide in Texas. It worked against racially based crimes, and included black police officers, which caused protest from former slaveowners (and future segregationists). Davis created the “State Guard of Texas” and the “Reserve Militia,” which were forerunners of the Texas National Guard. Davis’ government was marked by a commitment to the civil rights of African Americans. One of his protégés was Norris Wright Cuney of Galveston, who continued the struggle for equality until his own death in 1896 and is honored as one of the important figures in Texas and American black history. Though Davis was highly unpopular among former Confederates, and most material written about him for many years was unfavorable, he was considered to have been a hero for the Union Army. He also gained the respect and friendship of Spanish-speaking residents on the Rio Grande frontier. In 1873, Davis was defeated for reelection by Democrat Richard Coke (42,633 votes to 85,549 votes) in an election marked by irregularities. Davis contested the results and refused to leave his office on the ground floor of the Capitol. Democratic lawmakers and Governor-elect Coke reportedly had to climb ladders to the Capitol’s second story where the legislature convened. When President Grant refused to send troops to the defeated governor’s rescue, Davis reluctantly left the capital in January 1874. He locked the door to the governor’s office and took the key, forcing Coke’s supporters to break in with an axe. John Henninger Reagan helped to oust him after he tried to stay in office beyond the end of his term. Davis was the last Republican governor of Texas until Republican Bill Clements defeated the Democrat John Luke Hill in 1978 and assumed the governorship the following January, 105 years after Davis vacated the office. Following his defeat, Davis was nominated to be collector of customs at Galveston but declined the appointment because he disliked U.S. President Rutherford B. Hayes. He ran for governor again in 1880 but was soundly defeated. His name was placed in nomination for Vice President of the United States at the 1880 Republican National Convention, which met in Chicago and chose James A. Garfield as the standard-bearer. Had Davis succeeded, he might have wound up in the White House, as did Chester A. Arthur, the man who received the vice-presidential nomination that year. Davis lost an election for the United States House of Representatives in 1882. After Democrats regained power in the state legislature, they passed laws making voter registration more difficult, such as requiring payment of poll taxes, which worked to disfranchise blacks, Mexican Americans and poor whites. They also instituted a white primary. In the 1890s, more than 100,000 blacks were voting but by 1906, only 5,000 managed to get through these barriers. As Texas became essentially a one-party state, the white primary excluded minorities from the political competitive process. They did not fully recover their constitutional rights until after enforcement under the Voting Rights Act of 1965. Edmund J. Davis died in 1883 and was given a war hero’s burial at the Texas State Cemetery in Austin. A large gravestone was placed in Davis’ honor by a brother. Davis was survived by his wife, the former Anne Elizabeth Britton (whose father, Forbes Britton, had been chief of staff to Texas Governor Sam Houston), and two sons: Britton (a West Point graduate and military officer), and Waters (an attorney and merchant in El Paso). References and Resources Odie Arambula, "Young lawyer Davis had big local role," Laredo Morning Times, May 6, 2012, p. 17A Texas State Handbook Online. Moneyhon, Carl H. (30 May 2010). "Davis, Edmund Jackson". Texas State Historical Association. Retrieved 29 September 2010. Eicher, John H., and David J. Eicher, Civil War High Commands. Stanford: Stanford University Press, 2001. ISBN 0- 8047-3641-3. p. 720 Eicher, John H., and David J. Eicher, Civil War High Commands. Stanford: Stanford University Press, 2001. ISBN 0- 8047-3641-3. p. 720 Texas State Handbook Online. Olsen, Bruce A. (30 May 2010). "Texas National Guard". Texas State Historical Association. Retrieved 29 September 2010. Odie Arambula, Visiting the Past column, "Radical Republican Davis had support", Laredo Morning Times, 20 May 2012, p. 15A Brown, Lyle C., Langenegger, Joyce A., Garcia, Sonia R., et al. PRACTICING TEXAS POLITICS, Thirteenth Edition. Boston: Houghton Mifflin, 2006. (Page 67-68) African-American Pioneers of Texas: From the Old West to the New Frontiers (Teacher’s Manual) (PDF). Museum of Texas Tech University: Education Division. p. 25. Archived from the original (PDF) on 2007-02-05. Texas State Handbook Online. Moneyhon, Carl H. (30 May 2010). "Davis, Edmund Jackson". Texas State Historical Association. Retrieved 29 September 2010. Licenses and Attributions CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: Kris S. Seago. License: CC BY: Attribution	oercommons	2025-03-18T00:35:15.632440	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66249/overview", "title": "Texas Government 2.0, Introduction to Texas History and Politics", "author": null }
https://oercommons.org/courseware/lesson/66250/overview	Industries That Shaped Texas Politics Overview Industries That Shaped Texas Politics Learning Objective By the end of this section, you will be able to: - Summarize the various industries that helped shape Texas politics Introduction Industries that shaped Texas politics include oil, cotton, cattle, lumber, and high technology. Those industries have ebbed and flowed over time, which has been described as creative destruction. Today, Texas has a very diverse economy, with industries such as petroleum and natural gas, farming, steel, banking, health care, telecommunications, and tourism. King Cotton From the end of the Civil War through the turn of the century, cotton production increased dramatically as a result of several key developments. These included massive immigration from the deep South and Europe, removal of natives from prime cotton-growing areas, the invention of a new plow that more easily broke the thick black sod of the plains, the invention of barbed wire, the extension of railroads, the invention of cotton ginning, and perfection of cotton compressing at the side of railroads for easier shipping. Almost no cotton was grown in the United States in 1787, the year the federal constitution was written. However, following the War of 1812, a huge increase in production resulted in the so-called cotton boom, and by midcentury, cotton became the key cash crop (a crop grown to sell rather than for the farmer’s sole use) of the southern economy and the most important American commodity. The rapid expansion of the cotton industry in the Deep South after the invention of the cotton gin greatly increased demand for slave labor to pick cotton when it all ripened at once, and the Southern states continued as slave societies. By 1850, of the 3.2 million slaves in the country’s fifteen slave states, 1.8 million were producing cotton; by 1860, slave labor was producing over two billion pounds of cotton per year. Indeed, American cotton soon made up two-thirds of the global supply, and production continued to soar. By the time of the Civil War, South Carolina politician James Hammond confidently proclaimed that the North could never threaten the South because “cotton is king.” "King Cotton" became a central feature of the Texas economy, attracting considerable investment capital, labor power, and technological development. Other industries within the broader agricultural sector also grew considerably in late nineteenth-century Texas, including ranching, timber, and corn. Still, cotton was king until the 1920s when it began a decades-long decline in importance caused by the drop in demand during the Great Depression, the loss of labor power during World War II, the rise of other centers of cotton production abroad, and federal eﬀorts to hold down production to maintain prices. Railroads As the railroads extended their reach in the late nineteenth century across the state to the panhandle and the high plains of West Texas, their influence grew. At first, the combination of more extensive railroad service and the relocation of cotton compresses from the seaports to rail sidings helped cotton farmers break the power of the port facility operators. But, hostility and political competition between farmers and ranchers on the one hand and the railroads on the other quickly grew. Because railroads tend to be natural monopolies, they tended to exercise enormous market power over their customers--the farmers and ranchers. The railroads' power to set rates was perceived as injurious to farmers and ranchers. The struggle between railroads and their customers led to the victory of James Stephen Hogg in the gubernatorial election of 1890. Hogg ran chiefly on a populist platform whose main plank was the promise to regulate the railroads. In that same election, a proposed amendment to the Texas constitution was ratified that permitted the creation of a railroad regulating body that among other things would regulate freight rates. Hogg made the first appointments to the new Texas Railroad Commission in 1891. Three years later in 1894, the legislature made those positions elective. The creation of the Railroad Commission represented the most significant and direct political clash between competing economic interests since the Civil War pitted slaveholding cotton growers against northern industrialists. Governor Hogg pushed through a series of laws, known as "Hogg's Laws," aimed at reining in the railroads, out-of-state corporations, and insurance companies. The Texas Oil Boom and Bust The Texas oil boom, sometimes called the gusher age, was a period of dramatic change and economic growth in the U.S. state of Texas during the early 20th century that began with the discovery of a large petroleum reserve near Beaumont, Texas. The find was unprecedented in its size and ushered in an age of rapid regional development and industrialization that has few parallels in U.S. history. Texas quickly became one of the leading oil- producing states in the U.S., along with Oklahoma and California; soon the nation overtook the Russian Empire as the top producer of petroleum. By 1940 Texas had come to dominate U.S. production. Some historians even define the beginning of the world’s Oil Age as the beginning of this era in Texas. The major petroleum strikes that began the rapid growth in petroleum exploration and speculation occurred in Southeast Texas, but soon reserves were found across Texas and wells were constructed in North Texas, East Texas, and the Permian Basin in West Texas. Although limited reserves of oil had been struck during the 19th century, the strike at Spindletop near Beaumont in 1901 gained national attention, spurring exploration and development that continued through the 1920s and beyond. Spindletop and the Joiner strike in East Texas, at the outset of the Great Depression, were the key strikes that launched this era of change in the state. This period had a transformative effect on Texas. At the turn of the century, the state was predominantly rural with no large cities. By the end of World War II, the state was heavily industrialized, and the populations of Texas cities had broken into the top 20 nationally. The city of Houston was among the greatest beneficiaries of the boom, and the Houston area became home to the largest concentration of refineries and petrochemical plants in the world. The city grew from a small commercial center in 1900 to one of the largest cities in the United States during the decades following the era. This period, however, changed all of Texas’ commercial centers (and developed the Beaumont/Port Arthur area, where the boom began). H. Roy Cullen, H. L. Hunt, Sid W. Richardson, and Clint Murchison were the four most influential businessmen during this era. These men became among the wealthiest and most politically powerful in the state and the nation. Transportation The creation of the Interstate Highway System, which was initiated under 1956 legislation creating the National System of Interstate and Defense Highways, was ostensibly for the rapid movement of troops and material for the defense of the national territory. The interstate highway system gave a considerable boost to the development of corporate chains. The prominence of numerous corporate chain companies among the state's top employers in recent years confirms the symbiotic relationship of the dining and entertainment sector to the national highway system. The size of these corporate chains also reflects the explosion of suburbs and exurbs across the state, which was in turn facilitated by extensive highways. The development of this emerging socio-economic complex--whose key components included petroleum, automobiles, highways, suburbanization, and chain retail and restaurants--was reinforced by forces already operating within the state. The Texas Good Roads and Transportation Association had already been established in 1932 to promote public expenditure on the building and maintenance of roads in Texas. As early as 1946--well before President Eisenhower's push for a national highway system--the Good Roads Association was instrumental in pushing through the 1946 "Good Roads Amendment" to the Texas Constitution. This amendment required that three-quarters of all revenue from state gasoline taxes be "used for the sole purpose of acquiring rights of way, constructing, maintaining, and policing... public roadways" and for the administration of traﬃc safety laws. Technology Although Texas-based companies are not so dominant in other economic sectors, they do represent some of the leading businesses in their industries. The high-technology sector includes such recognizable names as personal computer manufacturer Dell Computer Corporation (based in Round Rock, Texas), telecommunications giant AT&T (bought in 2005 by Southwestern Bell Communications headquartered in San Antonio), and chipmaker Texas Instruments (Dallas). All three companies are among the top 100 employers in Texas. Silicon Hills is the nickname for the cluster of high-tech companies in the Austin metropolitan area. The name is analogous to Silicon Valley, but refers to the hilly terrain on the west side of Austin. High tech industries in the area include enterprise software, semiconductors, corporate R&D, biotechnology, the video game industry, and a variety of startup companies. Technology companies with offices in the area include Advanced Micro Devices,Amazon.com ARM Holdings, AppleInc., Cisco, eBay, ESO, Facebook, Google, IBM, Indeed, Intel, PayPal, Procore, Silicon Labs, Texas Instruments, Oracle Corporation, VMWare, and many others. Dell's worldwide headquarters are located in Round Rock, a suburb of Austin. References and Further Reading African Americans slaves using the First cotton-gin, 1790- 1800, by William L. Sheppard. Illustration in Harper's Weekly, 1869 Dec. 18, p. 813. The Library of Congress, Card 91784966, Call Number: Illus. in AP2.H32 Case Y [P&P], Reproduction number: LC-USZ62-103801 (b&w film copy neg.), Medium: 1 print: wood engraving. CREATED/PUBLISHED: 1869 Dec. 18. Olson, James Stuart (2001). Encyclopedia of the industrial revolution in America. Westport, CT: Greenwood Press. ISBN 978-0-313-30830-7. p.238. Population of the 100 Largest Urban Places: 1900". U.S. Census Bureau. Retrieved November 3, 2009. "Chapter Two: Galveston Bay" (PDF). Texas A&M University- Galveston: Galveston Bay Information Center (Galveston Bay Estuary Project). Archived from the original (PDF) on July 20, 2011. Retrieved September 8, 2009. "It [Galveston Bay] is at the center of the state's petrochemical industry, with 30 percent of U.S. petroleum industry and nearly 50 percent of U.S. production of ethylene and propylene Occuring [sic] on its shores. Weisman (2008), p. 166, "The industrial megaplex that begins on the east side of Houston and continues uninterrupted to the Gulf of Mexico, 50 miles away, is the largest concentration of petroleum refineries, petrochemical companies, and storage structures on Earth." Licenses And Attributions CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: Kris S. Seago. License: CC BY: Attribution Industries That Shaped American Politics: Revision and Adaptation. Authored by: John Osterman. License: CC BY: Attribution	oercommons	2025-03-18T00:35:15.658785	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66250/overview", "title": "Texas Government 2.0, Introduction to Texas History and Politics", "author": null }
https://oercommons.org/courseware/lesson/66251/overview	Texas’ Demographics Overview Texas’ Demographics Learning Objective By the end of this section, you will be able to: - Discuss how the demographic changes Texas is undergoing influences its government, public policy, and the challenges it faces today Introduction Texas is the second most populous U.S. state, second only to California. In recent decades, it has experienced strong population growth. Texas has many major cities and metropolitan areas, along with many towns and rural areas. Much of the population is in the major cities of Houston, San Antonio, Dallas, Fort Worth, Austin, and El Paso. Three Texas cities (Houston, Dallas, and San Antonio) are among the nation's top 10 in population, and Austin is just outside the top 10 at number 11. Population The United States Census Bureau estimates the population of Texas was 28,995,881 on July 1, 2019, a 15.31 percent increase since the 2010 United States Census. The 2010 US Census recorded Texas as having a population of 25.1 million—an increase of 4.3 million since the year 2000, involving an increase in population in all three subcategories of population growth: natural increase (births minus deaths), net immigration, and net migration. The state passed New York in the 1990s to become the second-largest U.S. state in population, after California. Texas’ population growth between 2000 and 2010 represents the highest population increase, by number of people, for any U.S. state during this time period. The state has a bigger population than that of Australia. As of 2015, Texas had 4.7 million foreign-born residents, about 17% of the population and 21.6% of the state workforce. The major countries of origin for Texan immigrants were Mexico (55.1% of immigrants), India (5%), El Salvador (4.3%), Vietnam (3.7%), and China (2.3%). Of immigrant residents, some 35.8 percent were naturalized U.S. citizens. In 2014, there were an estimated 1.7 million undocumented immigrants in Texas, making up 35% of the total Texas immigrant population and 6.1% of the total state population.[209] In addition to the state's foreign-born population, an additional 4.1 million Texans (15% of the stats's population) were born in the United States and had at least one immigrant parent. U.S. Census data from 2010 indicate that 7.7% of Texas’ population is under 5 years old, 27.3% is under 18, and 10.3% is aged 65 and older. Females make up 50.4% of the population. Texas expects to record another decade of population growth in the 2020 Census. You Might Be Wondering... \| Texas is growing at a rate of 1,000 people per day, and for the second year in a row, most of the people who moved to the state came from other countries in 2018. And the biggest growth in international migration isn't from Latin America. Find out more from Texplainer at the Texas Tribune. \| Ethnicity As of the 2010 US Census, the racial distribution in Texas was as follows: 70.4% of the population of Texas was White American; 11.8% African American; 3.8%, Asian American; 0.7%, American Indian; 0.1%, native Hawaiian or Pacific islander only; 10.5% of the population were of some other race only; and 2.7% were of two or more races. Hispanics (of any race) were 37.6% of the population of the state, while Non-Hispanic Whites composed 45.3%. English Americans predominate in eastern, central, and northern Texas; German Americans, in central and western Texas. African Americans, who historically made up one-third of the state population, are concentrated in parts of northern, eastern and east central Texas as well as in the Dallas-Fort Worth, San Antonio and Houston metropolitan areas. As in other Southern states settled largely in the 19th century, the vast majority have European ancestry: Irish, English and German. Texas includes a diverse set of European ancestries, due both to historical patterns of settlement as well as contemporary dynamics. Frontier Texas saw settlements of Germans, particularly in Fredericksburg and New Braunfels. Many Romanians, Dutch, Germans from Switzerland and Austria, Poles, Russians, Swedes, Norwegians, Czechs, Slovaks, Italians, and French immigrated at least in part because of the European revolutions of 1848. This immigration continued until World War I and the 1920s. The influence of these diverse European immigrants survives in the town names, architectural styles, music, and cuisine in Texas. Hispanic Texans As of 2010, 37% of Texas residents had Hispanic ancestry; these include recent immigrants from Mexico, Central America, and South America, as well as Tejanos, whose ancestors have lived in Texas as early as the 1700s. Tejanos are the largest ancestry group in southern Duval County and amongst the largest in and around Bexar County, including San Antonio, where over one million Hispanics live. The state has the second largest Hispanic population in the United States, behind California. Hispanics dominate southern, south-central, and western Texas and form a significant portion of the residents in the cities of Dallas, Houston, and Austin. The Hispanic population contributes to Texas having a younger population than the American average, because Hispanic births have outnumbered non-Hispanic white births since the early 1990s. In 2007, for the first time since the early nineteenth century, Hispanics accounted for more than half of all births (50.2%), while non-Hispanic whites accounted for just 34%. In 2016 the state had 59,115 persons of Cuban origin. 6,157 of them lived in Travis County. African-American Texans Texas has one of the largest African-American populations in the country. African Americans are concentrated in northern, eastern and east-central Texas as well as the Dallas, Houston, and San Antonio metropolitan areas. African Americans form 24% of both the cities of Dallas and Houston, 19% of Fort Worth, 8.1% of Austin, and 6.9% of San Antonio. They form a majority in sections of eastern San Antonio, southern Dallas, eastern Fort Worth, and southern Houston. A strong labor market between 1995 and 2000 contributed to Texas being one of three states in the South receiving the highest numbers of black college graduates in a New Great Migration. Asian-American Texans In recent years, the Asian American population in Texas has grown, especially in west Houston, Fort Bend County southwest of Houston, the western and northern suburbs of Dallas, and Arlington near Fort Worth. Vietnamese Americans, South Asian Americans, Chinese Americans, Filipino Americans, Korean Americans, and Japanese Americans make up the largest Asian American groups in Texas. The Gulf Coast also has large numbers of Asian Americans, because the shrimp fishing industry attracted tens of thousands of Vietnamese, Filipinos, and Chinese from the coast of the South China Sea in the late 1970s and 1980s References and Resources Texas Population 2017 Archived 2017-01-21 at the Wayback Machine. World Population Review "United State Census Bureau". 2008-2012 American Community Survey 5-Year Estimates. Archived from the original on 2014-08-15. Retrieved Feb 28, 2014. "Pew Research Center". Archived from the original on 2014- 02-21. Retrieved Feb 28, 2014. Bagden, Samantha. "Cubans in Texas see some hope in new relations" (Archive) Austin American-Statesman. Monday, January 18, 2016. Retrieved on January 19, 2016. William H. Frey, "The New Great Migration: Black Americans' Return to the South, 1965-2000", May 2004, The Brookings Institution, p.1 Archived April 28, 2008, at the Wayback Machine. Licenses And Attributions CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: Kris S. Seago. License: CC BY: Attribution Texas Demographics: Revision and Adaptation. Authored by: John Osterman. License: CC BY: Attribution	oercommons	2025-03-18T00:35:15.684122	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66251/overview", "title": "Texas Government 2.0, Introduction to Texas History and Politics", "author": null }
https://oercommons.org/courseware/lesson/66252/overview	State Political Culture Overview State Political Culture Learning Objective By the end of this section, you will be able to: - Discuss how the political culture of Texas influences its government, public policy, and the challenges it faces today Introduction: Daniel Elazar's Cultural Classification Some states, such as Alaska, are endowed with natural resources. They can use their oil or natural gas reserves to their advantage to fund education or reduce taxes. Other states, like Florida, are favored with a climate that attracts tourists and retirees each winter, drawing in revenues to support infrastructure improvements throughout the state. These differences can lead to strategic advantages in the economic fortunes of a state, which can translate into differences in the levels of taxes that must be collected from citizens. But their economic fortunes are only one component of what makes individual states unique. Theorists have long proposed that states are also unique as a function of their differing political cultures, or their attitudes and beliefs about the functions and expectations of the government. In the book, American Federalism: A View from the States, Daniel Elazar first theorized in 1966 that the United States could be divided into three distinct political cultures: moralistic, individualistic, and traditionalistic. The diffusion of these cultures throughout the United States is attributed to the migratory patterns of immigrants who settled in and spread out across the country from the east to the west coast. These settlers had distinct political and religious values that influenced their beliefs about the proper role of government, the need for citizen involvement in the democratic process, and the role of political parties. Moralistic Political Culture In Elazar’s framework, states with a moralistic political culture see the government as a means to better society and promote the general welfare. They expect political officials to be honest in their dealings with others, put the interests of the people they serve above their own, and commit to improving the area they represent. The political process is seen in a positive light and not as a vehicle tainted by corruption. In fact, citizens in moralistic cultures have little patience for corruption and believe that politicians should be motivated by a desire to benefit the community rather than by a need to profit financially from service. Moralistic states thus tend to support an expanded role for government. They are more likely to believe government should promote the general welfare by allocating funds to programs that will benefit the poor. In addition, they see it as the duty of public officials to advocate for new programs that will benefit marginal citizens or solve public policy problems, even when public pressure to do so is nonexistent. The moralistic political culture developed among the Puritans in upper New England. After several generations, these settlers moved westward, and their values diffused across the top of the United States to the upper Great Lakes. In the middle of the 1800s, Scandinavians and Northern Europeans joined this group of settlers and reinforced the Puritans’ values. Together, these groups pushed further west through the northern portion of the Midwest and West and then along the West Coast. States that identify with this culture value citizen engagement and desire citizen participation in all forms of political affairs. In Elazar’s model, citizens from moralistic states should be more likely to donate their time and/or resources to political campaigns and to vote. This occurs for two main reasons. First, state law is likely to make it easier for residents to register and to vote because mass participation is valued. Second, citizens who hail from moralistic states should be more likely to vote because elections are truly contested. In other words, candidates will be less likely to run unopposed and more likely to face genuine competition from a qualified opponent. According to Elazar, the heightened competition is a function of individuals’ believing that public service is a worthwhile endeavor and an honorable profession. Individualistic Political Culture States that align with Elazar’s individualistic political culture see the government as a mechanism for addressing issues that matter to individual citizens and for pursuing individual goals. People in this culture interact with the government in the same manner they would interact with a marketplace. They expect the government to provide goods and services they see as essential, and the public officials and bureaucrats who provide them expect to be compensated for their efforts. The focus is on meeting individual needs and private goals rather than on serving the best interests of everyone in the community. New policies will be enacted if politicians can use them to garner support from voters or other interested stakeholders, or if there is great demand for these services on the part of individuals. According to Elazar, the individualist political culture originated with settlers from non-Puritan England and Germany. The first settlements were in the mid-Atlantic region of New York, Pennsylvania, and New Jersey and diffused into the middle portion of the United States in a fairly straight line from Ohio to Wyoming. Given their focus on pursuing individual objectives, states with an individualistic mindset will tend to advance tax breaks as a way of trying to boost a state’s economy or as a mechanism for promoting individual initiative and entrepreneurship. For instance, New Jersey governor Chris Christie made headlines in 2015 when discussing the incentives he used to attract businesses to the state. Christie encouraged a number of businesses to move to Camden, where unemployment has risen to almost 14 percent, by providing them with hundreds of millions of dollars in tax breaks. The governor hopes these corporate incentives will spur job creation for citizens who need employment in an economically depressed area of the state. Since this theoretical lens assumes that the objective of politics and the government is to advance individual interests, Elazar argues that individuals are motivated to become engaged in politics only if they have a personal interest in this area or wish to be in charge of the provision of government benefits. They will tend to remain involved if they get enjoyment from their participation or rewards in the form of patronage appointments or financial compensation. As a result of these personal motivations, citizens in individualistic states will tend to be more tolerant of corruption among their political leaders and less likely to see politics as a noble profession in which all citizens should engage. Finally, Elazar argues that in individualistic states, electoral competition does not seek to identify the candidate with the best ideas. Instead it pits against each other political parties that are well organized and compete directly for votes. Voters are loyal to the candidates who hold the same party affiliation they do. As a result, unlike the case in moralistic cultures, voters do not pay much attention to the personalities of the candidates when deciding how to vote and are less tolerant of third-party candidates. Traditionalistic Political Culture Given the prominence of slavery in its formation, a traditionalistic political culture, in Elazar’s argument, sees the government as necessary to maintaining the existing social order, the status quo. Only elites belong in the political enterprise, and as a result, new public policies will be advanced only if they reinforce the beliefs and interests of those in power. Elazar associates traditionalistic political culture with the southern portion of the United States, where it developed in the upper regions of Virginia and Kentucky before spreading to the Deep South and the Southwest. Like the individualistic culture, the traditionalistic culture believes in the importance of the individual. But instead of profiting from corporate ventures, settlers in traditionalistic states tied their economic fortunes to the necessity of slavery on plantations throughout the South. When elected officials do not prioritize public policies that benefit them, those on the social and economic fringes of society can be plagued by poverty and pervasive health problems. For example, although the map below shows that poverty is a problem across the entire United States, the South has the highest incidence. According to the Centers for Disease Control and Prevention, the South also leads the nation in self-reported obesity, closely followed by the Midwest. These statistics present challenges for lawmakers not only in the short term but also in the long term because they must prioritize fiscal constraints in the face of a growing demand for services. While moralistic cultures expect and encourage political participation by all citizens, traditionalistic cultures are more likely to see it as a privilege reserved for only those who meet the qualifications. As a result, voter participation will generally be lower in a traditionalistic culture, and there will be more barriers to participation (e.g., a requirement to produce a photo ID at the voting booth). Conservatives argue that these laws reduce or eliminate fraud on the part of voters, while liberals believe they disproportionally disenfranchise the poor and minorities and constitute a modern-day poll tax. Finally, under a traditionalistic political culture, Elazar argues that party competition will tend to occur between factions within a dominant party. Historically, the Democratic Party dominated the political structure in the South before realignment during the civil rights era. Today, depending on the office being sought, the parties are more likely to compete for voters. Texas Political Culture and Elazar’s Theory Elazar’s Theory claims that Texas is a mixture of traditional and individualistic political cultures. As a result, the voter turnout in Texas is lower than most other American states, with the argument that Texans view political participation as an economic perk versus the value of contributing to society. Critiques of Elazar’s Theory Several critiques have come to light since Elazar first introduced his theory of state political culture fifty years ago. The original theory rested on the assumption that new cultures could arise with the influx of settlers from different parts of the world; however, since immigration patterns have changed over time, it could be argued that the three cultures no longer match the country’s current reality. Today’s immigrants are less likely to come from European countries and are more likely to originate in Latin American and Asian countries. In addition, advances in technology and transportation have made it easier for citizens to travel across state lines and to relocate. Therefore, the pattern of diffusion on which the original theory rests may no longer be accurate, because people are moving around in more, and often unpredictable, directions. It is also true that people migrate for more reasons than simple economics. They may be motivated by social issues such as widespread unemployment, urban decay, or low-quality health care of schools. Such trends may aggravate existing differences, for example the difference between urban and rural lifestyles (e.g., the city of Atlanta vs. other parts of Georgia), which are not accounted for in Elazar’s classification. Finally, unlike economic or demographic characteristics that lend themselves to more precise measurement, culture is a comprehensive concept that can be difficult to quantify. This can limit its explanatory power in political science research. References and Further Reading Daniel Elazar. 1972. American Federalism: A View from the States, 2nd ed. New York: Thomas Y. Crowell Company. Dean DeChiaro, “$830M in Tax Breaks Later, Christie Says His Camden Plan Won’t Work for America,” U.S. News and World Report, 19 August 2015. “Division of Nutrition, Physical Activity, and Obesity: Data, Trends and Maps” (March 14, 2016). Jie Zong and Jeanne Batalova. 26 February 2015. “Frequently Requested Statistics on Immigrants and Immigration in the United States.” Licenses and Attributions CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: Daniel M. Regalado. License: CC BY: Attribution CC LICENSED CONTENT, SHARED PREVIOUSLY American Government. Authored by: OpenStax. Provided by: OpenStax; Rive University. License: License: CC BY: Attribution	oercommons	2025-03-18T00:35:15.712561	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66252/overview", "title": "Texas Government 2.0, Introduction to Texas History and Politics", "author": null }
https://oercommons.org/courseware/lesson/66253/overview	Glossary Overview Glossary Glossary: Introduction to Texas History and Politics alcalde: a Mexican oﬃcial who often served as combined civil administrator, judge, and law enforcement oﬃcer cash crop: a crop grown to sell rather than for the farmer's sole use. cotton boom: the huge increase in cotton production that occurred in the U.S. following the War of 1812. empresario: a person who brought new settlers to Texas in exchange for a grant of land individualistic political culture: the belief that government should limit its role to providing order in society so that citizens can pursue their economic self-interests. mestizo: people of mixed Indian and European ancestry moralistic political culture: the belief that government should be active in promoting the public good and that citizens should participate in politics and civic activities to ensure that good. Tejanos: Mexican residents of Texas traditionalistic political culture: the belief that government should be dominated by political elites and guided by tradition Licenses and Attributions CC LICENSED CONTENT, ORIGINAL Introduction to Texas History and Politics: Glossary. Authored by: John Osterman. License: CC BY: Attribution	oercommons	2025-03-18T00:35:15.730237	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66253/overview", "title": "Texas Government 2.0, Introduction to Texas History and Politics", "author": null }
https://oercommons.org/courseware/lesson/66254/overview	Assessment Overview This is a quiz for Chapter One. Texas Government Chapter One Quiz Check your knowledge of Chapter One by taking the quiz linked below. The quiz will open in a new browser window or tab. This is a quiz for Chapter One. Check your knowledge of Chapter One by taking the quiz linked below. The quiz will open in a new browser window or tab.	oercommons	2025-03-18T00:35:15.748675	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66254/overview", "title": "Texas Government 2.0, Introduction to Texas History and Politics", "author": null }
https://oercommons.org/courseware/lesson/89521/overview	Time Management for College Students Overview Time management is arguably the most important skill one can master to maximize daily happiness & success. Introduction to Time Management Introduction to Time Management Time…something it seems we never have enough of at certain seasons in our lives, yet we seem to have too much time in other seasons. The question is, how do we manage it? In Ecclesiastes chapter 3 verses 1-8, Solomon wrote, “There is a time for everything, and a season for every activity under the heavens: a time to be born and a time to die, a time to plant and a time to uproot, a time to kill and a time to heal, a time to tear down and a time to build, a time to weep and a time to laugh, a time to mourn and a time to dance, a time to scatter stones and a time to gather them, a time to embrace and a time to refrain from embracing, a time to search and a time to give up, a time to keep and a time to throw away, a time to tear and a time to mend, a time to be silent and a time to speak, a time to love and a time to hate, a time for war and a time for peace.” (NIV) I would add an additional verse that goes something like this: “a time for writing papers, reading textbooks, and doing research.” The following are ten effective and helpful strategies to assist anyone, especially college students, in managing the one resource that we never seem to have enough of, yet we cannot buy it anywhere. When God created us, we were given an absolute number of hours, minutes, and seconds on this earth. The catch is we have to manage them wisely and make the most out of every minute we have here on earth. Put Into Practice Instructions: Read the ten strategies below and develop a plan to implement them into your daily routine. For each strategy, describe the benefits and challenges of each. 1. Know How to Spend Your Time 2. Set Priorities 3. Use a Planning Tool 4. Get Organized 5. Schedule Appropriately 6. Delegate - Get Help from Others 7. Stop Procrastinating 8. Manage Time-Wasters 9. Avoid Multi-Tasking 10. Stay Healthy	oercommons	2025-03-18T00:35:15.765391	01/24/2022	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/89521/overview", "title": "Time Management for College Students", "author": "Houston Logsdon" }
https://oercommons.org/courseware/lesson/103899/overview	Growth Media_CC Introduction to Microbiology_CC Microbial Cell Wall Structure_CC Microbial Classification and Cellular Morpholog_CC Microbial Transport_CC Microbiology History_CC Other Microbial Structures_CC Staining_CC PowerPoint Slides for use in a Majors Microbiology Course Overview Powerpoint Slides for use with a Majors Microbiology course developed from the OpenStax Microbiology Textbook. Currently in development and will be updated as progress is made. Most slide decks are built using Assertion-Evidence principles. Microbiology Powerpoint Slides for use with a Majors Microbiology course developed from the OpenStax Microbiology Textbook. Currently in development and will be updated as progress is made. Most slide decks are built using Assertion-Evidence principles.	oercommons	2025-03-18T00:35:15.787840	05/15/2023	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/103899/overview", "title": "PowerPoint Slides for use in a Majors Microbiology Course", "author": "Candice Damiani" }
https://oercommons.org/courseware/lesson/107962/overview	Learning Domain: Social Studies Skills Standard: Create and use research questions to guide inquiry on an issue or event Learning Domain: Civics Standard: Describe ways in which people benefit from and are challenged by working together, including through government, workplaces, voluntary organizations, and families WA.SEL.6-8.4A Washington Social Emotional Learning Standards Grades 6-8 Learning Domain: 4: Social Awareness Standard: Demonstrates awareness of other people’s emotions, perspectives, cultures, languages, histories, identities, and abilities WA.SEL.6-8.6C Washington Social Emotional Learning Standards Grades 6-8 Learning Domain: 6: Social Engagement Standard: Contributes productively to one’s school, workplace, and community. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Introduce claim(s) about a topic or issue, acknowledge and distinguish the claim(s) from alternate or opposing claims, and organize the reasons and evidence logically. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Support claim(s) with logical reasoning and relevant, accurate data and evidence that demonstrate an understanding of the topic or text, using credible sources. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Use words, phrases, and clauses to create cohesion and clarify the relationships among claim(s), counterclaims, reasons, and evidence. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Write informative/explanatory texts, including the narration of historical events, scientific procedures/ experiments, or technical processes. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Introduce a topic clearly, previewing what is to follow; organize ideas, concepts, and information into broader categories as appropriate to achieving purpose; include formatting (e.g., headings), graphics (e.g., charts, tables), and multimedia when useful to aiding comprehension. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Develop the topic with relevant, well-chosen facts, definitions, concrete details, quotations, or other information and examples. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Use appropriate and varied transitions to create cohesion and clarify the relationships among ideas and concepts. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Gather relevant information from multiple print and digital sources, using search terms effectively; assess the credibility and accuracy of each source; and quote or paraphrase the data and conclusions of others while avoiding plagiarism and following a standard format for citation. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Draw evidence from informational texts to support analysis reflection, and research. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Write arguments focused on discipline-specific content. Learning Domain: Reading for Literature Standard: Determine a theme or central idea of a text and how it is conveyed through particular details; provide a summary of the text distinct from personal opinions or judgments. Learning Domain: Reading for Literature Standard: Describe how a particular story’s or drama’s plot unfolds in a series of episodes as well as how the characters respond or change as the plot moves toward a resolution. Learning Domain: Reading for Literature Standard: Determine the meaning of words and phrases as they are used in a text, including figurative and connotative meanings; analyze the impact of a specific word choice on meaning and tone. Learning Domain: Reading for Literature Standard: Explain how an author develops the point of view of the narrator or speaker in a text. Learning Domain: Reading for Literature Standard: Compare and contrast the experience of reading a story, drama, or poem to listening to or viewing an audio, video, or live version of the text, including contrasting what they “see” and “hear” when reading the text to what they perceive when they listen or watch. Learning Domain: Reading for Literature Standard: Cite textual evidence to support analysis of what the text says explicitly as well as inferences drawn from the text. Learning Domain: Reading for Informational Text Standard: Determine a central idea of a text and how it is conveyed through particular details; provide a summary of the text distinct from personal opinions or judgments. Learning Domain: Reading for Informational Text Standard: Analyze in detail how a key individual, event, or idea is introduced, illustrated, and elaborated in a text (e.g., through examples or anecdotes). Learning Domain: Reading for Informational Text Standard: Determine the meaning of words and phrases as they are used in a text, including figurative, connotative, and technical meanings. Learning Domain: Reading for Informational Text Standard: Integrate information presented in different media or formats (e.g., visually, quantitatively) as well as in words to develop a coherent understanding of a topic or issue. Learning Domain: Reading for Informational Text Standard: Cite textual evidence to support analysis of what the text says explicitly as well as inferences drawn from the text. Learning Domain: Speaking and Listening Standard: Present claims and findings, sequencing ideas logically and using pertinent descriptions, facts, and details to accentuate main ideas or themes; use appropriate eye contact, adequate volume, and clear pronunciation. Learning Domain: Speaking and Listening Standard: Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 6 topics, texts, and issues, building on others’ ideas and expressing their own clearly. Learning Domain: Speaking and Listening Standard: Present claims and findings, emphasizing salient points in a focused, coherent manner with pertinent descriptions, facts, details, and examples; use appropriate eye contact, adequate volume, and clear pronunciation. Learning Domain: Speaking and Listening Standard: Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 7 topics, texts, and issues, building on others’ ideas and expressing their own clearly. Learning Domain: Speaking and Listening Standard: Present claims and findings, emphasizing salient points in a focused, coherent manner with relevant evidence, sound valid reasoning, and well-chosen details; use appropriate eye contact, adequate volume, and clear pronunciation. Learning Domain: Speaking and Listening Standard: Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 8 topics, texts, and issues, building on others’ ideas and expressing their own clearly. Learning Domain: Writing Standard: Introduce claim(s), acknowledge alternate or opposing claims, and organize the reasons and evidence logically. Learning Domain: Writing Standard: Support claim(s) with logical reasoning and relevant evidence, using accurate, credible sources and demonstrating an understanding of the topic or text. Learning Domain: Writing Standard: Gather relevant information from multiple print and digital sources, using search terms effectively; assess the credibility and accuracy of each source; and quote or paraphrase the data and conclusions of others while avoiding plagiarism and following a standard format for citation. Learning Domain: Writing Standard: Draw evidence from literary or informational texts to support analysis, reflection, and research. Learning Domain: Writing Standard: Apply grade 7 Reading standards to literary nonfiction (e.g. “Trace and evaluate the argument and specific claims in a text, assessing whether the reasoning is sound and the evidence is relevant and sufficient to support the claims”). Learning Domain: Writing Standard: Write arguments to support claims with clear reasons and relevant evidence. Learning Domain: Writing Standard: Introduce claim(s), acknowledge and distinguish the claim(s) from alternate or opposing claims, and organize the reasons and evidence logically. Learning Domain: Writing Standard: Support claim(s) with logical reasoning and relevant evidence, using accurate, credible sources and demonstrating an understanding of the topic or text. Learning Domain: Writing Standard: Produce clear and coherent writing in which the development, organization, and style are appropriate to task, purpose, and audience. (Grade-specific expectations for writing types are defined in standards 1–3 above.) Learning Domain: Writing Standard: Write arguments to support claims with clear reasons and relevant evidence. Learning Domain: Reading for Literature Standard: Determine a theme or central idea of a text and analyze its development over the course of the text; provide an objective summary of the text. Learning Domain: Reading for Literature Standard: Analyze how particular elements of a story or drama interact (e.g., how setting shapes the characters or plot). Learning Domain: Reading for Literature Standard: Cite several pieces of textual evidence to support analysis of what the text says explicitly as well as inferences drawn from the text. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Introduce claim(s) about a topic or issue, acknowledge and distinguish the claim(s) from alternate or opposing claims, and organize the reasons and evidence logically. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Support claim(s) with logical reasoning and relevant, accurate data and evidence that demonstrate an understanding of the topic or text, using credible sources. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Use words, phrases, and clauses to create cohesion and clarify the relationships among claim(s), counterclaims, reasons, and evidence. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Write informative/explanatory texts, including the narration of historical events, scientific procedures/ experiments, or technical processes. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Introduce a topic clearly, previewing what is to follow; organize ideas, concepts, and information into broader categories as appropriate to achieving purpose; include formatting (e.g., headings), graphics (e.g., charts, tables), and multimedia when useful to aiding comprehension. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Develop the topic with relevant, well-chosen facts, definitions, concrete details, quotations, or other information and examples. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Use appropriate and varied transitions to create cohesion and clarify the relationships among ideas and concepts. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Gather relevant information from multiple print and digital sources, using search terms effectively; assess the credibility and accuracy of each source; and quote or paraphrase the data and conclusions of others while avoiding plagiarism and following a standard format for citation. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Draw evidence from informational texts to support analysis reflection, and research. Learning Domain: Writing for Literacy in History/Social Studies, Science, and Technical Subjects Standard: Write arguments focused on discipline-specific content. Learning Domain: Reading Literature Standard: Determine a theme or central idea of a text and how it is conveyed through particular details; provide a summary of the text distinct from personal opinions or judgments. Learning Domain: Reading Literature Standard: Describe how a particular story's or drama's plot unfolds in a series of episodes as well as how the characters respond or change as the plot moves toward a resolution. Learning Domain: Reading Literature Standard: Determine the meaning of words and phrases as they are used in a text, including figurative and connotative meanings; analyze the impact of a specific word choice on meaning and tone. Learning Domain: Reading Literature Standard: Explain how an author develops the point of view of the narrator or speaker in a text. Learning Domain: Reading Literature Standard: Compare and contrast the experience of reading a story, drama, or poem to listening to or viewing an audio, video, or live version of the text, including contrasting what they ��see� and ��hear� when reading the text to what they perceive when they listen or watch. Learning Domain: Reading Literature Standard: Cite textual evidence to support analysis of what the text says explicitly as well as inferences drawn from the text. Learning Domain: Reading for Informational Text Standard: Determine a central idea of a text and how it is conveyed through particular details; provide a summary of the text distinct from personal opinions or judgments. Learning Domain: Reading for Informational Text Standard: Analyze in detail how a key individual, event, or idea is introduced, illustrated, and elaborated in a text (e.g., through examples or anecdotes). Learning Domain: Reading for Informational Text Standard: Determine the meaning of words and phrases as they are used in a text, including figurative, connotative, and technical meanings. Learning Domain: Reading for Informational Text Standard: Integrate information presented in different media or formats (e.g., visually, quantitatively) as well as in words to develop a coherent understanding of a topic or issue. Learning Domain: Reading for Informational Text Standard: Cite textual evidence to support analysis of what the text says explicitly as well as inferences drawn from the text. Learning Domain: Speaking and Listening Standard: Present claims and findings, sequencing ideas logically and using pertinent descriptions, facts, and details to accentuate main ideas or themes; use appropriate eye contact, adequate volume, and clear pronunciation. Learning Domain: Speaking and Listening Standard: Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 6 topics, texts, and issues, building on others�۪ ideas and expressing their own clearly. Learning Domain: Speaking and Listening Standard: Present claims and findings, emphasizing salient points in a focused, coherent manner with pertinent descriptions, facts, details, and examples; use appropriate eye contact, adequate volume, and clear pronunciation. Learning Domain: Speaking and Listening Standard: Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 7 topics, texts, and issues, building on others�۪ ideas and expressing their own clearly. Learning Domain: Speaking and Listening Standard: Present claims and findings, emphasizing salient points in a focused, coherent manner with relevant evidence, sound valid reasoning, and well-chosen details; use appropriate eye contact, adequate volume, and clear pronunciation. Learning Domain: Speaking and Listening Standard: Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 8 topics, texts, and issues, building on others�۪ ideas and expressing their own clearly. Learning Domain: Writing Standard: Introduce claim(s), acknowledge alternate or opposing claims, and organize the reasons and evidence logically. Learning Domain: Writing Standard: Support claim(s) with logical reasoning and relevant evidence, using accurate, credible sources and demonstrating an understanding of the topic or text. Learning Domain: Writing Standard: Gather relevant information from multiple print and digital sources, using search terms effectively; assess the credibility and accuracy of each source; and quote or paraphrase the data and conclusions of others while avoiding plagiarism and following a standard format for citation. Learning Domain: Writing Standard: Draw evidence from literary or informational texts to support analysis, reflection, and research. Learning Domain: Writing Standard: Apply grade 7 Reading standards to literary nonfiction (e.g. "Trace and evaluate the argument and specific claims in a text, assessing whether the reasoning is sound and the evidence is relevant and sufficient to support the claims"). Learning Domain: Writing Standard: Write arguments to support claims with clear reasons and relevant evidence. Learning Domain: Writing Standard: Introduce claim(s), acknowledge and distinguish the claim(s) from alternate or opposing claims, and organize the reasons and evidence logically. Learning Domain: Writing Standard: Support claim(s) with logical reasoning and relevant evidence, using accurate, credible sources and demonstrating an understanding of the topic or text. Learning Domain: Writing Standard: Produce clear and coherent writing in which the development, organization, and style are appropriate to task, purpose, and audience. (Grade-specific expectations for writing types are defined in standards 1��3 above.) Learning Domain: Writing Standard: Write arguments to support claims with clear reasons and relevant evidence. Learning Domain: Reading Literature Standard: Determine a theme or central idea of a text and analyze its development over the course of the text; provide an objective summary of the text. Learning Domain: Reading Literature Standard: Analyze how particular elements of a story or drama interact (e.g., how setting shapes the characters or plot). Learning Domain: Reading Literature Standard: Cite several pieces of textual evidence to support analysis of what the text says explicitly as well as inferences drawn from the text. Cluster: Text Types and Purposes. Standard: Introduce claim(s) about a topic or issue, acknowledge and distinguish the claim(s) from alternate or opposing claims, and organize the reasons and evidence logically. Cluster: Text Types and Purposes. Standard: Support claim(s) with logical reasoning and relevant, accurate data and evidence that demonstrate an understanding of the topic or text, using credible sources. Cluster: Text Types and Purposes. Standard: Use words, phrases, and clauses to create cohesion and clarify the relationships among claim(s), counterclaims, reasons, and evidence. Cluster: Text Types and Purposes. Standard: Write informative/explanatory texts, including the narration of historical events, scientific procedures/ experiments, or technical processes. Cluster: Text Types and Purposes. Standard: Introduce a topic clearly, previewing what is to follow; organize ideas, concepts, and information into broader categories as appropriate to achieving purpose; include formatting (e.g., headings), graphics (e.g., charts, tables), and multimedia when useful to aiding comprehension. Cluster: Text Types and Purposes. Standard: Develop the topic with relevant, well-chosen facts, definitions, concrete details, quotations, or other information and examples. Cluster: Text Types and Purposes. Standard: Use appropriate and varied transitions to create cohesion and clarify the relationships among ideas and concepts. Cluster: Research to Build and Present Knowledge. Standard: Gather relevant information from multiple print and digital sources, using search terms effectively; assess the credibility and accuracy of each source; and quote or paraphrase the data and conclusions of others while avoiding plagiarism and following a standard format for citation. Cluster: Research to Build and Present Knowledge. Standard: Draw evidence from informational texts to support analysis reflection, and research. Cluster: Text Types and Purposes. Standard: Write arguments focused on discipline-specific content. Cluster: Key Ideas and Details. Standard: Determine a theme or central idea of a text and how it is conveyed through particular details; provide a summary of the text distinct from personal opinions or judgments. Cluster: Key Ideas and Details. Standard: Describe how a particular story’s or drama’s plot unfolds in a series of episodes as well as how the characters respond or change as the plot moves toward a resolution. Cluster: Craft and Structure. Standard: Determine the meaning of words and phrases as they are used in a text, including figurative and connotative meanings; analyze the impact of a specific word choice on meaning and tone. Cluster: Craft and Structure. Standard: Explain how an author develops the point of view of the narrator or speaker in a text. Cluster: Integration of Knowledge and Ideas. Standard: Compare and contrast the experience of reading a story, drama, or poem to listening to or viewing an audio, video, or live version of the text, including contrasting what they “see” and “hear” when reading the text to what they perceive when they listen or watch. Cluster: Key Ideas and Details. Standard: Cite textual evidence to support analysis of what the text says explicitly as well as inferences drawn from the text. Cluster: Key Ideas and Details. Standard: Determine a central idea of a text and how it is conveyed through particular details; provide a summary of the text distinct from personal opinions or judgments. Cluster: Key Ideas and Details. Standard: Analyze in detail how a key individual, event, or idea is introduced, illustrated, and elaborated in a text (e.g., through examples or anecdotes). Cluster: Craft and Structure. Standard: Determine the meaning of words and phrases as they are used in a text, including figurative, connotative, and technical meanings. Cluster: Integration of Knowledge and Ideas. Standard: Integrate information presented in different media or formats (e.g., visually, quantitatively) as well as in words to develop a coherent understanding of a topic or issue. Cluster: Key Ideas and Details. Standard: Cite textual evidence to support analysis of what the text says explicitly as well as inferences drawn from the text. Cluster: Presentation of Knowledge and Ideas. Standard: Present claims and findings, sequencing ideas logically and using pertinent descriptions, facts, and details to accentuate main ideas or themes; use appropriate eye contact, adequate volume, and clear pronunciation. Cluster: Comprehension and Collaboration. Standard: Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 6 topics, texts, and issues, building on others’ ideas and expressing their own clearly. Cluster: Presentation of Knowledge and Ideas. Standard: Present claims and findings, emphasizing salient points in a focused, coherent manner with pertinent descriptions, facts, details, and examples; use appropriate eye contact, adequate volume, and clear pronunciation. Cluster: Comprehension and Collaboration. Standard: Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 7 topics, texts, and issues, building on others’ ideas and expressing their own clearly. Cluster: Presentation of Knowledge and Ideas. Standard: Present claims and findings, emphasizing salient points in a focused, coherent manner with relevant evidence, sound valid reasoning, and well-chosen details; use appropriate eye contact, adequate volume, and clear pronunciation. Cluster: Comprehension and Collaboration. Standard: Engage effectively in a range of collaborative discussions (one-on-one, in groups, and teacher-led) with diverse partners on grade 8 topics, texts, and issues, building on others’ ideas and expressing their own clearly. Cluster: Text Types and Purposes. Standard: Introduce claim(s), acknowledge alternate or opposing claims, and organize the reasons and evidence logically. Cluster: Text Types and Purposes. Standard: Support claim(s) with logical reasoning and relevant evidence, using accurate, credible sources and demonstrating an understanding of the topic or text. Cluster: Research to Build and Present Knowledge. Standard: Gather relevant information from multiple print and digital sources, using search terms effectively; assess the credibility and accuracy of each source; and quote or paraphrase the data and conclusions of others while avoiding plagiarism and following a standard format for citation. Cluster: Research to Build and Present Knowledge. Standard: Draw evidence from literary or informational texts to support analysis, reflection, and research. Cluster: Research to Build and Present Knowledge. Standard: Apply grade 7 Reading standards to literary nonfiction (e.g. “Trace and evaluate the argument and specific claims in a text, assessing whether the reasoning is sound and the evidence is relevant and sufficient to support the claims”). Cluster: Text Types and Purposes. Standard: Write arguments to support claims with clear reasons and relevant evidence. Cluster: Text Types and Purposes. Standard: Introduce claim(s), acknowledge and distinguish the claim(s) from alternate or opposing claims, and organize the reasons and evidence logically. Cluster: Text Types and Purposes. Standard: Support claim(s) with logical reasoning and relevant evidence, using accurate, credible sources and demonstrating an understanding of the topic or text. Cluster: Production and Distribution of Writing. Standard: Produce clear and coherent writing in which the development, organization, and style are appropriate to task, purpose, and audience. (Grade-specific expectations for writing types are defined in standards 1–3 above.) Cluster: Text Types and Purposes. Standard: Write arguments to support claims with clear reasons and relevant evidence. Cluster: Key Ideas and Details. Standard: Determine a theme or central idea of a text and analyze its development over the course of the text; provide an objective summary of the text. Cluster: Key Ideas and Details. Standard: Analyze how particular elements of a story or drama interact (e.g., how setting shapes the characters or plot). Cluster: Key Ideas and Details. Standard: Cite several pieces of textual evidence to support analysis of what the text says explicitly as well as inferences drawn from the text.	oercommons	2025-03-18T00:35:15.996471	Lesson Plan	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/107962/overview", "title": "Animating Civic Action: Middle School Lesson - Homelessness", "author": "Lesson" }
https://oercommons.org/courseware/lesson/15206/overview	Intergovernmental Relationships Learning Objectives By the end of this section, you will be able to: - Explain how federal intergovernmental grants have evolved over time - Identify the types of federal intergovernmental grants - Describe the characteristics of federal unfunded mandates The national government’s ability to achieve its objectives often requires the participation of state and local governments. Intergovernmental grants offer positive financial inducements to get states to work toward selected national goals. A grant is commonly likened to a “carrot” to the extent that it is designed to entice the recipient to do something. On the other hand, unfunded mandates impose federal requirements on state and local authorities. Mandates are typically backed by the threat of penalties for non-compliance and provide little to no compensation for the costs of implementation. Thus, given its coercive nature, a mandate is commonly likened to a “stick.” GRANTS The national government has used grants to influence state actions as far back as the Articles of Confederation when it provided states with land grants. In the first half of the 1800s, land grants were the primary means by which the federal government supported the states. Millions of acres of federal land were donated to support road, railroad, bridge, and canal construction projects, all of which were instrumental in piecing together a national transportation system to facilitate migration, interstate commerce, postal mail service, and movement of military people and equipment. Numerous universities and colleges across the country, such as Ohio State University and the University of Maine, are land-grant institutions because their campuses were built on land donated by the federal government. At the turn of the twentieth century, cash grants replaced land grants as the main form of federal intergovernmental transfers and have become a central part of modern federalism.Dilger, “Federal Grants to State and Local Governments.” Federal cash grants do come with strings attached; the national government has an interest in seeing that public monies are used for policy activities that advance national objectives. Categorical grants are federal transfers formulated to limit recipients’ discretion in the use of funds and subject them to strict administrative criteria that guide project selection, performance, and financial oversight, among other things. These grants also often require some commitment of matching funds. Medicaid and the food stamp program are examples of categorical grants. Block grants come with less stringent federal administrative conditions and provide recipients more flexibility over how to spend grant funds. Examples of block grants include the Workforce Investment Act program, which provides state and local agencies money to help youths and adults obtain skill sets that will lead to better-paying jobs, and the Surface Transportation Program, which helps state and local governments maintain and improve highways, bridges, tunnels, sidewalks, and bicycle paths. Finally, recipients of general revenue sharing faced the least restrictions on the use of federal grants. From 1972 to 1986, when revenue sharing was abolished, upwards of $85 billion of federal money was distributed to states, cities, counties, towns, and villages.John Mikesell. 2014. Fiscal Administration, 9th ed. Boston: Wadsworth Publishing. During the 1960s and 1970s, funding for federal grants grew significantly, as the trend line shows in Figure. Growth picked up again in the 1990s and 2000s. The upward slope since the 1990s is primarily due to the increase in federal grant money going to Medicaid. Federally funded health-care programs jumped from $43.8 billion in 1990 to $320 billion in 2014.Dilger, “Federal Grants to State and Local Governments,” 5. Health-related grant programs such as Medicaid and the Children’s Health Insurance Program (CHIP) represented more than half of total federal grant expenses. The federal government uses grants and other tools to achieve its national policy priorities. Take a look at the National Priorities Project to find out more. The national government has greatly preferred using categorical grants to transfer funds to state and local authorities because this type of grant gives them more control and discretion in how the money is spent. In 2014, the federal government distributed 1,099 grants, 1,078 of which were categorical, while only 21 were block grants.——, “Federal Grants to State and Local Governments,” Table 4. In response to the terrorist attack on the United States on September 11, 2001, more than a dozen new federal grant programs relating to homeland security were created, but as of 2011, only three were block grants. There are a couple of reasons that categorical grants are more popular than block grants despite calls to decentralize public policy. One reason is that elected officials who sponsor these grants can take credit for their positive outcomes (e.g., clean rivers, better-performing schools, healthier children, a secure homeland) since elected officials, not state officials, formulate the administrative standards that lead to the results. Another reason is that categorical grants afford federal officials greater command over grant program performance. A common criticism leveled against block grants is that they lack mechanisms to hold state and local administrators accountable for outcomes, a reproach the Obama administration has made about the Community Services Block Grant program. Finally, once categorical grants have been established, vested interests in Congress and the federal bureaucracy seek to preserve them. The legislators who enact them and the federal agencies that implement them invest heavily in defending them, ensuring their continuation.Schick, The Federal Budget. Reagan’s “devolution revolution” contributed to raising the number of block grants from six in 1981 to fourteen in 1989. Block grants increased to twenty-four in 1999 during the Clinton administration and to twenty-six during Obama’s presidency, but by 2014 the total had dropped to twenty-one, accounting for 10 percent of total federal grant outlay.Robert Jay Dilger and Eugene Boyd, “Block Grants: Perspectives and Controversies,” Congressional Research Service, Report R40486, 15 July 2014, 1–3. In 1994, the Republican-controlled Congress passed legislation that called for block-granting Medicaid, which would have capped federal Medicaid spending. President Clinton vetoed the legislation. However, congressional efforts to convert Aid to Families with Dependent Children (AFDC) to a block grant succeeded. The Temporary Assistance for Needy Families (TANF) block grant replaced the AFDC in 1996, marking the first time the federal government transformed an entitlement program (which guarantees individual rights to benefits) into a block grant. Under the AFDC, the federal government had reimbursed states a portion of the costs they bore for running the program without placing a ceiling on the amount. In contrast, the TANF block grant caps annual federal funding at $16.489 billion and provides a yearly lump sum to each state, which it can use to manage its own program. Block grants have been championed for their cost-cutting effects. By eliminating uncapped federal funding, as the TANF issue illustrates, the national government can reverse the escalating costs of federal grant programs. This point has not been lost on Speaker of the House Paul Ryan (R-WI), former chair of the House Budget Committee and the House Ways and Means Committee, who has tried multiple times but without success to convert Medicaid into a block grant, a reform he estimates could save the federal government upwards of $732 billion over ten years.Jonathan Weisman, “Ryan’s Budget Would Cut $5 trillion in Spending Over a Decade,” New York Times, 1 April 2014. Another noteworthy characteristic of block grants is that their flexibility has been undermined over time as a result of creeping categorization, a process in which the national government places new administrative requirements on state and local governments or supplants block grants with new categorical grants.Kenneth Finegold, Laura Wherry, and Stephanie Schardin. 2014. “Block Grants: Historical Overview and Lessons Learned,” New Federalism: Issues and Options for States Series A, No A-63: 1–7. Among the more common measures used to restrict block grants’ programmatic flexibility are set-asides (i.e., requiring a certain share of grant funds to be designated for a specific purpose) and cost ceilings (i.e., placing a cap on funding other purposes). UNFUNDED MANDATES Unfunded mandates are federal laws and regulations that impose obligations on state and local governments without fully compensating them for the administrative costs they incur. The federal government has used mandates increasingly since the 1960s to promote national objectives in policy areas such as the environment, civil rights, education, and homeland security. One type of mandate threatens civil and criminal penalties for state and local authorities that fail to comply with them across the board in all programs, while another provides for the suspension of federal grant money if the mandate is not followed. These types of mandates are commonly referred to as crosscutting mandates. Failure to fully comply with crosscutting mandates can result in punishments that normally include reduction of or suspension of federal grants, prosecution of officials, fines, or some combination of these penalties. If only one requirement is not met, state or local governments may not get any money at all. For example, Title VI of the Civil Rights Act of 1964 authorizes the federal government to withhold federal grants as well as file lawsuits against state and local officials for practicing racial discrimination. Finally, some mandates come in the form of partial preemption regulations, whereby the federal government sets national regulatory standards but delegates the enforcement to state and local governments. For example, the Clean Air Act sets air quality regulations but instructs states to design implementation plans to achieve such standards (Figure).Martha Derthick. 1987. “American Federalism: Madison’s Middle Ground in the 1980s,” Public Administration Review 47, No. 1: 66–74. The widespread use of federal mandates in the 1970s and 1980s provoked a backlash among state and local authorities, which culminated in the Unfunded Mandates Reform Act (UMRA) in 1995. The UMRA’s main objective has been to restrain the national government’s use of mandates by subjecting rules that impose unfunded requirements on state and local governments to greater procedural scrutiny. However, since the act’s implementation, states and local authorities have obtained limited relief. A new piece of legislation aims to take this approach further. The 2015 Unfunded Mandates and Information Transparency Act, HR 50, passed the House early in 2015 before being referred to the Senate, where it waits committee consideration.U.S. Congress. Senate. 2015–2016. H. R. 50 – Unfunded Mandates Information and Transparency Act of 2015 H. Rept. 114-11. https://www.congress.gov/bill/114th-congress/house-bill/50 The number of mandates has continued to rise, and some have been especially costly to states and local authorities. Consider the Real ID Act of 2005, a federal law designed to beef up homeland security. The law requires driver’s licenses and state-issued identification cards (DL/IDs) to contain standardized anti-fraud security features, specific data, and machine-readable technology. It also requires states to verify the identity of everyone being reissued DL/IDs. The Department of Homeland Security announced a phased enforcement of the law in 2013, which requires individuals to present compliant DL/IDs to board commercial airlines starting in 2016. The cost to states of re-issuing DL/IDs, implementing new identity verification procedures, and redesigning DL/IDs is estimated to be $11 billion, and the federal government stands to reimburse only a small fraction.National Governors Association, National Conference of State Legislatures, and American Association of Motor Vehicle Administrators. 2006. The Real ID Act: National Impact Analysis. http://www.ncsl.org/print/statefed/real_id_impact_report_final_sept19.pdf Compliance with the federal law has been onerous for many states; only twenty-two were in full compliance with Real ID in 2015.Homeland Security. “REAL ID Enforcement in Brief.” http://www.dhs.gov/real-id-enforcement-brief# (June 12, 2015); National Conference of State Legislatures. “Countdown to REAL ID.” http://www.ncsl.org/research/transportation/count-down-to-real-id.aspx (June 12, 2015). The continued use of unfunded mandates clearly contradicts new federalism’s call for giving states and local governments more flexibility in carrying out national goals. The temptation to use them appears to be difficult for the federal government to resist, however, as the UMRA’s poor track record illustrates. This is because mandates allow the federal government to fulfill its national priorities while passing most of the cost to the states, an especially attractive strategy for national lawmakers trying to cut federal spending.Robert Jay Dilger and Richard S. Beth, “Unfunded Mandates Reform Act: History, Impact, and Issues,” Congressional Research Service, Report 7-5700, 17 November 2014. Some leading federalism scholars have used the term coercive federalism to capture this aspect of contemporary U.S. federalism.John Kincaid. 1990. “From Cooperative Federalism to Coercive Federalism,” Annals of the American Academy of Political and Social Science 509: 139–152. In other words, Washington has been as likely to use the stick of mandates as the carrot of grants to accomplish its national objectives. As a result, there have been more instances of confrontational interactions between the states and the federal government. The Clery Act The Clery Act of 1990, formally the Jeanne Clery Disclosure of Campus Security Policy and Campus Crime Statistics Act, requires public and private colleges and universities that participate in federal student aid programs to disclose information about campus crime. The Act is named after Jeanne Clery, who in 1986 was raped and murdered by a fellow student in her Lehigh University dorm room. The U.S. Department of Education’s Clery Act Compliance Division is responsible for enforcing the 1990 Act. Specifically, to remain eligible for federal financial aid funds and avoid penalties, colleges and universities must comply with the following provisions: - Publish an annual security report and make it available to current and prospective students and employees; - Keep a public crime log that documents each crime on campus and is accessible to the public; - Disclose information about incidents of criminal homicide, sex offenses, robbery, aggravated assault, burglary, motor vehicle theft, arson, and hate crimes that occurred on or near campus; - Issue warnings about Clery Act crimes that pose a threat to students and employees; - Develop a campus community emergency response and notification strategy that is subject to annual testing; - Gather and report fire data to the federal government and publish an annual fire safety report; - Devise procedures to address reports of missing students living in on-campus housing. For more about the Clery Act, see Clery Center for Security on Campus, http://clerycenter.org. Were you made aware of your campus’s annual security report before you enrolled? Do you think reporting about campus security is appropriately regulated at the federal level under the Clery Act? Why or why not? To accomplish its policy priorities, the federal government often needs to elicit the cooperation of states and local governments, using various strategies. Block and categorical grants provide money to lower government levels to subsidize the cost of implementing policy programs fashioned in part by the federal government. This strategy gives state and local authorities some degree of flexibility and discretion as they coordinate with the federal government. On the other hand, mandate compels state and local governments to abide by federal laws and regulations or face penalties. Which statement about federal grants in recent decades is most accurate? - The federal government allocates the most grant money to income security. - The amount of federal grant money going to states has steadily increased since the 1960s. - The majority of federal grants are block grants. - Block grants tend to gain more flexibility over time. Which statement about unfunded mandates is false? - The Unfunded Mandates Reform Act has prevented Congress from using unfunded mandates. - The Clean Air Act is a type of federal partial preemptive regulation. - Title VI of the Civil Rights Act establishes crosscutting requirements. - New federalism does not promote the use of unfunded mandates. Hint: D What does it mean to refer to the carrot of grants and the stick of mandates?	oercommons	2025-03-18T00:35:16.023689	07/10/2017	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/15206/overview", "title": "American Government, Students and the System, American Federalism, Intergovernmental Relationships", "author": null }
https://oercommons.org/courseware/lesson/61954/overview	Essay Outline Handout English Composition I Overview This lesson includes information on how to write an English Composition I essay. Essay Organization Lecture Material This lesson includes material on how to write an essay - lecture material and an essay outline handout.	oercommons	2025-03-18T00:35:16.042707	01/27/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/61954/overview", "title": "English Composition I", "author": "Kristy Perry" }
https://oercommons.org/courseware/lesson/91219/overview	Products and Marketing Mix Overview Provided by: Lumen Learning. License: CC BY: Attribution Outcome: Products and Marketing Mix What you’ll learn to do: explain what a product is and the importance of products in the marketing mix We’ll start this module by defining what a product is and seeing how it fits in the marketing mix. When thinking about the target customer’s perspective, it’s useful to have an “expansive” view of product and keep in mind that the customer experience is not only about the tangible aspects of a good. For example, imagine that you stop at a fast-food restaurant for a quick sandwich. The sandwich is fresh and delicious and is exactly what you wanted to eat. However, the wait for the sandwich was exceptionally long, the restaurant was filthy, and the sales clerk was rude. Does that change your level of satisfaction? Or, have you ever been excited to get a bargain on an airline ticket and then been surprised by additional fees for what seem like basic services, such as checking your luggage? Do the fees change your level of satisfaction with the product? As we explore products and product marketing, you will find that most products include a broader range of components than you might first expect. The specific things you’ll learn in this section include: - Define a product - Identify difference between products that offer goods versus services - Explain how to augment a product with services - Define product marketing - Explain the role of product marketing in the marketing mix Learning Activities The learning activities for this section include the following: - Reading: Defining Product - Reading: Consumer Product Categories - Reading: Products and Services - Reading: Augmenting Products with Services - Reading: Product Marketing and the Marketing Mix Licenses and Attributions CC licensed content, Shared previously - Outcome: Products and Marketing Mix. Provided by: Lumen Learning. License: CC BY: Attribution Reading: Defining Product A product is a bundle of attributes (features, functions, benefits, and uses) that a person receives in an exchange. In essence, the term “product” refers to anything offered by a firm to provide customer satisfaction, tangible or intangible. Thus, a product may be an idea (recycling), a physical good (a pair of jeans), a service (banking), or any combination of the three.1 Broadly speaking, products fall into one of two categories: consumer products and business products (also called industrial products and B2B products). Consumer products are purchased by the final consumer. Business products are purchased by other industries or firms and can be classified as production goods—i.e., raw materials or component parts used in the production of the final product—or support goods—such as machinery, fixed equipment, software systems, and tools that assist in the production process.[2] Some products, like computers, for instance, may be both consumer products and business products, depending on who purchases and uses them. The product fills an important role in the marketing mix because it is the core of the exchange. Does the product provide the features, functions, benefits, and uses that the target customer expects and desires? Throughout our discussion of product we will focus on the target customer. Often companies become excited about their capabilities, technologies, and ideas and forget the perspective of the customer. This leads to investments in product enhancements or new products that don’t provide value to the customer—and, as a result, are unsuccessful. Four Levels of the Product There are four levels of a product (shown in the figure below): core, tangible, augmented, and promised. Each is important to understand in order to address the customer needs and offer the customer a complete experience. The Core Product The core product satisfies the most basic need of the customer. For example, a consumer who purchases a healthy snack bar may be seeking health, convenience, or simply hunger relief. A student who buys low-priced, sturdy sneakers may just be seeking footwear. A student on a tight budget who buys top-of-the-line sneakers might be hoping to achieve status. Or, the student might be seeking a sense of freedom by splurging on an item that represents a true sense of style, even though he can’t really afford it. Footwear, status, and freedom are all legitimate core products. The core product is complex because it is so individualized, and, often, vague. The marketer must have a strong understanding of the target customer (and the different segments of target customers) in order to accurately identify the core product. The Tangible Product Once the core product has been identified, the tangible product becomes important. Tangible means “perceptible by touch,” so the tangible aspects of a product are those that can be touched and held. This idea can be expanded to also include the characteristics of the product that directly touch the buyer in the buying decision. These are the product elements that the customer will use to evaluate and make choices: the product features, quality level, brand name, styling, and packaging. Every product contains these components to a greater or lesser extent, and they are what the consumer uses when evaluating alternatives. The importance of each aspect of the tangible product will vary across products, situations, and individuals. For example, at age twenty, a consumer might choose a particular brand of new car (core product=transportation) based on features such as gas mileage, styling, and price (choice=Toyota Yaris); at age forty-five, the core product remains the same, while the tangible components such as quality level, power, features, and brand prestige become important (choice=Audi A6). The Augmented Product Every product is backed up by a host of supporting services. The augmented product includes the tangible product and all of the services that support it. Often, the buyer expects these services and would reject the tangible product if they were not available. For example, if you shop at a department store, you are likely focused on a core and tangible product that centers on the merchandise, but you will still expect the store to have restrooms, escalators, and elevators. Dow Chemical has earned a reputation as a company that will bend over backward in order to service an account. It means that a Dow sales representative will visit a troubled farmer after hours in order to solve a serious problem. This extra service is an integral part of the augmented product and a key to their success. When the tangible product is a service, there is still an augmented product that includes support services. Westin hotels offer hotel nights with a specific set of features as their tangible product. The augmented product also includes dry cleaning services, concierge services, and shuttle services, among others. In a world with many strong competitors and few unique products, the augmented product is gaining ground, since it creates additional opportunities to differentiate the product from competitive offerings. The Promised Product The outer ring of the product is referred to as the promised product. Every product has an implied promise, which is a characteristic that is attached to the product over time. The promised product is the long-term result that the customer hopes to achieve by selecting the product. The promised product may be financial—the resale value of a car, home, or property, for example—but it is often more aspirational. The customer hopes to be healthier, happier, more productive, more successful, or enjoy greater status. Like the core product, the promised product is highly personal. Generally, marketers find that there will be groupings of customers seeking a similar promise but that there is not a single promised product across all customers. Can the core product and the promised product be the same thing? Yes, they can, but often the core product is more focused on the immediate need and the promised product has a longer-term element. Let’s compare two different examples of the same purchase to understand how the product levels might change for different customers. \| Impetus to Buy \| I need to be in Miami for a meeting next Thursday \| I need a break from my stressful life \| \|---\|---\|---\| \| Core Product \| Transportation \| Escape, peace of mind \| \| Tangible Product \| Airline ticket from New York to Miami \| Airline ticket from New York to Miami \| \| Augmented Product \| \| \| \| Promised Product \| Productivity, convenience, success \| Escape, peace of mind, happiness \| In the first case, the customer’s impetus to buy is transportation, so that is the core product. In the second case, the purchase is more aspirational and less concrete, so the core product and the promised product are quite similar. For a marketer, the most important element is to have a holistic view of the product. If I believe that I’m simply selling airline tickets, then I fail to provide the full product offering that will satisfy either of my customers in the example above. And of course, it is always key to truly understand the motivation and perspective of the target customer. Licenses and Attributions CC licensed content, Original - Revision and adaptation. Provided by: Lumen Learning. License: CC BY: Attribution CC licensed content, Shared previously - Chapter 7: Introducing and Managing the Product, from Introducing Marketing. Authored by: John Burnett. Project: Global Text. License: CC BY: Attribution - New Kicks. Authored by: Grace Miller. Located at: https://www.flickr.com/photos/gracemillerphotography/6101851438/. License: CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives Reading: Consumer Product Categories Consumer products are often classified into four groups related to different kinds of buying decisions: convenience, shopping, specialty, and unsought products. These are described below. Convenience Products A convenience product is an inexpensive product that requires a minimum amount of effort on the part of the consumer in order to select and purchase it. Examples of convenience products are bread, soft drinks, pain reliever, and coffee. They also include headphones, power cords, and other items that are easily misplaced. From the consumer’s perspective, little time, planning, or effort go into buying convenience products. Often product purchases are made on impulse, so availability is important. Consumers have come to expect a wide variety of products to be conveniently located at their local supermarkets. They also expect easy online purchase options and low-cost, quick shipping for those purchases. Convenience items are also found in vending machines and kiosks. For convenience products, the primary marketing strategy is extensive distribution. The product must be available in every conceivable outlet and must be easily accessible in these outlets. These products are usually of low unit value, and they are highly standardized. Marketers must establish a high level of brand awareness and recognition. This is accomplished through extensive mass advertising, sales promotion devices such as coupons and point-of-purchase displays, and effective packaging. Yet, the key is to convince resellers (wholesalers and retailers) to carry the product. If the product is not available when, where, and in a form the consumer desires, the convenience product will fail. Shopping Products In contrast, consumers want to be able to compare products categorized as shopping products. Shopping products are usually more expensive and are purchased occasionally. The consumer is more likely to compare a number of options to assess quality, cost, and features. Although many shopping goods are nationally advertised, in the marketing strategy it is often the ability of the retailer to differentiate itself that generates the sale. If you decide to buy a TV at BestBuy, then you are more likely to evaluate the range of options and prices that BestBuy has to offer. It becomes important for BestBuy to provide a knowledgeable and effective sales person and have the right pricing discounts to offer you a competitive deal. BestBuy might also offer you an extended warranty package or in-store service options. While shopping in BestBuy, consumers can easily check prices and options for online retailers, which places even greater pressure on BestBuy to provide the best total value to the shopper. If the retailer can’t make the sale, product turnover is slower, and the retailer will have a great deal of their capital tied up in inventory. There is a distinction between heterogeneous and homogeneous shopping products. Heterogeneous shopping products are unique. Think about shopping for clothing or furniture. There are many stylistic differences, and the shopper is trying to find the best stylistic match at the right price. The purchase decision with heterogeneous shopping products is more likely to be based on finding the right fit than on price alone. In contrast, homogeneous shopping products are very similar. Take, for example, refrigerators. Each model has certain features that are available at different price points, but the basic functions of all of the models are very similar. A typical shopper will look for the lowest price available for the features that they desire. Speciality Products Specialty goods represent the third product classification. From the consumer’s perspective, these products are so unique that it’s worth it to go to great lengths to find and purchase them. Almost without exception, price is not the principle factor affecting the sales of specialty goods. Although these products may be custom-made or one-of-a-kind, it is also possible that the marketer has been very successful in differentiating the product in the mind of the consumer. For example, some consumers feel a strong attachment to their hair stylist or barber. They are more likely to wait for an appointment than schedule time with a different stylist. Another example is the annual Blizzcon event produced by Blizzard Entertainment. The $200 tickets sell out minutes after they are released, and they are resold at a premium. At the event, attendees get the chance to learn about new video games and play games that have not yet been released. They can also purchase limited-edition promotional items. From a marketer’s perspective, in Blizzcon the company has succeeded in creating a specialty product that has incredibly high demand. Moreover, Blizzard’s customers are paying for the opportunity to be part of a massive marketing event. It is generally desirable for a marketer to lift her product from the shopping to the specialty class—and keep it there. With the exception of price-cutting, the entire range of marketing activities is needed to accomplish this. Unsought Products Unsought products are those the consumer never plans or hopes to buy. These are either products that the customer is unaware of or products the consumer hopes not to need. For example, most consumers hope never to purchase pest control services and try to avoid purchasing funeral plots. Unsought products have a tendency to draw aggressive sales techniques, as it is difficult to get the attention of a buyer who is not seeking the product. Licenses and Attributions CC licensed content, Original - Revision and adaptation. Provided by: Lumen Learning. License: CC BY: Attribution CC licensed content, Shared previously - Chapter 7: Introducing and Managing the Product, from Introducing Marketing. Authored by: John Burnett. Project: Global Text. License: CC BY: Attribution - Walmart's Action Alley. Provided by: Walmart. Located at: https://www.flickr.com/photos/walmartcorporate/5684811762/. License: CC BY: Attribution - Blizzcon 2014. Authored by: V Threepio. Located at: https://www.flickr.com/photos/warriorpoet/15592693770/. License: CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives Reading: Products and Services Goods vs. Services In marketing, are services considered products? Should products that are predominately goods be treated differently than products that are predominantly services? Whether or not there are substantial differences between goods, products, and service products has been the source of great debate in marketing. Opponents of the division assert that “products are products,” and just because there are some characteristics associated with service products and not goods products and vice versa, it doesn’t mean that customized strategies are necessary for each. Advocates on the other side offer evidence that the differences are significant indeed. You may have noticed that throughout this course we use the term “product” broadly to address the full product offering that is comprised of goods, services, and often a combination of both. We’ve given examples of service products (hotel stays, for instance) and goods products (sneakers and bread, for instance). Thinking inclusively about the tangible and intangible aspects of all products is useful because it creates a more complete view of the customer’s product needs and experience. Still, there are unique characteristics of services that set them apart from goods. It is important to understand the differences and to consider them in the development of strategies, tactics, and objectives. Service products are reflected by a wide variety of industries: utilities, restaurants, educational institutions, consulting firms, hotels, medical care providers, and banking, to name but a few. Beyond these traditional industries there is a growing sector of software as a service offered by companies that provide individuals and other companies with hosted and managed access to software systems. In 2013, software as a service was a $22.6 billion industry, it is projected to hit $100 billion in 20191. Services account for nearly 50 percent of the average consumer’s total expenditures, 70 percent of the jobs, and two-thirds of the U.S. Gross National Product (GNP). Clearly, the service sector is large and is growing. While all products share certain common facets, service products tend to differ from goods products in a number of ways. Characteristics of Service Products As you can see from the examples above, service products are quite diverse. Nonetheless, they tend to have the following characteristics. Intangible Leonard Berry offers this useful differentiation: “A good is an object, a device, a thing; a service is a deed, a performance, an effort.”2 With the purchase of a good, you have something tangible—an item that can be seen, touched, tasted, worn, or displayed. That’s not true of a service, which is intangible (quite literally, “not able to be touched”). Although you pay your money and consume the service, there is nothing tangible to show for it. For example, if you attend a professional football game, you spend money for a ticket and spend nearly three hours taking in the entertainment. After the game, you leave. Unless you have purchased a good at the game, you will not take anything tangible to take away (except, perhaps, the ticket stub). Simultaneous Production and Consumption Service products are consumed at the same time they are being produced. The tourist attraction is producing entertainment or pleasure at the same time it is being consumed. In contrast, goods products are produced, stored, and then consumed. A result of this characteristic is that the provider of the service is often present when consumption takes place. Dentists, hotel staff, hair stylists, and ballet dancers are all present when the product is used. Little Standardization Because service products are so closely related to the people providing the service, ensuring the same level of satisfaction every time is very difficult. Dentists have their bad days, not every baseball game is exciting, and the second vacation to Walt Disney World Resort may not be as wonderful as the first. High Buyer Involvement With many service products, the purchaser may provide a great deal of input into the final form of the product. For example, if you wanted to go on a Caribbean cruise, you would visit a number of websites describing the various cruise locations, review the available options for cabin location and size, islands visited, food, entertainment, prices, and whether they accommodate children. Although the task would be very time consuming, you could, if you wanted, practically design every moment of your vacation. It should be noted that the four characteristics associated with service products described above vary in intensity from product to product. In fact, service products are best treated as existing on a continuum, shown in the following figure. When marketing a service, it’s important to remember that (a) service products on the right side of the continuum (i.e., those with greater intangibility) are different from goods products on the left side of the continuum, and (b) service products tend to require certain adjustments in their marketing strategy on account of these differences. All products, whether they are goods, services, blankets, diapers, or plate glass, possess peculiarities that require adjustments in the marketing effort. However, “pure” goods products and “pure” service products (i.e. those on the extreme ends of the continuum) tend to reflect characteristics and responses from customers that suggest different marketing strategies. Admittedly, offering an exceptional product at the right price, through the most accessible channels, promoted extensively and accurately, should work for any type of product. The goods/services classification provides the same useful insights provided by the B2B/B2C classification discussed earlier. - https://www.cbronline.com/news/saas-market - Leonard L. Berry, "Services Marketing Is Different," Business May/June 1980: 24–29. Licenses and Attributions CC licensed content, Original - Revision and adaptation. Provided by: Lumen Learning. License: CC BY: Attribution CC licensed content, Shared previously - Chapter 7: Introducing and Managing the Product, from Introducing Marketing. Authored by: John Burnett. Project: Global Text. License: CC BY: Attribution - Cruise Ship Deck. Authored by: Bob Jagendorf. Located at: https://www.flickr.com/photos/bobjagendorf/465126372/. License: CC BY-NC: Attribution-NonCommercial - allStarGame_1971. Authored by: Doug Berger. Located at: https://www.flickr.com/photos/27703647@N04/5442111811/. License: CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives Reading: Augmenting Products with Services Earlier we touched on “augmented products,” which are tangible products, along with all of the services that support them. When companies devise product strategies and decide whether or not to augment their products with additional services, they typically evaluate whether the following criteria will be met: - Services can provide a more complete and satisfying customer experience. - Services can increase the total revenue for each sale. Improved Customer Experience Relatively speaking, goods tend to be more fixed, and services are more variable. If you’re trying to control the quality of a product, the “fixedness” of goods is obviously problematic—perhaps you’ll need costly new equipment or production methods or a new product design to make improvements. If you’re focused on personalizing the customer experience, though, the variability of services can be a tremendous benefit. A company can provide a range of services around a tangible product—whether that product is a good or a service—thereby providing an enhanced experience for the customer. Zappos Zappos provides the quintessential example of an augmented product that adds tremendous value by offering an improved customer experience. You’ll recall from the module on corporate strategy that Zappos sells shoes and apparel online. The tangible products are the shoes and clothing items that are delivered to the customer’s doorstep. The company has a broad selection and has invested significant capital and effort to create an online shopping experience that is easy and pleasant. The company’s tangible products are very good. However, Zappos is not the low price leader. In fact, its prices are often 5–10 percent higher than other online shoe retailers. Nor does the company do a lot of national advertising to build its brand. Instead, Zappos has focused on creating a “wow” customer-service experience that not only exceeds customers’ expectations but brings people back again and again. In fact, the company’s goal is to be the company that provides the best service online, period—not just in shoes, but in any category. When customers buy shoes online they expect the product to be accurately presented. They expect to receive what they order in a timely fashion. They expect to receive help with any questions and have any problems with orders resolved. These are fairly standard customer-service features that customers expect along with the delivery of their shoes or clothes. Zappos goes a step further, though, to provide an even higher level of service to all its customers—at no extra charge: Zappos has a 100-percent-satisfaction-guaranteed return policy—at no cost to the customer and no complaints about items returned. Customer-service employees encourage customers to order two sizes of shoes to make sure they get a pair that fits, and return the other. The company frequently upgrades orders from valued clients to one-day shipping and sends personal notes expressing appreciation for their business. Zappos posts a support phone number on every page of its Web site. The company has found that only 5 percent of sales come through the phone, but when customers do call, there is an opportunity to create a deeper relationship. As a result of these services, Zappos’ augmented product is significantly more valuable and more differentiated than its tangible product, and it’s helped to set Zappos apart as a company that treats its customers well. Increased Revenue per Customer It is often the case that augmented services do create new revenue opportunities for the company. Some customers want a different level of service and are willing to pay more for it. By adding services a company can customize its product offering for the segments that desire something more. Many of these services have become so standard that we hardly think about them. Most electronics come with an option to buy an extended warranty or a higher level of customer support. Airlines provide in-flight meals and drinks; many hotel and rental car packages are essentially augmented products. Many online services such as LinkedIn and the Slack team messaging service offer tiered packages, or offer a free version and a version that includes additional services for a fee. These services can prove to be highly profitable. Despite LinkedIn’s free offering, 16 percent of its three million users pay for premium services.1 In 2017, airlines earned $82.2 billion in non-ticket revenue.2 Companies often struggle to determine when it is best to add a fee for additional services and when the augmented services should be a free extension of the tangible product. The question often ties back to the company mission and objectives, as well as to the competitive landscape. If Zappos charged customers for the various services the company provides, customers would probably feel irritated instead of pampered. Also, Zappos’ extensive customer services are core to the company’s mission and strategy. If American Airlines decided not to charge the baggage and change fees that Delta charges, then it would likely need to recoup those costs in higher ticket prices for all customers. Generally when customers purchase tickets, they consider the base ticket price and not the price that includes all fees. As a result, American would struggle to compete on ticket price in a highly price-sensitive market. Augmented services give marketers a valuable approach to customizing products and better meeting the needs of all target customers. - http://www.forbes.com/sites/cherylsnappconner/2014/05/04/new-research-2014-linkedin-user-trends-and-10-top-surprises/ - https://www.phocuswire.com/cartrawler-ideaworkscompany-2018-ancillary-revenue Licenses and Attributions CC licensed content, Original - Revision and adaptation. Provided by: Lumen Learning. License: CC BY: Attribution CC licensed content, Shared previously - Chapter 7: Introducing and Managing the Product, from Introducing Marketing. Authored by: John Burnett. Project: Global Text. License: CC BY: Attribution - Zappos concept. Authored by: Alberto Cerriteu00f1o. Located at: https://www.flickr.com/photos/acerriteno/3850366833/. License: CC BY-NC-ND: Attribution-NonCommercial-NoDerivatives - planes-2. Authored by: Ian Ransley. Located at: https://www.flickr.com/photos/design-dog/13475654373/. License: CC BY: Attribution Reading: Product Marketing in the Marketing Mix The Role of Product Marketing Product marketing is the function of understanding the target customer’s needs, and promoting and selling the product to the target customer. In many organizations this is a different function from product management, which is responsible for defining the product that the company will build. Obviously the two functions must interact closely, but each has a different primary focus. The product marketer is focused on the market. This includes analyzing and understanding the market, and presenting the product to the market. In other words, product marketers must bring information in and get it out. These activities are summarized in the table below: \| Inputs to the company \| Outputs to the market \| \|---\|---\| \| Define market needs or problems that the product should address \| Define key messages to the communicate product benefits to the target market \| \| Complete a competitive analysis to understand other offerings in the market \| Create marketing materials about the product \| \| Identify which market segments the product will target \| Define the sales approach \| \| Define market requirements for the product \| Create lead generation plans \| \| Create buyer persona documents that describe the personality, behavior, and desires of buyer types \| Develop sales materials such as Web site content, brochures, presentations, and product demonstrations \| \| Determine price \| Provide training and support to distribution channel partners \| The product management function will use the inputs from product marketing to define detailed product requirements and oversee the development of products that meet those requirements. We will discuss the complexity of this process further when we delve into new-product development. Product marketing and product management are both functions that must be managed well, but in different organizations they are managed differently. The specific roles of individuals will vary significantly depending on the company and the types of products. In a very large company there may be teams of individuals in the product marketing function filling very specialized roles. In a very small company, a single individual may fill both the product marketing and product management functions. In general, it is difficult to span both product marketing and product management because the skills needed to understand and translate broad market needs are different from the skills needed to create detailed product requirements. The Marketing Mix As you can see from the list of responsibilities, the product marketing function is not confined to only one aspect of the marketing mix. Instead, the product marketing function focuses on a single product or product line across the marketing mix. Let’s look at a specific example of the product marketing role and a corporate marketing role, and see how they each use the marketing mix. Apple Watch When Apple introduced the Apple Watch, they had a large team responsible for product marketing. The team was following emerging technology, consumer, and societal trends and identifying what would impact customer needs. They became experts in the features and marketing of competitive products. Product marketers defined the target buyer for the watch and identified the key features the buyer would require. They met with distribution partners. The product marketing team developed pricing recommendations. They managed tradeoffs involving features, schedule, cost, and pricing. They also traveled to trade shows, customer briefings, and press visits to talk about the watch. The product marketing team was Apple’s resident expert on the target market for the Apple watch and the marketing strategy for that product. Prior to the product launch, product marketing worked with Apple’s marketing communications team to develop the press releases, press strategy, and marketing materials for the launch and ongoing sales. Marketing communications is a corporate function that works across all products. They do not try to become experts in each product but look to the product marketing team to bring that expertise. Instead, the marketing communications team are experts in promotion across all of Apple’s products. Product marketing understands the right message for the Apple watch’s target market. The marketing communications team knows how to get a writer at the New York Times to write a story about that message. Licenses and Attributions CC licensed content, Original - Reading: Product Marketing in the Marketing Mix. Provided by: Lumen Learning. License: CC BY: Attribution	oercommons	2025-03-18T00:35:16.097944	03/22/2022	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/91219/overview", "title": "Statewide Dual Credit Principles of Marketing, Product Marketing, Products and Marketing Mix", "author": "Anna McCollum" }
https://oercommons.org/courseware/lesson/86603/overview	Before the Mayflower-A History of the Negro in America, 1619-1962 by Lerone Bennett, Jr. Overview Download the ebook at https://ebooksforstudents.org/before-the-mayflower-a-history-of-the-negro-in-america-1619-1962-by-lerone-bennett-jr/ Reviews from Goodreads.com where the ebook received a 4.45 out of 5 rating: This a great introduction, if not then the best introduction, to African American History. If you are wanting to know more about the story of African Americans this book is very readable and accurate. When I taught our school African American History class this was my text. My students liked it so much most of them went out and bought their own copies. * * * * * Mr. Bennett gives voice to Black Americans, and to the cultures they brought with them. Through impeccable research, he has uncovered history and culture that was not readily available those many years ago. This book was published and available at almost the same time I finished my degree. I found it later when I had the luxury of being able to read what I wanted, rather than that which was assigned, and have used it to some degree in home schooling my son (though it is too difficult for most high school students). Highly readable and enormously enlightening. * * * * * This was an amazing piece of work. I knew that people of color in this country had it rough but this truly shows just how bad. Even with all of the hardships people of color tried again and again to be the best that society would not let them. I was inspired by this book to continue to strive for progress and thus success. The stories of my ancestors have shown me that I come from a strong stock that can survived the worst of times so that I may have the best of times. * * * * * From the inside flap of the print edition of 1962: This is a history of the American Negro, whose ancestors arrived at Jamestown a year before the arrival of the “Mayflower.” The book begins in Africa with the great empires of the Nile Valley and the western Sudan and ends with the Second Reconstruction, which Martin Luther King Jr. and the Sit-in Generation are fashioning in the North and South. Written in a dramatic, readable style, Before The Mayflower throws a great deal of light on today’s headlines. As such, it will be a valuable addition to the library of every discerning American. Grounded on the work of scholars and specialists, the book is designed for the non-specialist. Based on the trials and triumphs of Negro Americans, the book tells a story which is relevant to all men. Here are the Negro Minute Men of Lexington and Concord and the black soldiers who stood with Andrew Jackson at New Orleans and Ulysses S. Grant at Petersburg. Here also are the forgotten figures of American history: Phillis Wheatley, the slave poet who became the second American woman to write a book; Nat Turner, the mystic who led a bloody slave revolt; P. B. S. Pinchback, the Negro who sat in the Louisiana governor’s mansion and dreamed of the vice presidency.	oercommons	2025-03-18T00:35:16.113969	10/08/2021	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/86603/overview", "title": "Before the Mayflower-A History of the Negro in America, 1619-1962 by Lerone Bennett, Jr.", "author": "Jim McCabe" }
https://oercommons.org/courseware/lesson/14935/overview	Preface to Biology Overview Biology is designed for multi-semester biology courses for science majors. It is grounded on an evolutionary basis and includes exciting features that highlight careers in the biological sciences and everyday applications of the concepts at hand. To meet the needs of today’s instructors and students, some content has been strategically condensed while maintaining the overall scope and coverage of traditional texts for this course. Instructors can customize the book, adapting it to the approach that works best in their classroom. Biology also includes an innovative art program that incorporates critical thinking and clicker questions to help students understand—and apply—key concepts. Welcome to Biology, an OpenStax resource. This textbook was written to increase student access to high-quality learning materials, maintaining highest standards of academic rigor at little to no cost. About OpenStax OpenStax is a nonprofit based at Rice University, and it’s our mission to improve student access to education. Our first openly licensed college textbook was published in 2012, and our library has since scaled to over 20 books for college and AP courses used by hundreds of thousands of students. Our adaptive learning technology, designed to improve learning outcomes through personalized educational paths, is being piloted in college courses throughout the country. Through our partnerships with philanthropic foundations and our alliance with other educational resource organizations, OpenStax is breaking down the most common barriers to learning and empowering students and instructors to succeed. About OpenStax’s Resources Customization Biology is licensed under a Creative Commons Attribution 4.0 International (CC BY) license, which means that you can distribute, remix, and build upon the content, as long as you provide attribution to OpenStax and its content contributors. Because our books are openly licensed, you are free to use the entire book or pick and choose the sections that are most relevant to the needs of your course. Feel free to remix the content by assigning your students certain chapters and sections in your syllabus, in the order that you prefer. You can even provide a direct link in your syllabus to the sections in the web view of your book. Faculty also have the option of creating a customized version of their OpenStax book through the aerSelect platform. The custom version can be made available to students in low-cost print or digital form through their campus bookstore. Visit your book page on openstax.org for a link to your book on aerSelect. Errata All OpenStax textbooks undergo a rigorous review process. However, like any professional-grade textbook, errors sometimes occur. Since our books are web based, we can make updates periodically when deemed pedagogically necessary. If you have a correction to suggest, submit it through the link on your book page on openstax.org. Subject matter experts review all errata suggestions. OpenStax is committed to remaining transparent about all updates, so you will also find a list of past errata changes on your book page on openstax.org. Format You can access this textbook for free in web view or PDF through openstax.org, and in low-cost print and iBooks editions. About Biology Biology is designed to cover the scope and sequence requirements of a typical two-semester biology course for science majors. The text provides comprehensive coverage of foundational research and core biology concepts through an evolutionary lens. Biology includes rich features that engage students in scientific inquiry, highlight careers in the biological sciences, and offer everyday applications. The book also includes clicker questions to help students understand—and apply—key concepts. Coverage and Scope In developing Biology, we listened to hundreds of General Biology instructors who readily provided feedback about their courses, students, challenges, and hopes for innovation. The expense of textbooks and related items did prove to be a barrier to learning. But more importantly, these teachers suggested improvements for the textbook, which would ultimately lead to more meaningful and memorable learning experiences for students. The result is a book that addresses a core organizational reality of the course and its materials—the sheer breadth of the topical coverage. We provide a thorough treatment of biology’s foundational concepts while condensing selected topics in response to the market’s request for a textbook with a scope that is manageable for instructors and students alike. We also strive to make biology, as a discipline, interesting and accessible to students. In addition to a comprehensive coverage of core concepts and foundational research, we have incorporated features that draw learners into the discipline in meaningful ways. The pedagogical choices, chapter arrangements, and learning objective fulfillment were developed and vetted with the feedback of another one hundred reviewers, who thoroughly read the material and offered detailed critical commentary. - Unit 1: The Chemistry of Life. Our opening unit introduces students to the sciences, including the scientific method and the fundamental concepts of chemistry and physics that provide a framework within which learners comprehend biological processes. - Unit 2: The Cell. Students will gain solid understanding of the structures, functions, and processes of the most basic unit of life: the cell. - Unit 3: Genetics. Our comprehensive genetics unit takes learners from the earliest experiments that revealed the basis of genetics through the intricacies of DNA to current applications in the emerging studies of biotechnology and genomics. - Unit 4: Evolutionary Processes. The core concepts of evolution are discussed in this unit with examples illustrating evolutionary processes. Additionally, the evolutionary basis of biology reappears throughout the textbook in general discussion and is reinforced through special call-out features highlighting specific evolution-based topics. - Unit 5: Biological Diversity. The diversity of life is explored with detailed study of various organisms and discussion of emerging phylogenetic relationships. This unit moves from viruses to living organisms like bacteria, discusses the organisms formerly grouped as protists, and devotes multiple chapters to plant and animal life. - Unit 6: Plant Structure and Function. Our plant unit thoroughly covers the fundamental knowledge of plant life essential to an introductory biology course. - Unit 7: Animal Structure and Function. An introduction to the form and function of the animal body is followed by chapters on specific body systems and processes. This unit touches on the biology of all organisms while maintaining an engaging focus on human anatomy and physiology that helps students connect to the topics. - Unit 8: Ecology. Ecological concepts are broadly covered in this unit, with features highlighting localized, real-world issues of conservation and biodiversity. Pedagogical Foundation and Features Biology is grounded in a solid scientific base, with features that engage the students in scientific inquiry, including: - Evolution Connection features uphold the importance of evolution to all biological study through discussions like “The Evolution of Metabolic Pathways” and “Algae and Evolutionary Paths to Photosynthesis.” - Scientific Method Connection call-outs walk students through actual or thought experiments that elucidate the steps of the scientific process as applied to the topic. Features include “Determining the Time Spent in Cell Cycle Stages” and “Testing the Hypothesis of Independent Assortment.” - Career Connection features present information on a variety of careers in the biological sciences, introducing students to the educational requirements and day-to-day work life of a variety of professions, such as microbiologist, ecologist, neurologist, and forensic scientist. - Everyday Connection features tie biological concepts to emerging issues and discuss science in terms of everyday life. Topics include “Chesapeake Bay” and “Can Snail Venom Be Used as a Pharmacological Pain Killer?” Art and Animations That Engage Our art program takes a straightforward approach designed to help students learn the concepts of biology through simple, effective illustrations, photos, and micrographs. Biology also incorporates links to relevant animations and interactive exercises that help bring biology to life for students. - Art Connection features call out core figures in each chapter for student study. Questions about key figures, including clicker questions that can be used in the classroom, engage students’ critical thinking to ensure genuine understanding. - Link to Learning features direct students to online interactive exercises and animations to add a fuller context to core content. Additional Resources Student and Instructor ResourcesWe've compiled additional resources for both students and instructors, including Getting Started Guides, an instructor solution manual, supplemental test items, and PowerPoint slides. Instructor resources require a verified instructor account, which can be requested on your openstax.org log-in. Take advantage of these resources to supplement your OpenStax book. Partner ResourcesOpenStax Partners are our allies in the mission to make high-quality learning materials affordable and accessible to students and instructors everywhere. Their tools integrate seamlessly with our OpenStax titles at a low cost. To access the partner resources for your text, visit your book page on openstax.org. About the Authors Contributing Authors and Reviewers Julie Adams, Aurora University Summer Allen, Brown University James Bader, Case Western Reserve University David Bailey, St. Norbert College Mark Belk, Brigham Young University Nancy Boury, Iowa State University Lisa Bonneau, Metropolitan Community College – Blue River Graciela Brelles-Marino, California State University Pomona Mark Browning, Purdue University Sue Chaplin, University of St. Thomas George Cline, Jacksonville State University Deb Cook, Georgia Gwinnett College Diane Day, Clayton State University Frank Dirrigl, The University of Texas Pan American Waneene Dorsey, Grambling State University Nick Downey, University of Wisconsin La Crosse Rick Duhrkopf, Baylor University Kristy Duran, Adams State University Stan Eisen, Christian Brothers University Brent Ewers, University of Wyoming Myriam Feldman, Lake Washington Institute of Technology Michael Fine, Virginia Commonwealth University Linda Flora, Delaware County Community College Thomas Freeland, Walsh University David Grisé, Texas A & M University – Corpus Christi Andrea Hazard, SUNY Cortland Michael Hedrick, University of North Texas Linda Hensel, Mercer University Mark Kopeny, University of Virginia Norman Johnson, University of Massachusetts Amherst Grace Lasker, Lake Washington Institute of Technology; Walden University Sandy Latourelle, SUNY Plattsburgh Theo Light, Shippensburg University Clark Lindgren, Grinnell College James Malcolm, University of Redlands Mark Meade, Jacksonville State University Richard Merritt, Houston Community College James Mickle, North Carolina State University Jasleen Mishra, Houston Community College Dudley Moon, Albany College of Pharmacy and Health Sciences Shobhana Natarajan, Brookhaven College Jonas Okeagu, Fayetteville State University Diana Oliveras, University of Colorado Boulder John Peters, College of Charleston Joel Piperberg, Millersville University Johanna Porter-Kelley, Winston-Salem State University Robyn Puffenbarger, Bridgewater College Dennis Revie, California Lutheran University Ann Rushing, Baylor University Sangha Saha, City College of Chicago Edward Saiff, Ramapo College of New Jersey Brian Shmaefsky, Lone Star College System Robert Sizemore, Alcorn State University Marc Smith, Sinclair Community College Frederick Spiegel, University of Arkansas Frederick Sproull, La Roche College Bob Sullivan, Marist College Mark Sutherland, Hendrix College Toure Thompson, Alabama A&M University Scott Thomson, University of Wisconsin – Parkside Allison van de Meene, University of Melbourne Mary White, Southeastern Louisiana University Steven Wilt, Bellarmine University James Wise, Hampton University Renna Wolfe Virginia Young, Mercer University Leslie Zeman, University of Washington Daniel Zurek, Pittsburg State University Shobhana Natarajan, Alcon Laboratories, Inc. Senior Contributing Authors Yael Avissar (Cell Biology), Rhode Island College Jung Choi (Genetics), Georgia Institute of Technology Jean DeSaix (Evolution), University of North Carolina at Chapel Hill Vladimir Jurukovski (Animal Physiology), Suffolk County Community College Robert Wise (Plant Biology), University of Wisconsin, Oshkosh Connie Rye (General Content Lead), East Mississippi Community College	oercommons	2025-03-18T00:35:16.142556	null	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/14935/overview", "title": "Biology, Preface to Biology", "author": null }
https://oercommons.org/courseware/lesson/84261/overview	BIOL 011 Syllabus Biology 011 Overview This course will introduce biology to non-science majors, which provides an introduction to biochemistry, cell biology, genetics, evolution, biodiversity, physiology, ecology, and environmental biology. In this course we will actually be doing biological research. We will be working on researching real-life problems and the ways they may be solved. You will be working online with teammates to complete background research and solve problems. Syllabus and Sample Assignment This course will introduce biology to non-science majors, which provides an introduction to biochemistry, cell biology, genetics, evolution, biodiversity, physiology, ecology, and environmental biology. In this course we will actually be doing biological research. We will be working on researching real-life problems and the ways they may be solved. You will be working online with teammates to complete background research and solve problems.	oercommons	2025-03-18T00:35:16.162492	Open for Antiracism Program (OFAR)	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/84261/overview", "title": "Biology 011", "author": "Syllabus" }
https://oercommons.org/courseware/lesson/102004/overview	Education Standards AI Writing Prompts Overview This resource includes traditional writing prompts as well as prompts and assignments that utilize AI-generated text. It covers the fields of Creative Writing, Composition, and Business and Technical Writing. Introduction This resource provides a repository of writing prompts that writing instructors can use in their classes. Please feel free to use anything you find here or remix it. If you would like to add to this resource, you can copy the entire thing, and create your own. Otherwise, you can email your prompt suggestions to brewerwriter@gmail.com. For now, this resource will cover Creative Writing, Composition, and Business/Tech Writing. Creative Writing Prompts I put creative writing first, because it seems to be the most amenable to AI text generation. Take your dialogue and ask the chatbot to rewrite it in, say, the style of Tarantino or Mamet. ============ Summarize the plot of a famous work of literature. Then ask AI to write this in a completely different genre (or at least to give you the outline for rewriting the entire novel in a new genre). For example, have it rewrite Frankenstein as a romantic comedy. ============ Ask AI to write a poem in a very challenging form with several other restrictions. For example, you could ask it to write a crown of sonnets in anapestic tetrameter. Now, it won't be able to do that, but see if it doesn't give you some ideas for a poem anyway. Composition Prompts AI-resistant prompts: I’ve used the following AI-resistant writing prompt in both composition and creative writing classes. I usually require students to write early drafts/answers by hand, which keeps the writing process more manual than artificial. (The hand-eye-brain connection has been well documented in writing studies!) At the end, though, we do turn to ChatGPT to improve our writing and to cobble our answers together into an essay. Here’s the prompt: Look at the art in the hallway and throughout the building. Pick only one painting, portrait, landscape, 3D artwork, or mural panel to write about. You may write about the mural called “The Spirit of the Land Grant College,” which is found above the entrance to the HSSE Library. You may not do any research in these initial drafting stages. That will come later. Describe the painting by paying attention to details. * What specifics make it unique? * What theme do you see here? Where do you see it? (Be specific, in other words.) * How do the parts make a whole or what doesn’t fit? * Describe an artistic technique or its effect on you as you look. Discuss colors. * What does this person say? What’s the tone of voice, personality, or context? * Where is this? What happens or does not happen here? * What was the painter thinking? AI Component: Ask a chatbot, such as ChatGPT, how you could improve your answers to the questions above in terms of specificity, clarity, and vocabulary. Then engage it in a conversation about how you could take your answers and write an essay with them. Include a transcript of your conversation with the chatbot or AI-text-generator in your final submission, along with a reflection statement about the process.” ========= Clothes Prompts for Description: Think about a single article of clothing that you own. Pick something you’ve had for years or your go-to outfit for certain situations (working, relaxing with friends, sleepovers, game day, formal wear). Describe it in great detail, far beyond the words below. You can talk about the size and fit, sure, but how does it feel in your hands, on your shoulder, head, or waistline? Where is it worn or stained? Describe that. What colors can you see? Don’t just tell me about the red stiletto; tell me about the shape of the sole on the bottom of the spike. It isn’t round, is it? Enumerate things. Work around the clock (12/3/6/9), describing all sides and angles, and don’t forget the inside of the garment, shoe, or hat. Shoes: your most comfortable house slippers rainy day shoes Summer/beachwear Work boots Your favorite running shoes Pumps, stilettoes Tops: shawl Polo Shirt that you wear when you… / when you want to … Flannel windbreaker hoodie camisole tank blouse T-shirt Bottoms: mini skirt khakis sweatpants pajamas favorite jeans Yoga/bicycle shorts/shorts I wear when you… / when you want to… underwear socks classy shorts Hats: baseball cap bowler hardhat cowboy/girl hat beach/sun hat FREEWRITE: fill at least two paragraphs with as much detail as you can about your chosen article of clothing. AI Component: Have a conversation with a chatbot about how to organize your writing about your article of clothing. Also, you might do a little research to find the right vocabulary (so that you don't have to say "that thing that looks like clear tape around the end of my shoelaces"). ============== Tell a story: Put yourself (or a character you’ve invented) in that piece of clothing. Tell a story in which a bit of the description you used above comes into play. You can use real dialogue (or fake) or no dialogue. If you can’t remember the actual words, make some up. Build on memories or create them. Otherwise, you can write in the first person about another character’s clothing. Or you can write about someone else’s garment that you now own—something that means a lot to you. Don’t just focus on your feelings or emotions! Note changes over time, if any, or different occasions when you’ve worn this item. The point is to use your senses to describe it: * How does it smell? * How does it feel? * How does it look? * Does it make a sound? Business and Technical Writing Prompts Write a company profile for a regional or national company. You can also pick a nonprofit. Try prompting ChatGPT to write the first draft. However, this chatbot does not use the most up-to-date information. Therefore, you'll need to do research. Start with the company website, but don't forget its social media presence as well. Follow or join platforms where this company is active. Tell the story of the company's history. They will likely leave out the rough spots. Check local newspapers, online reviews, former employee blogs, or social media posts from customers. These can help you make this an objective history. If you use ChatGPT for this section, be sure to double check the facts. Sometimes it just makes up falsehoods, so edit the history carefully. What products or services is this company known for? Has it won any awards? Can you find opinions from customers, vendors, employees, or neighbors of this organization or its products? Can you find their company rating with the Better Business Bureau or similar websites? What business sectors do they operate in? (Retail, financial services, charity, website design?) What is the market outlook for such companies? How do they compare to similar companies? Would an investor be wise to invest in them? ChatGPT can help you orient yourself to some of these ideas, but the market changes daily, so do your own research. What are the values, goals, and mission statements of this company? Again, you may need to move beyond their website and infer things that they don't necessarily say about themselves. Use your critical thinking skills to do so. Is this company growing, shrinking, or merging with another organization? Search through job advertisements on sites such as Indeed, LinkedIn, and ZipRecruiter. See if you can guess the new directions for this company based on job ads they have posted recently. What is their current address? How do they ask to be contacted? Who are the leaders in this company, and what's the contact information for them? Writing for Yourself or Your Company on LinkedIn You need to learn how to write your LinkedIN profile. You also should know about how to market yourself or your products on LinkedIn. PROMPT: You are a career building expert. I am a young student. How should I write my LinkedIn profile summary? Use facts only. Give examples of language that I should use and also what to avoid. Answer: Sure, I'd be happy to help you with that. Here are some tips for writing a strong LinkedIn profile summary as a young student: 1. Keep it concise: Your LinkedIn summary should be a brief overview of your professional experience and goals. Aim for a summary of 3-5 sentences or bullet points. 2. Highlight your unique selling points: Focus on your strengths and achievements that make you stand out. For example, you might mention any academic honors or awards, relevant coursework, or extracurricular activities. 3. Use action-oriented language: Start your sentences with action verbs that showcase your skills and accomplishments. For example, instead of saying "I am interested in marketing," say "I have experience creating and executing successful marketing campaigns." 4. Avoid clichés and vague language: Phrases like "team player" and "hard worker" are overused and don't provide specific details about your skills or accomplishments. Also, avoid using buzzwords and jargon that may not be easily understood by everyone. 5. Customize for your audience: Consider the industry or job function you're interested in and tailor your summary to highlight relevant skills or experience. Here's an example of a strong LinkedIn summary for a young student: "Motivated student with a strong academic record and passion for marketing. Completed coursework in digital marketing and advertising, and gained hands-on experience through internships at XYZ company and ABC nonprofit. Excited to apply my skills and knowledge to a marketing role in the technology industry." Remember to proofread your summary and ensure that it is free of spelling or grammatical errors. A well-crafted LinkedIn summary can make a big difference in attracting attention from potential employers or professional connections. PROMPT: I want you to be an expert in <topic>. You have all the information about anything to do with <topic>. I will ask about different subjects within <topic>. You will provide me with clear, concise, accurate information. Ensure that you only respond back with answers that you know are true or factual. Please limit your responses to the specific information requested. Avoid providing unnecessary details. Topic = LinkedIN Marketing Sure, I'll do my best to assist you with your questions about LinkedIn marketing. Please go ahead and ask me any specific questions you have on this topic. Question: Do I have to own a business to engage in LinkedIn marketing? If not, how do I get started? Answer: No, you don't need to own a business to engage in LinkedIn marketing. LinkedIn provides opportunities for individuals to market themselves as professionals and to build their personal brand. Here are some steps to get started with LinkedIn marketing as an individual: 1. Create a LinkedIn profile: The first step is to create a LinkedIn profile that highlights your professional skills, experience, and accomplishments. Ensure that your profile is complete and professional-looking. 2. Build your network: Connect with other professionals in your industry, clients, and colleagues on LinkedIn to expand your network. Share your profile link with your contacts to invite them to connect with you. 3. Share valuable content: Share relevant articles, insights, and updates related to your industry or area of expertise. This will help you establish yourself as a thought leader and attract more followers. 4. Participate in LinkedIn groups: Join LinkedIn groups related to your industry and participate in discussions to engage with other professionals and expand your reach. 5. Consider LinkedIn advertising: If you have a budget for advertising, LinkedIn offers a variety of advertising options to target specific audiences based on their job title, company, and other demographics. By following these steps, you can effectively leverage LinkedIn marketing to build your personal brand and expand your professional network. Q: How much does it cost for an individual to market themselves on LinkedIn? Are there multiple price points? What different services do they offer for targeting specific audiences? A: Marketing yourself on LinkedIn as an individual is free, but if you want to take advantage of additional features and advertising options, there may be costs involved. LinkedIn offers a range of advertising options that allow you to target specific audiences based on their job title, industry, location, and other demographics. These advertising options include sponsored content, sponsored InMail, display ads, and dynamic ads. The cost of advertising on LinkedIn varies depending on the advertising option you choose and the size of your target audience. LinkedIn advertising operates on a bidding system, where advertisers bid for ad placement and pay-per-click (PPC) or per-impression (CPM). You can set your own budget and bid for ad placement, and LinkedIn will provide an estimated range for the minimum bid required to reach your target audience. In terms of pricing, LinkedIn offers multiple price points for advertising depending on your budget and advertising goals. For example, sponsored content ads can start at $10 per day, while sponsored InMail campaigns can cost upwards of $3000 depending on the size of the target audience and the number of messages sent. LinkedIn also offers targeting options such as job title, job function, company size, industry, location, and more. These targeting options allow you to reach the most relevant audience for your business or professional goals. Overall, the cost of LinkedIn marketing can vary widely depending on your goals, targeting options, and budget. LinkedIn provides a range of options to suit different marketing needs and budgets. ================== Write a company profile for a regional or national company. You can also pick a nonprofit. Try prompting ChatGPT to write the first draft. However, this chatbot does not use the most up-to-date information. Therefore, you'll need to do research. Start with the company website, but don't forget its social media presence as well. Follow or join platforms where this company is active. Tell the story of the company's history. They will likely leave out the rough spots. Check local newspapers, online reviews, former employee blogs, or social media posts from customers. These can help you make this an objective history. If you use ChatGPT for this section, be sure to double check the facts. Sometimes it just makes up falsehoods, so edit the history carefully. What products or services is this company known for? Has it won any awards? Can you find opinions from customers, vendors, employees, or neighbors of this organization or its products? Can you find their company rating with the Better Business Bureau or similar websites? What business sectors do they operate in? (Retail, financial services, charity, website design?) What is the market outlook for such companies? How do they compare to similar companies? Would an investor be wise to invest in them? ChatGPT can help you orient yourself to some of these ideas, but the market changes daily, so do your own research. What are the values, goals, and mission statements of this company? Again, you may need to move beyond their website and infer things that they don't necessarily say about themselves. Use your critical thinking skills to do so. Is this company growing, shrinking, or merging with another organization? Search through job advertisements on sites such as Indeed, LinkedIn, and ZipRecruiter. See if you can guess the new directions for this company based on job ads they have posted recently. What is their current address? How do they ask to be contacted? Who are the leaders in this company, and what's the contact information for them? Writing for Yourself or Your Company on LinkedIn You need to learn how to write your LinkedIN profile. You also should know about how to market yourself or your products on LinkedIn. PROMPT: You are a career building expert. I am a young student. How should I write my LinkedIn profile summary? Use facts only. Give examples of language that I should use and also what to avoid. Answer: Sure, I'd be happy to help you with that. Here are some tips for writing a strong LinkedIn profile summary as a young student: Keep it concise: Your LinkedIn summary should be a brief overview of your professional experience and goals. Aim for a summary of 3-5 sentences or bullet points. Highlight your unique selling points: Focus on your strengths and achievements that make you stand out. For example, you might mention any academic honors or awards, relevant coursework, or extracurricular activities. Use action-oriented language: Start your sentences with action verbs that showcase your skills and accomplishments. For example, instead of saying "I am interested in marketing," say "I have experience creating and executing successful marketing campaigns." Avoid clichés and vague language: Phrases like "team player" and "hard worker" are overused and don't provide specific details about your skills or accomplishments. Also, avoid using buzzwords and jargon that may not be easily understood by everyone. Customize for your audience: Consider the industry or job function you're interested in and tailor your summary to highlight relevant skills or experience. Here's an example of a strong LinkedIn summary for a young student: "Motivated student with a strong academic record and passion for marketing. Completed coursework in digital marketing and advertising, and gained hands-on experience through internships at XYZ company and ABC nonprofit. Excited to apply my skills and knowledge to a marketing role in the technology industry." Remember to proofread your summary and ensure that it is free of spelling or grammatical errors. A well-crafted LinkedIn summary can make a big difference in attracting attention from potential employers or professional connections. PROMPT: I want you to be an expert in <topic>. You have all the information about anything to do with <topic>. I will ask about different subjects within <topic>. You will provide me with clear, concise, accurate information. Ensure that you only respond back with answers that you know are true or factual. Please limit your responses to the specific information requested. Avoid providing unnecessary details. Topic = LinkedIN Marketing Sure, I'll do my best to assist you with your questions about LinkedIn marketing. Please go ahead and ask me any specific questions you have on this topic. Question: Do I have to own a business to engage in LinkedIn marketing? If not, how do I get started? Answer: No, you don't need to own a business to engage in LinkedIn marketing. LinkedIn provides opportunities for individuals to market themselves as professionals and to build their personal brand. Here are some steps to get started with LinkedIn marketing as an individual: Create a LinkedIn profile: The first step is to create a LinkedIn profile that highlights your professional skills, experience, and accomplishments. Ensure that your profile is complete and professional-looking. Build your network: Connect with other professionals in your industry, clients, and colleagues on LinkedIn to expand your network. Share your profile link with your contacts to invite them to connect with you. Share valuable content: Share relevant articles, insights, and updates related to your industry or area of expertise. This will help you establish yourself as a thought leader and attract more followers. Participate in LinkedIn groups: Join LinkedIn groups related to your industry and participate in discussions to engage with other professionals and expand your reach. Consider LinkedIn advertising: If you have a budget for advertising, LinkedIn offers a variety of advertising options to target specific audiences based on their job title, company, and other demographics. By following these steps, you can effectively leverage LinkedIn marketing to build your personal brand and expand your professional network. Q: How much does it cost for an individual to market themselves on LinkedIn? Are there multiple price points? What different services do they offer for targeting specific audiences? A: Marketing yourself on LinkedIn as an individual is free, but if you want to take advantage of additional features and advertising options, there may be costs involved. LinkedIn offers a range of advertising options that allow you to target specific audiences based on their job title, industry, location, and other demographics. These advertising options include sponsored content, sponsored InMail, display ads, and dynamic ads. The cost of advertising on LinkedIn varies depending on the advertising option you choose and the size of your target audience. LinkedIn advertising operates on a bidding system, where advertisers bid for ad placement and pay-per-click (PPC) or per-impression (CPM). You can set your own budget and bid for ad placement, and LinkedIn will provide an estimated range for the minimum bid required to reach your target audience. In terms of pricing, LinkedIn offers multiple price points for advertising depending on your budget and advertising goals. For example, sponsored content ads can start at $10 per day, while sponsored InMail campaigns can cost upwards of $3000 depending on the size of the target audience and the number of messages sent. LinkedIn also offers targeting options such as job title, job function, company size, industry, location, and more. These targeting options allow you to reach the most relevant audience for your business or professional goals. Overall, the cost of LinkedIn marketing can vary widely depending on your goals, targeting options, and budget. LinkedIn provides a range of options to suit different marketing needs and budgets.	oercommons	2025-03-18T00:35:16.204909	Assessment	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/102004/overview", "title": "AI Writing Prompts", "author": "English Language Arts" }
https://oercommons.org/courseware/lesson/89735/overview	Hist 2010-2020 Open Stax Textbook Overview U.S. History is designed to meet the scope and sequence requirements of most introductory courses. The text provides a balanced approach to U.S. history, considering the people, events, and ideas that have shaped the United States from both the top down (politics, economics, diplomacy) and bottom up (eyewitness accounts, lived experience). U.S. History covers key forces that form the American experience, with particular attention to issues of race, class, and gender. Corbett, P. Scott, Volker Janssen, John M Lund, Todd Pfannestiel, Sylvie Waskiewicz, and Paul Vickery. U.S. History. Houston, TX: OpenStax, 2014. https://openstax.org/books/us-history/pages/1-introduction . U.S. History Textbook U.S. History is designed to meet the scope and sequence requirements of most introductory courses. The text provides a balanced approach to U.S. history, considering the people, events, and ideas that have shaped the United States from both the top down (politics, economics, diplomacy) and bottom up (eyewitness accounts, lived experience). U.S. History covers key forces that form the American experience, with particular attention to issues of race, class, and gender. From OpenStax	oercommons	2025-03-18T00:35:16.219595	Christopher Gilliland	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/89735/overview", "title": "Hist 2010-2020 Open Stax Textbook", "author": "Susan Jennings" }
https://oercommons.org/courseware/lesson/72731/overview	The Tissue Level of Organization Overview Information on tissues for anatomy and physiology. Introduction Figure 4.1 Micrograph of Cervical Tissue This figure is a view of the regular architecture of normal tissue contrasted with the irregular arrangement of cancerous cells. (credit: “Haymanj”/Wikimedia Commons) CHAPTER OBJECTIVES After studying this chapter, you will be able to: - Identify the main tissue types and discuss their roles in the human body - Identify the four types of tissue membranes and the characteristics of each that make them functional - Explain the functions of various epithelial tissues and how their forms enable their functions - Explain the functions of various connective tissues and how their forms enable their functions - Describe the characteristics of muscle tissue and how these enable function - Discuss the characteristics of nervous tissue and how these enable information processing and control of muscular and glandular activities The body contains at least 200 distinct cell types. These cells contain essentially the same internal structures yet they vary enormously in shape and function. The different types of cells are not randomly distributed throughout the body; rather they occur in organized layers, a level of organization referred to as tissue. The micrograph that opens this chapter shows the high degree of organization among different types of cells in the tissue of the cervix. You can also see how that organization breaks down when cancer takes over the regular mitotic functioning of a cell. The variety in shape reflects the many different roles that cells fulfill in your body. The human body starts as a single cell at fertilization. As this fertilized egg divides, it gives rise to trillions of cells, each built from the same blueprint, but organizing into tissues and becoming irreversibly committed to a developmental pathway. Types of Tissues - Identify the four main tissue types - Discuss the functions of each tissue type - Relate the structure of each tissue type to their function - Discuss the embryonic origin of tissue - Identify the three major germ layers - Identify the main types of tissue membranes The term tissue is used to describe a group of cells found together in the body. The cells within a tissue share a common embryonic origin. Microscopic observation reveals that the cells in a tissue share morphological features and are arranged in an orderly pattern that achieves the tissue’s functions. From the evolutionary perspective, tissues appear in more complex organisms. For example, multicellular protists, ancient eukaryotes, do not have cells organized into tissues. Although there are many types of cells in the human body, they are organized into four broad categories of tissues: epithelial, connective, muscle, and nervous. Each of these categories is characterized by specific functions that contribute to the overall health and maintenance of the body. A disruption of the structure is a sign of injury or disease. Such changes can be detected through histology, the microscopic study of tissue appearance, organization, and function. The Four Types of Tissues Epithelial tissue, also referred to as epithelium, refers to the sheets of cells that cover exterior surfaces of the body, lines internal cavities and passageways, and forms certain glands. Connective tissue, as its name implies, binds the cells and organs of the body together and functions in the protection, support, and integration of all parts of the body. Muscle tissue is excitable, responding to stimulation and contracting to provide movement, and occurs as three major types: skeletal (voluntary) muscle, smooth muscle, and cardiac muscle in the heart. Nervous tissue is also excitable, allowing the propagation of electrochemical signals in the form of nerve impulses that communicate between different regions of the body (Figure 4.2). The next level of organization is the organ, where several types of tissues come together to form a working unit. Just as knowing the structure and function of cells helps you in your study of tissues, knowledge of tissues will help you understand how organs function. The epithelial and connective tissues are discussed in detail in this chapter. Muscle and nervous tissues will be discussed only briefly in this chapter. Figure 4.2 Four Types of Tissue: Body The four types of tissues are exemplified in nervous tissue, stratified squamous epithelial tissue, cardiac muscle tissue, and connective tissue in small intestine. Clockwise from nervous tissue, LM × 872, LM × 282, LM × 460, LM × 800. (Micrographs provided by the Regents of University of Michigan Medical School © 2012) Embryonic Origin of Tissues The zygote, or fertilized egg, is a single cell formed by the fusion of an egg and sperm. After fertilization the zygote gives rise to rapid mitotic cycles, generating many cells to form the embryo. The first embryonic cells generated have the ability to differentiate into any type of cell in the body and, as such, are called totipotent, meaning each has the capacity to divide, differentiate, and develop into a new organism. As cell proliferation progresses, three major cell lineages are established within the embryo. As explained in a later chapter, each of these lineages of embryonic cells forms the distinct germ layers from which all the tissues and organs of the human body eventually form. Each germ layer is identified by its relative position: ectoderm (ecto- = “outer”), mesoderm (meso- = “middle”), and endoderm (endo- = “inner”). Figure 4.3 shows the types of tissues and organs associated with the each of the three germ layers. Note that epithelial tissue originates in all three layers, whereas nervous tissue derives primarily from the ectoderm and muscle tissue from mesoderm. Figure 4.3 Embryonic Origin of Tissues and Major Organs INTERACTIVE LINK View this slideshow to learn more about stem cells. How do somatic stem cells differ from embryonic stem cells? Tissue Membranes A tissue membrane is a thin layer or sheet of cells that covers the outside of the body (for example, skin), the organs (for example, pericardium), internal passageways that lead to the exterior of the body (for example, abdominal mesenteries), and the lining of the moveable joint cavities. There are two basic types of tissue membranes: connective tissue and epithelial membranes (Figure 4.4). Figure 4.4 Tissue Membranes The two broad categories of tissue membranes in the body are (1) connective tissue membranes, which include synovial membranes, and (2) epithelial membranes, which include mucous membranes, serous membranes, and the cutaneous membrane, in other words, the skin. Connective Tissue Membranes The connective tissue membrane is formed solely from connective tissue. These membranes encapsulate organs, such as the kidneys, and line our movable joints. A synovial membrane is a type of connective tissue membrane that lines the cavity of a freely movable joint. For example, synovial membranes surround the joints of the shoulder, elbow, and knee. Fibroblasts in the inner layer of the synovial membrane release hyaluronan into the joint cavity. The hyaluronan effectively traps available water to form the synovial fluid, a natural lubricant that enables the bones of a joint to move freely against one another without much friction. This synovial fluid readily exchanges water and nutrients with blood, as do all body fluids. Epithelial Membranes The epithelial membrane is composed of epithelium attached to a layer of connective tissue, for example, your skin. The mucous membrane is also a composite of connective and epithelial tissues. Sometimes called mucosae, these epithelial membranes line the body cavities and hollow passageways that open to the external environment, and include the digestive, respiratory, excretory, and reproductive tracts. Mucous, produced by the epithelial exocrine glands, covers the epithelial layer. The underlying connective tissue, called the lamina propria (literally “own layer”), help support the fragile epithelial layer. A serous membrane is an epithelial membrane composed of mesodermally derived epithelium called the mesothelium that is supported by connective tissue. These membranes line the coelomic cavities of the body, that is, those cavities that do not open to the outside, and they cover the organs located within those cavities. They are essentially membranous bags, with mesothelium lining the inside and connective tissue on the outside. Serous fluid secreted by the cells of the thin squamous mesothelium lubricates the membrane and reduces abrasion and friction between organs. Serous membranes are identified according locations. Three serous membranes line the thoracic cavity; the two pleura that cover the lungs and the pericardium that covers the heart. A fourth, the peritoneum, is the serous membrane in the abdominal cavity that covers abdominal organs and forms double sheets of mesenteries that suspend many of the digestive organs. The skin is an epithelial membrane also called the cutaneous membrane. It is a stratified squamous epithelial membrane resting on top of connective tissue. The apical surface of this membrane is exposed to the external environment and is covered with dead, keratinized cells that help protect the body from desiccation and pathogens. Epithelial Tissue - Explain the structure and function of epithelial tissue - Distinguish between tight junctions, anchoring junctions, and gap junctions - Distinguish between simple epithelia and stratified epithelia, as well as between squamous, cuboidal, and columnar epithelia - Describe the structure and function of endocrine and exocrine glands and their respective secretions Most epithelial tissues are essentially large sheets of cells covering all the surfaces of the body exposed to the outside world and lining the outside of organs. Epithelium also forms much of the glandular tissue of the body. Skin is not the only area of the body exposed to the outside. Other areas include the airways, the digestive tract, as well as the urinary and reproductive systems, all of which are lined by an epithelium. Hollow organs and body cavities that do not connect to the exterior of the body, which includes, blood vessels and serous membranes, are lined by endothelium (plural = endothelia), which is a type of epithelium. Epithelial cells derive from all three major embryonic layers. The epithelia lining the skin, parts of the mouth and nose, and the anus develop from the ectoderm. Cells lining the airways and most of the digestive system originate in the endoderm. The epithelium that lines vessels in the lymphatic and cardiovascular system derives from the mesoderm and is called an endothelium. All epithelia share some important structural and functional features. This tissue is highly cellular, with little or no extracellular material present between cells. Adjoining cells form a specialized intercellular connection between their cell membranes called a cell junction. The epithelial cells exhibit polarity with differences in structure and function between the exposed or apicalfacing surface of the cell and the basal surface close to the underlying body structures. The basal lamina, a mixture of glycoproteins and collagen, provides an attachment site for the epithelium, separating it from underlying connective tissue. The basal lamina attaches to a reticular lamina, which is secreted by the underlying connective tissue, forming a basement membrane that helps hold it all together. Epithelial tissues are nearly completely avascular. For instance, no blood vessels cross the basement membrane to enter the tissue, and nutrients must come by diffusion or absorption from underlying tissues or the surface. Many epithelial tissues are capable of rapidly replacing damaged and dead cells. Sloughing off of damaged or dead cells is a characteristic of surface epithelium and allows our airways and digestive tracts to rapidly replace damaged cells with new cells. Generalized Functions of Epithelial Tissue Epithelial tissues provide the body’s first line of protection from physical, chemical, and biological wear and tear. The cells of an epithelium act as gatekeepers of the body controlling permeability and allowing selective transfer of materials across a physical barrier. All substances that enter the body must cross an epithelium. Some epithelia often include structural features that allow the selective transport of molecules and ions across their cell membranes. Many epithelial cells are capable of secretion and release mucous and specific chemical compounds onto their apical surfaces. The epithelium of the small intestine releases digestive enzymes, for example. Cells lining the respiratory tract secrete mucous that traps incoming microorganisms and particles. A glandular epithelium contains many secretory cells. The Epithelial Cell Epithelial cells are typically characterized by the polarized distribution of organelles and membrane-bound proteins between their basal and apical surfaces. Particular structures found in some epithelial cells are an adaptation to specific functions. Certain organelles are segregated to the basal sides, whereas other organelles and extensions, such as cilia, when present, are on the apical surface. Cilia are microscopic extensions of the apical cell membrane that are supported by microtubules. They beat in unison and move fluids as well as trapped particles. Ciliated epithelium lines the ventricles of the brain where it helps circulate the cerebrospinal fluid. The ciliated epithelium of your airway forms a mucociliary escalator that sweeps particles of dust and pathogens trapped in the secreted mucous toward the throat. It is called an escalator because it continuously pushes mucous with trapped particles upward. In contrast, nasal cilia sweep the mucous blanket down towards your throat. In both cases, the transported materials are usually swallowed, and end up in the acidic environment of your stomach. Cell to Cell Junctions Cells of epithelia are closely connected and are not separated by intracellular material. Three basic types of connections allow varying degrees of interaction between the cells: tight junctions, anchoring junctions, and gap junctions (Figure 4.5). Figure 4.5 Types of Cell Junctions The three basic types of cell-to-cell junctions are tight junctions, gap junctions, and anchoring junctions. At one end of the spectrum is the tight junction, which separates the cells into apical and basal compartments. When two adjacent epithelial cells form a tight junction, there is no extracellular space between them and the movement of substances through the extracellular space between the cells is blocked. This enables the epithelia to act as selective barriers. An anchoring junction includes several types of cell junctions that help stabilize epithelial tissues. Anchoring junctions are common on the lateral and basal surfaces of cells where they provide strong and flexible connections. There are three types of anchoring junctions: desmosomes, hemidesmosomes, and adherens. Desmosomes occur in patches on the membranes of cells. The patches are structural proteins on the inner surface of the cell’s membrane. The adhesion molecule, cadherin, is embedded in these patches and projects through the cell membrane to link with the cadherin molecules of adjacent cells. These connections are especially important in holding cells together. Hemidesmosomes, which look like half a desmosome, link cells to the extracellular matrix, for example, the basal lamina. While similar in appearance to desmosomes, they include the adhesion proteins called integrins rather than cadherins. Adherens junctions use either cadherins or integrins depending on whether they are linking to other cells or matrix. The junctions are characterized by the presence of the contractile protein actin located on the cytoplasmic surface of the cell membrane. The actin can connect isolated patches or form a belt-like structure inside the cell. These junctions influence the shape and folding of the epithelial tissue. In contrast with the tight and anchoring junctions, a gap junction forms an intercellular passageway between the membranes of adjacent cells to facilitate the movement of small molecules and ions between the cytoplasm of adjacent cells. These junctions allow electrical and metabolic coupling of adjacent cells, which coordinates function in large groups of cells. Classification of Epithelial Tissues Epithelial tissues are classified according to the shape of the cells and number of the cell layers formed (Figure 4.6). Cell shapes can be squamous (flattened and thin), cuboidal (boxy, as wide as it is tall), or columnar (rectangular, taller than it is wide). Similarly, the number of cell layers in the tissue can be one—where every cell rests on the basal lamina—which is a simple epithelium, or more than one, which is a stratified epithelium and only the basal layer of cells rests on the basal lamina. Pseudostratified (pseudo- = “false”) describes tissue with a single layer of irregularly shaped cells that give the appearance of more than one layer. Transitional describes a form of specialized stratified epithelium in which the shape of the cells can vary. Figure 4.6 Cells of Epithelial Tissue Simple epithelial tissue is organized as a single layer of cells and stratified epithelial tissue is formed by several layers of cells. Simple Epithelium The shape of the cells in the single cell layer of simple epithelium reflects the functioning of those cells. The cells in simple squamous epithelium have the appearance of thin scales. Squamous cell nuclei tend to be flat, horizontal, and elliptical, mirroring the form of the cell. The endothelium is the epithelial tissue that lines vessels of the lymphatic and cardiovascular system, and it is made up of a single layer of squamous cells. Simple squamous epithelium, because of the thinness of the cell, is present where rapid passage of chemical compounds is observed. The alveoli of lungs where gases diffuse, segments of kidney tubules, and the lining of capillaries are also made of simple squamous epithelial tissue. The mesothelium is a simple squamous epithelium that forms the surface layer of the serous membrane that lines body cavities and internal organs. Its primary function is to provide a smooth and protective surface. Mesothelial cells are squamous epithelial cells that secrete a fluid that lubricates the mesothelium. In simple cuboidal epithelium, the nucleus of the box-like cells appears round and is generally located near the center of the cell. These epithelia are active in the secretion and absorptions of molecules. Simple cuboidal epithelia are observed in the lining of the kidney tubules and in the ducts of glands. In simple columnar epithelium, the nucleus of the tall column-like cells tends to be elongated and located in the basal end of the cells. Like the cuboidal epithelia, this epithelium is active in the absorption and secretion of molecules. Simple columnar epithelium forms the lining of some sections of the digestive system and parts of the female reproductive tract. Ciliated columnar epithelium is composed of simple columnar epithelial cells with cilia on their apical surfaces. These epithelial cells are found in the lining of the fallopian tubes and parts of the respiratory system, where the beating of the cilia helps remove particulate matter. Pseudostratified columnar epithelium is a type of epithelium that appears to be stratified but instead consists of a single layer of irregularly shaped and differently sized columnar cells. In pseudostratified epithelium, nuclei of neighboring cells appear at different levels rather than clustered in the basal end. The arrangement gives the appearance of stratification; but in fact all the cells are in contact with the basal lamina, although some do not reach the apical surface. Pseudostratified columnar epithelium is found in the respiratory tract, where some of these cells have cilia. Both simple and pseudostratified columnar epithelia are heterogeneous epithelia because they include additional types of cells interspersed among the epithelial cells. For example, a goblet cell is a mucous-secreting unicellular “gland” interspersed between the columnar epithelial cells of mucous membranes (Figure 4.7). Figure 4.7 Goblet Cell (a) In the lining of the small intestine, columnar epithelium cells are interspersed with goblet cells. (b) The arrows in this micrograph point to the mucous-secreting goblet cells. LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK View the University of Michigan WebScope to explore the tissue sample in greater detail. Stratified Epithelium A stratified epithelium consists of several stacked layers of cells. This epithelium protects against physical and chemical wear and tear. The stratified epithelium is named by the shape of the most apical layer of cells, closest to the free space. Stratified squamous epithelium is the most common type of stratified epithelium in the human body. The apical cells are squamous, whereas the basal layer contains either columnar or cuboidal cells. The top layer may be covered with dead cells filled with keratin. Mammalian skin is an example of this dry, keratinized, stratified squamous epithelium. The lining of the mouth cavity is an example of an unkeratinized, stratified squamous epithelium. Stratified cuboidal epithelium and stratified columnar epithelium can also be found in certain glands and ducts, but are uncommon in the human body. Another kind of stratified epithelium is transitional epithelium, so-called because of the gradual changes in the shapes of the apical cells as the bladder fills with urine. It is found only in the urinary system, specifically the ureters and urinary bladder. When the bladder is empty, this epithelium is convoluted and has cuboidal apical cells with convex, umbrella shaped, apical surfaces. As the bladder fills with urine, this epithelium loses its convolutions and the apical cells transition from cuboidal to squamous. It appears thicker and more multi-layered when the bladder is empty, and more stretched out and less stratified when the bladder is full and distended. Figure 4.8 summarizes the different categories of epithelial cell tissue cells. Figure 4.8 Summary of Epithelial Tissue Cells INTERACTIVE LINK Watch this video to find out more about the anatomy of epithelial tissues. Where in the body would one find non-keratinizing stratified squamous epithelium? Glandular Epithelium A gland is a structure made up of one or more cells modified to synthesize and secrete chemical substances. Most glands consist of groups of epithelial cells. A gland can be classified as an endocrine gland, a ductless gland that releases secretions directly into surrounding tissues and fluids (endo- = “inside”), or an exocrine gland whose secretions leave through a duct that opens directly, or indirectly, to the external environment (exo- = “outside”). Endocrine Glands The secretions of endocrine glands are called hormones. Hormones are released into the interstitial fluid, diffused into the bloodstream, and delivered to targets, in other words, cells that have receptors to bind the hormones. The endocrine system is part of a major regulatory system coordinating the regulation and integration of body responses. A few examples of endocrine glands include the anterior pituitary, thymus, adrenal cortex, and gonads. Exocrine Glands Exocrine glands release their contents through a duct that leads to the epithelial surface. Mucous, sweat, saliva, and breast milk are all examples of secretions from exocrine glands. They are all discharged through tubular ducts. Secretions into the lumen of the gastrointestinal tract, technically outside of the body, are of the exocrine category. Glandular Structure Exocrine glands are classified as either unicellular or multicellular. The unicellular glands are scattered single cells, such as goblet cells, found in the mucous membranes of the small and large intestine. The multicellular exocrine glands known as serous glands develop from simple epithelium to form a secretory surface that secretes directly into an inner cavity. These glands line the internal cavities of the abdomen and chest and release their secretions directly into the cavities. Other multicellular exocrine glands release their contents through a tubular duct. The duct is single in a simple gland but in compound glands is divided into one or more branches (Figure 4.9). In tubular glands, the ducts can be straight or coiled, whereas tubes that form pockets are alveolar (acinar), such as the exocrine portion of the pancreas. Combinations of tubes and pockets are known as tubuloalveolar (tubuloacinar) compound glands. In a branched gland, a duct is connected to more than one secretory group of cells. Figure 4.9 Types of Exocrine Glands Exocrine glands are classified by their structure. Methods and Types of Secretion Exocrine glands can be classified by their mode of secretion and the nature of the substances released, as well as by the structure of the glands and shape of ducts (Figure 4.10). Merocrine secretion is the most common type of exocrine secretion. The secretions are enclosed in vesicles that move to the apical surface of the cell where the contents are released by exocytosis. For example, watery mucous containing the glycoprotein mucin, a lubricant that offers some pathogen protection is a merocrine secretion. The eccrine glands that produce and secrete sweat are another example. Figure 4.10 Modes of Glandular Secretion (a) In merocrine secretion, the cell remains intact. (b) In apocrine secretion, the apical portion of the cell is released, as well. (c) In holocrine secretion, the cell is destroyed as it releases its product and the cell itself becomes part of the secretion. Apocrine secretion accumulates near the apical portion of the cell. That portion of the cell and its secretory contents pinch off from the cell and are released. Apocrine sweat glands in the axillary and genital areas release fatty secretions that local bacteria break down; this causes body odor. Both merocrine and apocrine glands continue to produce and secrete their contents with little damage caused to the cell because the nucleus and golgi regions remain intact after secretion. In contrast, the process of holocrine secretion involves the rupture and destruction of the entire gland cell. The cell accumulates its secretory products and releases them only when it bursts. New gland cells differentiate from cells in the surrounding tissue to replace those lost by secretion. The sebaceous glands that produce the oils on the skin and hair are holocrine glands/cells (Figure 4.11). Figure 4.11 Sebaceous Glands These glands secrete oils that lubricate and protect the skin. They are holocrine glands and they are destroyed after releasing their contents. New glandular cells form to replace the cells that are lost. LM × 400. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Glands are also named after the products they produce. The serous gland produces watery, blood-plasma-like secretions rich in enzymes such as alpha amylase, whereas the mucous gland releases watery to viscous products rich in the glycoprotein mucin. Both serous and mucous glands are common in the salivary glands of the mouth. Mixed exocrine glands contain both serous and mucous glands and release both types of secretions. Connective Tissue Supports and Protects - Identify and distinguish between the types of connective tissue: proper, supportive, and fluid - Explain the functions of connective tissues As may be obvious from its name, one of the major functions of connective tissue is to connect tissues and organs. Unlike epithelial tissue, which is composed of cells closely packed with little or no extracellular space in between, connective tissue cells are dispersed in a matrix. The matrix usually includes a large amount of extracellular material produced by the connective tissue cells that are embedded within it. The matrix plays a major role in the functioning of this tissue. The major component of the matrix is a ground substance often crisscrossed by protein fibers. This ground substance is usually a fluid, but it can also be mineralized and solid, as in bones. Connective tissues come in a vast variety of forms, yet they typically have in common three characteristic components: cells, large amounts of amorphous ground substance, and protein fibers. The amount and structure of each component correlates with the function of the tissue, from the rigid ground substance in bones supporting the body to the inclusion of specialized cells; for example, a phagocytic cell that engulfs pathogens and also rids tissue of cellular debris. Functions of Connective Tissues Connective tissues perform many functions in the body, but most importantly, they support and connect other tissues; from the connective tissue sheath that surrounds muscle cells, to the tendons that attach muscles to bones, and to the skeleton that supports the positions of the body. Protection is another major function of connective tissue, in the form of fibrous capsules and bones that protect delicate organs and, of course, the skeletal system. Specialized cells in connective tissue defend the body from microorganisms that enter the body. Transport of fluid, nutrients, waste, and chemical messengers is ensured by specialized fluid connective tissues, such as blood and lymph. Adipose cells store surplus energy in the form of fat and contribute to the thermal insulation of the body. Embryonic Connective Tissue All connective tissues derive from the mesodermal layer of the embryo (see Figure 4.3). The first connective tissue to develop in the embryo is mesenchyme, the stem cell line from which all connective tissues are later derived. Clusters of mesenchymal cells are scattered throughout adult tissue and supply the cells needed for replacement and repair after a connective tissue injury. A second type of embryonic connective tissue forms in the umbilical cord, called mucous connective tissue or Wharton’s jelly. This tissue is no longer present after birth, leaving only scattered mesenchymal cells throughout the body. Classification of Connective Tissues The three broad categories of connective tissue are classified according to the characteristics of their ground substance and the types of fibers found within the matrix (Table 4.1). Connective tissue proper includes loose connective tissue and dense connective tissue. Both tissues have a variety of cell types and protein fibers suspended in a viscous ground substance. Dense connective tissue is reinforced by bundles of fibers that provide tensile strength, elasticity, and protection. In loose connective tissue, the fibers are loosely organized, leaving large spaces in between. Supportive connective tissue—bone and cartilage—provide structure and strength to the body and protect soft tissues. A few distinct cell types and densely packed fibers in a matrix characterize these tissues. In bone, the matrix is rigid and described as calcified because of the deposited calcium salts. In fluid connective tissue, in other words, lymph and blood, various specialized cells circulate in a watery fluid containing salts, nutrients, and dissolved proteins. Connective Tissue Proper Fibroblasts are present in all connective tissue proper (Figure 4.12). Fibrocytes, adipocytes, and mesenchymal cells are fixed cells, which means they remain within the connective tissue. Other cells move in and out of the connective tissue in response to chemical signals. Macrophages, mast cells, lymphocytes, plasma cells, and phagocytic cells are found in connective tissue proper but are actually part of the immune system protecting the body. Figure 4.12 Connective Tissue Proper Fibroblasts produce this fibrous tissue. Connective tissue proper includes the fixed cells fibrocytes, adipocytes, and mesenchymal cells. LM × 400. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Cell Types The most abundant cell in connective tissue proper is the fibroblast. Polysaccharides and proteins secreted by fibroblasts combine with extra-cellular fluids to produce a viscous ground substance that, with embedded fibrous proteins, forms the extra-cellular matrix. As you might expect, a fibrocyte, a less active form of fibroblast, is the second most common cell type in connective tissue proper. Adipocytes are cells that store lipids as droplets that fill most of the cytoplasm. There are two basic types of adipocytes: white and brown. The brown adipocytes store lipids as many droplets, and have high metabolic activity. In contrast, white fat adipocytes store lipids as a single large drop and are metabolically less active. Their effectiveness at storing large amounts of fat is witnessed in obese individuals. The number and type of adipocytes depends on the tissue and location, and vary among individuals in the population. The mesenchymal cell is a multipotent adult stem cell. These cells can differentiate into any type of connective tissue cells needed for repair and healing of damaged tissue. The macrophage cell is a large cell derived from a monocyte, a type of blood cell, which enters the connective tissue matrix from the blood vessels. The macrophage cells are an essential component of the immune system, which is the body’s defense against potential pathogens and degraded host cells. When stimulated, macrophages release cytokines, small proteins that act as chemical messengers. Cytokines recruit other cells of the immune system to infected sites and stimulate their activities. Roaming, or free, macrophages move rapidly by amoeboid movement, engulfing infectious agents and cellular debris. In contrast, fixed macrophages are permanent residents of their tissues. The mast cell, found in connective tissue proper, has many cytoplasmic granules. These granules contain the chemical signals histamine and heparin. When irritated or damaged, mast cells release histamine, an inflammatory mediator, which causes vasodilation and increased blood flow at a site of injury or infection, along with itching, swelling, and redness you recognize as an allergic response. Like blood cells, mast cells are derived from hematopoietic stem cells and are part of the immune system. Connective Tissue Fibers and Ground Substance Three main types of fibers are secreted by fibroblasts: collagen fibers, elastic fibers, and reticular fibers. Collagen fiber is made from fibrous protein subunits linked together to form a long and straight fiber. Collagen fibers, while flexible, have great tensile strength, resist stretching, and give ligaments and tendons their characteristic resilience and strength. These fibers hold connective tissues together, even during the movement of the body. Elastic fiber contains the protein elastin along with lesser amounts of other proteins and glycoproteins. The main property of elastin is that after being stretched or compressed, it will return to its original shape. Elastic fibers are prominent in elastic tissues found in skin and the elastic ligaments of the vertebral column. Reticular fiber is also formed from the same protein subunits as collagen fibers; however, these fibers remain narrow and are arrayed in a branching network. They are found throughout the body, but are most abundant in the reticular tissue of soft organs, such as liver and spleen, where they anchor and provide structural support to the parenchyma (the functional cells, blood vessels, and nerves of the organ). All of these fiber types are embedded in ground substance. Secreted by fibroblasts, ground substance is made of polysaccharides, specifically hyaluronic acid, and proteins. These combine to form a proteoglycan with a protein core and polysaccharide branches. The proteoglycan attracts and traps available moisture forming the clear, viscous, colorless matrix you now know as ground substance. Loose Connective Tissue Loose connective tissue is found between many organs where it acts both to absorb shock and bind tissues together. It allows water, salts, and various nutrients to diffuse through to adjacent or imbedded cells and tissues. Adipose tissue consists mostly of fat storage cells, with little extracellular matrix (Figure 4.13). A large number of capillaries allow rapid storage and mobilization of lipid molecules. White adipose tissue is most abundant. It can appear yellow and owes its color to carotene and related pigments from plant food. White fat contributes mostly to lipid storage and can serve as insulation from cold temperatures and mechanical injuries. White adipose tissue can be found protecting the kidneys and cushioning the back of the eye. Brown adipose tissue is more common in infants, hence the term “baby fat.” In adults, there is a reduced amount of brown fat and it is found mainly in the neck and clavicular regions of the body. The many mitochondria in the cytoplasm of brown adipose tissue help explain its efficiency at metabolizing stored fat. Brown adipose tissue is thermogenic, meaning that as it breaks down fats, it releases metabolic heat, rather than producing adenosine triphosphate (ATP), a key molecule used in metabolism. Figure 4.13 Adipose Tissue This is a loose connective tissue that consists of fat cells with little extracellular matrix. It stores fat for energy and provides insulation. LM × 800. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Areolar tissue shows little specialization. It contains all the cell types and fibers previously described and is distributed in a random, web-like fashion. It fills the spaces between muscle fibers, surrounds blood and lymph vessels, and supports organs in the abdominal cavity. Areolar tissue underlies most epithelia and represents the connective tissue component of epithelial membranes, which are described further in a later section. Reticular tissue is a mesh-like, supportive framework for soft organs such as lymphatic tissue, the spleen, and the liver (Figure 4.14). Reticular cells produce the reticular fibers that form the network onto which other cells attach. It derives its name from the Latin reticulus, which means “little net.” Figure 4.14 Reticular Tissue This is a loose connective tissue made up of a network of reticular fibers that provides a supportive framework for soft organs. LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Dense Connective Tissue Dense connective tissue contains more collagen fibers than does loose connective tissue. As a consequence, it displays greater resistance to stretching. There are two major categories of dense connective tissue: regular and irregular. Dense regular connective tissue fibers are parallel to each other, enhancing tensile strength and resistance to stretching in the direction of the fiber orientations. Ligaments and tendons are made of dense regular connective tissue, but in ligaments not all fibers are parallel. Dense regular elastic tissue contains elastin fibers in addition to collagen fibers, which allows the ligament to return to its original length after stretching. The ligaments in the vocal folds and between the vertebrae in the vertebral column are elastic. In dense irregular connective tissue, the direction of fibers is random. This arrangement gives the tissue greater strength in all directions and less strength in one particular direction. In some tissues, fibers crisscross and form a mesh. In other tissues, stretching in several directions is achieved by alternating layers where fibers run in the same orientation in each layer, and it is the layers themselves that are stacked at an angle. The dermis of the skin is an example of dense irregular connective tissue rich in collagen fibers. Dense irregular elastic tissues give arterial walls the strength and the ability to regain original shape after stretching (Figure 4.15). Figure 4.15 Dense Connective Tissue (a) Dense regular connective tissue consists of collagenous fibers packed into parallel bundles. (b) Dense irregular connective tissue consists of collagenous fibers interwoven into a mesh-like network. From top, LM × 1000, LM × 200. (Micrographs provided by the Regents of University of Michigan Medical School © 2012) DISORDERS OF THE... Connective Tissue: Tendinitis Your opponent stands ready as you prepare to hit the serve, but you are confident that you will smash the ball past your opponent. As you toss the ball high in the air, a burning pain shoots across your wrist and you drop the tennis racket. That dull ache in the wrist that you ignored through the summer is now an unbearable pain. The game is over for now. After examining your swollen wrist, the doctor in the emergency room announces that you have developed wrist tendinitis. She recommends icing the tender area, taking non-steroidal anti-inflammatory medication to ease the pain and to reduce swelling, and complete rest for a few weeks. She interrupts your protests that you cannot stop playing. She issues a stern warning about the risk of aggravating the condition and the possibility of surgery. She consoles you by mentioning that well known tennis players such as Venus and Serena Williams and Rafael Nadal have also suffered from tendinitis related injuries. What is tendinitis and how did it happen? Tendinitis is the inflammation of a tendon, the thick band of fibrous connective tissue that attaches a muscle to a bone. The condition causes pain and tenderness in the area around a joint. On rare occasions, a sudden serious injury will cause tendinitis. Most often, the condition results from repetitive motions over time that strain the tendons needed to perform the tasks. Persons whose jobs and hobbies involve performing the same movements over and over again are often at the greatest risk of tendinitis. You hear of tennis and golfer’s elbow, jumper's knee, and swimmer’s shoulder. In all cases, overuse of the joint causes a microtrauma that initiates the inflammatory response. Tendinitis is routinely diagnosed through a clinical examination. In case of severe pain, X-rays can be examined to rule out the possibility of a bone injury. Severe cases of tendinitis can even tear loose a tendon. Surgical repair of a tendon is painful. Connective tissue in the tendon does not have abundant blood supply and heals slowly. While older adults are at risk for tendinitis because the elasticity of tendon tissue decreases with age, active people of all ages can develop tendinitis. Young athletes, dancers, and computer operators; anyone who performs the same movements constantly is at risk for tendinitis. Although repetitive motions are unavoidable in many activities and may lead to tendinitis, precautions can be taken that can lessen the probability of developing tendinitis. For active individuals, stretches before exercising and cross training or changing exercises are recommended. For the passionate athlete, it may be time to take some lessons to improve technique. All of the preventive measures aim to increase the strength of the tendon and decrease the stress put on it. With proper rest and managed care, you will be back on the court to hit that slice-spin serve over the net. INTERACTIVE LINK Watch this animation to learn more about tendonitis, a painful condition caused by swollen or injured tendons. Supportive Connective Tissues Two major forms of supportive connective tissue, cartilage and bone, allow the body to maintain its posture and protect internal organs. Cartilage The distinctive appearance of cartilage is due to polysaccharides called chondroitin sulfates, which bind with ground substance proteins to form proteoglycans. Embedded within the cartilage matrix are chondrocytes, or cartilage cells, and the space they occupy are called lacunae (singular = lacuna). A layer of dense irregular connective tissue, the perichondrium, encapsulates the cartilage. Cartilaginous tissue is avascular, thus all nutrients need to diffuse through the matrix to reach the chondrocytes. This is a factor contributing to the very slow healing of cartilaginous tissues. The three main types of cartilage tissue are hyaline cartilage, fibrocartilage, and elastic cartilage (Figure 4.16). Hyaline cartilage, the most common type of cartilage in the body, consists of short and dispersed collagen fibers and contains large amounts of proteoglycans. Under the microscope, tissue samples appear clear. The surface of hyaline cartilage is smooth. Both strong and flexible, it is found in the rib cage and nose and covers bones where they meet to form moveable joints. It makes up a template of the embryonic skeleton before bone formation. A plate of hyaline cartilage at the ends of bone allows continued growth until adulthood. Fibrocartilage is tough because it has thick bundles of collagen fibers dispersed through its matrix. Menisci in the knee joint and the intervertebral discs are examples of fibrocartilage. Elastic cartilage contains elastic fibers as well as collagen and proteoglycans. This tissue gives rigid support as well as elasticity. Tug gently at your ear lobes, and notice that the lobes return to their initial shape. The external ear contains elastic cartilage. Figure 4.16 Types of Cartilage Cartilage is a connective tissue consisting of collagenous fibers embedded in a firm matrix of chondroitin sulfates. (a) Hyaline cartilage provides support with some flexibility. The example is from dog tissue. (b) Fibrocartilage provides some compressibility and can absorb pressure. (c) Elastic cartilage provides firm but elastic support. From top, LM × 300, LM × 1200, LM × 1016. (Micrographs provided by the Regents of University of Michigan Medical School © 2012) Bone Bone is the hardest connective tissue. It provides protection to internal organs and supports the body. Bone’s rigid extracellular matrix contains mostly collagen fibers embedded in a mineralized ground substance containing hydroxyapatite, a form of calcium phosphate. Both components of the matrix, organic and inorganic, contribute to the unusual properties of bone. Without collagen, bones would be brittle and shatter easily. Without mineral crystals, bones would flex and provide little support. Osteocytes, bone cells like chondrocytes, are located within lacunae. The histology of transverse tissue from long bone shows a typical arrangement of osteocytes in concentric circles around a central canal. Bone is a highly vascularized tissue. Unlike cartilage, bone tissue can recover from injuries in a relatively short time. Cancellous bone looks like a sponge under the microscope and contains empty spaces between trabeculae, or arches of bone proper. It is lighter than compact bone and found in the interior of some bones and at the end of long bones. Compact bone is solid and has greater structural strength. Fluid Connective Tissue Blood and lymph are fluid connective tissues. Cells circulate in a liquid extracellular matrix. The formed elements circulating in blood are all derived from hematopoietic stem cells located in bone marrow (Figure 4.17). Erythrocytes, red blood cells, transport oxygen and some carbon dioxide. Leukocytes, white blood cells, are responsible for defending against potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting. Some white blood cells have the ability to cross the endothelial layer that lines blood vessels and enter adjacent tissues. Nutrients, salts, and wastes are dissolved in the liquid matrix and transported through the body. Lymph contains a liquid matrix and white blood cells. Lymphatic capillaries are extremely permeable, allowing larger molecules and excess fluid from interstitial spaces to enter the lymphatic vessels. Lymph drains into blood vessels, delivering molecules to the blood that could not otherwise directly enter the bloodstream. In this way, specialized lymphatic capillaries transport absorbed fats away from the intestine and deliver these molecules to the blood. Figure 4.17 Blood: A Fluid Connective Tissue Blood is a fluid connective tissue containing erythrocytes and various types of leukocytes that circulate in a liquid extracellular matrix. LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK View the University of Michigan Webscope to explore the tissue sample in greater detail. INTERACTIVE LINK Visit this link to test your connective tissue knowledge with this 10-question quiz. Can you name the 10 tissue types shown in the histology slides? Muscle Tissue and Motion - Identify the three types of muscle tissue - Compare and contrast the functions of each muscle tissue type - Explain how muscle tissue can enable motion Muscle tissue is characterized by properties that allow movement. Muscle cells are excitable; they respond to a stimulus. They are contractile, meaning they can shorten and generate a pulling force. When attached between two movable objects, in other words, bones, contractions of the muscles cause the bones to move. Some muscle movement is voluntary, which means it is under conscious control. For example, a person decides to open a book and read a chapter on anatomy. Other movements are involuntary, meaning they are not under conscious control, such as the contraction of your pupil in bright light. Muscle tissue is classified into three types according to structure and function: skeletal, cardiac, and smooth (Table 4.2). Skeletal muscle is attached to bones and its contraction makes possible locomotion, facial expressions, posture, and other voluntary movements of the body. Forty percent of your body mass is made up of skeletal muscle. Skeletal muscles generate heat as a byproduct of their contraction and thus participate in thermal homeostasis. Shivering is an involuntary contraction of skeletal muscles in response to perceived lower than normal body temperature. The muscle cell, or myocyte, develops from myoblasts derived from the mesoderm. Myocytes and their numbers remain relatively constant throughout life. Skeletal muscle tissue is arranged in bundles surrounded by connective tissue. Under the light microscope, muscle cells appear striated with many nuclei squeezed along the membranes. The striation is due to the regular alternation of the contractile proteins actin and myosin, along with the structural proteins that couple the contractile proteins to connective tissues. The cells are multinucleated as a result of the fusion of the many myoblasts that fuse to form each long muscle fiber. Cardiac muscle forms the contractile walls of the heart. The cells of cardiac muscle, known as cardiomyocytes, also appear striated under the microscope. Unlike skeletal muscle fibers, cardiomyocytes are single cells typically with a single centrally located nucleus. A principal characteristic of cardiomyocytes is that they contract on their own intrinsic rhythms without any external stimulation. Cardiomyocyte attach to one another with specialized cell junctions called intercalated discs. Intercalated discs have both anchoring junctions and gap junctions. Attached cells form long, branching cardiac muscle fibers that are, essentially, a mechanical and electrochemical syncytium allowing the cells to synchronize their actions. The cardiac muscle pumps blood through the body and is under involuntary control. The attachment junctions hold adjacent cells together across the dynamic pressures changes of the cardiac cycle. Smooth muscle tissue contraction is responsible for involuntary movements in the internal organs. It forms the contractile component of the digestive, urinary, and reproductive systems as well as the airways and arteries. Each cell is spindle shaped with a single nucleus and no visible striations (Figure 4.18). Figure 4.18 Muscle Tissue (a) Skeletal muscle cells have prominent striation and nuclei on their periphery. (b) Smooth muscle cells have a single nucleus and no visible striations. (c) Cardiac muscle cells appear striated and have a single nucleus. From top, LM × 1600, LM × 1600, LM × 1600. (Micrographs provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK Watch this video to learn more about muscle tissue. In looking through a microscope how could you distinguish skeletal muscle tissue from smooth muscle? Nervous Tissue Mediates Perception and Response By the end of this section, you will be able to:- Identify the classes of cells that make up nervous tissue - Discuss how nervous tissue mediates perception and response Nervous tissue is characterized as being excitable and capable of sending and receiving electrochemical signals that provide the body with information. Two main classes of cells make up nervous tissue: the neuron and neuroglia (Figure 4.19). Neurons propagate information via electrochemical impulses, called action potentials, which are biochemically linked to the release of chemical signals. Neuroglia play an essential role in supporting neurons and modulating their information propagation. Figure 4.19 The Neuron The cell body of a neuron, also called the soma, contains the nucleus and mitochondria. The dendrites transfer the nerve impulse to the soma. The axon carries the action potential away to another excitable cell. LM × 1600. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) INTERACTIVE LINK Follow this link to learn more about nervous tissue. What are the main parts of a nerve cell? Neurons display distinctive morphology, well suited to their role as conducting cells, with three main parts. The cell body includes most of the cytoplasm, the organelles, and the nucleus. Dendrites branch off the cell body and appear as thin extensions. A long “tail,” the axon, extends from the neuron body and can be wrapped in an insulating layer known as myelin, which is formed by accessory cells. The synapse is the gap between nerve cells, or between a nerve cell and its target, for example, a muscle or a gland, across which the impulse is transmitted by chemical compounds known as neurotransmitters. Neurons categorized as multipolar neurons have several dendrites and a single prominent axon. Bipolar neurons possess a single dendrite and axon with the cell body, while unipolar neurons have only a single process extending out from the cell body, which divides into a functional dendrite and into a functional axon. When a neuron is sufficiently stimulated, it generates an action potential that propagates down the axon towards the synapse. If enough neurotransmitters are released at the synapse to stimulate the next neuron or target, a response is generated. The second class of neural cells comprises the neuroglia or glial cells, which have been characterized as having a simple support role. The word “glia” comes from the Greek word for glue. Recent research is shedding light on the more complex role of neuroglia in the function of the brain and nervous system. Astrocyte cells, named for their distinctive star shape, are abundant in the central nervous system. The astrocytes have many functions, including regulation of ion concentration in the intercellular space, uptake and/or breakdown of some neurotransmitters, and formation of the blood-brain barrier, the membrane that separates the circulatory system from the brain. Microglia protect the nervous system against infection but are not nervous tissue because they are related to macrophages. Oligodendrocyte cells produce myelin in the central nervous system (brain and spinal cord) while the Schwann cell produces myelin in the peripheral nervous system (Figure 4.20). Figure 4.20 Nervous Tissue Nervous tissue is made up of neurons and neuroglia. The cells of nervous tissue are specialized to transmit and receive impulses. LM × 872. (Micrograph provided by the Regents of University of Michigan Medical School © 2012) Tissue Injury and Aging - Identify the cardinal signs of inflammation - List the body’s response to tissue injury - Explain the process of tissue repair - Discuss the progressive impact of aging on tissue - Describe cancerous mutations’ effect on tissue Tissues of all types are vulnerable to injury and, inevitably, aging. In the former case, understanding how tissues respond to damage can guide strategies to aid repair. In the latter case, understanding the impact of aging can help in the search for ways to diminish its effects. Tissue Injury and Repair Inflammation is the standard, initial response of the body to injury. Whether biological, chemical, physical, or radiation burns, all injuries lead to the same sequence of physiological events. Inflammation limits the extent of injury, partially or fully eliminates the cause of injury, and initiates repair and regeneration of damaged tissue. Necrosis, or accidental cell death, causes inflammation. Apoptosis is programmed cell death, a normal step-by-step process that destroys cells no longer needed by the body. By mechanisms still under investigation, apoptosis does not initiate the inflammatory response. Acute inflammation resolves over time by the healing of tissue. If inflammation persists, it becomes chronic and leads to diseased conditions. Arthritis and tuberculosis are examples of chronic inflammation. The suffix “-itis” denotes inflammation of a specific organ or type, for example, peritonitis is the inflammation of the peritoneum, and meningitis refers to the inflammation of the meninges, the tough membranes that surround the central nervous system The four cardinal signs of inflammation—redness, swelling, pain, and local heat—were first recorded in antiquity. Cornelius Celsus is credited with documenting these signs during the days of the Roman Empire, as early as the first century AD. A fifth sign, loss of function, may also accompany inflammation. Upon tissue injury, damaged cells release inflammatory chemical signals that evoke local vasodilation, the widening of the blood vessels. Increased blood flow results in apparent redness and heat. In response to injury, mast cells present in tissue degranulate, releasing the potent vasodilator histamine. Increased blood flow and inflammatory mediators recruit white blood cells to the site of inflammation. The endothelium lining the local blood vessel becomes “leaky” under the influence of histamine and other inflammatory mediators allowing neutrophils, macrophages, and fluid to move from the blood into the interstitial tissue spaces. The excess liquid in tissue causes swelling, more properly called edema. The swollen tissues squeezing pain receptors cause the sensation of pain. Prostaglandins released from injured cells also activate pain neurons. Non-steroidal anti-inflammatory drugs (NSAIDs) reduce pain because they inhibit the synthesis of prostaglandins. High levels of NSAIDs reduce inflammation. Antihistamines decrease allergies by blocking histamine receptors and as a result the histamine response. After containment of an injury, the tissue repair phase starts with removal of toxins and waste products. Clotting (coagulation) reduces blood loss from damaged blood vessels and forms a network of fibrin proteins that trap blood cells and bind the edges of the wound together. A scab forms when the clot dries, reducing the risk of infection. Sometimes a mixture of dead leukocytes and fluid called pus accumulates in the wound. As healing progresses, fibroblasts from the surrounding connective tissues replace the collagen and extracellular material lost by the injury. Angiogenesis, the growth of new blood vessels, results in vascularization of the new tissue known as granulation tissue. The clot retracts pulling the edges of the wound together, and it slowly dissolves as the tissue is repaired. When a large amount of granulation tissue forms and capillaries disappear, a pale scar is often visible in the healed area. A primary union describes the healing of a wound where the edges are close together. When there is a gaping wound, it takes longer to refill the area with cells and collagen. The process called secondary unionoccurs as the edges of the wound are pulled together by what is called wound contraction. When a wound is more than one quarter of an inch deep, sutures (stitches) are recommended to promote a primary union and avoid the formation of a disfiguring scar. Regeneration is the addition of new cells of the same type as the ones that were injured (Figure 4.21). Figure 4.21 Tissue Healing During wound repair, collagen fibers are laid down randomly by fibroblasts that move into repair the area. INTERACTIVE LINK Watch this video to see a hand heal. Over what period of time do you think these images were taken? Tissue and Aging According to poet Ralph Waldo Emerson, “The surest poison is time.” In fact, biology confirms that many functions of the body decline with age. All the cells, tissues, and organs are affected by senescence, with noticeable variability between individuals owing to different genetic makeup and lifestyles. The outward signs of aging are easily recognizable. The skin and other tissues become thinner and drier, reducing their elasticity, contributing to wrinkles and high blood pressure. Hair turns gray because follicles produce less melanin, the brown pigment of hair and the iris of the eye. The face looks flabby because elastic and collagen fibers decrease in connective tissue and muscle tone is lost. Glasses and hearing aids may become parts of life as the senses slowly deteriorate, all due to reduced elasticity. Overall height decreases as the bones lose calcium and other minerals. With age, fluid decreases in the fibrous cartilage disks intercalated between the vertebrae in the spine. Joints lose cartilage and stiffen. Many tissues, including those in muscles, lose mass through a process called atrophy. Lumps and rigidity become more widespread. As a consequence, the passageways, blood vessels, and airways become more rigid. The brain and spinal cord lose mass. Nerves do not transmit impulses with the same speed and frequency as in the past. Some loss of thought clarity and memory can accompany aging. More severe problems are not necessarily associated with the aging process and may be symptoms of underlying illness. As exterior signs of aging increase, so do the interior signs, which are not as noticeable. The incidence of heart diseases, respiratory syndromes, and type 2 diabetes increases with age, though these are not necessarily age-dependent effects. Wound healing is slower in the elderly, accompanied by a higher frequency of infection as the capacity of the immune system to fend off pathogen declines. Aging is also apparent at the cellular level because all cells experience changes with aging. Telomeres, regions of the chromosomes necessary for cell division, shorten each time cells divide. As they do, cells are less able to divide and regenerate. Because of alterations in cell membranes, transport of oxygen and nutrients into the cell and removal of carbon dioxide and waste products from the cell are not as efficient in the elderly. Cells may begin to function abnormally, which may lead to diseases associated with aging, including arthritis, memory issues, and some cancers. The progressive impact of aging on the body varies considerably among individuals, but Studies indicate, however, that exercise and healthy lifestyle choices can slow down the deterioration of the body that comes with old age. HOMEOSTATIC IMBALANCES Tissues and Cancer Cancer is a generic term for many diseases in which cells escape regulatory signals. Uncontrolled growth, invasion into adjacent tissues, and colonization of other organs, if not treated early enough, are its hallmarks. Health suffers when tumors “rob” blood supply from the “normal” organs. A mutation is defined as a permanent change in the DNA of a cell. Epigenetic modifications, changes that do not affect the code of the DNA but alter how the DNA is decoded, are also known to generate abnormal cells. Alterations in the genetic material may be caused by environmental agents, infectious agents, or errors in the replication of DNA that accumulate with age. Many mutations do not cause any noticeable change in the functions of a cell. However, if the modification affects key proteins that have an impact on the cell’s ability to proliferate in an orderly fashion, the cell starts to divide abnormally. As changes in cells accumulate, they lose their ability to form regular tissues. A tumor, a mass of cells displaying abnormal architecture, forms in the tissue. Many tumors are benign, meaning they do not metastasize nor cause disease. A tumor becomes malignant, or cancerous, when it breaches the confines of its tissue, promotes angiogenesis, attracts the growth of capillaries, and metastasizes to other organs (Figure 4.22). The specific names of cancers reflect the tissue of origin. Cancers derived from epithelial cells are referred to as carcinomas. Cancer in myeloid tissue or blood cells form myelomas. Leukemias are cancers of white blood cells, whereas sarcomas derive from connective tissue. Cells in tumors differ both in structure and function. Some cells, called cancer stem cells, appear to be a subtype of cell responsible for uncontrolled growth. Recent research shows that contrary to what was previously assumed, tumors are not disorganized masses of cells, but have their own structures. Figure 4.22 Development of Cancer Note the change in cell size, nucleus size, and organization in the tissue. INTERACTIVE LINK Watch this video to learn more about tumors. What is a tumor? Cancer treatments vary depending on the disease’s type and stage. Traditional approaches, including surgery, radiation, chemotherapy, and hormonal therapy, aim to remove or kill rapidly dividing cancer cells, but these strategies have their limitations. Depending on a tumor’s location, for example, cancer surgeons may be unable to remove it. Radiation and chemotherapy are difficult, and it is often impossible to target only the cancer cells. The treatments inevitably destroy healthy tissue as well. To address this, researchers are working on pharmaceuticals that can target specific proteins implicated in cancer-associated molecular pathways. Key Terms - adipocytes - lipid storage cells - adipose tissue - specialized areolar tissue rich in stored fat - anchoring junction - mechanically attaches adjacent cells to each other or to the basement membrane - apical - that part of a cell or tissue which, in general, faces an open space - apocrine secretion - release of a substance along with the apical portion of the cell - apoptosis - programmed cell death - areolar tissue - (also, loose connective tissue) a type of connective tissue proper that shows little specialization with cells dispersed in the matrix - astrocyte - star-shaped cell in the central nervous system that regulates ions and uptake and/or breakdown of some neurotransmitters and contributes to the formation of the blood-brain barrier - atrophy - loss of mass and function - basal lamina - thin extracellular layer that lies underneath epithelial cells and separates them from other tissues - basement membrane - in epithelial tissue, a thin layer of fibrous material that anchors the epithelial tissue to the underlying connective tissue; made up of the basal lamina and reticular lamina - cardiac muscle - heart muscle, under involuntary control, composed of striated cells that attach to form fibers, each cell contains a single nucleus, contracts autonomously - cell junction - point of cell-to-cell contact that connects one cell to another in a tissue - chondrocytes - cells of the cartilage - clotting - also called coagulation; complex process by which blood components form a plug to stop bleeding - collagen fiber - flexible fibrous proteins that give connective tissue tensile strength - connective tissue - type of tissue that serves to hold in place, connect, and integrate the body’s organs and systems - connective tissue membrane - connective tissue that encapsulates organs and lines movable joints - connective tissue proper - connective tissue containing a viscous matrix, fibers, and cells. - cutaneous membrane - skin; epithelial tissue made up of a stratified squamous epithelial cells that cover the outside of the body - dense connective tissue - connective tissue proper that contains many fibers that provide both elasticity and protection - ectoderm - outermost embryonic germ layer from which the epidermis and the nervous tissue derive - elastic cartilage - type of cartilage, with elastin as the major protein, characterized by rigid support as well as elasticity - elastic fiber - fibrous protein within connective tissue that contains a high percentage of the protein elastin that allows the fibers to stretch and return to original size - endocrine gland - groups of cells that release chemical signals into the intercellular fluid to be picked up and transported to their target organs by blood - endoderm - innermost embryonic germ layer from which most of the digestive system and lower respiratory system derive - endothelium - tissue that lines vessels of the lymphatic and cardiovascular system, made up of a simple squamous epithelium - epithelial membrane - epithelium attached to a layer of connective tissue - epithelial tissue - type of tissue that serves primarily as a covering or lining of body parts, protecting the body; it also functions in absorption, transport, and secretion - exocrine gland - group of epithelial cells that secrete substances through ducts that open to the skin or to internal body surfaces that lead to the exterior of the body - fibroblast - most abundant cell type in connective tissue, secretes protein fibers and matrix into the extracellular space - fibrocartilage - tough form of cartilage, made of thick bundles of collagen fibers embedded in chondroitin sulfate ground substance - fibrocyte - less active form of fibroblast - fluid connective tissue - specialized cells that circulate in a watery fluid containing salts, nutrients, and dissolved proteins - gap junction - allows cytoplasmic communications to occur between cells - goblet cell - unicellular gland found in columnar epithelium that secretes mucous - ground substance - fluid or semi-fluid portion of the matrix - histamine - chemical compound released by mast cells in response to injury that causes vasodilation and endothelium permeability - histology - microscopic study of tissue architecture, organization, and function - holocrine secretion - release of a substance caused by the rupture of a gland cell, which becomes part of the secretion - hyaline cartilage - most common type of cartilage, smooth and made of short collagen fibers embedded in a chondroitin sulfate ground substance - inflammation - response of tissue to injury - lacunae - (singular = lacuna) small spaces in bone or cartilage tissue that cells occupy - lamina propria - areolar connective tissue underlying a mucous membrane - loose connective tissue - (also, areolar tissue) type of connective tissue proper that shows little specialization with cells dispersed in the matrix - matrix - extracellular material which is produced by the cells embedded in it, containing ground substance and fibers - merocrine secretion - release of a substance from a gland via exocytosis - mesenchymal cell - adult stem cell from which most connective tissue cells are derived - mesenchyme - embryonic tissue from which connective tissue cells derive - mesoderm - middle embryonic germ layer from which connective tissue, muscle tissue, and some epithelial tissue derive - mesothelium - simple squamous epithelial tissue which covers the major body cavities and is the epithelial portion of serous membranes - mucous connective tissue - specialized loose connective tissue present in the umbilical cord - mucous gland - group of cells that secrete mucous, a thick, slippery substance that keeps tissues moist and acts as a lubricant - mucous membrane - tissue membrane that is covered by protective mucous and lines tissue exposed to the outside environment - muscle tissue - type of tissue that is capable of contracting and generating tension in response to stimulation; produces movement. - myelin - layer of lipid inside some neuroglial cells that wraps around the axons of some neurons - myocyte - muscle cells - necrosis - accidental death of cells and tissues - nervous tissue - type of tissue that is capable of sending and receiving impulses through electrochemical signals. - neuroglia - supportive neural cells - neuron - excitable neural cell that transfer nerve impulses - oligodendrocyte - neuroglial cell that produces myelin in the brain - parenchyma - functional cells of a gland or organ, in contrast with the supportive or connective tissue of a gland or organ - primary union - condition of a wound where the wound edges are close enough to be brought together and fastened if necessary, allowing quicker and more thorough healing - pseudostratified columnar epithelium - tissue that consists of a single layer of irregularly shaped and sized cells that give the appearance of multiple layers; found in ducts of certain glands and the upper respiratory tract - reticular fiber - fine fibrous protein, made of collagen subunits, which cross-link to form supporting “nets” within connective tissue - reticular lamina - matrix containing collagen and elastin secreted by connective tissue; a component of the basement membrane - reticular tissue - type of loose connective tissue that provides a supportive framework to soft organs, such as lymphatic tissue, spleen, and the liver - Schwann cell - neuroglial cell that produces myelin in the peripheral nervous system - secondary union - wound healing facilitated by wound contraction - serous gland - group of cells within the serous membrane that secrete a lubricating substance onto the surface - serous membrane - type of tissue membrane that lines body cavities and lubricates them with serous fluid - simple columnar epithelium - tissue that consists of a single layer of column-like cells; promotes secretion and absorption in tissues and organs - simple cuboidal epithelium - tissue that consists of a single layer of cube-shaped cells; promotes secretion and absorption in ducts and tubules - simple squamous epithelium - tissue that consists of a single layer of flat scale-like cells; promotes diffusion and filtration across surface - skeletal muscle - usually attached to bone, under voluntary control, each cell is a fiber that is multinucleated and striated - smooth muscle - under involuntary control, moves internal organs, cells contain a single nucleus, are spindle-shaped, and do not appear striated; each cell is a fiber - stratified columnar epithelium - tissue that consists of two or more layers of column-like cells, contains glands and is found in some ducts - stratified cuboidal epithelium - tissue that consists of two or more layers of cube-shaped cells, found in some ducts - stratified squamous epithelium - tissue that consists of multiple layers of cells with the most apical being flat scale-like cells; protects surfaces from abrasion - striation - alignment of parallel actin and myosin filaments which form a banded pattern - supportive connective tissue - type of connective tissue that provides strength to the body and protects soft tissue - synovial membrane - connective tissue membrane that lines the cavities of freely movable joints, producing synovial fluid for lubrication - tight junction - forms an impermeable barrier between cells - tissue - group of cells that are similar in form and perform related functions - tissue membrane - thin layer or sheet of cells that covers the outside of the body, organs, and internal cavities - totipotent - embryonic cells that have the ability to differentiate into any type of cell and organ in the body - transitional epithelium - form of stratified epithelium found in the urinary tract, characterized by an apical layer of cells that change shape in response to the presence of urine - vasodilation - widening of blood vessels - wound contraction - process whereby the borders of a wound are physically drawn together Chapter Review 4.1 Types of Tissues The human body contains more than 200 types of cells that can all be classified into four types of tissues: epithelial, connective, muscle, and nervous. Epithelial tissues act as coverings controlling the movement of materials across the surface. Connective tissue integrates the various parts of the body and provides support and protection to organs. Muscle tissue allows the body to move. Nervous tissues propagate information. The study of the shape and arrangement of cells in tissue is called histology. All cells and tissues in the body derive from three germ layers in the embryo: the ectoderm, mesoderm, and endoderm. Different types of tissues form membranes that enclose organs, provide a friction-free interaction between organs, and keep organs together. Synovial membranes are connective tissue membranes that protect and line the joints. Epithelial membranes are formed from epithelial tissue attached to a layer of connective tissue. There are three types of epithelial membranes: mucous, which contain glands; serous, which secrete fluid; and cutaneous which makes up the skin. 4.2 Epithelial Tissue In epithelial tissue, cells are closely packed with little or no extracellular matrix except for the basal lamina that separates the epithelium from underlying tissue. The main functions of epithelia are protection from the environment, coverage, secretion and excretion, absorption, and filtration. Cells are bound together by tight junctions that form an impermeable barrier. They can also be connected by gap junctions, which allow free exchange of soluble molecules between cells, and anchoring junctions, which attach cell to cell or cell to matrix. The different types of epithelial tissues are characterized by their cellular shapes and arrangements: squamous, cuboidal, or columnar epithelia. Single cell layers form simple epithelia, whereas stacked cells form stratified epithelia. Very few capillaries penetrate these tissues. Glands are secretory tissues and organs that are derived from epithelial tissues. Exocrine glands release their products through ducts. Endocrine glands secrete hormones directly into the interstitial fluid and blood stream. Glands are classified both according to the type of secretion and by their structure. Merocrine glands secrete products as they are synthesized. Apocrine glands release secretions by pinching off the apical portion of the cell, whereas holocrine gland cells store their secretions until they rupture and release their contents. In this case, the cell becomes part of the secretion. 4.3 Connective Tissue Supports and Protects Connective tissue is a heterogeneous tissue with many cell shapes and tissue architecture. Structurally, all connective tissues contain cells that are embedded in an extracellular matrix stabilized by proteins. The chemical nature and physical layout of the extracellular matrix and proteins vary enormously among tissues, reflecting the variety of functions that connective tissue fulfills in the body. Connective tissues separate and cushion organs, protecting them from shifting or traumatic injury. Connect tissues provide support and assist movement, store and transport energy molecules, protect against infections, and contribute to temperature homeostasis. Many different cells contribute to the formation of connective tissues. They originate in the mesodermal germ layer and differentiate from mesenchyme and hematopoietic tissue in the bone marrow. Fibroblasts are the most abundant and secrete many protein fibers, adipocytes specialize in fat storage, hematopoietic cells from the bone marrow give rise to all the blood cells, chondrocytes form cartilage, and osteocytes form bone. The extracellular matrix contains fluid, proteins, polysaccharide derivatives, and, in the case of bone, mineral crystals. Protein fibers fall into three major groups: collagen fibers that are thick, strong, flexible, and resist stretch; reticular fibers that are thin and form a supportive mesh; and elastin fibers that are thin and elastic. The major types of connective tissue are connective tissue proper, supportive tissue, and fluid tissue. Loose connective tissue proper includes adipose tissue, areolar tissue, and reticular tissue. These serve to hold organs and other tissues in place and, in the case of adipose tissue, isolate and store energy reserves. The matrix is the most abundant feature for loose tissue although adipose tissue does not have much extracellular matrix. Dense connective tissue proper is richer in fibers and may be regular, with fibers oriented in parallel as in ligaments and tendons, or irregular, with fibers oriented in several directions. Organ capsules (collagenous type) and walls of arteries (elastic type) contain dense irregular connective tissue. Cartilage and bone are supportive tissue. Cartilage contains chondrocytes and is somewhat flexible. Hyaline cartilage is smooth and clear, covers joints, and is found in the growing portion of bones. Fibrocartilage is tough because of extra collagen fibers and forms, among other things, the intervertebral discs. Elastic cartilage can stretch and recoil to its original shape because of its high content of elastic fibers. The matrix contains very few blood vessels. Bones are made of a rigid, mineralized matrix containing calcium salts, crystals, and osteocytes lodged in lacunae. Bone tissue is highly vascularized. Cancellous bone is spongy and less solid than compact bone. Fluid tissue, for example blood and lymph, is characterized by a liquid matrix and no supporting fibers. 4.4 Muscle Tissue and Motion The three types of muscle cells are skeletal, cardiac, and smooth. Their morphologies match their specific functions in the body. Skeletal muscle is voluntary and responds to conscious stimuli. The cells are striated and multinucleated appearing as long, unbranched cylinders. Cardiac muscle is involuntary and found only in the heart. Each cell is striated with a single nucleus and they attach to one another to form long fibers. Cells are attached to one another at intercalated disks. The cells are interconnected physically and electrochemically to act as a syncytium. Cardiac muscle cells contract autonomously and involuntarily. Smooth muscle is involuntary. Each cell is a spindle-shaped fiber and contains a single nucleus. No striations are evident because the actin and myosin filaments do not align in the cytoplasm. 4.5 Nervous Tissue Mediates Perception and Response The most prominent cell of the nervous tissue, the neuron, is characterized mainly by its ability to receive stimuli and respond by generating an electrical signal, known as an action potential, which can travel rapidly over great distances in the body. A typical neuron displays a distinctive morphology: a large cell body branches out into short extensions called dendrites, which receive chemical signals from other neurons, and a long tail called an axon, which relays signals away from the cell to other neurons, muscles, or glands. Many axons are wrapped by a myelin sheath, a lipid derivative that acts as an insulator and speeds up the transmission of the action potential. Other cells in the nervous tissue, the neuroglia, include the astrocytes, microglia, oligodendrocytes, and Schwann cells. 4.6 Tissue Injury and Aging Inflammation is the classic response of the body to injury and follows a common sequence of events. The area is red, feels warm to the touch, swells, and is painful. Injured cells, mast cells, and resident macrophages release chemical signals that cause vasodilation and fluid leakage in the surrounding tissue. The repair phase includes blood clotting, followed by regeneration of tissue as fibroblasts deposit collagen. Some tissues regenerate more readily than others. Epithelial and connective tissues replace damaged or dead cells from a supply of adult stem cells. Muscle and nervous tissues undergo either slow regeneration or do not repair at all. Age affects all the tissues and organs of the body. Damaged cells do not regenerate as rapidly as in younger people. Perception of sensation and effectiveness of response are lost in the nervous system. Muscles atrophy, and bones lose mass and become brittle. Collagen decreases in some connective tissue, and joints stiffen.	oercommons	2025-03-18T00:35:16.299378	09/20/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/72731/overview", "title": "Anatomy and Physiology, Levels of Organization, The Tissue Level of Organization", "author": "Allyson Ortner" }
https://oercommons.org/courseware/lesson/123284/overview	Education Standards Persuasive Writing Rubric Practice Spoon Writing paper Persuasive Writing Overview This unit on persuasive writing is perfect for kindergarten and first grade students. This lesson will help students to understand the meaning of persuasive writing while allowing them time to write their own persuasive writing. Understanding Persuasive Writing Review or introduce what pursuasive writing means and give examples of facts and opinions for them to answer. Create your own or use the link as a whole group or assign individually. https://www.ixl.com/ela/kindergarten/complete-the-opinion-passage-with-an-example 1-Blue is the best color-opinion 2-George Washington was the 1st president-fact 3-Dogs can bark-fact 4-Summer is the best season-opinion Watch the video on persuasive writing and then practice using the resource below. Spoon Read Aloud If possible, have some hard copies of the story for students to refer back to if need be. Listen to the story Spoon. Think about how each utensil is different in the story as you listen. Get Ready to Write Watch the video and then use the attached brainstorming paper to identify what utensil you think is best. Give examples as to why the one you chose is the best. Rough Draft and Final Copy Review the student's rough draft with them while making corrections. Once corrections are made, students will complete the final draft on a new piece of paper. Students will glue the utensil on the paper in the empty rectangle. Remind students to add a background and other detail to the picture. Students will each recieve the utensil of their choice. Plastic silverware works best and most chinese restaurants are willing to donate a few pairs of chopsticks. Write your rough draft using the attachment. When ready for the final draft, use a new paper and be sure to add the utensil you have chosen. Don't foget to add detail to your picture. Writing Rubric After grading, have a one on one meeting with students to go over the rubric and score with them. Use the attached rubric to grade your own work before turning in for a grade.	oercommons	2025-03-18T00:35:16.333039	12/19/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/123284/overview", "title": "Persuasive Writing", "author": "Melony Cobb" }
https://oercommons.org/courseware/lesson/66354/overview	Measuring Public Opinion in Texas Overview Measuring Public Opinion in Texas Learning Objectives By the end of this section, you will be able to: - Identify common ways to measure and quantify public opinion Introduction Public opinion polls tell us what proportion of a population has a specific viewpoint. They do not explain why respondents believe as they do or how to change their minds. This is the work of social scientists and scholars. Polls are simply a measurement tool that tells us how a population thinks and feels about any given topic. This can be useful in helping different cultures understand one another because it gives the people a chance to speak for themselves instead of letting only vocal media stars speak on behalf of all. Opinion polling gives people who do not usually have access to the media an opportunity to be heard. Taking a Poll Most public opinion polls aim to be accurate, but this is not an easy task. Political polling is a science. From design to implementation, polls are complex and require careful planning and care. Mitt Romney’s campaign polls are only a recent example of problems stemming from polling methods. Our history is littered with examples of polling companies producing results that incorrectly predicted public opinion due to poor survey design or bad polling methods. In 1936, Literary Digest continued its tradition of polling citizens to determine who would win the presidential election. The magazine sent opinion cards to people who had a subscription, a phone, or a car registration. Only some of the recipients sent back their cards. The result? Alf Landon was predicted to win 55.4 percent of the popular vote; in the end, he received only 38 percent. Franklin D. Roosevelt won another term, but the story demonstrates the need to be scientific in conducting polls. A few years later, Thomas Dewey lost the 1948 presidential election to Harry Truman, despite polls showing Dewey far ahead and Truman destined to lose. More recently, John Zogby, of Zogby Analytics, went public with his prediction that John Kerry would win the presidency against incumbent president George W. Bush in 2004, only to be proven wrong on election night. These are just a few cases, but each oﬀers a diﬀerent lesson. In 1948, pollsters did not poll up to the day of the election, relying on old numbers that did not include a late shift in voter opinion. Zogby’s polls did not represent likely voters and incorrectly predicted who would vote and for whom. These examples reinforce the need to use scientific methods when conducting polls, and to be cautious when reporting the results. Most polling companies employ statisticians and methodologists trained in conducting polls and analyzing data. A number of criteria must be met if a poll is to be completed scientifically. First, the methodologists identify the desired population, or group, of respondents they want to interview. For example, if the goal is to project who will win the presidency, citizens from across the United States should be interviewed. If we wish to understand how voters in Colorado will vote on a proposition, the population of respondents should only be Colorado residents. When surveying on elections or policy matters, many polling houses will interview only respondents who have a history of voting in previous elections, because these voters are more likely to go to the polls on Election Day. Politicians are more likely to be influenced by the opinions of proven voters than of everyday citizens. Once the desired population has been identified, the researchers will begin to build a sample that is both random and representative. A random sample consists of a limited number of people from the overall population, selected in such a way that each has an equal chance of being chosen. In the early years of polling, telephone numbers of potential respondents were arbitrarily selected from various areas to avoid regional bias. While landline phones allow polls to try to ensure randomness, the increasing use of cell phones makes this process diﬃcult. Cell phones, and their numbers, are portable and move with the owner. To prevent errors, polls that include known cellular numbers may screen for zip codes and other geographic indicators to prevent regional bias. A representative sample consists of a group whose demographic distribution is similar to that of the overall population. For example, nearly 51 percent of the U.S. population is female. To match this demographic distribution of women, any poll intended to measure what most Americans think about an issue should survey a sample containing slightly more women than men. Pollsters try to interview a set number of citizens to create a reasonable sample of the population. This sample size will vary based on the size of the population being interviewed and the level of accuracy the pollster wishes to reach. If the poll is trying to reveal the opinion of a state or group, such as the opinion of Wisconsin voters about changes to the education system, the sample size may vary from five hundred to one thousand respondents and produce results with relatively low error. For a poll to predict what Americans think nationally, such as about the White House’s policy on greenhouse gases, the sample size should be larger. The sample size varies with each organization and institution due to the way the data are processed. Gallup often interviews only five hundred respondents, while Rasmussen Reports and Pew Research often interview one thousand to fifteen hundred respondents. Academic organizations, like the American National Election Studies, have interviews with over twenty-five-hundred respondents. A larger sample makes a poll more accurate, because it will have relatively fewer unusual responses and be more representative of the actual population. Pollsters do not interview more respondents than necessary, however. Increasing the number of respondents will increase the accuracy of the poll, but once the poll has enough respondents to be representative, increases in accuracy become minor and are not cost-eﬀective. When the sample represents the actual population, the poll’s accuracy will be reflected in a lower margin of error. The margin of error is a number that states how far the poll results may be from the actual opinion of the total population of citizens. The lower the margin of error, the more predictive the poll. Large margins of error are problematic. For example, if a poll that claims Hillary Clinton is likely to win 30 percent of the vote in the 2016 New York Democratic primary has a margin of error of +/-6, it tells us that Clinton may receive as little as 24 percent of the vote (30 – 6) or as much as 36 percent (30 + 6). A lower margin of error is clearly desirable because it gives us the most precise picture of what people actually think or will do. With many polls out there, how do you know whether a poll is a good poll and accurately predicts what a group believes? First, look for the numbers. Polling companies include the margin of error, polling dates, number of respondents, and population sampled to show their scientific reliability. Was the poll recently taken? Is the question clear and unbiased? Was the number of respondents high enough to predict the population? Is the margin of error small? It is worth looking for this valuable information when you interpret poll results. While most polling agencies strive to create quality polls, other organizations want fast results and may prioritize immediate numbers over random and representative samples. For example, instant polling is often used by news networks to quickly assess how well candidates are performing in a debate. Technology and Polling The days of randomly walking neighborhoods and phone book cold-calling to interview random citizens are gone. Scientific polling has made interviewing more deliberate. Historically, many polls were conducted in person, yet this was expensive and yielded problematic results. In some situations and countries, face-to-face interviewing still exists. Exit polls, focus groups, and some public opinion polls occur in which the interviewer and respondents communicate in person. Exit polls are conducted in person, with an interviewer standing near a polling location and requesting information as voters leave the polls. Focus groups often select random respondents from local shopping places or pre-select respondents from Internet or phone surveys. The respondents show up to observe or discuss topics and are then surveyed. When organizations like Gallup or Roper decide to conduct face-to-face public opinion polls, however, it is a time-consuming and expensive process. The organization must randomly select households or polling locations within neighborhoods, making sure there is a representative household or location in each neighborhood. Then it must survey a representative number of neighborhoods from within a city. At a polling location, interviewers may have directions on how to randomly select voters of varied demographics. If the interviewer is looking to interview a person in a home, multiple attempts are made to reach a respondent if he or she does not answer. Gallup conducts face-to-face interviews in areas where less than 80 percent of the households in an area have phones because it gives a more representative sample. Most polling now occurs over the phone or through the Internet. Some companies, like Harris Interactive, maintain directories that include registered voters, consumers, or previously interviewed respondents. If pollsters need to interview a particular population, such as political party members or retirees of a specific pension fund, the company may purchase or access a list of phone numbers for that group. Other organizations, like Gallup, use random-digit-dialing (RDD), in which a computer randomly generates phone numbers with desired area codes. Using RDD allows the pollsters to include respondents who may have unlisted and cellular numbers. Questions about ZIP code or demographics may be asked early in the poll to allow the pollsters to determine which interviews to continue and which to end early. The interviewing process is also partly computerized. Many polls are now administered through computer-assisted telephone interviewing (CATI) or through robo-polls. A CATI system calls random telephone numbers until it reaches a live person and then connects the potential respondent with a trained interviewer. As the respondent provides answers, the interviewer enters them directly into the computer program. These polls may have some errors if the interviewer enters an incorrect answer. The polls may also have reliability issues if the interviewer goes oﬀ the script or answers respondents’ questions. Robo-polls are entirely computerized. A computer dials random or pre-programmed numbers and a prerecorded electronic voice administers the survey. The respondent listens to the question and possible answers and then presses numbers on the phone to enter responses. Proponents argue that respondents are more honest without an interviewer. However, these polls can suﬀer from error if the respondent does not use the correct keypad number to answer a question or misunderstands the question. Robo-polls may also have lower response rates because there is no live person to persuade the respondent to answer. There is also no way to prevent children from answering the survey. Lastly, the Telephone Consumer Protection Act (1991) made automated calls to cell phones illegal, which leaves a large population of potential respondents inaccessible to robo-polls. The latest challenges in telephone polling come from the shift in phone usage. A growing number of citizens, especially younger citizens, use only cell phones, and their phone numbers are no longer based on geographic areas. The millennial generation (currently aged 18–33) is also more likely to text than to answer an unknown call, so it is harder to interview this demographic group. Polling companies now must reach out to potential respondents using email and social media to ensure they have a representative group of respondents. Yet, the technology required to move to the Internet and handheld devices presents further problems. Web surveys must be designed to run on a varied number of browsers and handheld devices. Online polls cannot detect whether a person with multiple email accounts or social media profiles answers the same poll multiple times, nor can they tell when a respondent misrepresents demographics in the poll or on a social media profile used in a poll. These factors also make it more diﬃcult to calculate response rates or achieve a representative sample. Yet, many companies are working with these diﬃculties, because it is necessary to reach younger demographics in order to provide accurate data. The Ins and Outs Of Polls Ever wonder what happens behind the polls? To find out, we posed a few questions to Scott Keeter, Director of Survey Research at Pew Research Center. Q: What are some of the most common misconceptions about polling? A: A couple of them recur frequently. The first is that it is just impossible for one thousand or fifteen hundred people in a survey sample to adequately represent a population of 250 million adults. But of course it is possible. Random sampling, which has been well understood for the past several decades, makes it possible. If you don’t trust small random samples, then ask your doctor to take all of your blood the next time you need a diagnostic test. The second misconception is that it is possible to get any result we want from a poll if we are willing to manipulate the wording suﬃciently. While it is true that question wording can influence responses, it is not true that a poll can get any result it sets out to get. People aren’t stupid. They can tell if a question is highly biased and they won’t react well to it. Perhaps more important, the public can read the questions and know whether they are being loaded with words and phrases intended to push a respondent in a particular direction. That’s why it’s important to always look at the wording and the sequencing of questions in any poll. Q: How does your organization choose polling topics? A: We choose our topics in several ways. Most importantly, we keep up with developments in politics and public policy, and try to make our polls reflect relevant issues. Much of our research is driven by the news cycle and topics that we see arising in the near future. We also have a number of projects that we do regularly to provide a look at long-term trends in public opinion. For example, we’ve been asking a series of questions about political values since 1987, which has helped to document the rise of political polarization in the public. Another is a large (thirty-five thousand interviews) study of religious beliefs, behaviors, and aﬃliations among Americans. We released the first of these in 2007, and a second in 2015. Finally, we try to seize opportunities to make larger contributions on weighty issues when they arise. When the United States was on the verge of a big debate on immigration reform in 2006, we undertook a major survey of Americans’ attitudes about immigration and immigrants. In 2007, we conducted the first-ever nationally representative survey of Muslim Americans. Q: What is the average number of polls you oversee in a week? A: It depends a lot on the news cycle and the needs of our research groups. We almost always have a survey in progress, but sometimes there are two or three going on at once. At other times, we are more focused on analyzing data already collected or planning for future surveys. Q: Have you placed a poll in the field and had results that really surprised you? A: It’s rare to be surprised because we’ve learned a lot over the years about how people respond to questions. But here are some findings that jumped out to some of us in the past: In 2012, we conducted a survey of people who said their religion is “nothing in particular.” We asked them if they are “looking for a religion that would be right” for them, based on the expectation that many people without an aﬃliation—but who had not said they were atheists or agnostic—might be trying to find a religion that fit. Only 10 percent said that they were looking for the right religion. We—and many others—were surprised that public opinion about Muslims became more favorable after the 9/11 terrorist attacks. It’s possible that President Bush’s strong appeal to people not to blame Muslims in general for the attack had an eﬀect on opinions. It’s also surprising that basic public attitudes about gun control (whether pro or anti) barely move after highly publicized mass shootings. Were you surprised by the results Scott Keeter reported in response to the interviewer’s final question? Why or why not? Conduct some research online to discover what degree plans or work experience would help a student find a job in a polling organization. \| Problems in Polling For a number of reasons, polls may not produce accurate results. Two important factors a polling company faces are timing and human nature. Unless you conduct an exit poll during an election and interviewers stand at the polling places on Election Day to ask voters how they voted, there is always the possibility the poll results will be wrong. The simplest reason is that if there is time between the poll and Election Day, a citizen might change his or her mind, lie, or choose not to vote at all. Timing is very important during elections, because surprise events can shift enough opinions to change an election result. Of course, there are many other reasons why polls, even those not time-bound by elections or events, may be inaccurate. Polls begin with a list of carefully written questions. The questions need to be free of framing, meaning they should not be worded to lead respondents to a particular answer. For example, take two questions about presidential approval. Question 1 might ask, “Given the high rate of mass shootings in the U.S., do you approve of the job President Trump is doing?” Question 2 might ask, “Do you approve of the job President Trump is doing?” Both questions want to know how respondents perceive the president’s success, but the first question sets up a frame for the respondent to believe the President is performing poorly before answering. This is likely to make the respondent’s answer more negative. Similarly, the way we refer to an issue or concept can aﬀect the way listeners perceive it. The phrase “estate tax” did not rally voters to protest the inheritance tax, but the phrase “death tax” sparked debate about whether taxing estates imposed a double tax on income. Many polling companies try to avoid leading questions, which lead respondents to select a predetermined answer, because they want to know what people really think. Some polls, however, have a diﬀerent goal. Their questions are written to guarantee a specific outcome, perhaps to help a candidate get press coverage or gain momentum. These are called push polls. In the 2016 presidential primary race, MoveOn tried to encourage Senator Elizabeth Warren (D- MA) to enter the race for the Democratic nomination. Its poll used leading questions for what it termed an “informed ballot,” and, to show that Warren would do better than Hillary Clinton, it included ten positive statements about Warren before asking whether the respondent would vote for Clinton or Warren. The poll results were blasted by some in the media for being fake. Sometimes lack of knowledge aﬀects the results of a poll. Respondents may not know that much about the polling topic but are unwilling to say, “I don’t know.” For this reason, surveys may contain a quiz with questions that determine whether the respondent knows enough about the situation to answer survey questions accurately. A poll to discover whether citizens support changes to the Aﬀordable Care Act or Medicaid might first ask who these programs serve and how they are funded. Polls about territory seizure by the Islamic State (or ISIS) or Russia’s aid to rebels in Ukraine may include a set of questions to determine whether the respondent reads or hears any international news. Respondents who cannot answer correctly may be excluded from the poll, or their answers may be separated from the others. People may also feel social pressure to answer questions in accordance with the norms of their area or peers. If they are embarrassed to admit how they would vote, they may lie to the interviewer. In the 1982 governor’s race in California, Los Angeles Mayor Tom Bradley was far ahead in the polls, yet on Election Day he lost. This result was nicknamed the Bradley eﬀect, a theory based on observed discrepancies between voter opinion polls and election outcomes in government elections where a white candidate and a non-white candidate run against each other. The theory proposes that some voters who intend to vote for the white candidate would nonetheless tell pollsters that they are undecided or likely to vote for the non-white candidate. In this case, voters who answered the poll succumbed to social desirability bias, and were afraid to admit they would not vote for a black man because it would appear politically incorrect and racist. In 2010, Proposition 19, which would have legalized and taxed marijuana in California, met with a new version of the Bradley eﬀect. Nate Silver, a political blogger, noticed that polls on the marijuana proposition were inconsistent, sometimes showing the proposition would pass and other times showing it would fail. Silver compared the polls and the way they were administered because some polling companies used an interviewer and some used robo-calling. He then proposed that voters speaking with a live interviewer gave the socially acceptable answer that they would vote against Proposition 19, while voters interviewed by a computer felt free to be honest. Interviewer demographics may also aﬀect respondents’ answers. African Americans, for example, may give diﬀerent responses to interviewers who are white than to interviewers who are black. Push Polls One of the newer byproducts of polling is the creation of push polls, which consist of political campaign information presented as polls. A respondent is called and asked a series of questions about his or her position or candidate selections. If the respondent’s answers are for the wrong candidate, the next questions will give negative information about the candidate in an eﬀort to change the voter’s mind. In 2014, a fracking ban was placed on the ballot in Denton, Texas. Fracking, which includes injecting pressurized water into drilled wells, helps energy companies collect additional gas from the earth. It is controversial, with opponents arguing it causes water pollution, sound pollution, and earthquakes. During the campaign, a number of local voters received a call that polled them on how they planned to vote on the proposed fracking ban. If the respondent was unsure about or planned to vote for the ban, the questions shifted to provide negative information about the organizations proposing the ban. One question asked, “If you knew the following, would it change your vote . . . two Texas railroad commissioners, the state agency that oversees oil and gas in Texas, have raised concerns about Russia’s involvement in the anti-fracking eﬀorts in the U.S.?” The question played upon voter fears about Russia and international instability in order to convince them to vote against the fracking ban. These techniques are not limited to issue votes; candidates have used them to attack their opponents. The hope is that voters will think the poll is legitimate and believe the negative information provided by a “neutral” source. Check Your Knowledge Check your knowledge of this section by taking the quiz linked below. The quiz will open in a new browser window or tab. Polling in Texas Most polling is conducted at the national level–there are far fewer polls conducted at the state level. In Texas we’re fortunate to have the University of Texas/Texas Tribune Poll. Beginning in 2008, the Texas Politics Project at the University of Texas (UT), under the direction of James Henson and Joshua Blank, has conducted three to four statewide public opinion polls each year to assess the opinions of registered voters on upcoming elections, public policy, and attitudes towards politics, politicians, and government. In 2009, UT partnered with the Texas Tribune, and continued to regularly measure public opinion in Texas, making the data freely available to students, researchers, and the general public in their data archive. To see what Texans are thinking about politics, or to do some of your own analysis, please visit their polling page where you’ll find a wealth of information on public opinion in Texas. References and Further Reading Gallup. 2015. “Gallup Daily: Obama Job Approval.” Gallup. June 6, 2015. (February 17, 2016); Rasmussen Reports. 2015. “Daily Presidential Tracking Poll.” Rasmussen Reports, June 6, 2015. (February 17, 2016); Roper Center. 2015. “Obama Presidential Approval.” Roper Center. June 6, 2015. V. O. Key, Jr. (1966). The Responsible Electorate: Rationality in Presidential Voting, 1936– 1960. Harvard University: Belknap Press. Arthur Evans, “Predict Landon Electoral Vote to be 315 to 350,” Chicago Tribune, 18 October 1936. United States Census Bureau. 2012. “Age and Sex Composition in the United States: 2012.” United States Census Bureau. Rasmussen Reports. 2015. “Daily Presidential Tracking Poll” Rasmussen Reports. September 27, 2015. (February 17, 2016); Pew Research Center. 2015. “Sampling” Pew Research Center. (February 17, 2016). American National Election Studies (ANES) Data Center. 2016 Time Series Study. Retrieved September 5, 2019. Michael W. Link and Robert W. Oldendick. 1997. "Good” Polls / “Bad” Polls—How Can You Tell? Ten Tips for Consumers of Survey Research. South Carolina Policy Forum; Pew Research Center (2015). Sampling Retrieved September 5, 2019. Cornell University (2015). Polling Fundamentals – Sampling Roper Center for Public Opinion Research. Retrieved September 5, 2019. Gallup. How Does the Gallup World Poll Work? Retrieved September 5, 2019. Gallup. Does Gallup Call Cellphones? Retrieved September 5, 2019. Mark Blumenthal, “The Case for Robo-Pollsters: Automated Interviewers Have Their Drawbacks, But Fewer Than Their Critics Suggest,” National Journal, 14 September 2009. Mark Blumenthal, “Is Polling As We Know It Doomed?” National Journal, 10 August 2009. Frank Luntz. 2007. Words That Work: It’s Not What You Say, It’s What People Hear. New York: Hyperion. Aaron Blake, “This terrible polls shows Elizabeth Warren beating Hillary Clinton,” Washington Post, 11 February 2015. Nate Silver (2010). “The Broadus Effect? Social Desirability Bias and California Proposition 19.” FiveThirtyEightPolitics. Retrieved October 19, 2019. Gary Langer (November 8, 1989). "Election Poll Problems: Did Some Voters Lie?" Associated Press. Retrieved October 28, 2019. Elder, J. (May 16, 2007). Will There Be an 'Obama Effect?’The New York Times. Retrieved October 28, 2019. Davis, D. (1997). The Direction of Race of Interviewer Effects among African-Americans: Donning the Black Mask American Journal of Political Science, 41(1). 309–322. Retrieved October 22, 2019. Kate Sheppard (2014, July 16). “Top Texas Regulator: Could Russia be Behind City’s Proposed Fracking Ban?” Huffington Post. Jim Henson & Joshua Blank (2019, June 21). The Public Opinion Underpinning of Texas GOP Leaders' Pivot Back to Immigration and Border Security Texas Politics Project - University of Texas at Austin Licensing and Attribution CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: Daniel M. Regalado. License: CC BY: Attribution CC LICENSED CONTENT, SHARED PREVIOUSLY American Government. Authored by: OpenStax. Provided by: OpenStax; Rice University. Located at: http://cnx.org/contents/5bcc0e59-7345-421d-8507- a1e4608685e8@18.11 License: CC BY: Attribution. License Terms: Download for free at http://cnx.org/contents/5bcc0e59-7345-421d-8507-a1e4608685e8@18.11	oercommons	2025-03-18T00:35:16.389816	05/05/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66354/overview", "title": "Texas Government 2.0, Public Opinion and the Media in Texas, Measuring Public Opinion in Texas", "author": "Kris Seago" }
https://oercommons.org/courseware/lesson/66301/overview	Voting in Texas Overview Voting in Texas Learning Objective By the end of this section, you will be able to: - Explain the current requirements to vote in Texas and the registration process Introduction Before most voters are allowed to cast a ballot, they must register to vote in their state. This process may be as simple as checking a box on a driver’s license application or as difficult as filling out a long form with complicated questions. Registration allows governments to determine which citizens are allowed to vote and, in some cases, from which list of candidates they may select a party nominee. Ironically, while the government wants to increase voter turnout, the registration process may prevent various groups of citizens and non-citizens from participating in the electoral process. Voter Registration Across the United States Elections in the United States are state-by-state contests. They include general elections for president and statewide offices (e.g., governor and U.S. senator), and they are often organized and paid for by the states. Because political cultures vary from state to state, the process of voter registration similarly varies. For example, suppose an 85-year-old retiree with an expired driver’s license wants to register to vote. He or she might be able to register quickly in California or Florida, but a current government ID might be required prior to registration in Texas or Indiana. The varied registration and voting laws across the United States have long caused controversy. In the aftermath of the Civil War, southern states enacted literacy tests, grandfather clauses, and other requirements intended to disenfranchise black voters in Alabama, Georgia, and Mississippi. Literacy tests were long and detailed exams on local and national politics, history, and more. They were often administered arbitrarily with more blacks required to take them than whites. Who is Allowed to Vote? In order to be eligible to vote in the United States, a person must be a citizen, resident, and eighteen years old. But states often place additional requirements on the right to vote. The most common requirement is that voters must be mentally competent and not currently serving time in jail. Some states enforce more stringent or unusual requirements on citizens who have committed crimes. Florida and Kentucky permanently bar felons and ex-felons from voting unless they obtain a pardon from the governor, while Mississippi and Nevada allow former felons to apply to have their voting rights restored. On the other end of the spectrum, Vermont does ot limit voting based on incarceration unless the crime was election fraud. Maine citizens serving in Maine prisons also may vote in elections. Beyond those jailed, some citizens have additional expectations placed on them when they register to vote. Wisconsin requires that voters “not wager on an election,” and Vermont citizens must recite the “Voter’s Oath” before they register, swearing to cast votes with a conscience and “without fear or favor of any person.” How Does Someone Register to Vote? The National Commission on Voting Rights completed a study in September 2015 that found state registration laws can either raise or reduce voter turnout rates, especially among citizens who are young or whose income falls below the poverty line. States with simple voter registration had more registered citizens. Another aspect of registering to vote is the timeline. States may require registration to take place as much as thirty days before voting, or they may allow same-day registration. Maine first implemented same-day registration in 1973. Fourteen states and the District of Columbia now allow voters to register the day of the election if they have proof of residency, such as a driver’s license or utility bill. Many of the more populous states (e.g., Michigan and Texas), require registration forms to be mailed thirty days before an election. Moving means citizens must re-register or update addresses. College students, for example, may have to re-register or update addresses each year as they move. States that use same-day registration had a 4 percent higher voter turnout in the 2012 presidential election than states that did not. In all states except North Dakota, a citizen wishing to vote must complete an application. Whether the form is online or on paper, the prospective voter will list his or her name, residency address, and in many cases party identification (with Independent as an option) and affirm that he or she is competent to vote. States may also have a residency requirement, which establishes how long a citizen must live in a state before becoming eligible to register: it is often 30 days. Beyond these requirements, there may be an oath administered or more questions asked, such as felony convictions. If the application is completely online and the citizen has government documents (e.g., driver’s license or state identification card), the system will compare the application to other state records and accept an online signature or affidavit if everything matches up correctly. Citizens who do not have these state documents are often required to complete paper applications. States without online registration often allow a citizen to fill out an application on a website, but the citizen will receive a paper copy in the mail to sign and mail back to the state. Voter Registration Rates in Texas Texas fares poorly in recent comparisons of registration rates among states. In the 2016 elections, Texas ranked 46 out of 51 (including the District of Columbia) for the percentage of eligible population (excluding non-citizens for instance). Qualifications to Vote in Texas To be eligible to register to vote in Texas, a person must be: - A United States citizen; - A resident of the Texas county in which application for registration is made; - At least 18 years old on Election Day; - Not finally convicted of a felony, or, if so convicted must have (1) fully discharged the sentence, including any term of incarceration, parole, or supervision, or completed a period of probation ordered by any court; or (2) been pardoned or otherwise released from the resulting disability to vote; and - Not determined by a final judgment of a court exercising probate jurisdiction to be (1) totally mentally incapacitated; or (2) partially mentally incapacitated without the right to vote. Registration in Texas is generally done by signing a postage-paid voter registration application and dropping it in the mail. In most counties, the Tax Assessor-Collector is also the county voter registrar. Applications are available at county facilities and at many libraries, post offices, and schools. You must be at least 17 years and 10 months of age on the date you apply, and the application must be received by the county or postmarked 30 days before any election in which you wish to vote. Need to register to vote? You can fill out an application online or request to have an application mailed to you by calling the Texas Secretary of State’s office toll-free at 1.800.252.VOTE (8683). \| Votes For 17-Year Olds? To vote in Texas, it is helpful, but not required, that you have your voter registration card with you. You are required to have one of seven forms of photo identification, like a driver’s license or a passport, to vote. Citizens can also obtain an Election Identification Certificate free of charge at more than 225 Texas driver license offices throughout the state. Once you are registered, there are a number of different elections in which you can participate. Primary elections are conducted jointly by major political parties and the state, generally in March of even-numbered years, and is the process by which parties choose their nominees for a general election. Party nominees must receive a majority of the votes cast in their race – otherwise, a runoff election between the top two finishers is held several weeks later. Many states have closed primaries, meaning that a voter must declare their membership in a political party as part of the voter registration process. Only “registered Republicans” can vote in Republican primary elections in states like California. Texas is an open primary state – meaning you simply register as a voter. A registered voter can participate in any party primary but can only participate in one party’s primary in each election and cannot vote in a party’s runoff election after voting in another party’s primary in the same election. General elections are held in November, with the nominees of the major and minor parties, as well as independent candidates running for each position. Winning a general election does not require a majority, just a plurality – more votes than anybody else in the race. Rick Perry was reelected Governor of Texas in 2006 with just 39% of the vote in a four-way race against Democratic nominee Chris Bell and two well-known independent candidates, former Texas Comptroller Carole Strayhorn and writer/musician Kinky Friedman. Registered voters in Texas can also participate in local elections to choose mayors and city council members, school board and special district board members – all of which must be elected with a majority. Constitutional Amendment Elections, generally in November following a session of the Texas Legislature, allow voters to consider changes to the state’s constitution recommended by two-thirds of the Texas House and Senate. Bond elections involve voters deciding whether or not to authorize government entities to borrow money. Recall elections allow voters who live in home rule cities to remove an official from office, and are held only when citizens gather a required number of signatures on petitions demanding the removal of the official. In Groves, a city near Beaumont, a petition resulted in a November recall election for City Council Member Cross Coburn following the release of controversial photos from an online dating app. More than 62 percent of Groves voters chose to remove Coburn from office. Home rule cities can also hold charter change elections – with voters choosing whether or not to adopt changes to the city’s basic governing document recommended by city officials. In 2018, Houston voters adopted a pay parity provision sought by the local firefighters’ union, which requires the city to pay firefighters the same as police officers of equivalent rank. Rollback elections can be triggered automatically or by petition and allow voters to choose whether or not to decrease a jurisdiction’s property tax rate. In August, 2018, voters in the Amarillo area voted nearly 2-to-1 to roll back the property tax rate for the Pampa Independent School District. In March 2019, voters in Gonzalez, Texas, voted against a petition-driven proposal to reduce the city’s property tax rate. LICENSES AND ATTRIBUTIONS CC LICENSED MATERIAL, ORIGINAL Authored by: Andrew Teas. License: CC BY: Attribution (https://www.google.com/url? q=https://creativecommons.org/licenses/by/4.0/&sa=D&ust=1552704204322000) CC LICENSED CONTENT, SHARED PREVIOUSLY American Government: Voter Registration Across the United States. Authored by: OpenStax. Provided by: OpenStax; Rice University. Located at: https://cnx.org/contents/W8wOWXNF@12.1:Y1CfqFju@5/Preface (https://cnx.org/contents/W8wOWXNF@12.1:Y1CfqFju@5/Preface). License: CC BY: Attribution (https://creativecommons.org/licenses/by/4.0/). License Terms: Download for free at http://cnx.org/contents/9e28f580-0d1b-4d72- 8795-c48329947ac2@1.	oercommons	2025-03-18T00:35:16.424973	05/05/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66301/overview", "title": "Texas Government 2.0, Voting and Political Participation in Texas, Voting in Texas", "author": "Kris Seago" }
https://oercommons.org/courseware/lesson/66304/overview	Political Participation Overview Political Participation Learning Objective By the end of this section, you will be able to: - Summarize other forms of political participation Introduction While political scientists tend to focus on voting, there are other ways citizens participate in the policymaking process. Campaigning Citizens who want to do more than vote can involve themselves in political campaigns in a variety of ways from donating money to volunteering. Political campaigns are labor-intensive, and any candidate will tell you that volunteers are critical to a successful run for office. Campaign volunteers go door-to-door, distribute literature, post yard signs, make phone calls and help fold, stuff and stamp mailings. Running for Office While wealthy people with established careers have an advantage in elective politics, as in most things, ordinary people win elections throughout Texas every year, serving in positions from school board to the state legislature and beyond. In 1990, 18-year-old high school senior John Payton was elected Justice of the Peace in Collin County, Texas. His mother drove him to neighborhoods after school so he could campaign door-to-door. Payton defeated incumbent Jim Murrell in the Republican Primary before graduating from Plano East Senior High, then went on to win the November general election. Though dismissed initially as a “fluke,” Payton went on to serve nearly 30 years before stepping down in 2019. Political Activism On May 3, 1980, 13-year-old Cari Lightner was killed by a drunk driver, who had been released from jail two days before following his fourth DUI arrest. Cari’s mother, Candace Lightner and other parents of drunk driving accident victims formed Mothers Against Drunk Drivers, an interest group that has had a profound influence on the passage and enforcement of tougher laws against drunk driving. In Texas, political activists of every imaginable type have worked – alone or in groups – to influence public policy with varying degrees of success. Legal Some individuals and interest groups find the legal system to be an effective means of political participation. In 1973, there was almost no chance of elected officials overturning laws prohibiting abortion. Instead of seeking a political solution, activists sought relief through the courts. In Roe v. Wade, abortion advocates were able to overturn a Texas law prohibiting abortion, obtaining a court ruling that a woman’s right to an abortion is protected by an implied right of privacy in the Due Process clause of the Fourteenth Amendment. Supporters of environmental causes have found the court system to be similarly useful, stopping politically popular public works projects with lawsuits alleging violation of federal law, such as the Endangered Species Act. Licensing and Attribution CC LICENSED MATERIAL, ORIGINAL Political Participation. Authored by: Andrew Teas. License: CC BY: Attribution	oercommons	2025-03-18T00:35:16.445657	05/05/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66304/overview", "title": "Texas Government 2.0, Voting and Political Participation in Texas, Political Participation", "author": "Kris Seago" }
https://oercommons.org/courseware/lesson/66352/overview	Public Opinion and the Media in Texas Overview Public Opinion and the Media in Texas Chapter Learning Objective By the end of this chapter, you will be able to: - Evaluate the role of public opinion and the media in Texas politics Introduction The collection of public opinion through polling and interviews is a part of political culture. Politicians want to know what the public thinks. Campaign managers want to know how citizens will vote. Media members seek to write stories about what the public wants. Every day, polls take the pulse of the people and report the results. And yet we have to wonder: Why do we care what people think? Over time, our beliefs and our attitudes about people, events, and ideas will become a set of norms, or accepted ideas, about what we may feel should happen in our society or what is right for the government to do in a situation. In this way, attitudes and beliefs form the foundation for opinions. As many a disappointed candidate knows, public opinion matters. The way opinions are formed and the way we measure public opinion also matters. But how much, and why? These are some of the questions we’ll explore in this chapter. Licensing and Attribution CC LICENSED CONTENT, ORIGINAL Revision and Adaptation. Authored by: panOpen. License: CC BY: Attribution CC LICENSED CONTENT, SHARED PREVIOUSLY American Government. Authored by: OpenStax. Provided by: OpenStax; Rice University. Located at: http://cnx.org/contents/5bcc0e59-7345-421d-8507- a1e4608685e8@18.11. License: CC BY: Attribution. License Terms: Download for free at http://cnx.org/contents/5bcc0e59-7345- 421d-8507-a1e4608685e8@18.11.	oercommons	2025-03-18T00:35:16.462266	05/05/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/66352/overview", "title": "Texas Government 2.0, Public Opinion and the Media in Texas, Public Opinion and the Media in Texas", "author": "Kris Seago" }
https://oercommons.org/courseware/lesson/99333/overview	Lesson: Artificial Intelligence and XR Technologies Overview AI-generated art and text can play a significant role in XR (extended reality) technologies. As described earlier in the course, XR technologies refer to a group of technologies that include virtual reality (VR), augmented reality (AR), and mixed reality (MR), which are used to create immersive digital experiences. AI-generated art can be used to create realistic digital environments and avatars for VR, AR, and MR experiences. These environments and avatars can be used for a wide range of applications, including gaming, training, and education. AI-generated text can also be used to create interactive dialogue and narrative in XR experiences. This can help to make these experiences more engaging and immersive for users. In addition to creating digital environments and narrative, AI-generated art and text can also be used to improve the overall user experience in XR technologies. For example, AI algorithms can be used to analyze user data and adjust the XR experience in real-time based on the user's preferences and behavior. This can help to create a more personalized and engaging experience for users. Overall, AI-generated art and text can have a significant role in enhancing XR technologies by creating realistic digital environments, interactive dialogue, and improving the overall user experience. As AI technology continues to advance, it is likely that we will see even more impressive developments in this area. Artificial Intelligence and XR Technologies AI-generated art and text can play a significant role in XR (extended reality) technologies. As described earlier in the course, XR technologies refer to a group of technologies that include virtual reality (VR), augmented reality (AR), and mixed reality (MR), which are used to create immersive digital experiences. AI-generated art can be used to create realistic digital environments and avatars for VR, AR, and MR experiences. These environments and avatars can be used for a wide range of applications, including gaming, training, and education. AI-generated text can also be used to create interactive dialogue and narrative in XR experiences. This can help to make these experiences more engaging and immersive for users. In addition to creating digital environments and narrative, AI-generated art and text can also be used to improve the overall user experience in XR technologies. For example, AI algorithms can be used to analyze user data and adjust the XR experience in real-time based on the user's preferences and behavior. This can help to create a more personalized and engaging experience for users. Overall, AI-generated art and text can have a significant role in enhancing XR technologies by creating realistic digital environments, interactive dialogue, and improving the overall user experience. As AI technology continues to advance, it is likely that we will see even more impressive developments in this area. _____________________________________________________________________ Here is a list of some Web-based AI content generation applications (images and text) that you can explore to discover how to use them in your own work. Text Generation Programs GPTChat: "GPTChat is a type of AI-based chatbot that uses a GPT-3 model to generate responses to user input..." URL: chat.openai.com/chat Amazon LEX: “Amazon LEX is a web service that allows customers to include conversational interfaces for voice and text in the software applications they are developing.” URL: https://lexai.co/en RYTR: “Rytr is an AI writing assistant that helps you create high-quality content” URL: https://rytr.ai Word Hero: “Word Hero utomatically creates plagiarism-free, human-like content in seconds.” URL: https://wordhero.co/ ________________________________________________________________ Image Generation AI Programs Dall-E: “DALL-E is a large-scale language model developed by OpenAI. It is trained to generate images from text descriptions.. DALL-E is able to create a wide variety of images, from photorealistic to highly stylized, based on the text input it receives. DALL-E is an example of how advanced language models can be used to generate creative outputs.” URL: labs.openai.com Midjourney: “Midjourney is an independent research lab that produces a proprietary artificial intelligence program that creates images from textual descriptions, ...” URL: https://midjourney.com/ Stable Diffusion: “Stable Diffusion is a latent text-to-image diffusion model capable of generating photo-realistic images given any text input…” URL: https://stablediffusionweb.com/	oercommons	2025-03-18T00:35:16.477968	Raji Sundar	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/99333/overview", "title": "Lesson: Artificial Intelligence and XR Technologies", "author": "Bellevue College XR Lab" }
https://oercommons.org/courseware/lesson/117235/overview	Education Standards Electric Vehicle Presentation Electric Vehicles Overview In this lesson, students will learn about how we can take renewable sources and use them for energy. Students will start by building an electric vehicle and then discussing the benefits and drawbacks of electric vehicles. In partnership with the Washington State Office of the Superintendent of Public Instruction (OSPI) and the legislature-funded ClimeTie program, the Gonzaga Institute for Climate, Water, and the Environment has created the Climate Literacy Fellows program. Electric Vehicles Lesson Overview Lesson Title: Electric Vehicles Grade Level: 6th-8th Grade Disciplinary Area: Earth Science Duration: 45 minutes Big Question: What are advantages and disadvantages of using renewable resources? How can we use renewable resources to power electric vehicles? Learning Objectives: - Students will learn about renewable and non-renewable energy. - Students will learn how electric vehicles work by creating an EV model. - Students will learn about the benefits and drawbacks or electric vehicles through discussion with classmates. Key Terms Renewable Resource, Non-Renewable Resource, Greenhouse Gases, Electric Vehicle Standards: Next Generation Science Standards - MS-ESS3-5: Ask questions to clarify evidence of the factors that have caused the rise in global temperatures over the past century. - MS-ESS3-4: Construct an argument supported by evidence for how increases in human population and per-capita consumption of natural resources impact Earth's systems. Materials: \| Material: \| Link for Purchasing: \| \| Wind Turbine Kit \| Carolina Wind Power Kit \| \| Rechargeable Batteries \| Rechargeable Batteries \| \| Post-It Sticky Notes \| Post-It Sticky Notes \| Authors: Sarah La Carrubba, Gonzaga Class of 2023 Revised by Jordan Kremer, Gonzaga Class of 2025	oercommons	2025-03-18T00:35:16.505374	Technology	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/117235/overview", "title": "Electric Vehicles", "author": "Manufacturing" }
https://oercommons.org/courseware/lesson/16187/overview	10 rules of success for entrepreneurs Finding the gap in an established market How to build the business not the product Managerial skills entrepreneurs need Negotiating successfully Overcoming the fear of starting a business Resistance to change Working on your business idea Fundamentals of Entrepreneurship Overview Entrepreneurship is the cornerstone of any modern economy - everyday, entrepreneurs around the world are starting their own business. This free online course from The E-Learning Network (TELNET) examines how entrepreneurs can surmount obstacles and also examines how business ideas can be developed and habits an entrepreneur must adopt to be a success. Upon completion of this course you will develop an understanding of obstacles entrepreneurs face and how to overcome them. You will gain a good knowledge of the development process and the planning process involved in the launch of a new product. You will have a good understanding of the business ecosystem and a knowledge of successful entrepreneurial habits. This course is ideal for anyone who wants to learn more about entrepreneurship or who may be thinking about starting their own business. Section 1 Entrepreneurship is the cornerstone of any modern economy - everyday, entrepreneurs around the world are starting their own business. This free online course from The E-Learning Network (TELNET) examines how entrepreneurs can surmount obstacles and also examines how business ideas can be developed and habits an entrepreneur must adopt to be a success. Upon completion of this course you will develop an understanding of obstacles entrepreneurs face and how to overcome them. You will gain a good knowledge of the development process and the planning process involved in the launch of a new product. You will have a good understanding of the business ecosystem and a knowledge of successful entrepreneurial habits. This course is ideal for anyone who wants to learn more about entrepreneurship or who may be thinking about starting their own business.	oercommons	2025-03-18T00:35:16.583593	ROI Africa E-Learning Network	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/16187/overview", "title": "Fundamentals of Entrepreneurship", "author": "Module" }
https://oercommons.org/courseware/lesson/72657/overview	Investment Planning Activity Overview This particular activity will help the students to think creatively and apply the investment planning skills by considering the real market data. Through this activity, students explore various investment vehicles, understand various pros and cons of the investment vehicles. Investment Activity Activity: Learners have to identify various investment vehicles which are available in the Indian Financial System and prepare the list of investment vehicles suitable for the investors who are in the age group of (1) 25Years - 35 Years (2) 36Years - 45Years (3) 46 Years - 56 Years. Allocate Rs. 10000 based on the investment goals of the individual investor. Instructions to Students: 1. Students should have knowledge about investment, objectives, goals, and constraints. 2. Students have to prepare a minimum 9 scenarios based on the different age groups. 3. The given amount can be divisible in various investment vehicles. 4. In the comment section students has to write the justification of whether the investment goal acheived/acheivable/. 5. Students should consider short term objectives less than a Year. 6. Use the attached excel sheet to do the activity. 7. Submit or email the excel sheet to the instructors official email id gpm@bimsadoni.ac.in	oercommons	2025-03-18T00:35:16.602304	09/17/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/72657/overview", "title": "Investment Planning Activity", "author": "Gundupagi Manjunath" }
https://oercommons.org/courseware/lesson/123661/overview	NSG 143 Development of Nursing Practice 1 Overview This course introduces the theory that directs nursing skills and the development of nursing practice. These skills will help you to deliver care in a safe, patient-centered, and evidence-based manner. We will be using the nursing process as a framework for the care and implementation of appropriate nursing interventions. Basic to intermediate nursing skills are developed. NSG 143 Development of Nursing Practice 1 This course introduces the theory that directs nursing skills and the development of nursing practice. These skills will help you to deliver care in a safe, patient-centered, and evidence-based manner. We will be using the nursing process as a framework for the care and implementation of appropriate nursing interventions. Basic to intermediate nursing skills are developed. Canvas Commons Link Use this link to access the original course in the Canvas Commons. Use this link to access the updated course in the Canvas Commons. Common Cartridge Course File Use the attached IMSCC file to access the course in an LMS other than Canvas.	oercommons	2025-03-18T00:35:16.621965	Homework/Assignment	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/123661/overview", "title": "NSG 143 Development of Nursing Practice 1", "author": "Full Course" }
https://oercommons.org/courseware/lesson/77849/overview	Early Learning Inclusion Resources Overview Explore this resource guide with links and handouts detailing inclusionary resources in an Early Learning setting. Overview The Office of Superintendent of Public Instruction (OSPI) and the Department of Children, Youth, and Families ( DCYF) have collaborated to compile resources useful to the Preschool Development Grant Transitions initiatives to provide resources, research, and related tools around best practice related to inclusion. We invite you to explore this resource page. Resources on Early Childhood Inclusion Office of Head Start Webpage: https://www.acf.hhs.gov/ohs Washington State Department of Children, Youth, and Families Early Childhood and Assistance Program (ECEAP) and Head Start Webpage: https://www.dcyf.wa.gov/services/earlylearning-childcare/eceap-headstart Office of Superintendent of Public Instruction Webpage: https://www.k12.wa.us/ National Association for the Education of Young Children (NAEYC) Statement on Inclusion (2019): https://www.naeyc.org/resources/position-statements/equity Visit the Early Childhood Technical Assistance Center (ECTA) Improving Systems, Practices, and Outcomes for comprehensive and up-to-date early childhood technical assistance. Wepage: Early Childhood Technical Assistance (ECTA) Webpage Early Childhood Technical Assistance Center (ECTA) Research and Studies on Inclusion Webpage Resource. This webpage provides a comprehensive overview of current webinar(s) and finding(s) from the 2014 Preschool Inclusion Survey. Webpage: Early Childhood Technical Assistance (ECTA) Research and Studies on Inclusion Visit the National Center for Pyramid Model Innovations (NCPMI) webpage for comprehensive information around Pyramid Model Implementation supporting inclusionary practices for young children. Webpage: The National Center for Pyramid Model Innovations Fact Sheet: Fact Sheet of Preschool Inclusion Challenges and Solutions: A National Survey (2015): Developed by Dr. Erin Barton and Dr. Barbara Smith. Fact Sheet: Fact Sheet of Research on Preschool Inclusion (2014): Authored by Dr. Erin Barton and Dr. Barbara Smith. Handout: Inclusion for Preschool Children with Disabilities: What We Know and Should Be Doing (2014): Authored by Dr. Phil Strain. Resource Guide: Quality Indicators of Inclusive Early Childhood Programs/Practices: A Compliation of Selected Resources (2010). Authored by the NECTAC Preschool TA Team; Debbie Cate, Martha Diefendorf, Katy McCullough, Mary Peters, and Kathy Whaley. Publication: When In Doubt, Reach Out: Training Strategies for Inclusive Early Childhood Settings (2021). Authored by Christine M. Spence, Deserai Miller, Chatherine Corr, Rosa Milagros Santos,and Brandie Bentley. Publication: Builiding a More Inclusive Sandbox: Inviting Collaborators to Support Children, Families, and Early Learning (2016). Authored by Titus Dosremedios. Webinar Series: National Inclusion Webinar Series (Recorded). Resource Webpage: Visit the LEAP PreK Inclusion Model Program Website to learn about inclusion in pre-school settings. Resource Guide: The LEAP Preschool Model (2018). Authored by Nancy Draftina. License Except where otherwise noted, this website guidance document by Washington Office of Superintendent of Public Instruction is licensed under a Creative Commons Attribution License. All logos and trademarks are the property of their respective owners. This resource contain links to websites operated by third parties. These links are provided for your convenience only and do not constitute or imply any endorsement or monitoring by OSPI. Please confirm the license status of any third-party resources and understand their terms before use.	oercommons	2025-03-18T00:35:16.639652	Julie Dean	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/77849/overview", "title": "Early Learning Inclusion Resources", "author": "Teaching/Learning Strategy" }
https://oercommons.org/courseware/lesson/70007/overview	Protocol for Curating Accessible OER, Version 1.0 Overview The goal of the Protocol for Curating Accessible OER is to provide detailed yet easy to implement techniques for evaluating the accessibility of OER. Introduction Development of the Protocol The National Center on Accessible Educational Materials for Learning (AEM Center) at CAST is funded by the Office of Special Education Programs at the U.S. Department of Education to increase the availability, timely delivery, and use of high-quality accessible materials and related technologies by students with disabilities. Since May of 2019, the AEM Center has facilitated a #GoOpen Accessibility Community of Practice (CoP) to seek creative solutions to Open Educational Resources (OER) accessibility challenges. The work of the CoP contributed to this protocol, which is based on the best practices outlined in the Accessibility Checklist in ISKME's School Librarian OER Curation Framework. The rapid move to remote learning in response to COVID-19, and the challenges many school districts will continue to face in making sure students with disabilities have access to materials in a timely manner, made the development of such a protocol even more relevant and urgent for educators and families. Purpose The availability of high-quality OER plays an important role in addressing equity issues in education. For its full potential to be realized for every learner, however, OER must be more than openly licensed at a reasonable cost. They must also be usable across the variability learners bring to any learning environment. For this to be the case, OER must be designed according to accessibility best practices that ensure they will work with the assistive technologies many learners use to access the curriculum. As an added benefit, accessible OER are also often mobile-friendly, which is an important consideration for increasing participation through remote and distance learning. The goal of the Protocol for Curating Accessible OER is to provide detailed yet easy to implement techniques for evaluating the accessibility of OER in the following formats: - content created in OER Commons using the Open Author publication tool, - Microsoft Word and Google Suite documents that are often the source file for other formats such as PDF and EPUB publications, and - online resources such as websites and instructional videos. Use The Protocol for Curating Accessible OER can be implemented by a range of users, from an individual educator who is selecting materials for a lesson to a committee that is vetting curricula for statewide adoption. The protocol is organized by six areas that are relevant to accessibility practices. The mnemonic, “SLIDE,” makes the first five easy to remember: - Styles and Document Structure - Links and Navigation - Images - Design: Color and Typography - Evaluation with an Accessibility Checker The sixth area is Video. Each practice has its own section of the protocol, which begins with its importance for OER accessibility. Step-by-step instructions with screenshots show you how to check an OER for related accessibility practices. Techniques are categorized by the format of the material (e.g., Open Author publication, Word, Google, web page etc.). Styles and Document Structure Why is this important? A document with a good structure can improve understanding for everyone. Section headings “chunk” information into smaller segments that are easy to identify and process. Concise and descriptive section headings can also help with reader comprehension by highlighting the main ideas and relationships in a document. Not all headings are created equally, however. A common user practice is to select the heading text and make it larger and bold. While this will make the text look like a heading visually, it will not add the styles that are required to make it function like one. A style is the formatting instruction that you define in your word processor; set it once to format a heading and it applies that instruction across your document. A bonus of properly using styles to create section headings: You can create a table of contents that not only reveals how the information is organized but also improves document navigation. For accessibility, properly styled headings improve navigation for learners who are blind and use screen reader technology. A screen reader provides robust navigation options in addition to reading content aloud. Screen reader users do not always read a website or document from beginning to end in a linear way. Most screen readers support a keyboard shortcut or gesture that provides a list of the section headings. By selecting a heading from this list, learners can jump to specific sections of a long website or document. This capability significantly improves the efficiency with which learners can navigate the content using their assistive technology, allowing them to focus more of their energies on learning. What to Look For When Evaluating an OER - Content is organized into sections, and each section starts with a heading or subheading that succinctly describes what the section is about. - Section and subsection headings are created with proper markup. This means that the creator used styles rather than only formatting options such as making the text bigger and bold. - Headings and subheadings are used sequentially (e.g. Heading 1, Heading 2, etc.). Typically, a web page or document should have only one Level 1 Heading (H1) for the page/document title, with a Level 2 Heading (H2) used for the major sections, a Level 3 Heading (H3) for the subsections, and so on. You can think of this as an outline structure. How to Check for Proper Use of Styles and Document Structure Resources Created in OER Commons With Open Author With the OER resource open in Open Author, run the Accessibility Checker (the first icon on the left side of the editor’s toolbar): The Accessibility Checker in Open Author will point out when the wrong style is used to indicate a section heading. The Accessibility Checker will also allow you to make a quick fix by selecting a heading style from a dropdown menu: The Accessibility Checker in Open Author will also let you know if headings are not nested properly. Again, you will have the option to perform a quick fix by selecting the appropriate heading style from a dropdown menu: Microsoft Office Documents In Microsoft Word, place your cursor anywhere in a section heading’s text and check to make sure the appropriate heading style (Heading 1, Heading 2) has been selected in the Home tab of the Ribbon. To check the logical organization of the headings: - Open the Navigation Pane (View, Navigation Pane). - Choose the Document Map or Headings tab (this will vary according to your version of Office). - Confirm that every item that is styled to look like a heading in the document is listed in the Navigation Pane (has a heading style applied to it). As you select each heading in the Headings tab, you will navigate the section/subsection structure of the document in much the same way a screen reader user would (most screen readers support a keyboard shortcut to skip from one heading to the next). Another way to check the document structure in Microsoft Word is to add a table of contents based on the section headings by choosing References, Table of Contents. The table of contents should provide a logically organized outline of the document’s content. On a PowerPoint slide, the use of descriptive titles performs a similar function as the section headings in Word. Use the Outline View (View, Outline View) to confirm each slide has a descriptive and unique title. If the design requires it, the slide title can be hidden from view while keeping it in the reading order for screen readers: - Open the Selection Pane (Home, Arrange, Selection Pane). - Make sure the slide title (and optionally a slide number) is one of the first things listed near the bottom of the Selection Pane. Items near the bottom of the Selection Pane are read first, while those near the top are read last: - To hide a slide title, select the icon that looks like an eye to the right of its name. The title will be hidden in the slide but it will still keep its place in the reading order for screen reader users. Google Suite Documents The Grackle add-on for the Google Suite will identify improper use of styles to indicate section headings in Google Docs, including improper nesting. However, a subscription is needed to get guidance on how to fix the errors Grackle identifies: Alternatively, you can check the heading structure manually. Place the cursor anywhere inside the section heading text and confirm the appropriate style is selected in the styles dropdown menu in the Google Docs toolbar: A style of “Normal text” would indicate the heading has been created through formatting options only (making text larger and bold). As with Microsoft Word documents, another way to check the document structure is to add a table of contents based on the section headings, by choosing Insert, Table of Contents. Google Slides does not have an outline view or a selection pane similar to the one in Microsoft PowerPoint. For the best results, use the placeholders provided in the various templates to make sure each slide has a unique slide title and a reading order that makes sense. Web Pages Use the free tota11y bookmark or browser extension from Khan Academy to view the heading structure of a web page and confirm that headings are properly nested: - Once you have the extension installed, select the bookmark and the icon for tota11y (a set of glasses) will appear in the lower left corner of the screen. - Select this icon and choose Headings. A dialog in the lower right corner will show you the heading structure for the current web page, with errors explained in a separate tab: PDF Documents Use the free PDF Accessibility Checker (PAC 3) (available only for Windows) to check the document structure of a PDF document. PAC 3 will flag it as an error if a document has no assigned headings or if heading styles are not nested properly (if any headings are skipped over in the document structure). You can manually check the document structure with PAC 3 as follows: - Open the PDF document with PAC 3. - Choose the Logical Structure option. - Choose Structure Elements to see the document structure. - Confirm that text that looks like a heading in the Page View is marked up as such in the Structure Elements pane. Also, check to make sure the headings are properly nested in a logical way (e.g. Heading 3 is not used before Heading 2, etc.). If you have access to Adobe Acrobat DC (the version of Adobe Acrobat with editing capabilities), you can open the Tags panel (View, Show/Hide, Navigation, Tags) to review the tags assigned to the items in the PDF document. The Tags panel indicates the order in which items will be read by screen readers. You can select a tag to highlight the content in the document that corresponds to it. The tags should be in the correct order in the Tags panel (a level one heading should come before a level two heading): Links and Navigation Why is this important? Descriptive link text replaces a web address with a title or description of the link’s destination. The use of descriptive link text improves usability for all learners. The link text sets expectations about not just the content on the other side of the link but also any actions that might take place when it is selected: Will a new window or tab open? Will a file be downloaded? By helping learners quickly answer these questions, descriptive links improve the navigation and overall usability of educational materials for everyone. Descriptive links are especially helpful for learners who are blind and use screen reader technology to listen to the content of a web page or document. Most screen readers support a keyboard shortcut or gesture that brings up a list of all the links to assist with navigation. If a link reads as “click here” or “learn more” when presented on a list, it will be difficult to determine what will happen when the link is selected. For this reason, links need to be meaningful on their own, without relying on the surrounding content to provide context. What to Look For When Evaluating an OER - Links make sense on their own, without the surrounding text for context, and they do not use generic language such as “click here,” “about,” or “learn more.” - Links avoid the use of full web addresses as the link text. To provide a better experience for those listening with screen readers, the full web address is hidden behind more descriptive link text or a link shortener is used (with a descriptive custom ending). - Links prepare the reader for any unexpected actions such as the opening of a new window or tab, or the download of a file. - For resources that are also going to be printed (e.g. handouts for presentations, instructions, etc.) it may be helpful to use a link shortener and to include the shortened version of the full web address (with a custom ending) in parenthesis after the more descriptive link text. How to Check for Meaningful Links You may need to do a content review by scanning the document or website and flagging any links that do not follow best practices for meaningful, descriptive links. Some issues, such as links that use generic language (e.g. “click here”) or a full web address as the link text, will be easy to spot. Others, such as links that open new windows without warning, may require more careful testing - you may need to follow the link to confirm the action resulting from its selection. Resources Created in OER Commons With Open Author Run the Accessibility Checker and it should point out any links that use generic text (e.g. “click here”): You may need to manually check links to make sure they do not open new windows/tabs or download files without alerting the user. Microsoft Office Documents At the time of writing, the Microsoft Office Accessibility Checker does not flag links that use generic text (“click here”) or full web addresses. A content review is recommended. Google Suite Documents The Grackle accessibility add-on for Google Suite identifies links that are not meaningful under its Contents section. However, in testing this feature it missed a number of items that used generic text or a full web address. A content review is recommended. Web Pages Use the free tota11y bookmark from Khan Academy to check for meaningful links on a web page. Once you have the extension installed, select the bookmark and the icon for tota11y (a set of glasses) will appear in the lower left corner of the screen. Select this icon and choose Links: A dialog in the lower right corner will show you any errors related to links that are not meaningful and descriptive, along with suggestions for how to fix each error: You can also check the links by navigating through the web page using just your keyboard. As you press the Tab key, links (and other controls such as form fields) should receive a visible keyboard focus and this focus should move around the page in a logical order. As you tab through the page, review the link text to make sure it makes sense on its own, without the surrounding text providing context (as this is the way it may be accessed by assistive technology users). PDF Documents Open the PDF document in the free Acrobat Reader and perform a tab order test: press the tab key on your keyboard to navigate by links. Links should be highlighted in a logical order. As you review the tab order, you should also review the link text to make sure it follows best practices (the link text is descriptive and meaningful). Images Why is this important? The use of relevant images can make content more visually appealing and engaging. It can also support understanding by providing multiple representations of the information. Ideally, sufficient explanation is provided in the surrounding text to help everyone better understand the key ideas or relationships an image conveys. When this is not possible, a text alternative for the image needs to be provided. This text alternative should contain enough information to ensure no meaning is lost when the images are not available, either because they have been turned off or because the learner is using assistive technology to listen to the content. Another reason to provide text alternatives relates to connectivity issues, particularly in situations of remote learning: Turning images off speeds up browsing on a slow connection and saves bandwidth while accessing the content on a mobile device with a limited data plan. What to Look For When Evaluating an OER - Images that convey information include appropriate alternative text (a concise description of the image’s content). - Images that are purely decorative are marked up in such a way that they can be skipped by a screen reader. Not all authoring tools provide the option to indicate an image is decorative. For those that do not, the use of the word “decorative” for the alternative text is recommended. - Images that are functional (included in a link) have alternative text that reflects the action that will take place when the link is selected. How to Check Images for Alternative Text In addition to confirming that an image either has alternative text or has been marked as decorative (per instructions below), you will need to confirm the alternative text is appropriate for the purpose and context in which the image is used. Resources Created in OER Commons With Open Author The editor in Open Author will not allow you to add an image until you have provided alternative text. To review the existing alternative text, double-click the image and confirm an appropriate description has been provided in the alternative text field of the Image Properties dialog: Currently, there is no way to indicate that an image is decorative in Open Author. Simple text such as “null” or “decorative” should be used. An image can also have a caption in Open Author. The caption is additional information about the image, not a description of it. Thus, an image can have both alternative text and a caption, and the two should complement each other. Microsoft Office Documents The built-in accessibility checker (found in Review, Check Accessibility) will identify images that are missing alternative text. Selecting the item listed in the checker will highlight the image with the error in your content. The steps for confirming the image has appropriate alternative text will depend on the version of Office you have installed. In Microsoft Word and PowerPoint for Office 365: - With the image selected, choose Alt Text in the Picture Format tab of the Ribbon (or right-click the image and choose Edit Alt Text). This will open the Alt Text pane on the right side of the screen. - Make sure the image has an appropriate description, or check the box for “Mark as decorative” if the image does not add any meaning and is used purely for decoration: For older versions of Microsoft Office: - With the image selected, choose Format, Picture (or right click on the image and select "Format picture"). - Choose the Layout and Properties pane. - Expand the Alt Text section. - Make sure appropriate alt text is included in the Description field and the Title field is left blank. This will ensure the alt text is properly preserved if the document or presentation is converted to PDF. Google Suite Documents The free version of the Grackle accessibility checker for Google Suite will identify any images that are missing alternative text. However, you will need to manually inspect the images to make sure they have the appropriate alternative text. To confirm that an image has the appropriate alternative text, right-click on it and choose Alt Text. Google Suite (Docs and Slides) is similar to older versions of Microsoft Office in that it provides a Title and a Description field, but only the text entered in the Description field is preserved when the document or presentation is converted to PDF. Web Pages The free totally bookmarklet from Khan academy can help you identify images that are missing alternative text. Once you have totally installed, launch it by selecting the icon (eyeglasses) at the bottom of your web browser window, then choose “Image alt-text”: Each error will be explained in more detail on a pane that will open in the lower right corner of the screen. Select the magnifying glass next to each error to highlight the image that is missing alternative text: PDF Documents For PDF documents, use the free PDF Accessibility Checker (PAC 3) to confirm that appropriate alternative text is included with each image: - Open the PDF document in both Adobe Acrobat Reader and PAC 3 and arrange your windows so that you can see both views of the document side by side. - In PAC 3, select the Screenreader Preview option to view a linear version of the PDF document (the order shown is the order in which a screen reader will read the content). - Confirm that each image shown in Acrobat Reader has appropriate alternative text as shown with a white background in the screen reader preview PAC 3 provides. How to Check Alt Text for Purpose and Context Automated checkers can identify images that are missing alternative text, but they are not as good at analyzing the quality of that alternative text. More recently, artificial intelligence has been used to automatically generate alternative text. This feature will continue to improve with time, but the results typically require some editing for accuracy. Creating accurate and useful alternative text is more of an art than a science. It requires some judgement because the appropriate alternative text will require a consideration of the purpose for selecting an image and the context in which it is used. Given that, it is a skill that is improved with practice and collaboration. For more complex images such as charts and diagrams, we recommend approaching the creation of image descriptions (a longer version of alternative text) as a group activity that takes multiple interpretations into consideration to arrive at the best description. Images generally fall into three broad categories: - Decorative images are used to provide visual appeal and are not essential to understanding the content. These images should be marked up in such a way that they can be skipped by screen readers to reduce the “noise” in the content that is read aloud to learners. - Functional images are part of a link and should provide a description of the destination of the link or the action that will take place when the link is selected (e.g., downloading a file in another format). - Informative images are essential for understanding and need to have a concise description that starts with a broad overview of the key information followed by key details. The details you include in the description will depend on the purpose or goal for using the image. The alt decision tree from the World Wide Web Consortium (W3C) can help you determine what kind of image you are describing. As you review the alternative text, consider the context where the image is used. Is the image already described in the surrounding text? If so, it should be treated as a decorative image to avoid redundant information being read aloud to screen reader users. Color and Typography Why is this important? The effective use of color can add aesthetic appeal and make content more inviting to learners. However, text with low contrast may be difficult to perceive and require more effort for some learners, including those with low vision or those viewing the content in less than ideal lighting conditions (where glare can be an issue). Some learners may also have difficulty seeing certain colors due to color-blindness. With good color contrast, learners can focus more of their energies on gaining a better understanding of the information, rather than on overcoming barriers to perception. As with the use of color, typography (choice of fonts, text size, and spacing) can have an impact on how much energy learners need to spend perceiving and processing information. Preferences for fonts and spacing vary across learners, and ideally the reading application provides options for making individual adjustments to meet the unique needs of each individual. Starting with a good baseline for font choice, text size, and other elements of typography can provide a good experience by default. What to Look For When Evaluating an OER Use of color - Colors should meet a minimum color contrast requirement of 4.5:1 for body text and 3:1 for large text (18 pt or larger, typically the text used in section headings). Body text only needs to meet the lower 3:1 contrast ratio if it is 14 pt or larger and bold. - Color should not be used alone to convey meaning. An additional cue such as a text label should be used for those who are unable to distinguish between different colors (or between shades of the same color). - Links should not have their underline removed through styling. If the underline is removed, the link text needs to have a color contrast ratio of 3:1 with the surrounding text (in addition to the requirement of a color contrast ratio of 4.5:1 with the background color). - Review directions to make sure they do not refer to color and other visual characteristics (shape, size or location). Use of Typography - Use sans-serif fonts for body text. Sans-serif fonts, such as Arial or Verdana, lack any ornamentation at the end of their strokes. This lack of ornamentation increases the space between the letters and makes the text easier to read, especially at smaller text sizes. - Avoid the use of formatting alone (bold, or italics) for emphasis. Use text (e.g. “Important:” or “Note:”) to highlight information that needs focused attention from learners. Screen readers do not always announce changes in styling by default. - Left-align blocks of text, as full justification can add uneven spacing between words, resulting in distracting “rivers of whitespace” that run down the page where extra spacing has been added. - Begin with a good baseline text size. For documents, a baseline text size of 12 pt for body text is recommended. For slide decks, 22-24 pt for the body text is recommended as a minimum text size. How to Check for Color Contrast Use a free color contrast checker such as the Colour Contrast Analyzer from Paciello Group to make sure your choice of background and foreground colors meet the minimum contrast ratio requirements under Level AA of the Web Content Accessibility Guidelines (WCAG). On Windows, the Colour Contrast Analyzer includes a color picker to allow you to select the foreground and background color combination that will be checked. On the Mac, the Colour Contrast Analyzer will open up the Mac’s color picker tool when a color swatch is selected, but the functionality will be the same. This tutorial video from the AEM Center demonstrates the use of the Colour Contrast Analyzer to check color contrast on both Windows and the Mac. The option to check for color contrast is sometimes included in accessibility checkers for websites. For example, it is one of the options available in the tota11y tool from Khan academy as well as WAVE from WebAIM. How to Check Use of Color and Typography The use of colors and other visual characteristics (shape, size and location) in instructions will require a content review. The same is true for checking the typography (text size, fonts and spacing) used in a resource. One way to check that color alone is not used to convey meaning is to turn on the grayscale view in your operating system and confirm the content makes sense when color is removed. This option is especially helpful for reviewing charts and diagrams to make sure they include additional cues and do not rely on color alone for meaning. The option to switch to a grayscale view will typically be found in the settings or system preferences of your operating system: - Windows 10: Settings, Ease of Access, Color Filters - iOS 13 or later (iPad and iPhone): Settings, Accessibility, Display and Text Size, Color Filters - Mac: System Preferences, Accessibility, Display - Chromebooks do not have a grayscale option, but an extension such as High Contrast can provide similar functionality for any content accessed through the Chrome web browser. Evaluation with an Accessibility Checker Why is this important? Some authoring tools now include a built-in accessibility checker, but even the best of these automated accessibility checking tools have their limitations due to the subjective nature of many accessibility practices. For example, an automated checker may reveal that an image has alternative text, but it may not be able to determine if the alternative text accurately describes the content of the image. This determination will often require subject matter knowledge, as well as a consideration of the context and the purpose for using the image. As long as you keep the limitations of automated checkers in mind, and don’t see them as a replacement for best practices, they can make a valuable contribution to your accessibility work. Whenever possible, automated checkers should be used as a starting point for authentic evaluations that includes usability testing with a range of learners who can test how well the content will work with a variety of tools, including assistive technologies and mobile devices. What to Look For When Evaluating an OER - Use an accessibility checker to verify that a resource conforms to those accessibility practices that can be assessed with an automated check (e.g. missing alternative text). - Review the guidance provided by the accessibility checker (if any is available) to help you understand any recommended fixes and build up your knowledge of accessibility best practices. - Review your content on a mobile device to ensure it is not only accessible but also mobile-friendly. - Identify learners who can provide authentic feedback about the usability of resources and compatibility with the technologies they use (including assistive technology). How to Use Accessibility Checkers Resources Created in OER Commons With Open Author In the Open Author editor, the Accessibility Checker is the first item from the left (its icon looks like a human figure with open arms). Open the Accessibility Checker and select Previous or Next to review the errors the Accessibility Checker has identified. You should then see a description of each error. Depending on the error, there may be an option to perform a quick fix by entering a different value or selecting it from a dropdown menu. Microsoft Office Documents The Accessibility Checker for Microsoft Office applications is found in the Review tab of the Ribbon. Launching it will open an Accessibility Checker pane on the right side of the screen. Select any of the errors listed in this pane to highlight the element (image, heading, etc.) with the accessibility error in your document. Selecting an error will also display an explanation with steps for fixing the error at the bottom of the pane. The Windows version of the Office Accessibility Checker also provides Recommended Actions for quick fixes from a dropdown menu (e.g., adding an image description): Note: On older versions of Office, the Accessibility Checker may not be in the Ribbon. You may have to choose File, Info, Check for Issues. Google Suite Documents The Grackle add-on will identify accessibility errors in Google Suite applications (Docs, Sheet and Slides). Grackle can perform a check for free, but getting guidance on fixes requires a subscription. To install Grackle: Choose Add-ons, Get Add-ons, and do a search for Grackle. Once Grackle is installed, launch it by choosing Add-ons, Grackle (Docs, Sheets or Slides, depending on the Google Suite application), Launch. This will perform a check and list any errors in a pane to the right of the document. Select an error to expand it and read an explanation with a list of all instances of that error in the current document. For example, if there are multiple images with missing alternative text, Grackle will list each as a separate error so that you can directly move to that image in the document and perform a fix. Web Pages The tota11y extension from Khan Academy can perform some basic checks on a web page. It includes options for checking the document structure (headings), color contrast, link text and image alternative text. You have learned how to use these options for tota11y in the other sections of this protocol. For a more thorough check, the online WAVE tool from WebAIM (which can also be installed as a WAVE Google Chrome or Firefox extension) is also available. It provides a list of errors along with icons that highlight the error on the page when each icon is selected. A color contrast checker is also included in WAVE. To check a website with WAVE, you have two options: - Go to the WAVE website, enter the address of the website in the text field at the top of the page and press Enter/Return to view the results. - With the website to be checked open in Google Chrome or Firefox, select the icon for the WAVE extension and a pane with the results should appear on the left side of the screen. PDF Documents The free PAC 3 PDF Accessibility Checker for Windows can be used to check the accessibility of a PDF document if you don’t have access to Adobe’s Acrobat tool and its built-in checker. To perform a full accessibility check on a PDF document with PAC 3, select the browse button at the top of the screen and locate the document on your computer. A summary of the results will be shown, but you can choose Results in Detail to review any errors more carefully. This will open a tree view with errors organized into categories you can expand to see all instances of each error. When you select an instance, a pane on the right side will show you visually where the error is found in your document. Video Why is this important? Videos provide options for presenting information in a way that engages today’s learners. Videos that include closed captions are not only more accessible to learners who are deaf and hard of hearing, they support improved understanding and usability for everyone, including: - English language learners - Learners with limited or emerging literacy - Learners who are new to a topic that has specialized vocabulary or jargon - Anyone listening to the video in a public setting where the ambient sound is too loud Audio description consists of voice-over narration that describes important visual details that cannot be understood from the main soundtrack alone. The goal with audio description is to make the visual information in media accessible to people who are blind, but others may benefit from the explicit explanations as well. Videos should also have transcripts. Transcripts make it possible to quickly skim through or search the content without the need to play a long video to find the exact spot where an important piece of information has been shared. Transcripts also benefit learners who are deaf-blind. They can access the information in a transcript through the use of a braille display, which is a small device that converts text into braille in real time. What to Look For When Evaluating an OER - Videos have quality captions that include not only dialogue, but descriptions of sounds that are important for understanding, and speaker identification if there are multiple individuals. - Captions are accurate and in sync with the audio in the video. - A transcript is provided alongside the video, or a link to the transcript is located near the video. - Audio descriptions are provided, either as a secondary track or as a separate video that can be accessed from a link near the non-described video. - The video player can be controlled using only the keyboard. - Videos do not include blinking or flashing content that could result in a seizure. Checking for Video Accessibility Each video in a document or website should have alternative text that describes what it is about (see Protocol for Curating Accessible OER: Images for additional information on image accessibility). In addition it should include closed captions that can be turned on and off using a button in the player (usually indicated by the CC symbol). You should play the first minute or so of a video to quickly determine if it only has automatic captions available. You will note these captions by the missing punctuation and other obvious inaccuracies. You should also choose a random point later in the video to confirm your findings about the quality of the captions. Use the options menu of the player to determine if a track with quality captions is present. Sometimes the automatic captions are presented by default even if a high-quality caption track has been provided. Audio descriptions, which use narration to describe the action on screen, are also often provided as a secondary track that can be toggled on and off as needed. In addition to checking the video content for accessibility, you should make sure the player can be controlled using only the keyboard. You can try pressing the Tab key on your keyboard to make sure there is a visible focus indicator that moves around the various player controls in a logical order. Acknowledgments The AEM Center would like to thank the following members of the #GoOpen Accessibility Community of Practice for their contributions to the development of this protocol: - Maggie Pickett, Grantwood Area Educational Agency (Iowa). Maggie co-facilitated the monthly calls where individual sections of the protocol were reviewed. - Dr. Jeanette Westfall, Liberty Public Schools (Missouri). Liberty’s OER curriculum provided a “playground” for testing sections of the protocol as they were developed. - Amee Godwin, ISKME. Amee provided guidance, feedback and support throughout the development of the protocol. Disclaimers This protocol is intended as a decision-making tool to support the vetting of OER. It is not intended as a substitute for a full audit of conformance to accessibility standards. No conformance claims should be made based on the use of this protocol. The contents of this resource were developed under a cooperative agreement with the US Department of Education, #H327Z190004. However, those contents do not necessarily represent the policy of the US Department of Education and you should not assume endorsement by the Federal Government. Project Officer, Tara Courchaine, Ed.D.	oercommons	2025-03-18T00:35:16.693489	07/22/2020	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/70007/overview", "title": "Protocol for Curating Accessible OER, Version 1.0", "author": "Luis Perez" }
https://oercommons.org/courseware/lesson/84426/overview	Education Standards Clusive Mystery_image Video promo for "Pretty Little Liars" What's in a mystery? Clusive Lesson: It's a Mystery Overview This Lesson was created to use in conjunction with materials in Clusive [https://clusive.cast.org], a free, online learning environment that makes materials flexible and accessible. The Lesson is designed for students in grades 6-8, and targets ELA standards as well as SEL skills of self-awareness and learner agency. As you use this lesson, students will be guided to recognize, understand, and apply - key elements of a mystery story, - tools that they can use to build learner agency, self-awareness, and comprehension Clusive Lesson: It's a Mystery Name the lesson so that you and others can quickly find and use it. In preparation for this lesson, - Download the document What's in a Mystery? You can share this with students - through Clusive or another online platform - make paper copies for learners. - Assign these Clusive texts to students: - The Adventures of Sherlock Holmes - Short Fiction by Edgar Allan Poe Variability Consider the barriers that you can reduce; provide choice and options for the materials that students may use, for example. - I will make a few paper copies of stories and handouts as an option for students. - I will give choices for stories students can read. The options for stories: - The Boscombe Valley Mystery in The Adventures of Sherlock Holmes by Arthur Conan Doyle - The Murders in the Rue Morgue in Short Fiction by Edgar Allan Poe - The Mystery of Marie Rogêt in Short Fiction by Edgar Allan Poe - The Redheaded League in The Adventures of Sherlock Holmes by Arthur Conan Doyle It's a Mystery! About This Lesson Description Briefly describe the lesson topic, what students will be doing in this lesson, and why. About this Lesson: Mystery stories are not only fun, they get readers to use critical thinking and sensemaking skills. In this lesson, learners will start by watching a short video and identifying technique the video uses to build interest and suspense. Learners will then practice using the "What's in a Mystery?" as a whole group, then choose their own story to read and use the questions to evaluate six elements of the mystery genre. An optional culminating activity is for learners to write their own short mystery using the six key genre elements. - see a quick high-interest video - identify some ways that the video uses to build interest and suspense - identify characters, the problem, cliffhanger, and possible solutions - choose a mystery short story in Clusive - use the resource, "What's in a Mystery?" worksheet during or after reading to identify key parts of the mystery genre in their chosen story. Prerequisites In student friendly terms, describe the requirements that need to be in place for students to start this lesson. Students will know how to log into and find readings in the Clusive Library. Goals Clusive Goals: Clusive goals are skills and understanding that students will work toward to become more expert learners. Focus on one or two of these skills during a lesson to support learner growth. Engagement: Students can identify a topic or theme that they want to explore further. Self-awareness: Students can identify a tool or setting and explain how it is useful for their learning. Independence: Students can, and explain how, they choose and change settings in response to different needs and goals (e.g., purpose of reading, time of day) Comprehension: Students can use their notes and comments to answer recall or inference questions, or to develop a perspective on an issue. Instructional Goals: Instructional goals are the overall skills or understanding that students will work toward during a lesson. Unless a specific means (production type) is the instructional goal (i.e., writing), instructional goals should be unrestricted by the means students use to achieve the goal. By the end of the lesson, students will be able to - explain the main components or parts of a typical mystery, including common characters and plot structure. - identify how the author develops point of view in a mystery story. - describe how the elements of a mystery story are used to convey a central theme or idea. Learning Objectives: Create objectives that serve as concrete, specific, measurable steps that will lead students toward accomplishing the instructional goals and inform adjustments to instruction. Express the objectives in words that will be easy for your students to understand. - Look up words to understand their meaning in a story. - Identify the six elements of a typical mystery story in a real story. - Collect evidence to answer questions about mystery stories. - Identify and explain how a Clusive tool helped you collect evidence. - Optional Make-your-own: Use what you learned about the elements of a typical mystery story to write your own! Estimated Time Indicate the amount of time you think this lesson will take. 2-3 classes Description Mystery stories are not only fun, they get you thinking and figuring things out. In this lesson, you will - Watch a short video and brainstorm about what makes it a mystery - Read a mystery story in Clusive - Use the resource What's in a Mystery? to identify key parts of a mystery in the story. - Add key things that you think are part of mystery stories - Write your own mystery! How much time this wll take us: 2 classes By the end of this lesson, you will be able to - Look up words to understand their meaning in a story. - Identify the parts of a typical mystery story. - Collect evidence to answer questions. - Identify and explain how a Clusive tool helped you. Materials Variability In any class, there is wide variability in how students learn and express what they know. For this lesson, it is predictable that learners will come with varied levels of engagement, background knowledge, and skills. What are your thoughts on how this lesson can support this diversity as learners work through the lesson? - I will use more than just text to build background understanding - I will provide choice for - what students read (choice of mystery stories in Clusive), - how they read it (digital or paper), and - the tools they use to interact with the stories (digital highlight, comment, read aloud, lookup or highlighters, post-its, dictionary. Students can pair for read aloud) Clusive text(s) List the specific texts you will use. Find texts in Clusive Public Library or upload your own content into Clusive to provide students with accessible, customizable, and adaptive materials. - The Boscombe Valley Mystery in The Adventures of Sherlock Holmes by Arthur Conan Doyle - The Murders in the Rue Morgue in Short Fiction by Edgar Allan Poe - The Mystery of Marie Rogêt in Short Fiction by Edgar Allan Poe - The Redheaded League in The Adventures of Sherlock Holmes by Arthur Conan Doyle Clusive Feature or Tool Focus Identify the Clusive feature that you will encourage and support students to use. This lesson will support and encourage learners to practice with a few tools that can promote learner self-awareness, motivation, and comprehension. - Highlight and Comment Read Aloud Dictionary look-up Other Materials and Supplies List any other materials and supplies you and your students will use in this lesson. With your lesson goals and objectives in mind, use media and materials that address the variability in your classroom. - Background building activity: Video promo for Pretty Little Liars - What's in a Mystery? handout - options for students who prefer not to work digitally: - print outs of the stories and handout - highlighters - pencils - post-it notes - dictionary You have a choice to read ONE of these Clusive text(s): Choose ONE of these stories: - The Boscombe Valley Mystery in The Adventures of Sherlock Holmes by Arthur Conan Doyle - The Murders in the Rue Morgue in Short Fiction by Edgar Allan Poe - The Mystery of Marie Rogêt in Short Fiction by Edgar Allan Poe - The Redheaded League in The Adventures of Sherlock Holmes by Arthur Conan Doyle We will be focusing on these Clusive tools/features: Highlight and Comment Read Aloud Dictionary lookup Other materials and supplies you can use: - print outs of the story of your choice - highlighters - pencils - post-it notes - dictionary What makes something a mystery? Opening Encourage student motivation and persistence by helping learners relate the lesson to their own priorities and concerns. Think about varied and flexible ways to prompt students to relate the lesson to their real-life concerns and interests. - I'm going to open with a quick activity to get students' attention - I will ask them questions that will get their thinking primed about the six elements of a mystery story - I will ask them what questions or solutions they can think of - IF I do this as a whole group activity, I will see which one the students want to use, and then go through the questions with the class. What exactly makes something a mystery story? A mystery story is like a recipe. It has ingredients. Each ingredient adds something to the flavor of the story. And when the ingredients are combined, they make something that is delicious to read! Choose: watch the video OR look at the pictures Answer these questions: - Who are the characters? - What happens? - What is the problem? - What are some ways that suspense is built? - What is the cliffhanger? [look up this word if you need to!] - What are some possible solutions you can think of to this mystery? What makes something a mystery story? A mystery story is like a recipe. It has ingredients. Each ingredient adds something to the flavor of the story. And when the ingredients are combined, they make something that is delicious to watch or read! Choose: watch the video OR look at the picture Answer these questions: - Who are the characters? - What happens? - What is the problem? - What are some ways that suspense (tension) is built? - What is the cliffhanger? [look up this word if you need to!] - What are some possible solutions you can think of to this mystery? Guided practice During Think about the varied methods you will use during the lesson to support learner engagement, understanding and interaction with the lesson concepts. Include options and supports for how students get and process information, how students express their knowledge, and how you will support and evaluate progress toward the instructional goals. - I'll use "I do, we do, you do" modeling, guided, and independent practice Guided Practice - Model how to use each of these tools in a sample story. - In Clusive, display this section from The Boscombe Valley Mystery from The Adventures of Sherlock Holmes: - Look up: Click on and look up "paradoxical" - Highlight "It seems, from what I gather, to be one of those simple cases which are so extremely difficult." and use the comment feature to note: This is a clue that what seems to be true will probably not be true. - Use Read Aloud to hear this section of the text: “Well, it is conjectured to be so. I shall take nothing for granted until I have the opportunity of looking personally into it. I will explain the state of things to you, as far as I have been able to understand it, in a very few words." - As a class, read aloud the next paragraph (Options: teacher can read aloud, kids can read aloud, or have the text-to-speech tool read aloud). - Have students suggest what might be clues in the paragraph, - ask them to explain why these might be clues. - Highlight their ideas and note their comments using the highlight and record tool. Some clue ideas: - made his money in Australia - Mr. Charles McCarthy, who was also an ex-Australian - Turner was apparently the richer man, so McCarthy became his tenant but still remained, it seems, upon terms of perfect equality, as they were frequently together. - Stop after this paragraph and ask students what they think will happen in the story, based on the information they have so far. [possible solution] Exerpt: “The London press has not had very full accounts. I have just been looking through all the recent papers in order to master the particulars. It seems, from what I gather, to be one of those simple cases which are so extremely difficult.” “That sounds a little paradoxical.” “But it is profoundly true. Singularity is almost invariably a clue. The more featureless and commonplace a crime is, the more difficult it is to bring it home. In this case, however, they have established a very serious case against the son of the murdered man.” “It is a murder, then?” “Well, it is conjectured to be so. I shall take nothing for granted until I have the opportunity of looking personally into it. I will explain the state of things to you, as far as I have been able to understand it, in a very few words. “Boscombe Valley is a country district not very far from Ross, in Herefordshire. The largest landed proprietor in that part is a Mr. John Turner, who made his money in Australia and returned some years ago to the old country. One of the farms which he held, that of Hatherley, was let to Mr. Charles McCarthy, who was also an ex-Australian. The men had known each other in the colonies, so that it was not unnatural that when they came to settle down they should do so as near each other as possible. Turner was apparently the richer man, so McCarthy became his tenant but still remained, it seems, upon terms of perfect equality, as they were frequently together. McCarthy had one son, a lad of eighteen, and Turner had an only daughter of the same age, but neither of them had wives living. They appear to have avoided the society of the neighbouring English families and to have led retired lives, though both the McCarthys were fond of sport and were frequently seen at the race-meetings of the neighbourhood. McCarthy kept two servants —a man and a girl. Turner had a considerable household, some half-dozen at the least. That is as much as I have been able to gather about the families. Now for the facts. Let's look at a section of a mystery story together. We will - collect clues - find out what some confusing words mean - propose a possible solution to the mystery! Independent Practice During Think about the varied methods you will use during the lesson to support learner engagement, understanding and interaction with the lesson concepts. Include options and supports for how students get and process information, how students express their knowledge, and how you will support and evaluate progress toward the instructional goals. Guided Practice (continued) What's in a Mystery? Handout - Model: - Display the handout - Choose one or two questions from the handout - Use the Highlight and Comment feature to - identify possible evidence - answer the What's in a Mystery? question using the comment Independent Practice - Have students sign into Clusive - Show students how to find the story choices - Give them a few minutes to find and choose the story they want to work on - Choices: - continue this Sherlock Holmes story "The Boscombe Valley Mystery" in The Adventures of Sherlock Holmes by Arthur Conan Doyle - OR choose one of the other mystery stories - The Murders in the Rue Morgue in Short Fiction by Edgar Allan Poe - The Mystery of Marie Rogêt in Short Fiction by Edgar Allan Poe - The Redheaded League in The Adventures of Sherlock Holmes by Arthur Conan Doyle Tasks as students read... - USE "What's in a Mystery?" and answer the questions to find key parts of the mystery genre in your story. - Look up 2 words to understand their meaning in a story. - Collect evidence to answer questions about mystery stories. - Identify a Clusive tool that helps you collect evidence. Your turn! - Sign into Clusive - Go to our class' section of the Clusive Library - Choose ONE of these stories: - continue this Sherlock Holmes story "The Boscombe Valley Mystery" in The Adventures of Sherlock Holmes by Arthur Conan Doyle - OR choose one of the other mystery stories - The Murders in the Rue Morgue in Short Fiction by Edgar Allan Poe - The Mystery of Marie Rogêt in Short Fiction by Edgar Allan Poe - The Redheaded League in The Adventures of Sherlock Holmes by Arthur Conan Doyle As you read... - USE "What's in a Mystery?" and answer the questions to find key parts of the mystery genre in your story. - Look up at least 2 words to understand their meaning in a story. - Collect evidence to answer questions about mystery stories. - Identify a Clusive tool that helps you collect evidence. Day 1 Closing Did you... - Look up at least 2 words to understand their meaning in a story? - Check the words in your word bank! - Identify the six elements of a typical mystery story in a real story? - Look at your answers in the What's in a mystery? question sheet! - Collect evidence to answer questions about mystery stories? - Look at what you have highlighted! - Identify a Clusive tool helped you collect evidence? - What tool helped you? How did it help you? Before you leave today Finish reading the story Complete the exit ticket Next session Finish answering the questions on the What's in a Mystery? sheet Turn in your answers to me (in paper or through Google Classroom) Write your own mystery! Day 2 Opening What we are doing today Finish answering the questions on the What's in a Mystery? sheet Turn in your answers to me (in paper or through Google Classroom) Write your own mystery! Write your own mystery! Create a template for students to use to build their own stories Characters: - Who is the detective or crime-solver - What do they look like? - What do they sound like? - How do they behave? - the suspects - What do they look like? - What do they sound like? - How do they behave? - How are they different from each other? Setting: Where does your story happen? When does your story happen? Plot Beginning: how will you hook your audience and make them want to keep reading? the problem is usually somewhere toward the beginning of your story. Middle: characters are introduced, the main events and clues happen here Make sure to include clues (and false clues) to keep your reader guessing A cliffhanger usually goes somewhere near the later part of the middle. End: the mystery is solved and life returns to normal. Problem: What is the problem or question that needs to be solved? Cliffhanger: What exciting event will keep your readers wanting to read more? The Solution: What is the answer to the problem? Who did it? Why did they do it? Keep digging into mysteries: create your own! Create your own short mystery story using the six parts of a typical mystery story: Characters: - Who is the detective or crime-solver - What do they look like? - What do they sound like? - How do they behave? - the suspects - What do they look like? - What do they sound like? - How do they behave? - How are they different from each other? Setting: Where does your story happen? When does your story happen? Plot Beginning: how will you hook your audience and make them want to keep reading? the problem is usually somewhere toward the beginning of your story. Middle: characters are introduced, the main events and clues happen here Make sure to include clues (and false clues) to keep your reader guessing A cliffhanger usually goes somewhere near the later part of the middle. End: the mystery is solved and life returns to normal. Problem: What is the problem or question that needs to be solved? Cliffhanger: What exciting event will keep your readers wanting to read more? The Solution: What is the answer to the problem? Who did it? Why did they do it? Mystery wrap up Assessments Clusive Teacher Dashboard Before the lesson: Note what your Clusive teacher dashboard tells you about student reactions student interests student use Clusive features During / After the lesson: Check in on your Clusive Dashboard. What does it show you about student reactions, topics of interest, student use Clusive features? What was the level of student engagement during the lesson? What will you build on? What will you change in your next lesson? What will you do to further support learners to become more independent, self-directed learners? Formative Assessments List the formative assessments you will use to evaluate how students are progressing in the lesson. Formative assessments should be based on the lesson objectives. Use the feedback from these ongoing, formative assessments to monitor and adjust instruction, methods, or materials. - 3,2,1 Exit ticket - Looking at Clusive Dashboard to check in on student activity and identify barriers Summative Assessments Enter the assessment(s) you will use in your lesson. Summative Assessments are usually end-of-lesson or-unit measures that assess the depth to which students have learned the skill or content related to the instructional goal. - Answers to questions from What's in a Mystery? sheet - Mystery stories: did they identify and use the six characteristics of a mystery? Look at your Clusive Dashboard What does your Clusive dashboard tell you about your reactions? your interests? which Clusive tools and features are helpful for you? Before you leave today Complete the exit ticket Turn in your mystery story	oercommons	2025-03-18T00:35:16.819814	Lesson Plan	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/84426/overview", "title": "Clusive Lesson: It's a Mystery", "author": "Reading Literature" }
https://oercommons.org/courseware/lesson/83203/overview	Disproportionality ppt Unit 1 “Intersectionality of disability with other identities: Implications for inclusive practices in schools.” Overview In this module, teaching credential candidates in elementary, secondary, and special education will learn about the assets and inequities that a focus on intersectionality can illuminate, and how this learning will affect their future work in classrooms. About this module This module is being developed for a course that introduces knowledge about students with disabilities and the purpose and system of special education to our teaching credential candidates in elementary, secondary, and special education. The principles and practice of including students with disabilities in general education classrooms, while widely accepted, have been hampered by some entrenched, long-standing notions of “who should be there”. Lowered expectations, segregated instructional groups, and instructional strategies that are counter to cultural ways of knowing are examples of these often-unexamined ideas. The module will focus on how the intersectionality of disability and other identities, in particular the racial, ethnic, and language identities of students in our schools, contributes to exclusion and stigmatizing. Dr. Kimberle` Crenshaw, in a recent interview, explained her current meaning of the term “intersectionality” as, “It’s basically a lens, a prism, for seeing the way in which various forms of inequality often operate together and exacerbate each other” (Steinmetz, 2.20.20). In this module, candidates will start to learn about the assets and inequities that a focus on intersectionality can illuminate, and how this learning will affect their future work in classrooms. The goals of the module will be for students to: - Build awareness of historic and current systemic inequities and discriminatory practices in the identification and instruction of children and adolescents with disabilities. - Learn how to recognize educational practices that mitigate against effective inclusion of students with disabilities in general education classrooms, including recent challenges and inequities due to the pandemic. - Learn about the assets of community and identity that intersectionality can illuminate, and how to infuse these into their inclusive classrooms. - Learn and practice evidence-based equitable ways to design lessons, environments, and assessment of learning. The module will be taught over three university class sessions. Seminal readings and meaningful activities will be tied to practical applications for these preservice teachers, while provoking personal and professional explorations of held ideas. The understandings that the module is intended to elicit will serve as essential bases for the rest of the course, which develops knowledge and skills in lesson design using Universal Design for Learning principles as well as the devising of adaptations to instruction and materials, all essential to the truly inclusive classroom. The course then finishes with a panel discussion with parents of students with IEPs, a simulation of a collaborative conversation between a special education teacher and a general education teacher, and an introduction to teachers’ roles in Response to Intervention and Multi-Tiered Systems of Support structures. Steinmetz, K., (2.20.20). She Coined the Term ‘Intersectionality’ Over 30 Years Ago. Here’s What It Means to Her Today. TIME Magazine. https://time.com/5786710/kimberle-crenshaw-intersectionality/ Audience: This module is intended for preservice teacher credential candidates in elementary, secondary, and special education. adults, instructors and educators who work with adults, particularly in higher education. In California, most teaching credentials are earned at the post-graduate level. Length of module: This has been designed as a three-unit sequence, to be taught in three class sessions. Technology: - This module can be taught in F2F, synchronous, asynchronous, or hybrid (F2F + online or synchronous + asynchronous) formats. To be taught in an asynchronous format, the instructor would need to pre-record the lectures. - To be taught in a F2F, onsite classroom format, the classroom would need technology with internet access and the ability to project videos, powerpoints, etc. - In a completely F2F format, assignments could be completed on paper. In other formats, students will need to use technology to complete and submit their work to their Learning Management System or directly to the instructor. - In low-resource contexts, instructors could mail course reading materials, and students could mail back their work. Each unit will contain descriptions of the learning objectives, content, activities and assessment measures. “Intersectionality of disability with other identities: Implications for inclusive practices in schools.” Unit #1: Biases and inequities in assessment and identification of students with disabilities Objective 1: The learners will be able to identify and give examples of disability identification bias based on cultural, language, and socioeconomic factors that can produce inaccurate and harmful results. Objective 2: The learners will demonstrate their understanding of non-biased assessment by designing a formative classroom assessment that provides culturally and linguistically diverse response choices, e.g. writing, dictating, drawing. Content: Ppt to be developed based on “Significant Disproportionality in Special Education: Current Trends and Actions for Impact”. NCLD (National Center on Learning Disabilities), 2020. https://ncld.org/sigdispro/ Resources/ References: To read: How does linguistic bias affect language evaluations? https://www.leadersproject.org/2013/03/01/how-does-linguistic-bias-affect-language-evaluations/ Cultural bias in assessment: Can creativity assessment help? http://libjournal.uncg.edu/ijcp/article/viewFile/301/856 Top 10 UDL Tips for Assessment https://slds.osu.edu/posts/documents/top-10-udl-tips.pdf © CAST.org Using Formative Assessment to Help English Language Learners © ASCD 2021 Activity: As homework assigned before this module starts, students will complete the IRIS Module entitled,“ English Language Learners: Is This Child Mislabeled?” https://iris.peabody.vanderbilt.edu/wp-content/uploads/pdf_activities/case_based/IA_Is_This_Child_Mislabled.pdf In class, students will engage in a discussion, either as a full group or in breakout groups, of how this module connects with the ppt lecture. Assessment: Students will demonstrate their understanding of sources and effects of bias in assessment of students with disabilities by contributing to a padlet in breakout groups on which they list all the ways that biased assessment could potentially happen in their early fieldwork or student teaching placement. Unit #2: Understanding Intersectionality when designing instruction for students with IEPs. Objective 1: The learner will be able to identify the academic and behavioral support needs of students from diverse cultural and linguistic backgrounds, e.g., students with cognitive deficits, specific learning disabilities, autism spectrum disorders. Objective 2: The learner will be able to develop a universally-designed activity for an inclusive class of elementary or secondary students. (This will be their introduction to UDL, which will be further addressed throughout the rest of the course.) Content: Interactive PPT: Define and describe culturally responsive pedagogy, and assets and funds of knowledge when designing lessons for students with disabilities from diverse cultural and linguistic backgrounds. Some of the slides will pose questions about their own school experiences that they can answer in the chat (on zoom) or as a direct message to me. Activity: creative UDL lesson format and example We will walk through an example of a universally-designed activity, and then they will design one in breakout groups. Connecting Universal Design for Learning With Culturally Responsive Teaching Assignment/Assessment: Students will re-design a standard lesson activity to be linguistically, culturally, and ability-diverse and based on UDL principles. I will provide two standard lesson activities (elementary and secondary) for them to choose from. Unit 3: Intersectionality, special education, and family empowerment Objective #1: The learner will be able to identify possible systemic racism, linguicism, and ableism in school-wide structures. Objective #2: Locate a one-page handout/online document for parents, in two languages (English and one other), on community and professional resources, including support groups, that demonstrates understanding of different perspectives, resources, assets and needs of families. Content: California Department of Education (CDE) Annual Data on numbers of students with disabilities by type of disability, grades 1-12, and ethnicity. Videos - schools that have model practices in inclusive education, parents and their perspectives. General education teachers’ role in inclusive education Resources/ Reading: Andratesha Fritzgerald, “Power and Empowerment: Honoring by Decision and Design.” CA CEEDAR Collaborative Conversation webinar, 6.25.21. Chamberlain, S. (2005). Alfredo Artiles and Beth Harry: Issues of Overrepresentation and Educational Equity for Culturally and Linguistically Diverse Students. Intervention in School and Clinic, 41(2). https://doi.org/10.1177/10534512050410020101 Organizations offering families information about special education and inclusive education. Assignment/Assessment: Locate a one-page handout/online document for parents, in two languages (English and one other), on community and professional resources, including support groups, that demonstrates understanding of different perspectives, resources, assets and needs of families.	oercommons	2025-03-18T00:35:16.895990	Reading	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/83203/overview", "title": "“Intersectionality of disability with other identities: Implications for inclusive practices in schools.”", "author": "Homework/Assignment" }
https://oercommons.org/courseware/lesson/92922/overview	Break Cards Overview To reinforce the concept of tending to the child’s own emotions. Break cards are made to help the child address their emotions and choose the kind of break based on their emotion. Sensory Overload The child may not be using the cards at first or may resist them. It’s essential to keep reminding the child that they’re available to be used. ACTIVITY OBJECTIVE: To reinforce the concept of tending to the child’s own emotions. Break cards are made to help the child address their emotions and choose the kind of break based on their emotion. ACTIVITY DESCRIPTION: Remind the child of the break cards before any activity. Three color-coded cards, each with a different purpose. The first one is for when he’s feeling bored or uninterested in the task, the break is for 2 minutes, and he gets to stay in the classroom. The second one is for when he’s feeling anxious/stressed, it’s for 5 minutes, in the hallway. The third one is for when he feels overwhelmed by the noise in class, it’s for 10 minutes, in the playground. Printables: I printed a photo with an hourglass on it, in 3 different colors, and added the information on them manually.	oercommons	2025-03-18T00:35:16.910676	Activity/Lab	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/92922/overview", "title": "Break Cards", "author": "Special Education" }
https://oercommons.org/courseware/lesson/112668/overview	AI’s Role in Revolutionizing Open Educational Resources (OER) Overview Garnet Valley School District in PA established a deep commitment to open education when it first joined the #GoOpen Network over eight years ago to advance an OER initiative. Still on an innovative journey to transform teaching and learning, the district’s Director of Technology and Online Learning and Founder and Executive Director of nonprofit Edvative Learning, Sam Mormando is actively exploring the rapidly evolving landscape of AI technology and reflecting on ways it may be advantageous for education, and specifically, for OER. Introduction Introduction The pressure on educators to provide diverse, up-to-date, and engaging learning materials is immense. This isn’t new for teachers and one of the main reasons why my district joined the #GoOpen movement many years ago. But, creating and updating OER has been time and resource-intensive. But no more, thanks to artificial intelligence(AI). AI’s capability to generate educational content is nothing short of revolutionary. AI systems can already create textbooks, lessons, and activities tailored to specific curriculum guidelines and learning objectives. This new technology has significantly expanded the availability of OER, and has provided teachers and students with unprecedented access to customized learning materials. Click here to access the full resource. About Dr. Samuel Mormando is the founder of the award-winning education non-profit, Edvative Learning, and serves as the Director of Technology, Innovation, and Online Learning for the Garnet Valley School District in Glen Mills, Pennsylvania. With a doctorate in educational leadership from Widener University, Dr. Mormando has been a key figure in driving Garnet Valley to national recognition for its innovative teaching practices. These include the adoption of open education resources and the development of a student-centered course design process, catering to various learning preferences: traditional, online, or blended. Under his stewardship, Edvative Learning has achieved significant milestones, notably receiving the Best in Educational Coaching award from Exemplar Schools in 2023. This honor reflects the organization's dedication to empowering classroom teachers in personalizing education. Additionally, Dr. Mormando's pioneering efforts in distance learning earned him the 2020 K–12 Innovation Award from the United States Distance Learning Association (USDLA). Besides his leadership roles, Dr. Mormando is also an accomplished author. His book, "Effectively Designed Instruction," achieved notable success as the #1 new book release on Amazon books. This publication underscores his expertise in educational strategies and his commitment to sharing his knowledge and insights with a broader audience. Through his innovative leadership, dedication to educational coaching, and contributions as an author, Dr. Mormando continues to influence the landscape of modern education, shaping effective teaching methodologies and enhancing student learning experiences.	oercommons	2025-03-18T00:35:16.924799	02/12/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/112668/overview", "title": "AI’s Role in Revolutionizing Open Educational Resources (OER)", "author": "Rebecca Henderson" }
https://oercommons.org/courseware/lesson/112662/overview	State Guidance for Understanding Artificial Intelligence in K-12 Schools: Oregon Overview Several State Departments of Education have published guides for understanding issues around AI in education, including privacy, security, transparency, accessibility, and keeping humans at the center of learning. These and related resources are being curated on the #GoOpen Hub and are freely available and openly licensed. Introduction Prior to setting school and district policies on the use of AI technologies, it is vital that school and district leaders are aware of federal and state policies that impact the use of these technologies both regarding student data privacy in addition to other states and countries that lead in this area. While there are a number of schools across the nation (and world) that have made the decision to ban the use of AI technologies and ChatGPT, when making this decision it is important to consider the learning opportunities that might be limited for students. Being aware of other policies both within and outside of Oregon can be helpful in making informed decisions.	oercommons	2025-03-18T00:35:16.937111	02/12/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/112662/overview", "title": "State Guidance for Understanding Artificial Intelligence in K-12 Schools: Oregon", "author": "Rebecca Henderson" }
https://oercommons.org/courseware/lesson/115236/overview	CoSN Resources on AI Overview In an era defined by rapid technological advancements, artificial intelligence (AI) has emerged as a transformative force in education. However, the successful integration of AI into a school district’s strategy requires careful planning, preparation, and evaluation. CoSN's collection of resources helps districts in their AI implementation. Introduction The Consortium for School Networking (CoSN) has curated a collection of their AI Resources on their website. These resources include, but are not limited to: - CoSN/CGCS K-12 Gen AI Maturity Tool - K-12 Generative AI Readiness Checklist - AI Blogs, Resources, and Discussions for CoSN Members - Webinar Recordings	oercommons	2025-03-18T00:35:16.949662	04/14/2024	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/115236/overview", "title": "CoSN Resources on AI", "author": "Rebecca Henderson" }
https://oercommons.org/courseware/lesson/109712/overview	Instructional Design & Accessibility Overview This short course aims to increase educators' awareness of matters relating to accessibility and how they can remove these barriers to increase access for all to education. Instructional Design 1. Watch the video below about how we can use instructional design to create an accessible learning environment for all students. Source: Jóhanna Bjartmarsdóttir. (2023, October 14). Kennsluhönnun & aðgengi: Kynning. [Video]. YouTube. https://www.youtube.com/watch?v=-LXeb4larI0&t=2s Accessibility 2. After watching the video, identify the aspects of the course environment created in the online courses demonstrated in the video increases access to education, for what student populations, and why: For example, including audio options and text-to-speech software increases accessibility for deaf students and dyslexic students.	oercommons	2025-03-18T00:35:16.962734	Jóhanna Birna Bjartmarsdóttir	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/109712/overview", "title": "Instructional Design & Accessibility", "author": "Module" }
https://oercommons.org/courseware/lesson/82946/overview	Learning Domain: Engineering, Technology, & Applications of Science Standard: Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem. Learning Domain: Earth and Human Activity Standard: Construct an explanation based on evidence for how the availability of natural resources, occurrence of natural hazards, and changes in climate have influenced human activity. Learning Domain: Earth and Human Activity Standard: Evaluate competing design solutions for developing, managing, and using energy and mineral resources based on cost-benefit ratios. Learning Domain: Earth and Human Activity Standard: Use computational tools to illustrate the relationships among management of natural resources, the sustainability of human populations, and biodiversity. Learning Domain: Engineering, Technology, & Applications of Science Standard: Ask questions, make observations, and gather information about a situation people want to change to define a simple problem that can be solved through the development of a new or improved object or tool. Learning Domain: Earth and Human Activity Standard: Ask questions to clarify evidence of the factors that have caused changes in global temperatures over time. Science Domain: Engineering, Technology, and Applications of Science Topic: Engineering Design Standard: Ask questions, make observations, and gather information about a situation people want to change to define a simple problem that can be solved through the development of a new or improved object or tool. Science Domain: Engineering, Technology, and Applications of Science Topic: Engineering Design Standard: Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem. Science Domain: Earth and Space Sciences Topic: Weather and Climate Standard: Ask questions to clarify evidence of the factors that have caused the rise in global temperatures over the past century. [Clarification Statement: Examples of factors include human activities (such as fossil fuel combustion, cement production, and agricultural activity) and natural processes (such as changes in incoming solar radiation or volcanic activity). Examples of evidence can include tables, graphs, and maps of global and regional temperatures, atmospheric levels of gases such as carbon dioxide and methane, and the rates of human activities. Emphasis is on the major role that human activities play in causing the rise in global temperatures.] Science Domain: Earth and Space Sciences Topic: Human Sustainability Standard: Construct an explanation based on evidence for how the availability of natural resources, occurrence of natural hazards, and changes in climate have influenced human activity. [Clarification Statement: Examples of key natural resources include access to fresh water (such as rivers, lakes, and groundwater), regions of fertile soils such as river deltas, and high concentrations of minerals and fossil fuels. Examples of natural hazards can be from interior processes (such as volcanic eruptions and earthquakes), surface processes (such as tsunamis, mass wasting and soil erosion), and severe weather (such as hurricanes, floods, and droughts). Examples of the results of changes in climate that can affect populations or drive mass migrations include changes to sea level, regional patterns of temperature and precipitation, and the types of crops and livestock that can be raised.] Science Domain: Earth and Space Sciences Topic: Human Sustainability Standard: Evaluate competing design solutions for developing, managing, and utilizing energy and mineral resources based on cost-benefit ratios.* [Clarification Statement: Emphasis is on the conservation, recycling, and reuse of resources (such as minerals and metals) where possible, and on minimizing impacts where it is not. Examples include developing best practices for agricultural soil use, mining (for coal, tar sands, and oil shales), and pumping (for petroleum and natural gas). Science knowledge indicates what can happen in natural systems—not what should happen.] Science Domain: Earth and Space Sciences Topic: Human Sustainability Standard: Create a computational simulation to illustrate the relationships among management of natural resources, the sustainability of human populations, and biodiversity. [Clarification Statement: Examples of factors that affect the management of natural resources include costs of resource extraction and waste management, per-capita consumption, and the development of new technologies. Examples of factors that affect human sustainability include agricultural efficiency, levels of conservation, and urban planning.] [Assessment Boundary: Assessment for computational simulations is limited to using provided multi-parameter programs or constructing simplified spreadsheet calculations.]	oercommons	2025-03-18T00:35:16.996763	Becky Bronstein	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/82946/overview", "title": "EarthGen COVID & Climate Change Virtual STEM Seminar Template", "author": "Teaching/Learning Strategy" }
https://oercommons.org/courseware/lesson/104396/overview	OER and Digital Accessibility Overview On Thursday, March 9, 2023, as part of Open Education Week, the #GoOpen Network hosted the webinar, "OER and Accessibility," featuring Cynthia Curry of the National Center on Accessible Educational Materials for Learning (AEM Center) at CAST, in conversation with Oregon Department of Education leaders, Vanessa Clark and Aujalee Moore, who are deeply engaged in this work with educators. Webinar Resources On Thursday, March 9, 2023, during Open Education Week 2023, the #GoOpen National Network hosted the professional learning webinar titled, "OER and Digital Accessibility," featuring: - Cynthia Curry, Director of Technical Assistance/Project Director, AEM Center/CAST - Vanessa Clark, Program Analyst for Digital Innovations, ODE - Aujalee Moore, Program Analyst, Instructional Materials Coordinator, ODE - Matt Hiefield, Digital Instructional Materials Coordinator, ODE - Amee Evans Godwin, Senior Advisor, ISKME Links to the slides and recording of the webinar are below:	oercommons	2025-03-18T00:35:17.010242	Rebecca Henderson	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/104396/overview", "title": "OER and Digital Accessibility", "author": "Teaching/Learning Strategy" }
https://oercommons.org/courseware/lesson/91374/overview	Instructional Media/Methods Activity Overview This activity provides a hands-on experience with non-projected visuals, projected visuals, display surfaces, real objects, audio, and motion visuals, and the materials/technology needed to produce them. Through this activity, participants are introduced to the basic principles of effectively integrating methods, media, and materials into an instructional situation; effectively operating and utilizing media and materials in an instructional situation; and evaluating media and methods in terms of their effectiveness in instructional situations. Instructional Media/Methods Activity Process: - Prior to the first class meeting, set up a discussion forum in D2L called “Welcome, Introduce Yourselves”. - Divide the class into six groups. Give each group their instructions on how they will introduce themselves to the class. - Assist students as needed with the recording of video, audio, copying, etc. - Following the introduction of students, conduct debrief while showing corresponding slides on PowerPoint for Week 1 Materials needed: - PC/Laptop - Projector with speakers - Software: PowerPoint, Word - Webcam - Markers (dry erase if using dry erase board) or Chalk - Chalkboard, Dry Erase Board, Poster Board or Flip Chart - Access to a copy machine or printer - Flash Drive - Cut out each of the group instruction cards on Pages 2 through 4. Time Needed: 60 minutes. Allow 30 minutes for students to prepare introductions and 30 minutes for students to introduce themselves using the various media. This activity provides a hands-on experience with non-projected visuals, projected visuals, display surfaces, real objects, audio, and motion visuals and the materials/technology needed to produce them. Through this activity, participants are introduced to the basic principles of effectively integrating methods, media and materials into an instructional situation; effectively operating and utilizing media and materials in an instructional situation; and evaluating media and methods in terms of their effectiveness in instructional situations.	oercommons	2025-03-18T00:35:17.034716	Lesson	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/91374/overview", "title": "Instructional Media/Methods Activity", "author": "Activity/Lab" }
https://oercommons.org/courseware/lesson/12200/overview	Mass Murder in the Classroom: The Case Files of John Emil List, Family Annihilator Overview John Emil List murdered his mother, wife, and three teenaged children on November 9, 1971 in their dilapidated Westfield, NJ mansion. The victims were not discovered for nearly a month, and List escaped capture for nearly 18 years. This repository includes primary source materials and lesson plans for instructors in criminal justice, history, and psychology. https://unioncc.instructure.com/courses/11394 Section 1 John Emil List murdered his mother, wife, and three teenaged children on November 9, 1971 in their dilapidated Westfield, NJ mansion. The victims were not discovered for nearly a month, and List escaped capture for nearly 18 years. This repository includes primary source materials and lesson plans for instructors in criminal justice, history, and psychology. https://unioncc.instructure.com/courses/11394	oercommons	2025-03-18T00:35:17.053967	Technology	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/12200/overview", "title": "Mass Murder in the Classroom: The Case Files of John Emil List, Family Annihilator", "author": "Psychology" }
https://oercommons.org/courseware/lesson/126247/overview	Shared VOICES_Instructor_Manual - updated 2025 Instructor's Manual for Shared Voices: An Introduction to Cultural Anthropology Overview This Instructor's Manual was developed to facilitate teaching with Shared Voices: An Introduction to Cultural Anthropology. [Revised Edition] It was published in 2024 here: https://rotel.pressbooks.pub/culturalanthropology/ but may also be found on other OER-hosting platforms. Shared Voices is a student-centered cultural anthropology mini textbook built with an equity lens. The text aims to be accessible, interesting, accurate, and centered on marginalized voices. This text is a starting point for any introductory anthropology course recognizing that cultural change is constant and the familiar is cousin to the weird and unusual. Instructor's Manual for Shared Voices: An Introduction to Cultural Anthropology This is an Instructor's Manual to help teach using Shared Voices: An Introduction to Cultural Anthropology [Revised Edition]. It is available in word.docx and .PDF formats. Shared Voices is a student-centered cultural anthropology mini textbook built with an equity lens. It aims to be accessible, interesting, accurate, and centered on marginalized voices. This text is a starting point for any introductory anthropology course recognizing that cultural change is constant and the familiar is cousin to the weird and unusual. The revided edition OER textbook was originally published here: https://rotel.pressbooks.pub/culturalanthropology/ in 2024.	oercommons	2025-03-18T00:35:17.072903	Barbara Ambos	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/126247/overview", "title": "Instructor's Manual for Shared Voices: An Introduction to Cultural Anthropology", "author": "Teaching/Learning Strategy" }
https://oercommons.org/courseware/lesson/91194/overview	Putting it Together Overview "El Siglo llibreria" by Castellbo is licensed under CC BY-SA 4.0 Provided by: Lumen Learning. License: CC BY: Attribution Putting It Together: Marketing Information and Research Back to Bookends Let’s pay Uncle Dan and his bookstore another visit, now that you’re a little further along in your understanding of marketing research. You’ll remember that you and Dan conducted both primary and secondary research to get a handle on who Bookends’ customers are—and who they aren’t. With the help of your cousin Marina, you crunched the data and identified three target segments you believe Dan should focus on. Here is the profile data you compiled for them: \| Characteristics \| Bored Empty-Nesters \| Busy Families \| Hipster Wannabes \| \|---\|---\|---\|---\| \| Age & family status \| 45–75, mix of single and married \| 25–50, mostly married with kids under 12 \| 15–35, mostly single \| \| Times most likely to visit Bookends \| Daytime, evenings, weekends, holidays \| After school, weekends, summertime, holidays \| Evenings & weekends \| \| Most likely to buy \| Cards, gifts, novels, history/biography \| Kids’ books, how-to books, bestsellers \| Magazines, used books, graphic novels, snacks \| \| Why they come to Bookends \| Socialize, shop, read \| Family outing \| Socialize \| \| Communications preferences \| Hard copy, email, face-to-face \| Email, texting, Facebook \| Texting, Twitter, Instagram & beyond \| \| Effective promotions \| Coupons, loyalty cards \| Loyalty points (recorded electronically) \| Point-of-sale \| \| What they wish Bookends would offer \| Book clubs & discounts \| More hours in the day \| Coffee, beer & wine, live music \| \| % of all customers/month \| 36% \| 27% \| 21% \| \| Avg. # of customers/month \| 144 \| 108 \| 84 \| \| % of monthly revenue \| 43% \| 29% \| 18% \| \| Avg. monthly revenue/person \| $30 \| $27 \| $21 \| Together, these segments make up more than 80 percent of Bookends’ clientele and about 90 percent of its monthly revenue. Looking at what they buy and why they come to Bookends, you’re getting some good ideas for ways of making the store more attractive for current customers, and you’ve got some ideas for bringing in new ones. With this new and improved information, it’s time to get to work on a marketing strategy and mix for each target segment. Marketing Strategy: Bored Empty-Nesters Bookends’ Bored Empty-Nesters are both the largest and the most profitable of the target segments. They have more time and more disposable income, and they spend more of both at your uncle’s bookstore. They like to use Bookends as a meeting place with friends and acquaintances, and you think that is a promising direction. You and your uncle brainstorm about ways of using the four Ps to win over even more of these customers (and get them to spend). The “product” you’re adjusting is not just the books you carry, but the whole experience customers have when the come to Bookends. Dan is excited about introducing book clubs—one for fiction and one for nonfiction books—to cater to this segment’s interests. Since Empty-Nesters have told you they love both socializing and getting a discount, you and Dan are trying out a “buddy night” promotion, in which people get a better price if they talk their friends into spending at Bookends, too. Here is your Bored Empty-Nester game plan for the next couple of months: \| Element \| Marketing Mix Adjustment \| \|---\|---\| \| Marketing Goals \| 15% increase in store visitors for this segment 20% increase in monthly revenue per person \| \| Product \| Carry larger selection of history and biography Adjust shelves and seating to create more socializing spaces Launch two book clubs led by Dan and longtime employee Emma, one featuring new fiction and the other on new nonfiction \| \| Promotion \| Print flyers, posters, and send emails about book clubs, buddy discount Set up in-store sign-up table for book club Introduce Thursday night “buddy discount”: Get 5% off if you and a buddy each spend over $20 Explore interest in loyalty program: Spend $100 to get 10% discount on next purchase \| \| Price \| Offer 5% discount on monthly book club selection \| \| Place \| No changes (yet). Explore opening online store \| Marketing Strategy: Busy Families Research tells you that Busy Families come to Bookends as a family outing, so you need to make some aspects of the store more family-friendly, without ruining the atmosphere for your other target segments. The socializing-area adjustments you’re already planning for the Empty Nesters will be good for the Family segment, as well. You’re trying to get parents to spend a little more money at Bookends each month, so you’re adding a small toy section, a slightly expanded children’s book section, and also bottled drinks, packaged cookies, and brownies from a delicious local bakery. These adjustments add to the Bookends experience and include some new items Dan can sell with a nice profit markup. Your Busy Families marketing mix is shaping up like this: \| Element \| Marketing Mix Adjustment \| \|---\|---\| \| Marketing Goals \| 10% increase in store visitors for this segment 10% increase in monthly revenue per person \| \| Product \| Increase selection of DIY, crafting, and “How-To” books Slightly expand children’s book selection and add a small toy section Add child seating to the kids’ area, and donate your old train table to the Bookends cause Hold children’s story hour on Tuesdays and Saturdays with stories, songs, games Sell packaged baked goods from a local bakery and bottled drinks \| \| Promotion \| Send emails and post to Facebook about story time, bigger kids’ area, buddy discount, social media discount promo Explore interest in loyalty program: Spend $100 to get 10% discount on next purchase \| \| Price \| Run Facebook promotion offering 5% discount to people who post about Bookends \| \| Place \| No changes (yet). Explore opening online store \| Marketing Strategy: Wannabe Hipsters The Wannabe Hipsters are an interesting group. You almost didn’t include them in the three target segments because they are a smaller-sized group and don’t spend as much as the others. However, they do make up one in five Bookends customers, so it’s worth reaching out to see if you can bring more of them into the store and get them to spend more money while there. Fortunately, they like to come to Bookends during times when there aren’t many Busy Families around, so that opens some unique possibilities for ways of appealing to both segments. Dan is excited about your suggestion to invite local bands to perform on Saturday nights. The Hipsters you spoke with suggested Dan try this, and it could make Bookends more of a social draw for that crowd. By rearranging shelving to create more socializing space, it opens up enough area for a live band to play for a small audience. You’re not convinced it’s going to translate into more book sales, but it’s worth a try. The Hipster crowd has decidedly different communication preferences compared to the other groups, so your communication and promotion activities reflect this. To make sure they see the buddy discounts you’re offering, you suggest that Dan add signage about this promotion near the checkout counter, since that’s the place this audience is most likely to notice it. The broad strokes of your Hipster Wannabe strategy are the following: \| Element \| Marketing Mix Adjustment \| \|---\|---\| \| Marketing Goals \| 15% increase in store visitors for this segment 20% increase in monthly revenue per person \| \| Product \| Adjust shelves and seating to create more socializing spaces Invite local bands to play on Saturday evenings Add more prominent shelf placement to feature graphic novels Sell packaged baked goods from a local bakery and bottled drinks \| \| Promotion \| Promote live music nights and buddy discount nights via social media Add point-of-sale signage about Thursday and Saturday night “buddy discounts” Explore interest in loyalty program: Spend $100 to get 10% discount on next purchase \| \| Price \| Thursday and Saturday night “buddy discounts”: Get 5% off if you and a buddy each spend over $20 \| \| Place \| No changes (yet). Explore opening online store. \| Onward and Upward for Bookends After running the numbers with Dan, you are optimistic that outreach to these target audiences will be the jumpstart his business needs. Your use of near-term promotions and events will help generate renewed interest and traffic for the store. You have advised Dan to explore interest in and options for a customer loyalty program that rewards customers for spending more at Bookends. That’s what the next round of marketing research will investigate. In the meantime, you’ve learned a lot about the marketing research process and how to turn marketing information into future marketing strategies and plans. You’re excited to keep helping Dan as he puts your ideas to work, and, best of all, if business at the Bookends really starts to improve, you’ve got free graphic novels for life. Licenses and Attributions CC licensed content, Original - Putting It Together: Marketing Research. Provided by: Lumen Learning. License: CC BY: Attribution	oercommons	2025-03-18T00:35:17.104348	03/22/2022	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/91194/overview", "title": "Statewide Dual Credit Principles of Marketing, Marketing Information and Research, Putting it Together", "author": "Anna McCollum" }
https://oercommons.org/courseware/lesson/91192/overview	Customer Relationship Management (CRM) Systems Overview Provided by: Lumen Learning. License: CC BY: Attribution Outcome: Customer Relationship Management (CRM) Systems What you’ll learn to do: explain how customer relationship management (CRM) systems can help organizations manage and gain customer insights from marketing information To round out our discussion of marketing information and research, we need to add one more important tool to the mix: customer relationship management (CRM) systems. These increasingly prevalent systems are the centerpiece in how many organizations make sense of and manage marketing data about current and prospective customers. A basic understanding of CRM systems can help you recognize their potential for helping organizations use marketing information more effectively. The specific things you’ll learn in this section include: - Define CRM systems and explain their purpose - Describe the types of marketing information CRM systems can capture and why it is valuable for generating customer insights Learning Activities The learning activities for this section include the following: - Reading: Customer Relationship Management Systems Licenses and Attributions CC licensed content, Original - Outcome: Customer Relationship Management (CRM) Systems. Provided by: Lumen Learning. License: CC BY: Attribution Reading: Customer Relationship Management Systems Marketing Information and Customer Relationship Management (CRM) Earlier in this course, we cited the American Marketing Association’s definition of customer relationship management: “a discipline in marketing combining database and computer technology with customer service and marketing communications.” The AMA’s definition goes on to describe the ultimate goal of customer relationship management as the ability to provide “meaningful one-on-one communications with the customer by applying customer data (demographic, industry, buying history, etc.) to every communications vehicle. Because customer relationship management (CRM) relies on customer data—and specifically the effective use of internal data—it’s important to discuss CRM systems in the context of marketing information and research. CRM systems are powerful software systems that serve several essential functions for marketing, sales, and account management. Organizations use them to: - Capture internal data about customers and customer interactions and house these data in a central location - Provide business users with access to customer data in order to inform a variety of customer touch points and interactions - Conduct data analysis and generate insights about how to better meet the needs of target segments and individual customers - Deliver a marketing mix tailored to the needs and interests of these target segments and individual customers Leading providers of CRM systems include Salesforce.com, Oracle (Siebel), and Microsoft, among others. These large, many-faceted systems include several components. Databases and data warehouses provide information infrastructure for storing and accessing customer information. Contact management capabilities allow organizations to track a variety of customer interactions, including how each customer or prospective customer relationship is progressing over time. CRM packages also include sophisticated analytical tools to help marketing and sales analysts examine the data and find patterns and correlations that help them better anticipate and address customer needs (with the goal of strengthening each customer relationship). Does this analytical process sound familiar? It should. Marketing analysts working with CRM data follow the same basic process outlined previously for general marketing research activities: Identify a problem; develop a plan for the information and analysis needed to solve the problem; conduct research; analyze and report findings; and take action based on the results. The primary difference from traditional marketing research projects is that the CRM inquiries may be more self-contained because of the breadth of marketing information and tools these systems provide. The CRM system is especially effective at helping to surface a marketing problem, and it can provide the internal data needed for an analysis, which, in turn, is used to solve the problem. CRM systems are designed to capture data across the customer life cycle, starting with the initial contact point and progressing through each conversation and interaction that moves a prospective customer toward a purchasing decision. CRM systems also capture sales and spending data, and they enable analysts to project future spending patterns and lifetime value based on broader patterns in the customer data. These systems may also incorporate data about customer satisfaction and support, with accompanying insights into what is driving satisfaction ratings and customers’ perceptions of the company. In addition to bringing together disparate customer data, CRM systems can recommend an analytical approach and provide research tools to complete the analysis. Many CRM systems have mechanisms for reporting results, orchestrating plans for taking action on the results, and even evaluating the effectiveness of those actions. CRM and Marketing Automation in Action The following video from Salesforce describes the difference between a CRM and marketing automation to better understand and anticipate customer needs. It translates the information from the CRM system to more efficient marketing, better customer service, and increased sales. This video was produced by Salesforce.com. Notice that the video not only trumpets the value of these systems, but the video itself is a polished piece of marketing communication (promoting Salesforce.com). Licenses and Attributions CC licensed content, Original - Marketing Information and Customer Relationship Management. Authored by: Lumen Learning. License: CC BY: Attribution CC licensed content, Shared previously - Customer and Computer Cables. Provided by: Pixabay. Located at: https://pixabay.com/en/ball-about-cable-lan-connected-563972/. License: CC0: No Rights Reserved All rights reserved content - adidas is a Trailblazer. Provided by: Salesforce. Located at: https://youtu.be/OCj-L0vC42s. License: All Rights Reserved. License Terms: Standard YouTube license	oercommons	2025-03-18T00:35:17.130296	03/22/2022	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/91192/overview", "title": "Statewide Dual Credit Principles of Marketing, Marketing Information and Research, Customer Relationship Management (CRM) Systems", "author": "Anna McCollum" }
https://oercommons.org/courseware/lesson/128218/overview	S6 UNIT 2 Overview Key Unit Competence: By the end of this unit, Learners should be able to interpret photographs, video images and draw sketches by reduction or enlargement of the photographs. INTERPRETATION OF PHOTOGRAPHS AND VIDEO IMAGES 2.1. Definition and types of photographs 2.1.1. Definition A photograph is a picture of an object or environment taken by a camera at a particular time in a given place. some parts of the object or environment are seen while others may not be seen clearly. A hidden ground/area which cannot be seen by a camera when a photograph is taken is called a dead ground. 2.1.2. Major types of photographs There are basically two types of photographs: Ground photographs: These are photographs taken from the ground level x-stics - They record exactly what a person would see if he / she was standing on the ground level. - It gives a horizontal view - It gives great details of the landscape - It covers a small area. There are two categories of ground photographs: a) Ground horizontal photographs: This is a photograph taken when a camera is held horizontally to the ground. b) Ground oblique photographs: This is a photograph taken when the camera is titled at an angle facing the ground. 2. Aerial photographs: These are photographs taken from aerial station using aircrafts, satellites, and other flying objects. x-stics - They cover a wide area - Features are greatly reduced - Show the top of the object - They do not show the horizon - They are more difficult to analyse. There are two categories of aerial photographs: a) Vertical aerial photographs: These are photographs taken when the camera is directly above (overhead) the objects or when it is perpendicular to the ground. b) Oblique aerial photographs: These are photographs taken when the camera is titled at an angle below 90 degrees. 2.2. Sections of a photograph and interpretation of physical and human aspects 2.2.1. Sections of a photograph - The foreground: It is the part of the photograph located nearest to the camera. - The middle ground: It is the central part of the photograph. - The back ground: It is the farthest part of the photograph that includes the horizon. From vertical perspective, photographs are also divided in three parts: left, centre and right Categories of photographs depending on the position of photography Left background \| Centre background \| Right background \| Left middle ground \| Centre middle ground \| Right middle ground \| Left foreground \| Centre foreground \| Right foreground \| 2.2.2. Interpretation of physical and human aspects on photographs and video images a. Interpretation of physical aspects - Climate: Climate in a photograph is indicated by rainfall and temperature. Heavy rainfall can be observed by presence of dense forests and crops like sugar cane, rice and tea while high temperature may be observed by the presence of poor vegetation, people wearing light clothes etc. - Relief: The features of the relief depicted on a photograph include mountains, hills, valleys, escarpments, plateaus and plains. A hilly or mountainous landscape is indicated by the presence of steep slopes, presence of terraces, snow and glaciers on the top. Plateaus and plains are identified by a uniformly flat land with sloping edges and pools of water or irrigated land. Wide valleys with meanders and flood plains also suggest the presence of plain land. Relief on vertical aerial photographs can be interpreted by observing the following: - Flat areas can be identifiable by the presence of meandering rivers, straight roads and gentle bends. - Plateaus can be indicated by presence of flat topped hills. - Vegetation: This is the plant life that covers the earth surface; it is both natural and artificial. - Drainage: Drainage is shown by the presence of water bodies on a photograph, such as streams, rivers, lakes, swamps, seas, and oceans. Others are man-made water features like wells, ponds, valley dams and boreholes. In photographs, drainage is interpreted in the following ways: - Rivers appear with meandering channels with swampy vegetation along them. - Swamps appear with luxuriant vegetation dominated by papyrus reeds. - Soils: The types of soils can be identified by observing the types of crops grown there because there are crops that grow well in specific types of soils, for example, tea and coffee grow well in fertile volcanic soils. Where erosion took place, the soils are exposed. b. Interpretation of human aspects Photographs and video images can be very useful in the interpretation of human activities such as: - Forestry: A forest is evidenced by the presence of both artificial and natural forests. - Agriculture: Agricultural activities can be observed by the presence of food crops and cash crops as well as animals like cattle both exotic and traditional breeds. - Transport and communication: Both transport and communication networks are evidenced by presence of motor vehicles, bicycles, roads, ships, airports, and communication facilities such as telephone lines and masts. - Mining: This is shown by Open pits, people undertaking mining or a mineral processing plant show that there is mining taking place in that area. - Industry: Industrialization is shown by the presence of industries emitting smoke from huge chimneys. - Trade or commerce: the commerce is evidenced by trading centers with congested buildings and at times presence of markets. - Settlement: It is evidenced by the presence of houses in different patterns. 2.3. Drawing sketches of photographs by reduction or enlargement A sketch of a photograph focuses on the identification, marking using symbols and labeling marked features in their relative positions. To draw a sketch of a photograph by enlargement or reduction requires the following steps: - Draw a rectangle and a square of the size as requested on a piece of paper. - Draw horizontal lines across the photograph by using a pencil to subdivide it into three equal sections. These will be the foreground, middle ground and background either reduced or enlarged as instructed. - Draw vertical lines across the photograph by using a pencil. These will be left, centre and right. - Place the framework of a photograph onto the prepared rectangle or square. The framework could be the guider in placing the various features in their respective positions. - Enlarge or reduce the size of features and the frame as requested. - When filling in the main features, it is better to start with the background or right by drawing the skyline as it appears on the photograph. - It is better to place and label all important features either physical or human as they appear on the photograph, reduce or enlarge them as required. Choose a suitable title, key, orientation of a sketch. It is possible to put on a sketch other elements of a sketch map which are useful in reading and interpreting it. Therefore, a sketch of a photograph can be enlarged or reduced as shown below: 2.4. Relationship between physical and human aspects on photographs and video images - Relief and transport: Transport routes occur on gentle slopes and avoid steep slopes and valleys since it is very expensive to construct roads in hilly areas. - Relief and agriculture: On steep slopes, less agriculture takes place while on gentle slopes most agricultural practices are observed. The low lands are usually reserved for growing of vegetables, sugar cane, rice, and other crops that need enough water. - Relief and settlement: Steep slopes tend to discourage construction of houses while gentle slope encourage population settlement. - Drainage patterns and settlement: Settlement occurs in well drained areas and avoids lake shores or river banks because of floods and associated problems. - Drainage and transport: Transport routes are usually found in well drained areas. For example, roads cannot be constructed in swampy areas due to excessive water. Water transport occurs on water bodies like rivers, lakes,	oercommons	2025-03-18T00:35:17.182981	03/07/2025	{ "license": "Creative Commons - Attribution - https://creativecommons.org/licenses/by/4.0/", "url": "https://oercommons.org/courseware/lesson/128218/overview", "title": "S6 UNIT 2", "author": "NIYONKURU SELEMAN" }

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