The Human Body: An Orientation (Lecture 1) PDF

The Human Body: An Orientation In this chapter, you w ill learn that Anatomy and physiology provide a framework that helps us understand the human body I...

The Human Body: An Orientation In this chapter, you w ill learn that Anatomy and physiology provide a framework that helps us understand the human body I by asking ' What are anatomy What terms do we need ana physiology, and to describe anatomy? how are they related? I and exploring..... ' Body cavities and membranes What are the re(!uirements for life? Welcome to the study of one of the most fascinating subj ects possible-your own body. Such a study is not only highly personal, but tirnely as well. We get news of some medi- cal advance almost daily. To appreciate emerging discoveries in molecular genetics, to understand new techniques for detecting CAREER CONNECTION and treating disease, and to make use of published facts on how to stay healthy, you'll find it helps to learn about the workings of your body. If you are preparing for a career in the health sci- ences, the study of anatomy and physiology has added rewards because it provides the essential foundation for your clinical experiences. In this chapter we define and contras t anatomy and physio- logy and discuss how the human body is organ ized. Then we revie\v needs and processes common to all living organ isms. Watch a video to learn how Three essential concepts-the comple,nentarity of structure O t he chapter content is used in a real hea lth care setting. and function , the hierarchy of structural organization, and ho,neostasis-will unify and form the bedrock for your study Go to Mastering A&P®> Study Area > of the human body. And finally you ' ll learn the language of Animations and Videos or use qu ick anatorny-terminology that anatomists use to describe the body access URL https://goo.g l/88srfV and its parts. 1 2 UNIT 1 Organization of the Body bulging muscles beneath a bodybuilder's skin, and clinicians Form (anatomy) determines use it to locate appropriate blood vessels in which to feel function (physiology) pulses and draw blood. Microscopic aua to,uy deals with structures too small to be Learning Outcomes seen with the naked eye. For rnost such studies, exceedi ngly thin II- Define anatomy and physiology and descri be t heir slices of body tissues are stained and mounted o n glass slides to subdivisions. be exarnined under the microscope. Subdivisions of microscopic II- Explai n t he p rinciple of com plementarity. anatomy include cytology (si-tol'o-je), which considers the cells Two complementary branc hes o f science-an atomy a nd of the body, and histology (his-tol'o-je), the study of tissues. physiology-provide the concepts that help us to understand the Developm ental au ato,uy traces structural c hanges that human body. Ana tomy studies the structure of body parts and occur throughout the life span. E n1bryology (em"bre-ol'o-je), a their relationships to one another. Anatomy has a certain appeal subdivision of developmental anatomy, concerns developmental because it is co ncrete. Body structures can be seen, fel t, and changes that occur before birth. exaJnined closely. You don't need to imagine what they look like. Some highly specialized branches of anato my are used Physiology concerns the function of the body, in other primarily for medical diagnosis and scientific research. For words, ho\v the body parts work a nd carry out the ir life- example, pathological anato111y studies structural changes sustaining activities. When all is said and done, physiology is caused by disease. Radiographic anato111y studies internal explainable only in tenns of the underlying anatomy. struc tures as visualized by X-ray images or specialized scan- For simplicity, when we refer to body structures and physi- ning procedures. ological values (body temperature, heart rate, and the like), we will assume that we are talking about a healthy young reference Studying Anatomy 1na11 weighing about 155 lb [70 kilograms (kg)) or a healthy One essential tool for studying anatomy is a mastery of ana- you ng refere11ce wo1na11 weighing about 125 lb (57 kg). tomical terminology. Other tools are observation, mani pula- Although we use the reference values a nd common direc- tion, a nd, in a living person, palpation (feeling organs with tional and regional tenns to refer to all human bodies, you know your hands) and auscultation (listening to organ sounds with a from observing the faces and body shapes of people arou nd stethoscope). A simple exlllllple ill ustrates ho\v some of these you that we humans differ in our external anatomy. The same tools work together in an anatomical study. kind of variability holds for internal organs as well. In one per- Let's assume that your topic is freely movable joints of the son, for exlllllple, a nerve or blood vessel may be somewhat out body. In the laboratory, you will be able to observe an animal of place, or a small muscle may be missing. Nonetheless, well joint, noting how its parts fit together. You can work the j oint over 90o/o of all structures present in any human body match the (111anipulate it) to determ ine its range of motion. Using a11a- textbook descriptions. We seldom see extreme anatomical vari- to1nical termi110/ogy, you can name its parts and describe how ations because they are incompatible with life. they are related so that other students (and your instructor) will have no trouble understanding you. The list of word roots (at Topics of Anatomy the back of the book) and the glossary will help you with this Anatomy is a broad field with many subdivisions, each providing special vocabulary. enough information to be a course in itself. Gross, or 1nacro- Although you will make most of your observations with the scopic, anato,uy is the study of large body structures vis ible naked eye or with the help of a microscope, medical technol- to the naked eye, such as the heart, lungs, and kidneys. Indeed, ogy has developed a number of sophisticated tools that can the term anato,ny (from Greek, rneaning "to cut apart") relates peer into the body without disrupting it. See A Closer Look most closely to gross anatomy because in such studies preserved on pp. 16-17. anirnals or their organs are dissected (cut up) to be examined. Gross anatomy caJ1 be approached in different ways. Topics of Physiology In regional anatomy, all the structures (rnuscles, bones, blood Like anatomy, physiology has many subdivisions. Most of thern vessels, nerves, etc.) in a particular region of the body, such as consider the operation of specific organ systems. For example, the abdome n or leg, are exami ned at the same time. renal physiology concerns kidney function and uri ne produc- In systemic anatomy (sis-tem' ik),* body structure is studied tion. Neurophysiology explains the workings of the nervous system by system. For example, when studying the cardio- system. Cardiovascular physiology exlllllines the operation of vascular system, you would examine the heart and the blood the heart and blood vessels. While anatomy provides us with a vessels of the entire body. static image of the body' s architecture, physiology reveals the body's dynamic and an imated workings. Another subdivision of gross anatomy is surface anatomy, Physiology often focuses o n events at the cellular or molecu- the study of internal structures as they relate to the overlying lar level. This is because the body's abilities depend on those skin surface. You use surface anatomy when you identify the of its individual cells, and cells' abilities ulti mately depend on the che mical reactions that go on within them. Physiology also For the pronunciation gu ide rules, see the fi rst page of the glossary in the back of the book. rests o n principles of physics, which help to explain electrical  Chapter 1 The Human Body: An Orientation 3 - 4 I I I I I I I I I I I I I I I I I I I \ I I \ I I \ I I I I \ I I I \ I I I \ I I I I I I I I I I I I I The sharp edges of incisors The flat surfaces of molars (structure) (structure) make them ideal for make them ideal for grinding, like a cutting like scissors (function). mortar and pestle (function). Figure 1.1 Complementarity of structure and function. currents , blood pressure, and the way muscles use bones to cause body movements, among other things. We present basic chemical and physical principles in Chapter 2 and throughout the book as needed to explain physiological topics. Complementarity of Structure and Function Although it is possible to study anatomy and physiology individually, they are really inseparable because function always reflects structure. That is, what a structure can do depends on its specific fonn. This key concept is called the principle of complementa- rity of structure and function. For example, bones can support and protect body organs because they contain hard mi neral deposits. Blood flows in one direction through the heart because the heart has valves that prevent backflow. Another example is how the various shapes of our teeth reflect their different actions, as shown in Figure 1.1. Throughout this book, we accompany a description of a structure's anatomy with an explanat ion of its function, and we emphasize structural characteristics contributing to that function. Check Your Understanding 1. In what way does physiology depend on anatomy? 2. Would you be studying anatomy or physiology if you investigated how muscles shorten? If you explored the location of the lungs in the body? 3. t4144H Use the word root defin itions located at the back of this book to define each of the following terms: gastritis, leukocyte, nephropathy. - - - - - - - - - - - - - - - - - - - -. For answers, see A nswers Appendix. 4 UNIT 1 Organization of the Body the chemical level, which we study in Chapter 2. At this level, - The body's organization ranges ato1ns, tiny building blocks of matter, combine to form ,nol- from atoms to the entire organism ecules such as water and proteins. Molecules, in turn, associate in specific ways to form organelles that are the basic compo- Learning Outcomes nents of cells. Cells are the smallest units of living things. We II- Name the d ifferent levels of structural organization that exam ine the cellular level in Chapter 3. All cells share some make up the human body, and explain their relationsh ips. common functions, but individual cells vary widely in size and II- List the 11 organ systems of the body, identify their shape, reflecting their unique functions in the body. components, and briefly explain the major f unct ion(s) of The simplest living creatures are single cells, but in complex each system. organisms such a~ human beings, the hierarchy continues on to The human body has many levels of structural organization the tissue level. Tissues are groups of sim ilar cells that have a (Figure 1.2). The simplest level of the structural hierarchy is cornrnon function. The four basic tissue types in the lnunan body Molecules Smooth muscle cell Chemical level Cellular level Atoms combine to form molecules. Cells are made up of molecules. Smooth muscle tissue Cardiovascular Tissue level system Tissues consist of similar types of cells. Heart Blood Blood vessel (organ) r Smooth muscle tissue./,..., - Connective tissue Organ level Organs are made up of different types of tissues. I'' Organismal level Organ syst em level The human organism is made up of many Organ systems consist of different organ systems. organs that work together closely. Figure 1.2 Levels of structural organ ization. Components of the cardiovascular system are used to illustrate t he levels of structural organization in a human being.  Chapter 1 The Human Body: An Orientation 5 are epithelial tissue, muscle tissue, connective tissue, and ner- Like all complex animals, humans maintain their bounda- vous tissue. ries, move, respond to environmental changes, take in and Each tissue type has a characteristic role in the body, which digest nutrients, carry out metabolism, dispose of wastes, re- we explore in Chapter 4. Briefly, epithelial tissue covers the produce themselves, and grow. We will introduce these neces - body surface and lines its cavities. Muscle tissue provides sary life functions here and discuss them in more detail in later movement. Connective tissue supports and protects body chapters. organs. Nervous tissue provides a means of rapid internal com- We cannot emphasize too strongly that all body cells are munication by transmitting electrical impulses. interdependent. This interdependence is due to the fact that An organ is a discrete structure composed of at least two humans are multicellular organisms and our vital body func- tissue types (four is more common) that performs a specific tions are parceled out among different organ systems. Organ function for the body. The liver, the brain, and a blood vessel systems, in turn, work cooperatively to promote the well - are very different from the stomach, but each is an organ. You being of the enti re body. Figure 1.3 identifies some of the can think of each organ of the body as a specialized functional organ systems making major contributions to necessary life center responsible for a necessary activity that no other organ functions. Also, as you read this section, check Figu re 1.4 can perform. on pp. 6-7 for more detailed descriptions of the body's organ At the organ level, extremely complex functions become systems. possible. Let's take the stomach for an example. Its lining is an epithelium that produces digestive juices. The bulk of its wall is (Texr co111i1111es on p. 8.) muscle, which churns and ,nixes stomach contents (food). Its con- nective tissue reinforces the soft muscular walls. Its nerve fibers increase digestive activity by stimulating the muscle to contract Digestive system Respiratory system more vigorously and the glands to secrete more digestive juices. Takes in nutrients, breaks them Takes in oxygen and The next level of organization is the organ system level. down, and eliminates unabsorbed eliminates carbon dioxide Organs that work together to accomplish a common purpose matter (feces) make up an organ systern. For example, the heart and blood Food vessels of the cardiovascular system circulate blood continu- ously to carry oxygen and nutrients to all body cells. Besides ~~ Cardiovascular system the cardiovascular system, the other organ syste,us of the body Via the blood, distributes oxygen are the integumentary, skeletal, muscular, nervous, endocrine, and nutrients to all body cells and delivers wastes and carbon lymphatic, respiratory, digestive, urinary, and reproductive sys- dioxide to disposal organs tems. (Note that the immune system is closely associated with the lymphatic system.) Look ahead to Figure 1.4 on pp. 6-7 for \~ an overview of the 11 organ systems. The highest level of organization is the organisrn, the living htunan being. The orgauismal level represents the sum total of all structural levels working together to keep us alive. Heart Check Your Understanding Urinary system Eliminates 4. What level of structural organization is typical of a cytologist's nitrogenous field of study? wastes and 5. What is the correct structural order for the following terms: Interstitial fluid excess ions tissue, organism, organ, cell? I ==---------. For answers, see Answers Appendix. m What are the requirements for life? Nutrients and wastes pass Learning Outcomes between blood plasma and cells via the interstitial fluid... List the functional characteristics necessary to maintain life in humans.... List the su rvival needs o f t he bod y..........~!;____ Feces ln-t-e g_u_m _e_n_t_a _ ry_s_y_s-te- m Protects the body as a whole - - - - ~r-- ~ ~ Urine from the external environment Necessary Life Functions Now that you know the structural levels of the human body, the Figure 1.3 Examples of interrelat ionsh ips among body question that naturally follows is: What does this highly orga- org an systems. nized human body do? 6 UNIT 1 Organization of the Body (a) lntegumentary System (b) Skeletal System (c) Muscular System Forms the external body covering, and Protects and supports body organs, and Allows manipulation of the environment, protects deeper tissues from injury. provides a framework the muscles use locomotion, and facial expression. Synthesizes vitamin D, and houses to cause movement. Blood cells are Maintains posture, and produces heat cutaneous (pain, pressure, etc.) receptors, formed within bones. Bones store minerals. and sweat and oil glands. (d) Nervous System (e) Endocrine System (f) Card iovascular System As the last-acting control system of the Glands secrete hormones that regulate Blood vessels transport blood, which body, it responds to internal and external processes such as growth, reproduction, carries oxygen, carbon dioxide, changes by activating appropriate and nutrient use (metabolism) by body nutrients, wastes, etc. The heart pumps muscles and glands. cells. blood. Figure 1.4 The bod y's organ systems and their major fu nctions.  Chapter 1 The Human Body: An Orientation 7 (g) Lymphatic Systemllmmunity (h) Respiratory System (i) Digestive System Picks up fluid leaked from blood vessels Keeps blood constantly supplied with Breaks down food into absorbable units and returns it to blood. Disposes oxygen and removes carbon dioxide. that enter the blood for distribution to of debris in the lymphatic stream. These exchanges occur through body cells. Indigestible foodstuffs are Houses white blood cells (lymphocytes) the walls of the air sacs of the lungs. eliminated as feces. involved in immunity. The immune response mounts the attack against foreign substances within the body. (j) Ur inary System (k) Male Reproductive System (I) Female Reproductive System Eliminates nitrogenous wastes from the Overall function is production of offspring. Testes produce sperm and male sex hormone, body. Regulates water, electrolyte, and and male ducts and glands aid in delivery of sperm to the female reproductive tract. Ovaries acid-base balance of the blood. produce eggs and female sex hormones. The remaining female structures serve as sites for fertilization and development of the fetus. Mammary glands of female breasts produce milk to nourish the newborn. Figure 1.4 (cont inued) 8 UNIT 1 Organization of the Body Maintaining Boundaries Metabolism Every Jiving organism must 1n ainta in its b oun daries so that Meta b olis m (me-tab ' o-lizm; " a state of cha nge") is a broad its internal environment ( its inside) remains distinct from the term that inc ludes all c he mical reactio ns that occur withi n external e nvironment (its outside). In single-celled organisms, body cells. It includes breaki ng down substances into simpler the external bou ndary is a lirniting membrane that encloses its building blocks (the process of catabolisrn), synthesizing more contents and lets in needed substances while restricti ng entry of complex substances from si mpler building blocks (anabolisrn), potentially damagi ng or unnecessary substances. Similarly, all a nd using nutrients and oxygen to produce (via cellular res - body cells are surrounded by a selectively permeable plas,na piration) ATP, the energy-rich molecules that power cellu lar 11ie111brane. activities. Metabolism depends on the digestive and respiratory T he plasma membrane separates the intracellular fluid systems to make nutrients and oxygen available to the blood, inside cells from the extracellular fluid outside. Part of the and o n the cardiovascular system to d istribute them through- extracellular fluid (blood plas111a) is e nclosed in blood vessels. out the body (Figure I.4i, h , and f, respectively). Metabolism The remainder, the interstitial flu id, surrounds and bathes all of is regulated largely by hormones secreted by e ndocr ine system our cells (see Figure 1.3 o n p. 5). glands (Figure I.4e). Another important bou ndar y, the integu me ntary system, or sk in , e ncloses the body as a \vhole (Fig ure J.4a). Th is Excretion system protects our internal organs from dry ing out (a fatal E xcr et ion is the p rocess of removing wastes, or excreta change), infection, a nd the damaging effects of heat, sunl ight, (ek-skre' tah), from the body. If the body is to operate as we and an unb el ievable number of chemicals in the external expect it to, it must get rid of nonuseful substances produced environmen t. during digestion and metabolism. Several organ systems participate in excretion. For example, Movement the digestive system rids the body of indigestible food residues Movement includes the activities promoted by the muscular in feces, and the uri nary system disposes of nitrogen-containing system, such as propelling ourselves from o ne place to another metabolic wastes, such as urea, in urine (Figure l.4i and j). by running or swimming, and manipulating the exten1al envi- Carbon dioxide, a by-product of cellular respirat ion, is carried ronment with our nimble fingers (Figure l.4c). T he skeletal in the blood to the lungs, where it leaves the body in exhaled system provides the bony framework that the muscles pull on air (Figure l.4h). as they work (Figure J.4b ). Movement also occurs whe n sub- stances such as blood, foodstu ffs, a nd urine are propelled Repro duction through internal organs of the card iovascul ar, d igestive, and Reproduction occurs at the cellular and the organismal level. uri nary systems, respect ively. On the cellular level, the mus- In cellular reproduction, the origi nal cell divides, produc ing two cle cell 's ability to move by shortening is more precisely cal led ide ntical daughter cells that may then be used for body growth contra ctility. or repair. Reproductio n of the human organism, or making a whole new person, is the maj or task of the reproductive system. Responsiveness Whe n a sperm unites with an egg, a fertilized egg forms and Responsiven ess, or excitability, is the ability to sense changes develops into a baby within the mother's body. T he reproduc- (stimuli) in the enviro nment and then respo nd to them. For tive system is directly responsible for producing offspri ng, but examp le, if you cut your hand on broken g lass, a withdrawal its function is exquisitely regulated by hormones of the endo- reflex occurs-you involuntaril y pull your hand away frorn the cri ne system (Figure J.4e). painful stimulus (the broken glass). You don' t have to think Becau se ma les prod uce spe r m a nd femal es produce about it- it j ust happens! Likewise, when carbon diox ide in eggs ( ova), there is a division of labor in reproduction, and your blood rises to dangerously high levels, chemical sensors the reproductive organs of males and females are different respond by send ing messages to brain centers controlling respi- (Figure J.4k, I). Additionally, the female's reproductive struc- ration, and you breathe more rapidly. tures provide the site for fertilization of eggs by sperm, and then Because nerve cells are highly excitable and communicate protect and nurture the developing fetus until birth. rapidly with each other via electrical impulses, the nervous sys- te m is most involved with respons iveness (Figure J.4d). How- Growth ever, all body cells are excitable to some extent. G ro\vth is an increase in size of a body part or the organism as Digestion a whole. It is usually accornplished by increasi ng the number of cells. However, individual cells also increase in size when not Digestion is the breaking down of ingested foodstuffs to si mple dividing. For true growth to occur, constructive activities must molecules that can be absorbed into the blood. The nutrient-rich occur at a faster rate than destructive ones. blood is then distributed to all body cells by the card iovascular system. In a simple, o ne-celled organism suc h as a n amoeba, the cell itself is the "digestion factory," but in the multicellular Survival Needs human body, the d igestive system performs this function for the The ultimate goal of all body systems is to maintain life. How- e ntire body (Figure l.4i). ever, life is extraordi narily fragile and requires several factors.  Chapter 1 The Human Body: An Orientation 9 These survival needs include nutrients (food), oxygen, water, Check Your Understanding and appropriate temperature and atmospheric pressure. 6. What separates living beings from nonliving objects? Nut rient s. Nutrien ts, taken in via the diet, contain the 7. What name is given to all chemical reactions that occur with in chemical substances used for energy and cell building. Most body cells? plant-derived foods are rich in carbohydrates, vitamins, and 8. The image below shows tissue cells and part of a blood vessel. minerals, whereas most animal foods are richer in proteins The cells' nutrients and wastes are exchanged across an and fats. important bou ndary between two fluid compartments. Na me Carbohydrates are the major energy fuel for body cells. the boundary (a) and the fluid in the compartments (ba nd c). Proteins, and to a lesser extent fats, are essential for build- Be specific ing cell structures. Fats also provide a reserve of energy- rich fuel. Selected minerals and vitainins are required for the -----a Tissue cells --'K.~-- chemical reactions that go on in cells and for oxygen trans- { ,:- - - , - - b port in the blood. The mineral calcium helps to make bones hard and is required for blood clotting. Blood vessel - - Oxygen. All the nutrients in the world are useless unless oxygen is also available. Because the chemical reactions that release energy from foods are oxidative reactions that - - - - - - - - - - For answers, see Answers Appendix. require oxygen, human cells can survive for only a few minutes without oxygen. Approximately 20o/o of the air we breathe is oxygen. The cooperative efforts of the respiratory Homeostasis is maintained and cardiovascular systems make oxygen available to the by negative feedback blood and body cells. Water. Wa ter accounts for 50-60% of our body weight and Learning Outcomes is the single rnost abundant chemical substance in the body..... Define homeostasis and explain its significance. It provides the watery environment necessary for chernical.... Describe how negative and positive fe.e dback maintain reactions and the fluid base for body secretions and excre- body homeostasis. tions. We obtain water from ingested foods and liqu ids. We.... Describe the relationship between homeostatic imbalance and d isease. lose it frorn the body by evaporation from the lungs and skin and in body excretions. When you think about the fact that your body contains tril- Normal body tem perature. If chemical reac tions are to lions of cells in nearly constant activity, and that remarkably continue at life-sustaining rates, 11or1nal body tempera - little usually goes wrong with it, you begin to appreciate what a tu re must be maintained. As body temperature drops marvelous machine your body is. Walter Cannon, an American below 37°C (98.6°F), metabolic react ions become slower physiologist of the early t\ventieth century, spoke of the "wis- and slower, and finally stop. When body temperature is too dom of the body," and he coined the word ho111eostasis (ho"me- high, chemical reactions occur at a frantic pace ai1d body o -sta'sis) to describe its ability to maintain relatively stable systems stop functioning. At ei ther extreme, death occurs. internal cond itions even though the outside world changes The activity of the muscular system generates most body continuously. heat. Although the literal trai1slation of horneostasis is "unchai1g- ing," the term does not really mean a static, or unchanging, Appropriate atmospheric pressure. Atmospheric pressu re state. Rather, it indicates a dyna,nic state of equilibrium, or a is the force that air exerts on the surface of the body. Breath- balance, in which internal conditions vary, but always within ing and gas exchange in the lungs depend on appropriate relatively narrow limits. In general, the body is in homeosta- atmospheric pressure. At high altitudes, where atmospheric sis when its needs are adequately met and it is functioning pressure is lower and the air is thin, gas exchange may be smoothly. inadequate to support cellular metabolism. Maintaining homeostasis is more complicated than it The mere presence of these survival factors is not sufficient appears at first glance. Virtually every organ system plays a to sustain life. They rnust be present in the proper ainounts. Too role in maintaining the constancy of the internal environment. much and too little may be equally harmful. For example, oxy- Adequate blood levels of vital nutrients must be continuously gen is essential, but excessive ainounts are toxic to body cells. present, and heart activity and blood pressure must be con- Similarly, the food we eat must be of high quality ai1d in proper stantly monitored and adjusted so that the blood is propelled to amounts. Otherwise, nutritional disease, obesity, or starvation all body tissues. Also, wastes must not be allowed to accumu- is likely. Also, while the needs listed here are the most crucial, late, and body ternperature must be precisely controlled. A wide they do not even begin to encompass all of the body's needs. variety of chemical, thermal, and neural factors act and interact For example, we can live without gravity if \Ve must, but the in complex ways-sometimes helping and sometirnes hindering quality of life suffers. the body as it works to rnaintain its "steady rudder." 10 UNIT 1 Organization of the Body Homeostatic Control orig inal effect of the sti mulus or reduces its intensity. These mechanisms cause the variable to c hange in a d irection Communicat ion wi th in the body is essential for homeostasis. opposite to that of the initial change, returning it to its "ideal" Commu nication is accornplished chiefly by the nervous and en- value. docrine systems, which use neural electrical impulses or blood- Let's start w ith an example of a nonbiological negative borne horrnones, respectively, as inforrnation carriers. We cover feed back system: a home heating system connec ted to a the details of how these two great regulating systems operate in temperature-sensing thermostat. The thermostat houses both later chapters, but here \Ve explain the basic characteristics of the receptor (thermo,neter) and the control center. If the ther- control systems that promote homeostasis. mostat is set at 20°C (68°F), the heating system (effector) is The va riable is the factor or eve nt being regulated. All triggered ON when the house temperature drops below that homeostatic control mechanisms are processes involv ing at setting. As the furnace produces heat and warms the air, the least three components that work together to regulate the vari- temperature rises, and whe n it reaches 20°C or slightly higher, able (Figure 1.5). the thermostat triggers the furnace OFF. This process results 1. The receptor is the first component. It is a sensor that moni- in a cycling of the furnace between "ON" and "OFF' so that tors the enviro nment. It responds to stirnuli (changes) by the temperature in the house stays very near the desired tem- sending informatio n (input) along the afferent pathway to perature. Your body "thermostat," located in a part of your the second component, the control center. bra in called the hypothalamus, operates in a similar fashion 2. The control center determines the set point, which is the level (Figure 1.6). (or range of levels) at which a variable is to be maintained. It Regulation of body temperature is only one of the many analyzes the input it receives by comparing it to the set point ways the nervous system maintai ns the constancy of the internal and determines the appropriate response. Information (output) environment. Another type of neural control mechanism is seen then flows from the control center along the efferent pathway in the withdrawal reflex mentioned earlier, in which the hand is to the third component, the effector. (To help you remember the jerked away from a painful stimulus such as broken glass. difference between "afferent'' and "efferent," note that informa- The e ndocrine system is equally important in maintaining tion traveling along the afferent pathway approaches the control homeostasis. A good example of a hormonal negative feedback center and efferent information exits from the control center.) mechanism is the co ntrol of blood sugar (glucose) by insulin. 3. The effector carries out the control center's response to the As blood sugar rises, receptors in the body sense this change, stimulus. The results of the response then feed back to influ- and the pancreas (the control center) secretes insulin into the ence the effect of the sti mulus, either reducing it so that the blood. This change in turn prompts body cells to absorb more whole control process is shut off, or enhanci ng it so that the glucose, removing it from the bloodstream. As blood sugar whole process continues at an even faster rate. falls, the stimulus for insulin release ends. The body's ability to regulate its internal e nvironment is Negative Feedback Mechan isms fundamental. All negative feedback mechanisms have the same Most homeostatic control mechanis ms are nega tive feed back goal: preventing severe changes within the body. Body temper- 111echan is111s. In these systems, the o utput sh uts off the ature and blood sugar are only two of the variables that need to @ Input: Information © Output: Information sent along afferent Control sent along efferent pathway to control Center - - - pathway to effector. center. ,,;.e:::.._- Afferent Efferent-__::!oo.... pathway pathway @ Receptor detects change. I ,,.,, Receptor Effector @ Response r ,.,. of effector feeds back to reduce G) Stimulus the effect of stimu lus and produces returns variabl e change in BALANCE to homeost atic variable. level. ''1fe"t.i lic1, Figure 1.5 Interactions among the elements of a homeostatic control syst em maintain stable internal conditions.  Chapter 1 The Human Body: An Orientation 11 Control Center (thermoregulatory center in brain) r - - Afferent Efferent - --31. pathway pathway Receptors Temperature-sensitive Effectors cells in skin and brain Sweat glands Body temperature 1 Sweat glands activated Response Evaporation of sweat t Body temperature falls; rises stimulus ends Stimulus: Heat BALANCE Stimulus: Cold Response Body temperature rises; stimulus ends ! Body temperature falls Effectors Receptors Skeletal muscles Temperature-sensitive cells in skin and brain - - -Efferent Afferent - -- I Shivering begins pathway pathway Control Center (thermoregulatory center in brain) Figure 1.6 Body t emperat ure is regulated by a negative feedback mechanism. be regulated. There are many! Other negat ive feedback mech- 'Iypically, they set off a linked sequence of events. Once ini- anisms regulate heart rate, blood pressure, the rate a nd depth tiated, the resul ts of each reaction feed into the next like a of breathing, and blood levels of oxygen, carbon dioxide, and series of waterfalls on a river. Because of these character- minerals. ist ics, positive feedback mechanisms are often referred to as cascades (from the Italian word meaning "to fall ") that Positive Feedback Mechanisms amplify the original stimulus. Two familiar examples are the In positive feedback m echanism s, the in itial response enhancemen t of labor contractions during birth and blood enhances the original stimulus so that further responses are clotting. even greater. This feedback mechanism is "positive" because Chapter 28 describes the positive feedback mechanism in the change that results proceeds in the sa1ne direction as the which oxytocin, a hypothalarnic hormone, intensifies labor con- initial change, causing the variable to deviate further and further tractions during the birth of a baby (see Figure 28. 16, p. 1114). from its original value or range. Oxytocin causes the contractions to becorne both more frequent In contrast to negative feedback controls, which maintain and more powerful. The increased contractions cause more oxy- some physiological function or keep blood chemicals wi thin tocin to be released, wh ich causes more contractions, and so on narrow ranges, positive feedback mechanisms usually control until the baby is born. The birth ends the stimulus for oxytocin infrequent events that do not requ ire continuous adjustments. release and shuts off the positive feedback mechanisrn. 12 UNIT 1 Organization of the Body Another important source of homeostatic imbalance occurs G) Break o r tear occurs in blood whe n the usual negative feedb ack mechanisms are over- vessel wall. whelmed a nd destructive positive feedback mechanisms take over. Some instances of heart failure reflect this phenomenon. Examples of homeostatic imbalance appear throughout this , book to e nhance your understanding of normal physiological Cl:>-- Positive feedback cycle is initiated. mechanisms. This symbol ,, a introduces the homeostatic imbalance sections a nd alerts you to the fact that we are de- scribing an abnormal condition. Each Homeostatic Imbalance section is numbered to correspond with critical thinking ques- tions available in the Study Area of MasteringA&P·-visit the @Released @ Platelets chemicals.,..,, , adhere to site webs ite to fi nd Homeostatic Imbalance questions and other Positive 0 ~ helpful study tools. ·~ 01,~r.. IJ., attract more._ and release platelets. 0 ~ ! 0 feedback loop O chemicals. 0 Check Your Understanding 0 o~ 9. What process allows us to adjust to either extreme heat or 0 extreme cold? 10. Why is the control system shown in Figure 1.7 called a positive feedback mechanism? What event ends it? i CD- Feedback cycle ends when plug is formed. 11. M44H When we begin to get dehydrated, we usually get thirsty, wh ich causes us to dri nk fl uids. Is th irst part of a negative or a positive feedback control system? Explain you r choice. © Platelet plug is fully formed. - - - - - - - - - - For answers, see Answers Appen dix. Anatomical terms describe body Figure 1.7 A positive feedback mechanism regu lates formation of a platelet plug. directions, regions, and planes Learning Outcomes Ill> Describe the a na tomical position. Ill> Use correct a natomical terms to d escribe body direct ions, Blood clotting is a normal response to a break in the wall regions, a nd body pla nes or sections. of a blood vessel and is an excellent example of a n important Most of us are naturally curious about our bodies, bu t our body function controlled by positive feedback. Once a vessel interest someti mes dwindles when we are confronted with the has been damaged, blood elernents called platelets immediately terminology of a natomy and physiology. Let's face it-you beg in to cling to the injured site and release chem icals that can' t j ust pick up an anatomy and phys iology book and read attract more platelets. This rapidly growing pileup of platelets it as though it were a novel. Unfortunately, confusion is likely ternporarily "plugs" the tear and initiates the sequence of events that finally forms a clot (Figure 1.7). without precise, special ized term inology. To prevent misu nder- standing, anatomists use universally accepted terms to identify Positive feedback mechan isms are likely to race out of con- body structures precisely and with a minimum of words. We trol, so they are rarely used to promote the moment-to-moment present and explain the language of anatomy next. well-being of the body. Some positive feedback mecha nisms, including this one, may have only local effects. For example, blood clotting is accelerated in inj ured vessels, but does not Anatomical Position and Directional Terms normally spread to the entire circulation. To describe body parts and position accurately, we need an ini- tial reference point, and we must indicate d irection. The ana- Homeostatic Imbalance tomical reference point is a standard body position called the a natomical position. In the anatom ical pos ition, the body is Homeostasis is so important that most disease can be regarded as a result of its disturbance, a cond ition called ho1neostatic erect with feet slightly apart. This position is easy to remem- ber because it resembles "standing at attention," except that imbalance. As we age, our body's control systems become less efficient, and our internal e nvironment becomes Jess and Jess the palms face forward and the thumbs point a\vay from the body. You can see the anatomical position in Figure 1.Sa and stable. These events increase our risk for illness and produce Table 1.1 (top) o n p. 14. the changes we associate with aging. It is essential to understand the anatomical position because most of the directional terms used in this book refer to the body  Chapter 1 The Human Body:An Orientation 13 Cephalic Cephalic Frontal - -~ - - - Otic ==:: : : : : ~~:: Orbita.11 - Nasal - --Occipital (back of head) Buocal (cheek) Upper limb Oral ~ Acromial Mental (chin)-..---.,( ; -Brachia! (arm) Cervical Antecubital Thoracic__ --1--- ~- Olecranal - --.. Back (dorsal) Stemal Antebrachial ~ -- Scapular Axillary--Y (forearm) Mammary Carpal (wrist) r - i -- - - vertebral Abdominal Umbilical....--.............- - - 4--e----;,.-- - Lumbar Manus (hand} Pelvic - -f;.._ci-t--- - Metacarpal lnguinal --f-;7-f --.......,. Pal mar (groin) /~Pollex ?'rI Digital - -l,r-'.)-i- 3\---- Gluteal ~.....- - l---';--,-- - Perineal (between V Lower li mb anus and external '----'.. "-- - Coxal (hip) genitalia) Pubic (genital) ' - - - - - - Femoral (thigh) _..:.- -'[-:- , , - - - - Patellar Popliteal ~ - - - -J l.,--- Crural (leg) Sural (calf) ~ f f" _.,,-,---- Fibular or peroneal~ 1' V Pedal (foot) D Thorax ~--Tarsal (ankle) D Abdomen Calcaneal -------- I D Back (Dorsum) ,- ~ Metatarsal ~ Y.' ~ Digital y Plantar - - - - - - ~...;...:----- Hallux (a) Anterio rNentral (b) Posterior/Dorsal Figure 1.8 Regional terms used to desig nate specific body areas. Common terms a re shown in parentheses. (a) Anatomical position. (b) The heels are raised to show the plantar surface of the foot. as if it were in this position, regardless of its actual position. Regional Terms Another point to remember is that the terms "right" and "left" The two fundamental divisions of our body are its axial and refer to those sides of the person or the cadaver being viewed- appendicular (ap"en-d ik'u-lar) parts. The axial part, which not those of the observer. makes up the main axis of our body, includes the head, neck, Directional terms allow us to explain where one body struc- and trunk. The append icular par t consists of the appendages, ture is in relation to another. For example, we could describe or lin1bs, which are attached to the body's ax is. Regional tern1s the relationship between the ears and the nose by stati ng, "The used to designate specific areas within these major body divi- ears are located on each side of the head to the right and left of sions are indicated in Figure 1.8. the nose." Us ing anatomical terminology, this becomes "The ears are lateral to the nose." Using anatomical terms saves words and is less ambiguous. Body Planes and Sections Commonly used orie ntation and directional terms are de- For anatom ical studies, the body is often cut, or sectioned, fined and illustrated in Table 1.1. Many of these terms are also along a flat surface called a plane. The most frequently used used in everyday conversation, but remernber as you study thern body planes are sagittal,frontal, and transverse planes, wh ich that their anatomical meanings are very precise. 14 UNIT 1 Organization of the Body Table 1.1 Orientation and Directional Terms TERM DEFINITION EXAMPLE Superior (cranial) Toward the head end or upper The head is superior to the part of a structure or the body; abdomen. above Inferio r (caudal) Aw ay from the head end or The navel is inferior to the chin. toward the lower part of a structure or the body; below A nterior (ventral)* Toward o r at the front of the The breastbone is anterio r to body; in f ro nt of the spine. Posterior (dorsal)* Toward o r at the back of the The heart is posterior to the body; behind breastbone. Medial Toward o r at the mid line of the The heart is medial to the arm. body; o n the inner side of Lateral Away from the midline of the The arms are lateral to the body; o n the outer side of chest. Intermediate Between a more medial and a The collarbone is inter mediate more lateral structure between the breastbone and sho ulder. Proximal Closer to the o rigin of the body The elbow is proximal to the part o r the point of attach ment wrist. of a limb to the body trunk Distal Farther f rom the orig in of The knee is distal to the thigh. a body part o r the point of attachment of a limb to the body trunk I \ \ J Superficial (external) Deep (internal) Toward o r at the body surface Aw ay from the body surface; _J1_ The skin is superficial to the skeletal muscles. The lungs are deep to the skin. more internal 11 *The terms ventral and anterior are synonymous in humans. but this is not the case in four-legged animals. Anterior refers to the leading portion of the body (abdominal surface in humans, head in a cat), but ventral specifically refers to the "belly" of a vertebrate animal, so it is the inferior surface of four- legged animals. Likewise, although the dorsal and posterior surfaces are the same in humans, the term dorsal specifically refers to an animal's back (as in the dorsal fin of a shark). Thus, the dorsal surface of four-legged animals is their superior surface.  Chapter 1 The Human Body: An Orientation 15 ' (a) Median (midsagittal) plane (b) Frontal (coronal) plane (c) Transverse plane Vertebral Right Left column lung Heart lung Liver Aorta Pancreas Spleen Rectum Intestines Liver Stomach Spleen Subcutaneous Spinal fat layer cord Figure 1.9 Planes of the body with corresponding magnetic resonance imaging (MRI) scans. lie at right a ngles to one another (Figure 1.9). A sectio n is exist, at every possible level from head to foot. A transverse named for the plane along which it is cut. Thus, a cut along a section is also called a cross section. sagittal plane produces a sagittal section. Oblique sections are cuts made diagonally between the hori- A sagittal plane (saj 'T-tal; "arrow") is a vertical pla ne that zontal and the vertical planes. Because oblique sections are divides the body into right and left parts. A sagittal plane that often confusing and difficult to interpret, they are seldorn used. lies exactly in the midli ne is the median plane, or midsagit- Figure l.9 includes examples of magnetic resonance imag- tal plane (Figure l.9a). All other sagittal planes, offset from ing (MRI) scans that correspond to the three sections shown the midline, are parasagittal planes (para = near). in the figure. Clinicall y, the ab ility to interpret sections made Frontal planes, like sagittal planes, lie vertically. Frontal through the body, especially transverse sections, is impor- planes, however, divide the body into anterior and posterior tant. Additionally, certain medical imaging devices (A Closer parts (Figure L.9b). A frontal plane is also called a coronal Look, pp. L6-17) produce sectional images rather than three- plane (ko-ro' nal; "crown"). dimensional images. A transverse, or horizontal, plane runs horizontally from It takes practice to determine an object's overall shape from right to left, dividing the body into superior and inferior parts sectioned material. Section ing the body or an organ along dif- (Figure l.9c). Of course, many different transverse planes ferent planes often results in very different views. For example, 18 UNIT 1 Organization of the Body Dorsal Body Cavity The thoracic cavity is separated from the more inferior abdo1ninopelvic cavity (ab-dom'T-no-pel'vic) by the d ia- The dor sal body cavity, v,hich protects the fragile nerv- ous system organs, has t\vo subdivisions (Figure 1.10, gold phragm, a dome-shaped muscle important in breathing. The abdominopelv ic cavity, as its name suggests, has two parts. areas). The cranial ca vity, in the skull, encases the brain. The vertebral, or s pinal, cavity, which runs within the bony ver- However, these regions are not physically separated by a mus- cular or membrane \Vall. Its superior portion, the abdominal tebral column, encloses the delicate sp inal cord. The spinal cavity, contains the stomach, intestines, spleen, liver, and other cord is essentially a continuation of the brain, and the cranial organs. The inferior part, the pelvic ca vity, lies in the bony pel- and spinal cavities are continuous with one another. Both the vis and contains the urinary bladder, some reproductive organs, brain and the spinal cord are covered by membranes called and the rectum. The abdominal and pelvic cavities are not men inges. aligned with each other. Instead, the bowl-shaped pelvis tips away from the perpendicular as shown in Figure 1.1Oa. Ventral Body Cavity The more anterior and larger of the closed body cavities is the ventral body cavity (Figure I. I 0, deep-red areas). Like the --~J_. HOMEOSTATIC.....-2' IMBALANCE 1.1 dorsal cavity, it has two major subdivisions, the tlwracic cavity and the abdo,ninopelvic cavity. The ventral body cavity houses Each body cavi ty is un iquely suited to house its con tents. internal organs collectively called the viscera (vis' er-ah; visctL~ = Problems arrise when a struc ture strays into a neighboring cavity. A hiatal hernia occurs when part of the stomach slides an organ in a body cavity), or visceral organs. The superior subdivision, the thor acic ca vity (tho-ras'ik), through the diaphragm into the thoracic cavity, allowing stomach acid to cause heartburn (which is actually irritation is surrounded by the ribs and muscles of the chest. The tho- of the esophagus, not the heart). Severe cases may requ ire racic cavity is further subdivided into lateral pleural ca vities (ploo'ral), each enveloping a lung, and the medial mediasti- surgical repair. num (me"de-ah-sti' num). The mediastinum contains the peri- car dia) ca vity (per''T-kar' de-al), which encloses the heart, and Membranes i n the Ventra l Body Cavity it also surrounds the remaining thoracic organs (esophagus, tra- The walls of the ventral body cavity and the outer surfaces of chea, and others). the organs it contains are covered by a th in, double-layered membrane, the ser osa (se-ro'sah), or serous membrane. Cranial _ _ _ _ _ ___.::;.:__ Cranial cavity - -+- cavity (contains brain) Vertebral:- - - - - - -..:..__: cavity Superior - - - --:=::~- Dorsal body mediastinum t;::....- Thoracic cavity cavity Pleural - - - - - ' - - (contains cavity heart and lungs) Pericardial - - - - - cavity within the mediastinum Vertebral cavity ---,;- ( contains spinal '----Diaphragm _ _ _.,.. Ventral body cord) cavity (thoracic and ~ '--- - Abdominal cavit y - - ---'- abdominopelvic (contains digestive Abdomino- cavities) viscera) pelvic cavity ~ - - - Pelvic cavit y - - - - - - ' - - (contains urinary D Dorsal body cavity bladder, reproductive D Ventral body cavity organs, and rectum) (a) Lateral view (b) Anterio r view Fig ure 1.10 Dorsal and ventral body cavities and their subdivisions.  Chapter 1 The Human Body: An Orientation 19 ~ - Outer balloon wall w hich covers the heart. Li kew ise, the parietal pleurae FJ°'!!,,oli ,.....,..~ (comparable to parietal serosa) (ploo're) line the walls of the thoracic cavity, and the visceral pleurae cover the lungs. The parietal perito11eu,11 (per"T-to- ne'um) is associated with the walls of the abdom inopelvic ~,_- - Inner balloon wall cavity, while the visceral peritoneu,11 covers most of the or- ,.....~. , (comparable to visceral serosa) gans within that cavi ty. (The pleural and peritoneal serosae are illustrated in Figure 4. I4c on p. l 42.) (a) A fist t hrust into a flaccid b alloon demonstrates the relationship between the parietal and visceral serous membrane layers..J HOMEOSTATIC CLINICAL! ~-""J i~- IMBALANCE 1.2 When serous membranes are inflamed, their normall y srnooth Heart surfaces become roughened. This roughness causes the mem- branes to stick together and drag across one another. Excru- ciating pain results, as anyone who has experienced pleurisy (inflammation of the pleurae) or peritonitis (inflammation of __..-- -- Parietal the peritoneums) knows. pericardium , +-- - -.......- - Pericardia! Abd ominopelvic Regions and Quadrants space with serous fluid Because the abdominopelvic cavity is large and contains sev- eral organs, it helps to div ide it into smaller areas for study. E-- - Visoeral Medical perso nnel usually use a simple scheme to locate the pericardium abdominopelvic cavity organs (Figure 1.12). In this scheme, a transverse and a median plane pass throug h the umbili- cus at right angles. The four resulting quadrants are named according to their positions frorn the subject's point of view: the right upper q uadrant (RUQ), left u pper quadrant (b) The serosae associated with the heart. (L UQ), right Jo,ver q uadrant (RLQ), and left lower q uad- rant (LLQ). Figure 1.11 Serous membrane relat ionsh ips. Another division method, used primarily by anatomists, uses two transverse and two parasagittal planes. These planes, The part of the membrane lining the cavity walls is called the parietal serosa (pah-ri'e-tal; parie = wall). It folds in on itself to form the viscer al serosa, covering the organs in the cavity. You can visualize the relationship between the serosal lay- ers by pushing your fist into a limp balloo n (Figure 1.11a). The part of the balloon that clings to your fist can be compared to the visceral serosa clinging to an organ's external surface. The outer wall of the balloon represents the parietal serosa that lines the walls of the cavity. (However, unlike the ball oon, the parietal serosa is never exposed but is always fused to the cavity wall.) In the body, the serous membranes are separated not by air but by a thin layer of lubricating fluid, called serous fluid, Right upper - -;..:1-.ir, --:.....,.!':-':- , - - - Left upper which is secreted by both membranes. Although there is a po- quadrant quadrant (RUO) (LUO) tential space between the two membranes, the barely present, sli tlike serous cavity is filled with serous flu id. The slippery serous fluid allows the organs to slide without Right lower _ _.£.!:.::;.j~ ;;J~ ~ ~ - - Left lower friction across the cavity walls and one another as they carry quadrant quadrant out their routine functions. This freedom of movement is espe- (RLQ) (LLO) cially important for mobile organs such as the pumping heart and the churning stomach. The serous membranes are named for the specific cavity and organs with which they are associated. For example, as Figure 1.12 The four abdominopelvic quadrants. In this shown in Figure l. l I b, the parietal pericardiu,11 lines the scheme, t he abdominopelvic cavity is divided into four quadrants by pericardia! cavity and folds back as the visceral pericardiurn, two planes. 20 UNIT 1 Organization of the Body The righ t and left in guin al, or iliac, regions (ing' gwI-nal) are located lateral to the hypogastric region (iliac = superior part of the hip bone). The right and left lateral (lumbar) regions lie lateral to the umbi lical region (lurnbus = Join). T he righ t and left hypoch ondria c r eg ions lie la tera l to the ep igastric region and deep to the ri bs (cho11dro = cartilage). ~ HOMEOSTATIC ~--Ji~- IMBALANCE 1.3 You may have seen news stories about "wrong site surgery" and wondered how such serious mistakes can happen. Critical errors, including amputation, may result from confusion about right versus left or poor understanding of terminology. As you master the term inology of anatomy, you are he lping to elim i- nate these blunders. (a) Nine regions delineated by four planes Other Body Cavities In addition to the large closed body cavities, there are several smaller body cavities. Most of these are in the head and most open to the body ex terior. Figure 1.8 provides the terms that wi ll help you locate all but the last two cavities mentioned here. Oral and digestive cavities. The oral cavity, commonly called the mouth, contains the teeth and tongue. This cavity is part of and continuous with the cavity of the digestive organs, which ~~~'ii;.'.;:! c.__ _ Diaphragm opens to the body exterior at the anus. a,,:,..,--Spleen Nasa l cavity. Located within and posterior to the nose, the Gallbladder "!...~ i=,,f;-- Stomach nasal cavity is part of the respiratory system passageways. Orb ital cavities. The orb ital cavities (orbits) in the sku ll ~ ~ =-- Transverse colon house the eyes and present them in an anterior position. of large intestine ~ ,-.._- Descending colon Middle ear cavities. T he m iddle ear cavities in the skull of large intestine lie j ust medial to the eardrums. These cavities contain tiny ,_..--- Initial part of bones that transmit sou nd vibrations to the hearing receptors ~ sigmoid colon in the inner ears. ~ - ;- - -- Urinary bladder Synovial cavities. Sy novial (sI-no've-al) cavities are joint cavi ties. They are e nc losed withi n fibrous capsules that sur- (b) Anterior view of the nine regions showing the superficial organs rou nd freely movable j oints of the body (such as the el bow Figure 1.13 The n ine abdominopelvic reg ions. The superior a nd knee joints). L ike the serous membranes, membranes transverse plane is just inferior to the ribs; the inferior transverse lining synovial cavities secrete a lubricating flu id that re- plane is just superior to the hip bones; and the parasagittal planes lie duces friction as the bones move across one another. just medial to the nipples. Check Your Understanding 16. Of the uterus, small intestine, spinal cord, and heart, wh ich pos itio ned like a tic-tac-toe grid o n the abdomen, divide the is/are in the dorsal body cavity? cavity into nine regions (Figure 1.13): 17. M4#i1 Whe n you rub you r cold hands together, the friction The umb ilical region is the centermost region deep to and between them results in heat that warms you r ha nds. Why doesn't warming friction result during movements of the surrounding the umbilicus (navel). heart, lungs, and digestive organs? The ep igas tric region is located superior to the umbilical 18. j@;U )(il Joe went to the emergency room where he region (epi = upon, above; gastri = belly). complained of severe pains in the lower right quadrant of his The pubi c (h yp oga stric) region is located inferior to the abdomen. What might be his problem? umbilical region (hypo = below). - - - - - - - - - - - For answers, see Answers Appendix.