Sixth Edition & The Unity of Form and Function Kenneth S Saladin Georgia College & State University TM sal78259_fm_i-xxvi.indd i 11/19/10 9:31 AM TM ANATOMY & PHYSIOLOGY: THE UNITY OF FORM AND FUNCTION, SIXTH EDITION Published by McGraw-Hill, a business unit of The McGraw-Hill Companies, Inc., 1221 Avenue of the Americas, New York, NY 10020 Copyright © 2012 by The McGraw-Hill Companies, Inc All rights reserved Previous editions © 2010, 2007, and 2004 No part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written consent of The McGraw-Hill Companies, Inc., including, but not limited to, in any network or other electronic storage or transmission, or broadcast for distance learning Some ancillaries, including electronic and print components, may not be available to customers outside the United States This book is printed on acid-free paper QVR/QVR ISBN 978–0–07–337825–1 MHID 0–07–337825–9 Vice President, Editor-in-Chief: Marty Lange Vice President, EDP: Kimberly Meriwether David Senior Director of Development: Kristine Tibbetts Executive Editor: James F Connely Developmental Editor: Ashley Zellmer Marketing Manager: Denise M Massar Senior Project Manager: Vicki Krug Senior Buyer: Sandy Ludovissy Lead Media Project Manager: Stacy A Vath Senior Designer: David W Hash Cover Designer: John Joran Cover Art Overlay: Imagineering Cover Image: ©Mike Powell/Stone/Getty Images Senior Photo Research Coordinator: John C Leland Photo Research: Mary Reeg Compositor: Electronic Publishing Services Inc., NYC Typeface: 10/12 Melior Printer: Quad/Graphics All credits appearing on page or at the end of the book are considered to be an extension of the copyright page Library of Congress Cataloging-in-Publication Data Saladin, Kenneth S Anatomy & physiology : the unity of form and function / Kenneth S Saladin 6th ed p cm Includes index ISBN 978–0–07–337825–1 — ISBN 0–07–337825–9 (hard copy: alk paper) Human physiology Human anatomy I Title II Title: Anatomy and physiology QP34.5.S23 2012 612 dc22 2010042586 www.mhhe.com sal78259_fm_i-xxvi.indd ii 11/19/10 11:47 AM BRIEF About the Author iv Preface v Reviewers xxi Contents xxii Letter to the Students xxvi 16 17 Contents Sense Organs 582 The Endocrine System 633 PART FOUR Regulation and Maintenance PART ONE Organization of the Body Major Themes of Anatomy and Physiology Atlas A General Orientation to Human Anatomy 28 The Chemistry of Life 42 Cellular Form and Function 78 Genetics and Cellular Function 114 Histology 143 18 19 20 21 22 23 24 25 26 The Circulatory System: Blood 678 The Circulatory System: The Heart 714 The Circulatory System: Blood Vessels and Circulation 749 The Lymphatic and Immune Systems 808 The Respiratory System 854 The Urinary System 895 Water, Electrolyte, and Acid–Base Balance 930 The Digestive System 953 Nutrition and Metabolism 1000 PART TWO Support and Movement 10 11 The Integumentary System 180 Bone Tissue 206 The Skeletal System 233 Joints 278 The Muscular System 312 Atlas B Regional and Surface Anatomy 379 Muscular Tissue 401 PART THREE Integration and Control 12 13 14 15 sal78259_fm_i-xxvi.indd iii Nervous Tissue 439 The Spinal Cord, Spinal Nerves, and Somatic Reflexes 478 The Brain and Cranial Nerves 511 The Autonomic Nervous System and Visceral Reflexes 561 PART FIVE Reproduction and Development 27 28 29 The Male Reproductive System 1034 The Female Reproductive System 1064 Human Development and Aging 1102 Appendix A Periodic Table A-1 Appendix B Answer Keys A-2 Appendix C Symbols of Weight and Measures A-13 Appendix D Biomedical Abbreviations A-14 Glossary G-1 Credits C-1 Index I-1 11/19/10 9:53 AM ABOUT THE Author KENNETH S SALADIN has taught since 1977 at Georgia College and State University in Milledgeville, Georgia He earned a B.S in zoology at Michigan State University and a Ph.D in parasitology at Florida State University, with interests especially in the sensory ecology of freshwater invertebrates In addition to human anatomy and physiology, his teaching experience includes histology, parasitology, animal behavior, sociobiology, introductory biology, general zoology, biological etymology, and study abroad in the Galápagos Islands Ken has been recognized as “most significant undergraduate mentor” nine times over the years by outstanding students inducted into Phi Kappa Phi He received the university’s Excellence in Research and Publication Award for the first edition of this book, and was named Distinguished Professor in 2001 Ken is a member of the Human Anatomy and Physiology Society, the Society for Integrative and Comparative Biology, the American Association of Anatomists, and the American Association for the Advancement of Science He served as a developmental reviewer and wrote supplements for several other McGraw-Hill anatomy and physiology textbooks for a number of years before becoming a textbook writer Ken’s outside interests include the Big Brothers/ Big Sisters program for single-parent children, the Charles Darwin Research Station in the Galápagos, and student scholarships Ken is married to Diane Saladin, a registered nurse They have two adult children This book is dedicated to the memory of H Kenneth Hamill and with gratitude to Big Brothers–Big Sisters of Greater Kalamazoo Big Brothers–Big Sisters of America iv sal78259_fm_i-xxvi.indd iv 12/2/10 9:18 AM THE EVOLUTION OF A Storyteller Ken Saladin’s first step into authoring was a 318-page paper on the ecology of hydras written for his 10th-grade biology class With his “first book,” featuring 53 original India ink drawings and photomicrographs, a true storyteller was born “When I first became a textbook writer, I found myself bringing the same enjoyment of writing and illustrating to this book that I first discovered back when I was 15.” –Ken Saladin Ken's “first book,” Hydra Ecology, 1965 One of Ken’s drawings from Hydra Ecology Ken in 1964 Ken began working on his first book for McGraw-Hill in 1993, and in 1997 the first edition of The Unity of Form and Function was published In 2011 the story continues with the sixth edition of Ken’s best-selling A&P textbook The first edition (1997) The story continues (2011) v sal78259_fm_i-xxvi.indd v 11/19/10 9:31 AM SALADIN ANATOMY & PHYSIOLOGY A Good Story Anatomy & Physiology: The Unity of Form and Function tells a story made of many layers including the core science, clinical applications, the history of medicine, and the evolution of the human body Saladin combines this humanistic perspective on anatomy and physiology with vibrant photos and art to convey the beauty and excitement of the subject to beginning students To help students manage the tremendous amount of information in this introductory course, the narrative is broken into short segments, each framed by expected learning outcomes and self-testing review questions This presentation strategy works as a whole to create a more efficient and effective way for students to learn A&P “Ken Saladin’s Anatomy & Physiology: The Unity of Form and Function, 6th edition, provides a fresh approach to the study of A&P, with modern pedagogy, an abundance of ancillary learning resources, and the most up-to-date information Instructors and students alike will benefit from the Saladin experience.” Storytelling Writing Style viii–x Appropriate Level Interactive Material Interesting Reading Artwork That Encourages Learning xi–xii Sets the Standard Conducive to Learning Pedagogical Learning Tools xiii–xiv Engaging Chapter Layouts Tiered Assessments Based on Key Lists of Expected Learning Outcomes Innovative Chapter Sequencing xv The Saladin Digital Story xvi-xix –David Manry, Hillsborough Community College What’s New in the Sixth Edition? New Atlas Organization Many figures of regional anatomy (former figs A.12–A.22) are moved from atlas A to atlas B, now titled “Regional and Surface Anatomy.” Beside shortening atlas A and moving the student more quickly to chapter 2, this moves some anatomical detail to a later point where students will be better equipped to understand it and relate it to surface anatomy New Deeper Insight Essays New essays introduce contemporary issues in health science and a fascinating historical account that underscores some principles of respiratory physiology It’s not unusual to hear textbook cynics say that new editions are just the same material bound in new covers, but that certainly isn’t true of this one Just listing my sixth-edition changes came to 50 pages and 18,000 words —Ken Saladin • Trans fats and cardiovascular disease (Deeper Insight 2.3) • Bone marrow and cord blood transplants (Deeper Insight 18.3) • Altitude sickness and the Zenith ballooning tragedy (Deeper Insight 22.3) vi sal78259_fm_i-xxvi.indd vi 12/2/10 9:18 AM New Science New Art Saladin’s Anatomy & Physiology, sixth edition, stays abreast of key developments in science Yet, more efficient writing and illustration result in a book slightly shorter than the fifth edition even with these additions • Cis- and trans-fatty acids (fig 2.20) • Advances in tissue engineering (chapter 5) • The stem-cell controversy and induced pluripotent stem cells (chapter 5) • Melanoma (chapter 6) • Cola beverages and bone loss (chapter 7) • Bases of muscle fatigue (chapter 11) • Microglia and astrocyte functions (chapter 12) • Neural mechanism of working memory (chapter 12) • Hypothalamic control of hunger and satiety (chapter 14) • Orexins, sleep, and narcolepsy (chapter 14) • Vascular pathogenesis in diabetes mellitus (chapter 17) • Glycemic index of foods (chapter 26) • Treatment of alcoholism (chapter 26) • Vaccination against human papillomavirus (chapter 27) • In vitro fertilization and the 2010 Nobel Prize (chapter 29) New Writing Several sections have been rewritten for improved clarity, especially: • Carrier-mediated membrane transport (chapter 3) • Genetic translation and ribosomal function (chapter 4) • A better example of an anatomical second-class lever (chapter 9) • Muscle compartments and blood supply (chapter 10) • Smooth muscle physiology (chapter 11) • A view of saltatory conduction more accurate than most textbook presentations (chapter 12) • The adrenal cortex (chapter 17) • Causes of arteriosclerosis and distinctions between arteriosclerosis and atherosclerosis (chapter 20) New Photographs • Genetic translation (fig 4.8) • Types of cell junctions (fig 5.28) • Embryonic development of exocrine and endocrine glands (fig 5.29) • Serous membrane histology (fig 5.33b) • The femur as a second-class lever (fig 9.9b) • The spinal reflex arc (fig 13.21) • Oxyhemoglobin dissociation curves (figs 22.24 and 22.27) • Connective Issues art and layouts New Pedagogy • Brushing Up is fleshed out and repositioned to better catch the student’s attention and emphasize the importance of understanding earlier material before starting a new chapter • A list of Expected Learning Outcomes heads up each chapter subdivision and exercises called Assess Your Learning Outcomes end each chapter as a whole Instructors can now easily show how their courses are outcome-driven • Apply What You Know questions, formerly called Think About It, stress that these thought exercises are analytical applications of basic anatomy and physiology knowledge to clinical situations and other new contexts Students can see how the basic anatomy and physiology they are learning will be relevant to analyzing new problems • Building Your Medical Vocabulary, new to each endof-chapter Study Guide, focuses on familiarity with the most common and useful biomedical word roots and affixes Like a mini-medical vocabulary course, this will help students with retention, spelling, and insight into medical terms, and ability to more comfortably approach even new terms beyond the scope of this book • Muscle tables in chapter 10 are organized in a new, more columnar format and enhanced with new color shading for easier reading and learning • Male-female pelvic differences (fig 8.37) • Treatment of infant hip dislocation (fig 9.27) • External anatomy of the orbital region (fig 16.22) • Use of a spirometer (fig 22.17) vii sal78259_fm_i-xxvi.indd vii 11/19/10 9:31 AM STORYTELLING Writing Style Appropriate Level • Plain language for A&P students early in their curricula • Careful word selection and paragraph structure • Appropriate for all audiences (international readers, English as a second language, and nontraditional students) “The physiological mechanisms presented throughout the text emphasize the basic fundamental processes that occur in the human body I believe the information is simplistic enough for students to comprehend yet detailed to provide important information […] for students and for instructors to present during lectures.” • Avoidance of "dumbed down" content Interactive Material • Review activities integrated in the chapter • Self-teaching prompts and simple experiments liberally seeded through the narrative —Scott Pallotta, Baker College at Allen Park • Learning aids such as pronunciation guides and insights into the origins and root meanings of medical terms The Temporal Bones If you palpate your skull just above and anterior to the ear—that is, the temporal region—you can feel the temporal bone, which forms the lower wall and part of the floor of the cranial cavity (fig 8.10) The temporal bone derives its name from the fact that people often develop their first gray hairs on the temples with the passage of time.9 The relatively complex shape of the temporal bone is best understood by dividing it into four parts: Z Homeostasis and Negative Feedback e ● Self-teaching prompts make reading more active Word origins are footnoted Pro-NUN-see-AY-shun guides help beginning students master A&P Familiarity with word origins helps students retain meaning and spelling The human body has a remarkable capacity for selfrestoration Hippocrates commented that it usually returns to a state of equilibrium by itself, and people recover from most illnesses even without the help of a physician This tendency results from homeostasis18 (HO-me-oh-STAY-sis), the body’s ability to detect change, activate mechanisms that oppose it, and thereby maintain relatively stable internal conditions French physiologist Claude Bernard (1813–78) observed that the internal conditions of the body remain quite constant even when external conditions vary greatly For example, whether it is freezing cold or swelteringly hot outdoors, the internal temperature of the body stays within a range of about 36° to 37°C (97°–99°F) American physiologist Walter Cannon (1871–1945) coined the term homeostasis for this tendency to maintain internal stability Homeostasis has been one of the most enlightening theories in physiology We now see physiology as largely a group of mechanisms for maintaining homeostasis, and the loss of homeostatic control as the cause of illness and death Pathophysiology is essentially the study of 18 homeo = the same; stas = to place, stand, stay viii sal78259_fm_i-xxvi.indd viii 12/2/10 10:55 AM STORYTELLING Writing Style Interesting Reading • Students say the enlightening analogies, clinical applications, historical notes, biographical vignettes, and evolutionary insights make the book not merely informative, but a pleasure to read 458 Axon Signal Action potential in progress ++++–––+++++++++++ ––––+++––––––––––– Refractory membrane Excitable membrane ––––+++––––––––––– ++++–––+++++++++++ +++++++++–––++++++ –––––––––+++–––––– –––––––––+++–––––– +++++++++–––++++++ +++++++++++++–––++ –––––––––––––+++–– –––––––––––––+++–– +++++++++++++–––++ FIGURE 12.16 Conduction of a Nerve Signal in an Unmyelinated Fiber Note that the membrane polarity is reversed in the region of the action potential (red) A region of membrane in its refractory period (yellow) trails the action potential and prevents the nerve signal from going backward toward the soma The other membrane areas (green) are fully polarized and ready to respond voltage-gated channels immediately distal to the action potential Sodium and potassium channels open and close just as they did at the trigger zone, and a new action potential is produced By repetition, this excites the membrane immediately distal to that This chain reaction continues until the traveling signal reaches the end of the axon Note that an action potential itself does not travel along an axon; rather, it stimulates the production of a new action potential in the membrane just ahead of it Thus, we can distinguish an action potential from a nerve signal The nerve signal is a traveling wave of excitation produced by self-propagating action potentials It is like a line of falling dominoes No one domino travels to the end of the line, but each domino pushes over the next one and there is a transmission of energy from the first domino to the last Similarly, no one action potential travels to the end of an axon; a nerve signal is a chain reaction of action potentials production of a If one action potential stimulates the produ signal could new one next to it, you might think that the si also start traveling backward and return to the ssoma This membrane behind does not occur, however, because the membra CHAPTER Joints 305 the nerve signal is still in its refractory period aand cannot be restimulated Only the membrane ahead is ssensitive to Clinical applications make the abstract science more relevant Clinical Application Knee Injuries and Arthroscopic Surgery Although the knee can bear a lot of weight, it is highly vulnerable to rotational and horizontal stress, especially when the knee is flexed (as in skiing or running) and receives a blow from behind or from the side The most common injuries are to a meniscus or the anterior cruciate ligament (ACL) (fig 9.30) Knee injuries heal slowly because ligaments and tendons have a scanty blood supply and cartilage usually has no blood vessels at all The diagnosis and surgical treatment of knee injuries have been greatly improved by arthroscopy, a procedure in which the interior of a joint is viewed with a pencil-thin instrument, the arthroscope, inserted through a small incision The arthroscope has a light, a lens, and fiber optics that allow a viewer to see into the cavity and take photographs or video recordings A surgeon can also withdraw samples of synovial fluid by arthroscopy or inject saline into the joint cavity to expand it and provide a clearer view If surgery is required, additional small incisions can be made for the surgical instruments and the procedures can be observed through the arthroscope or on a monitor Arthroscopic surgery produces much less tissue damage than conventional surgery and enables patients to recover more quickly Orthopedic surgeons now often replace a damaged ACL with a graft from the patellar ligament or a hamstring tendon The surgeon “harvests” a strip from the middle of the patient’s ligament (or tendon), drills a hole into the femur and tibia within the joint cavity, threads the ligament through the holes, and fastens it with biodegradable screws The grafted ligament is more taut and “competent” than the damaged ACL It becomes ingrown with blood vessels and serves as a substrate for the deposition of more collagen, which further strengthens it in time Following arthroscopic ACL reconstruction, a patient typically must use crutches for to 10 days and undergo supervised physical therapy for to 10 weeks, followed by self-directed exercise therapy Healing is completed in about months stimulation The refractory period thus ensures that nerve signals are conducted in the proper direction, from the soma to the synaptic knobs A traveling nerve signal is an electrical current, but it is not the same as a current traveling through a wire A current in a wire travels millions of meters per second and is decremental—it gets weaker with distance A nerve signal is much slower (not more than m/s in unmyelinated fibers), but it is nondecremental Even in the longest axons, the last action potential generated at a synaptic knob has the same voltage oltage as the first one generated at the trigger la a zone To clarify this concept, we can compare the nerve b signal to a burning fuse When a fuse is lit, the heat ignites m powder immediately in front of this point, and this repeats itself in a self-propagating fashion until the end of the fuse e is reached A At the end, the fuse burns just as hotly as it did at the beginning In a fuse, the combustible powder is the n source of po potential energy that keeps the process going in o a nondecremental fashion In an axon, the potential energy m comes from m the ion gradient across the plasma membrane Thus, the signal does not grow weaker with distance; it is sii self-propagating, like the burning of a fuse a scientific content in a way students can understand voltage-gated channels immediately distal to the action potential Sodium and potassium channels open and close just as they did at the trigger zone, and a new action potential is produced By repetition, this excites the membrane immediately distal to that This chain reaction continues Myelinated e Fibers until the traveling signal reaches the end of the axon Matters are e somewhat different in myelinated fibers Voltage-gated scarce inthat the myelinte e ion channels are Note an action potential itself does not travel covered internodes—fewer than 25/μm in these regions te compared with 2,000 to 12,000/μm w the nodesrather, of along an ataxon; it stimulates the production of a new Ranvier There would be little point in having ion chanh nels in thee internodes—myelin insulates the fiber from action potential the ECF at these points, and Na from t the ECF could not in the membrane just ahead of it Thus, flow into the th h cell even if more channels were present can an action potential from a nerve signal Therefore, n no action we potentials can distinguish occur in the internodes, and d the nerve signal requires some other way of traversing th the from one node to thesignal next h distance The nerve is a traveling wave of excitation produced When Na N enters the axon at a node of Ranvier, it diffuses forr a short distance along the inner face of the by self-propagating action potentials It is like a line of axolemma (fig 12.17a) Each sodium ion has an electri( cal field around it When one Na moves toward another, o falling dominoes No one domino travels to the end of the its field repels the second ion, which moves slightly and p repels another, th h and so forth—like two magnets that repel but domino pushes over the next one and there each other if to push their northeach poles together i you try line, No one ion on n moves very far, but this energy transfer ismuch a transmission travels down faster and farther than any of energy from the first domino to the last w the axon of the individual ions The signal grows weaker with iv distance, h however, partly because the axoplasm o Similarly, no resists one action potential ential travels to the end of an the movement me of the ions and partly because Na leaks back out of along thea way Thereforesignal with o the axon axon; nerve is a chain n reaction of action potentials distance, there is a lower and lower concentration of th h Na to relay ay y the charge Furthermore, with a surplus of If one action potential stimulates timulates the production of a positive charges on the inner face of the axolemma and a surplus of o negative charges on the outer face, these new one to it, you might ht think that the signal could cations and  attracted to eachnext other through d anions are the membrane—like the opposite poles of two magnets a traveling backward d and return to the soma This attracting eeach through astart sheet of cardboard This a other also does not occur, however, because ecause the membrane behind the nerve signal is still in itss refractory period and cannot be restimulated Only the membrane embrane ahead is sensitive to 2 + + + + + Twisting motion Foot fixed Anterior cruciate ligament (torn) Tibial collateral ligament (torn) Medial meniscus (torn) Patellar ligament FIGURE 9.30 Knee Injuries The ligaments of the ankle include (1) anterior and posterior tibiofibular ligaments, which bind the tibia to the fibula; (2) a multipart medial (deltoid30) ligament, which binds the tibia to the foot on the medial side; and (3) a multipart lateral (collateral) ligament, which binds the fibula to the foot on the lateral side The calcaneal (Achilles) tendon extends from the calf muscles to the calcaneus It plantarflexes the foot and limits dorsiflexion Plantar flexion is limited by extensor tendons on the anterior side of the ankle and by the anterior part of the joint capsule Sprains (torn ligaments and tendons) are common at the ankle, especially when the foot is suddenly inverted or everted to excess They are painful and usually accompanied by immediate swelling They are best treated by immo- Analogies explain tough Integration and Control Cell body • Even instructors say they often learn something new and interesting from Saladin’s innovative perspectives DEEPER INSIGHT 9.4 PART THREE Dendrites bilizing the joint and reducing swelling with an ice pack, but in extreme cases may require a cast or surgery Sprains and other joint disorders are briefly described in table 9.1 “Saladin is a gifted author, and his conversational tone will be sure to keep students very engaged.” —Davonya Person, Auburn University Before You Go On Answer the following questions to test your understanding of the preceding section: 12 What keeps the mandibular condyle from slipping out of its fossa in a posterior direction? 13 Explain how the biceps tendon braces the shoulder joint 14 Identify the three joints found at the elbow and name the movements in which each joint is involved 15 What keeps the femur from slipping backward off the tibia? delt = triangular, Greek letter delta (∆); oid = resembling 30 16 What keeps the tibia from slipping sideways off the talus? ix sal78259_fm_i-xxvi.indd ix 11/19/10 9:32 AM 36 PART ONE Organization of the Body Posterior Back muscles 2nd lumbar vertebra Kidney Spinal cord Liver Renal vein and artery Fat Inferior vena cava Dorsal mesentery Aorta Parietal peritoneum Intestine Visceral peritoneum (serosa) Peritoneal cavity Omentum or other ventral mesentery Anterior FIGURE A.9 Transverse Section Through the Abdomen Shows the peritoneum, peritoneal cavity (with most viscera omitted), and some retroperitoneal organs and the parietal layer lines the inside of a body cavity We will see this pattern elsewhere, including the abdominopelvic cavity The Abdominopelvic Cavity The abdominopelvic cavity consists of the abdominal cavity superiorly and the pelvic cavity inferiorly The abdominal cavity contains most of the digestive organs as well as the spleen, kidneys, and ureters It extends inferiorly to the level of a bony landmark called the brim of the pelvis (see figs B.7, p 387, and 8.35, p 265) The pelvic cavity, below the brim, is continuous with the abdominal cavity (no wall separates them), but it is markedly narrower and tilts posteriorly (see fig A.7a) It contains the rectum, urinary bladder, urethra, and reproductive organs The abdominopelvic cavity contains a two-layered serous membrane called the peritoneum15 (PERR-ih-toeNEE-um) Its outer layer, the parietal peritoneum, lines the cavity wall The visceral peritoneum turns inward from the body wall, wraps around the abdominal viscera, binds them to the body wall or suspends them from it, and holds them in their proper place The peritoneal cavity is the space between the parietal and visceral layers It is lubricated by peritoneal fluid Some organs of the abdominal cavity lie against the posterior body wall and are covered by peritoneum only on the side facing the peritoneal cavity They are said to have a retroperitoneal16 position (fig A.9) These include the kidneys, ureters, adrenal glands, most of the pancreas, and abdominal portions of two major blood vessels—the aorta and inferior vena cava (see fig.  B.6, p.  386) Organs that are encircled by peritoneum and connected to the posterior body wall by peritoneal sheets are described as intraperitoneal.17 The intestines are suspended from the posterior (dorsal) abdominal wall by a translucent membrane called the posterior mesentery18 (MESS-en-tare-ee), an infolding of the peritoneum The posterior mesentery of the large intestine is called the mesocolon In some places, after wrapping around the intestines or other viscera, the mesentery continues toward the anterior body wall as the anterior mesentery The most significant example of this is a fatty membrane called the greater omentum,19 which hangs like an apron from the inferolateral margin of the stomach and overlies the intestines (figs A.10 and B.4, p 384) The greater omentum is unattached at its inferior border and can be lifted to reveal the intestines A smaller lesser omentum extends from the superomedial margin of the stomach to the liver Where the visceral peritoneum meets an organ such as the stomach or small intestine, it divides and wraps around it, forming an outer layer of the organ called the serosa (seer-OH-sa) (fig A.10) The visceral peritoneum thus consists of the mesenteries and serosae retro = behind intra = within 18 mes = in the middle; enter = intestine 19 omentum = covering 16 17 15 peri = around; tone = stretched sal78259_atlas_a_028-041.indd 36 11/2/10 4:20 PM ATLAS A Diaphragm Liver Serosae Lesser omentum Stomach Pancreas Greater omentum Duodenum Large intestine Dorsal mesentery Small intestine Parietal peritoneum Peritoneal cavity Urinary bladder Visceral peritoneum Rectum General Orientation to Human Anatomy 37 course, a growing fetus occupies this space and pushes the mucous membranes apart A.4 Organ Systems The human body has 11 organ systems (fig A.11) and an immune system, which is better described as a population of cells that inhabit multiple organs rather than as an organ system These systems are classified in the following list by their principal functions, but this is an unavoidably flawed classification Some organs belong to two or more systems—for example, the male urethra is part of both the urinary and reproductive systems; the pharynx is part of the respiratory and digestive systems; and the mammary glands can be considered part of the integumentary and female reproductive systems The organ systems are Systems of protection, support, and movement Integumentary system Skeletal system Muscular system FIGURE A.10 Serous Membranes of the Abdominal Cavity Sagittal section, left lateral view ● Is the urinary bladder in the peritoneal cavity? Potential Spaces Some of the spaces between body membranes are considered to be potential spaces, so named because under normal conditions, the membranes are pressed firmly together and there is no actual space between them The membranes are not physically attached, however, and under unusual conditions, they may separate and create a space filled with fluid or other matter Thus there is normally no actual space, but only a potential for membranes to separate and create one The pleural cavity is one example Normally the parietal and visceral pleurae are pressed together without a gap between them, but under pathological conditions, air or serous fluid can accumulate between the membranes and open up a space The internal cavity (lumen) of the uterus is another In a nonpregnant uterus, the mucous membranes of opposite walls are pressed together so that there is no open space in the organ In pregnancy, of sal78259_atlas_a_028-041.indd 37 Systems of internal communication and integration Nervous system Endocrine system Systems of fluid transport Circulatory system Lymphatic system Systems of input and output Respiratory system Urinary system Digestive system Systems of reproduction Male reproductive system Female reproductive system Some medical terms combine the names of two systems— for example, the musculoskeletal system, cardiopulmonary system, and urogenital (genitourinary) system These terms serve to call attention to the close anatomical or physiological relationships between two systems, but these are not literally individual organ systems 11/2/10 4:20 PM Principal organs: Skin, hair, nails, cutaneous glands Principal organs: Bones, cartilages, ligaments Principal functions: Protection, water retention, thermoregulation, vitamin D synthesis, cutaneous sensation, nonverbal communication Principal functions: Support, movement, protective enclosure of viscera, blood formation, mineral storage, electrolyte and acid–base balance Integumentary system Principal organs: Lymph nodes, lymphatic vessels, thymus, spleen, tonsils Principal functions: Recovery of excess tissue fluid, detection of pathogens, production of immune cells, defense against disease Lymphatic system Skeletal system Principal organs: Skeletal muscles Principal functions: Movement, stability, communication, control of body openings, heat production Muscular system Principal organs: Nose, pharynx, larynx, trachea, bronchi, lungs Principal organs: Kidneys, ureters, urinary bladder, urethra Principal functions: Absorption of oxygen, discharge of carbon dioxide, acid–base balance, speech Principal functions: Elimination of wastes; regulation of blood volume and pressure; stimulation of red blood cell formation; control of fluid, electrolyte, and acid-base balance; detoxification Respiratory system Urinary system FIGURE A.11 The Human Organ Systems 38 sal78259_atlas_a_028-041.indd 38 11/2/10 4:20 PM Principal organs: Brain, spinal cord, nerves, ganglia Principal organs: Pituitary gland, pineal gland, thyroid gland, parathyroid glands, thymus, adrenal glands, pancreas, testes, ovaries Principal functions: Rapid internal communication, coordination, motor control and sensation Nervous system Principal functions: Hormone production; internal chemical communication and coordination Endocrine system Principal organs: Teeth, tongue, salivary glands, esophagus, stomach, small and large intestines, liver, gallbladder, pancreas Principal organs: Testes, epididymides, spermatic ducts, seminal vesicles, prostate gland, bulbourethral glands, penis Principal functions: Nutrient breakdown and absorption Liver functions include metabolism of carbohydrates, lipids, proteins, vitamins, and minerals; synthesis of plasma proteins; disposal of drugs, toxins, and hormones; and cleansing of blood Digestive system Principal functions: Production and delivery of sperm; secretion of sex hormones Male reproductive system Principal organs: Heart, blood vessels Principal functions: Distribution of nutrients, oxygen, wastes, hormones, electrolytes, heat, immune cells, and antibodies; fluid, electrolyte, and acid-base balance Circulatory system Principal organs: Ovaries, uterine tubes, uterus, vagina, mammary glands Principal functions: Production of eggs; site of fertilization and fetal development; fetal nourishment; birth; lactation; secretion of sex hormones Female reproductive system FIGURE A.11 The Human Organ Systems (continued) 39 sal78259_atlas_a_028-041.indd 39 11/2/10 4:20 PM 40 PART ONE Organization of the Body STUDY GUIDE Assess Your Learning Outcomes To test your knowledge, discuss the following topics with a study partner or in writing, ideally from memory A.1 General Anatomical Terminology (p 29) Anatomical position and why it is important for anatomical description The position of the forearm and relative positions of its bones when it is pronated and supinated; how these terms differ from prone and supine Directions along which the body or an organ is divided by the sagittal, frontal, and transverse planes; how the median plane differs from other sagittal planes Meanings of each of the following pairs or groups of terms, and the ability to describe the relative locations of two body parts using these terms: ventral and dorsal; anterior and posterior; cephalic, rostral, and caudal; superior and inferior; medial and lateral; proximal and distal; superficial and deep Why the terms ventral and dorsal are ambiguous in human anatomy but less so in most other animals; what terms are used in their place in human anatomy; and reasons why they are occasionally appropriate or unavoidable in human anatomy A.2 Major Body Regions (p 31) Distinctions between the axial and appendicular regions of the body Subdivisions of the axial region and landmarks that divide and define them The abdomen’s four quadrants and nine regions; their defining landmarks; and why this scheme is clinically useful The segments of the upper and lower limbs; how the anatomical meanings of arm and leg differ from the colloquial meanings A.3 Body Cavities and Membranes (p 34) Locations and contents of the cranial cavity, vertebral canal, thoracic cavity, and abdominopelvic cavity; the membranes that line them; and the main viscera contained in each Contents of the mediastinum and its relationship to the thoracic cavity as a whole The pericardium, its two layers, the space and fluid between the layers, and its function The pleurae, their two layers, the space and fluid between the layers, and their function The two subdivisions of the abdominopelvic cavity and the skeletal landmark that divides them The peritoneum; its functions; its two layers and their relationship to the abdominal viscera; and the peritoneal fluid Intraperitoneal versus retroperitoneal organs, examples of both, and how one would identify an organ as being intra- or retroperitoneal Names and locations of the posterior and anterior mesenteries The serosa of an abdominopelvic organ and how it relates to the peritoneum 10 Examples of potential spaces and why they are so named A.4 Organ Systems (p 37) The 11 organ systems, the functions of each, and the principal organs of each system Testing Your Recall Which of the following is not an essential part of anatomical position? a feet together b feet flat on the floor c forearms supinated d mouth closed e arms down to the sides The greater omentum is small intestine a posterior b parietal c deep d superficial e proximal A ring-shaped section of the small intestine would be a section a sagittal b coronal c transverse d frontal e median A line passes through the sternum, umbilicus, and mons pubis a central b proximal c midclavicular d midsagittal e intertubercular The region is immediately medial to the coxal region a inguinal b hypochondriac c umbilical d popliteal e cubital The tarsal region is liteal region a medial b superficial c superior d dorsal e distal sal78259_atlas_a_028-041.indd 40 to the pop- to the Which of the following regions is not part of the upper limb? a plantar b carpal c cubital d brachial e palmar Which of these organs is within the peritoneal cavity? a urinary bladder b kidneys c heart d liver e brain In which area you think pain from the gallbladder would be felt? a umbilical region b right upper quadrant c hypogastric region d left hypochondriac region e left lower quadrant 11/2/10 4:20 PM ATLAS A 10 Which organ system regulates blood volume, controls acid–base balance, and stimulates red blood cell production? a digestive system b lymphatic system c nervous system d urinary system e circulatory system 14 The back of the neck is the region 11 The forearm is said to be when the palms are facing forward 17 Organs that lie within the abdominal cavity but not within the peritoneal cavity are said to have a position 12 The superficial layer of the pleura is called the pleura 13 The right and left pleural cavities are separated by a thick wall called the 15 The manus is more commonly known as the and the pes is more commonly known as the 16 The cranial cavity is lined by membranes called the 18 The sternal region is pectoral region General Orientation to Human Anatomy 41 19 The pelvic cavity can be described as to the abdominal cavity in position 20 The anterior pit of the elbow is the region, and the corresponding (but posterior) pit of the knee is the region Answers in appendix B to the Building Your Medical Vocabulary State a medical meaning of each word element below, and give a term in which it or a slight variation of it is used ante2 cervico- epi- parieto- hypo- peri- inguino- retro- intra- 10 sagittoAnswers in appendix B True or False Determine which five of the following statements are false, and briefly explain why A single sagittal section of the body can pass through one lung but not through both It would be possible to see both eyes in one frontal section of the head The knee is both superior and proximal to the tarsal region Both kidneys could be shown in a single coronal section of the body The diaphragm is posterior to the lungs The peritoneum lines the inside of the stomach and intestines The esophagus is inferior to the stomach The liver is in the lumbar region The heart is in the mediastinum 10 The sigmoid colon is in the lower right quadrant of the abdomen Answers in appendix B Testing Your Comprehension Identify which anatomical plane— sagittal, frontal, or transverse—is the only one that could not show (a) both the brain and tongue, (b) both eyes, (c) both the hypogastric and gluteal regions, (d) both kidneys, (e) both the sternum and vertebral column, and (f) both the heart and uterus Laypeople often misunderstand anatomical terminology What you think people really mean when they say they have “planter’s warts”? sal78259_atlas_a_028-041.indd 41 Name one structure or anatomical feature that could be found in each of the following locations relative to the ribs: medial, lateral, superior, inferior, deep, superficial, posterior, and anterior Try not to use the same example twice Based on the illustrations in this atlas, identify an internal organ that is (a) in the upper left quadrant and retroperitoneal; (b) in the lower right quadrant of the peritoneal cavity; (c) in the hypogastric region; (d) in the right hypochondriac region; and (e) in the pectoral region Why you think people with imaginary illnesses came to be called hypochondriacs? Answers at www.mhhe.com/saladin6 11/2/10 4:20 PM CHAPTER THE CHEMISTRY OF LIFE Cholesterol crystals seen through a polarizing microscope CHAPTER OUTLINE 2.1 Atoms, Ions, and Molecules 43 • The Chemical Elements 43 • Atomic Structure 44 • Isotopes and Radioactivity 45 • Ions, Electrolytes, and Free Radicals 46 • Molecules and Chemical Bonds 48 2.2 Water and Mixtures 50 • Water 50 • Solutions, Colloids, and Suspensions 52 • Measures of Concentration 53 • Acids, Bases, and pH 54 2.3 Energy and Chemical Reactions 56 • Energy and Work 56 • Classes of Chemical Reactions 56 • Reaction Rates 57 • Metabolism, Oxidation, and Reduction 58 2.4 Organic Compounds 59 • Carbon Compounds and Functional Groups 59 • Monomers and Polymers 59 • Carbohydrates 60 • Lipids 62 • Proteins 66 • Enzymes and Metabolism 69 • ATP, Other Nucleotides, and Nucleic Acids 71 Study Guide 75 DEEPER INSIGHTS 2.1 Medical History: Radiation and Madame Curie 46 2.2 Clinical Application: pH and Drug Action 55 2.3 Clinical Application: Trans Fats and Cardiovascular Health 64 2.4 Clinical Application: “Good” and “Bad” Cholesterol 66 2.5 Clinical Application: Blood Enzymes as Disease Markers 69 2.6 Clinical Application: Anabolic–Androgenic Steroids 74 Module 2: Cells and Chemistry 42 sal78259_ch02_042-077.indd 42 11/2/10 4:23 PM CHAPTER Brushing Up… Beginning here, each chapter builds on information presented in earlier ones If you not clearly remember these concepts, you may find that brushing up on them before you proceed will enable you to get more out of the new chapter • Chapter discusses metabolism as one of the fundamental characteristics of life, and mentions that it is divided into catabolism and anabolism (p. 15) Here we will delve more deeply into the chemical meaning of these two divisions Metabolism, in turn, provides the foundation for perhaps the most important of all concepts in chapter 1, homeostasis (p. 16) W hy is too much sodium or cholesterol harmful? Why does an iron deficiency cause anemia and an iodine deficiency cause a goiter? Why does a pH imbalance make some drugs less effective? Why some pregnant women suffer convulsions after several days of vomiting? How can radiation cause cancer as well as cure it? None of these questions can be answered, nor would the rest of this book be intelligible, without understanding the chemistry of life A little knowledge of chemistry can help you choose a healthy diet, use medications more wisely, avoid worthless health fads and frauds, and explain treatments and procedures to your patients or clients Thus, we begin our study of the human body with basic chemistry, the simplest level of the body’s structural organization We will progress from general chemistry to biochemistry, study of the molecules that compose living organisms—especially molecules unique to living things, such as carbohydrates, fats, proteins, and nucleic acids Most people have at least heard of these and it is common knowledge that we need proteins, fats, carbohydrates, vitamins, and minerals in our diet, and that we should avoid consuming too much saturated fat and cholesterol But most people have only a vague concept of what these molecules are, much less how they function in the body Such knowledge is very helpful in matters of personal fitness and patient education and is essential to the comprehension of the rest of this book 2.1 Atoms, Ions, and Molecules Expected Learning Outcomes When you have completed this section, you should be able to a name the chemical elements of the body from their chemical symbols; b distinguish between chemical elements and compounds; c state the functions of minerals in the body; sal78259_ch02_042-077.indd 43 The Chemistry of Life 43 d explain the basis for radioactivity and the types and hazards of ionizing radiation; e distinguish between ions, electrolytes, and free radicals; and f define the types of chemical bonds The Chemical Elements A chemical element is the simplest form of matter to have unique chemical properties Water, for example, has unique properties, but it can be broken down into two elements, hydrogen and oxygen, that have unique chemical properties of their own If we carry this process any further, however, we find that hydrogen and oxygen are made of protons, neutrons, and electrons—and none of these are unique A proton of gold is identical to a proton of oxygen Hydrogen and oxygen are the simplest chemically unique components of water and are thus elements Each element is identified by an atomic number, the number of protons in its nucleus The atomic number of carbon is and that of oxygen is 8, for example The periodic table of the elements (see appendix A) arranges the elements in order by their atomic numbers The elements are represented by one- or two-letter symbols, usually based on their English names: C for carbon, Mg for magnesium, Cl for chlorine, and so forth A few symbols are based on Latin names, such as K for potassium (kalium), Na for sodium (natrium), and Fe for iron (ferrum) There are 91 naturally occurring elements on earth, 24 of which play normal physiological roles in humans Table 2.1 groups these 24 according to their abundance in the body Six of them account for 98.5% of the body’s weight: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus The next 0.8% consists of another 6  elements: sulfur, potassium, sodium, chlorine, magnesium, and iron The remaining 12 elements account for 0.7% of body weight, and no one of them accounts for more than 0.02%; thus they are known as trace elements Despite their minute quantities, trace elements play vital roles in physiology Other elements without natural physiological roles can contaminate the body and severely disrupt its functions, as in heavy-metal poisoning with lead or mercury Several of these elements are classified as minerals— inorganic elements that are extracted from the soil by plants and passed up the food chain to humans and other organisms Minerals constitute about 4% of the human body by weight Nearly three-quarters of this is Ca and P; the rest is mainly Cl, Mg, K, Na, and S Minerals contribute significantly to body structure The bones and teeth consist partly of crystals of calcium, phosphate, magnesium, fluoride, and sulfate ions Many proteins include sulfur, and phosphorus is a major component of nucleic acids, ATP, and cell membranes Minerals also enable enzymes and other organic molecules to function Iodine is a component of thyroid hormone; iron is a component of hemoglobin; and some enzymes function only when 12/2/10 9:06 AM 44 PART ONE TABLE 2.1 Organization of the Body Atomic Structure Elements of the Human Body Name Symbol Percentage of Body Weight Major Elements (Total 98.5%) Oxygen Carbon Hydrogen Nitrogen Calcium Phosphorus O C H N Ca P 65.0 18.0 10.0 3.0 1.5 1.0 Lesser Elements (Total 0.8%) Sulfur Potassium Sodium Chlorine Magnesium Iron S K Na Cl Mg Fe 0.25 0.20 0.15 0.15 0.05 0.006 Trace Elements (Total 0.7%) Chromium Cobalt Copper Fluorine Iodine Manganese Cr Co Cu F I Mn Molybdenum Selenium Silicon Tin Vanadium Zinc Mo Se Si Sn V Zn manganese, zinc, copper, or other minerals are bound to them The electrolytes needed for nerve and muscle function are mineral salts The biological roles of minerals are discussed in more detail in chapters 24 and 26 In the fifth century BCE, the Greek philosopher Democritus reasoned that we can cut matter such as a gold nugget into smaller and smaller pieces, but there must ultimately be particles so small that nothing could cut them He called these imaginary particles atoms1 (“indivisible”) Atoms were only a philosophical concept until 1803, when English chemist John Dalton began to develop an atomic theory based on experimental evidence In 1913, Danish physicist Niels Bohr proposed a model of atomic structure similar to planets orbiting the sun (figs 2.1 and 2.2) Although this planetary model is too simple to account for many of the properties of atoms, it remains useful for elementary purposes At the center of an atom is the nucleus, composed of protons and neutrons Protons (p+) have a single positive charge and neutrons (n0) have no charge Each proton or neutron weighs approximately atomic mass unit (amu), defined as one-twelfth the mass of an atom of carbon-12 The atomic mass of an element is approximately equal to its total number of protons and neutrons Around the nucleus are one or more concentric clouds of electrons (e–), tiny particles with a single negative charge and very low mass It takes 1,836 electrons to equal amu, so for most purposes we can disregard their mass A person who weighs 64 kg (140 lb) contains less than 24 g (1 oz) of electrons This hardly means that we can ignore electrons, however They determine the chemical properties of an atom, thereby governing what molecules can exist and what chemical reactions can occur The number of electrons equals the number of protons, so their charges cancel each other and an atom is electrically neutral First energy level Carbon (C) 6p+, 6e-, 6n0 Atomic number = Atomic mass = 12 Second energy level Nitrogen (N) 7p+, 7e-, 7n0 Atomic number = Atomic mass = 14 a = not; tom = cut Third energy level Sodium (Na) 11p+, 11e-, 12n0 Atomic number = 11 Atomic mass = 23 Fourth energy level Potassium (K) 19p+, 19e-, 20n0 Atomic number = 19 Atomic mass = 39 FIGURE 2.1 Bohr Planetary Models of Four Representative Elements Note the filling of electron shells as atomic number increases (p+ = protons; e– = electrons; n0 = neutrons) ● Will potassium have a greater tendency to give up an electron or to take one away from another atom? sal78259_ch02_042-077.indd 44 11/2/10 4:23 PM CHAPTER Electrons swarm about the nucleus in concentric regions called electron shells (energy levels) The more energy an electron has, the farther away from the nucleus its orbit lies Each shell holds a limited number of electrons (fig 2.1) The elements known to date have up to seven electron shells, but those ordinarily involved in human physiology not exceed four Electrons of the outermost shell, called valence electrons, determine the chemical bonding properties of an atom An atom tends to bond with other atoms that will fill its outer shell and produce a stable number of valence electrons A hydrogen atom, with only one electron shell and one electron (fig 2.2), tends to react with other atoms that provide another electron and fill this shell with a stable number of two electrons All other atoms react in ways that produce eight electrons in the valence shell This tendency is called the octet rule (rule of eights) Hydrogen (1H) (1p+, 0n0, 1e–) The Chemistry of Life 45 Deuterium (2H) (1p+, 1n0, 1e–) Key = Proton (p+) = Neutron (n0) = Electron (e–) Isotopes and Radioactivity Dalton believed that every atom of an element was identical We now know, however, that all elements have varieties called isotopes,2 which differ from one another only in number of neutrons and therefore in atomic mass Hydrogen atoms, for example, have only one proton In the most common isotope, symbolized 1H, that is all there is to the nucleus Hydrogen has two other isotopes, however: deuterium (2H) with one proton and one neutron, and tritium (3H) with one proton and two neutrons (fig. 2.2) Over 99% of carbon atoms have an atomic mass of 12 (6p+, 6n0) and are called carbon-12 (12C), but a small percentage of carbon atoms are 13C, with seven neutrons, and 14C, with eight All isotopes of a given element behave the same chemically Deuterium (2H), for example, reacts with oxygen the same way 1H does to produce water The atomic weight (relative atomic mass) of an element accounts for the fact that an element is a mixture of isotopes If all carbon were 12C, the atomic weight of carbon would be the same as its atomic mass, 12.000 But since a sample of carbon also contains small amounts of the heavier isotopes 13C and 14C, the atomic weight is slightly higher, 12.011 Although different isotopes of an element exhibit identical chemical behavior, they differ in physical behavior Many of them are unstable and decay (break down) to more stable isotopes by giving off radiation Unstable isotopes are therefore called radioisotopes, and the process of decay is called radioactivity (see Deeper Insight 2.1) Every element has at least one radioisotope Oxygen, for example, has three stable isotopes and five radioisotopes All of us contain radioisotopes such as 14 C and 40K—that is, we are all mildly radioactive! Many forms of radiation, such as light and radio waves, have low energy and are harmless High-energy iso = same; top = place (same position in the periodic table) sal78259_ch02_042-077.indd 45 Tritium (3H) (1p+, 2n0, 1e–) FIGURE 2.2 Isotopes of Hydrogen The three isotopes differ only in the number of neutrons present radiation, however, ejects electrons from atoms, converting atoms to ions; thus, it is called ionizing radiation It destroys molecules and produces dangerous free radicals and ions in human tissues In high doses, ionizing radiation is quickly fatal In lower doses, it can be mutagenic (causing mutations in DNA) and carcinogenic (triggering cancer as a result of mutation) Examples of ionizing radiation include ultraviolet rays, X-rays, and three kinds of radiation produced by nuclear decay: alpha (α) particles, beta (β) particles, and gamma (γ) rays An alpha particle is composed of two protons and two neutrons (equivalent to a helium nucleus), and a beta particle is a free electron Alpha particles are too large to penetrate the skin, and beta particles can penetrate only a few millimeters They are relatively harmless when emitted by sources outside the body, but they are very dangerous when emitted by radioisotopes that have gotten into the body Strontium-90 (90Sr), for example, has been released by nuclear accidents and the atmospheric testing of nuclear weapons It settles onto pastures and contaminates cow’s milk In the body, it behaves chemically like calcium, becoming incorporated into the bones, where it emits beta particles for years Uranium and plutonium emit electromagnetic gamma rays, which have high energy and penetrating power Gamma rays are very dangerous even when emitted by sources outside the body Each radioisotope has a characteristic physical halflife, the time required for 50% of its atoms to decay to a more stable state One gram of 90Sr, for example, would be half gone in 28 years In 56 years, there would still be 11/2/10 4:23 PM 46 PART ONE Organization of the Body DEEPER INSIGHT 2.1 Medical History Radiation and Madame Curie In 1896, French scientist Henri Becquerel (1852–1908) discovered that uranium darkened photographic plates through several thick layers of paper Marie Curie (1867–1934) and Pierre Curie (1859–1906), her husband, discovered that polonium and radium did likewise Marie Curie coined the term radioactivity for the emission of energy by these elements Becquerel and the Curies shared a Nobel Prize in 1903 for this discovery Marie Curie (fig 2.3) was not only the first woman in the world to receive a Nobel Prize but also the first woman in France even to receive a Ph.D She received a second Nobel Prize in 1911 for further work in radiation Curie crusaded to train women for careers in science, and in World War I, she and her daughter, Irène Joliot-Curie (1897–1956), trained physicians in the use of X-ray machines Curie pioneered radiation therapy for breast and uterine cancer In the wake of such discoveries, radium was regarded as a wonder drug Unaware of its danger, people drank radium tonics and flocked to health spas to bathe in radium-enriched waters Marie herself suffered extensive damage to her hands from handling radioactive minerals and died of radiation poisoning at age 67 The following year, Irène and her husband, Frédéric Joliot (1900–1958), were awarded a Nobel Prize for work in artificial radioactivity and synthetic radioisotopes Apparently also a martyr to her science, Irène died of leukemia, possibly induced by radiation exposure FIGURE 2.3 Marie Curie (1867–1934) This portrait was made in 1911, when Curie received her second Nobel Prize 0.25 g left, in 84 years 0.125 g, and so forth Many radioisotopes are much longer-lived The half-life of 40K, for example, is 1.3 billion years Nuclear power plants produce hundreds of radioisotopes that will be intensely radioactive for at least 10,000 years—longer than the life of any disposal container yet conceived The biological half-life of a radioisotope is the time required for half of it to disappear from the body Some of it is lost by radioactive decay and even more of it by excretion from the body Cesium-137, for example, has a physical half-life of 30 years but a biological half-life of only 17 days Chemically, it behaves like potassium; it is quite mobile and rapidly excreted by the kidneys There are several ways to measure the intensity of ionizing radiation, the amount absorbed by the body, and its biological effects To understand the units of measurement requires a grounding in physics beyond the scope of this book, but the standard international (SI) unit of radiation exposure is the sievert3 (Sv), which takes into account the type and intensity of radiation and its biological effect Doses of Sv or more are usually fatal The average American receives about 3.6 millisieverts (mSv) per year in background radiation from natural sources and another 0.6 mSv from artificial sources The  most Rolf Maximillian Sievert (1896–1966), Swedish radiologist sal78259_ch02_042-077.indd 46 significant natural source is radon, a gas produced by the decay of uranium in the earth; it can accumulate in buildings to unhealthy levels Artificial sources of radiation exposure include medical X-rays, radiation therapy, and consumer products such as color televisions, smoke detectors, and luminous watch dials Such voluntary exposure must be considered from the standpoint of its risk-to-benefit ratio The benefits of a smoke detector or mammogram far outweigh the risk from the low levels of radiation involved Radiation therapists and radiologists face a greater risk than their patients, however, and astronauts and airline flight crews receive more than average exposure U.S federal standards set a limit of 50 mSv/ year as acceptable occupational exposure to ionizing radiation Ions, Electrolytes, and Free Radicals Ions are charged particles with unequal numbers of protons and electrons An ion can consist of a single atom with a positive or negative charge, or it can be as large as a protein with many charges on it Ions form because elements with one to three valence electrons tend to give them up, and those with four to seven electrons tend to gain more If an atom of the first kind is exposed to an atom of the second, electrons may transfer from one to the other and turn both of them into ions 11/2/10 4:23 PM CHAPTER This process is called ionization The particle that gains electrons acquires a negative charge and is called an anion (AN-eye-on) The one that loses electrons acquires a positive charge (because it then has a surplus of protons) and is called a cation (CAT-eye-on) Consider, for example, what happens when sodium and chlorine meet (fig 2.4) Sodium has three electron shells with a total of 11 electrons: in the first shell, in the second, and in the third If it gives up the electron in the third shell, its second shell becomes the valence shell and has the stable configuration of electrons Chlorine has 17 electrons: in the first shell, in the second, and 7 in the third If it can gain one more electron, it can fill the third shell with electrons and become stable Sodium and chlorine seem “made for each other”—one needs to lose an electron and the other needs to gain one This is just what they When they interact, an electron transfers from sodium to chlorine Now, sodium has 11 protons in its nucleus but only 10 electrons This imbalance gives it a positive charge, so we symbolize the sodium ion Na+ 11 protons 12 neutrons 11 electrons Sodium atom (Na) 17 protons 18 neutrons 17 electrons Chlorine atom (Cl) Transfer of an electron from a sodium atom to a chlorine atom + The Chemistry of Life Chlorine has been changed to the chloride ion with a surplus negative charge, symbolized Cl– Some elements exist in two or more ionized forms Iron, for example, has ferrous (Fe2+) and ferric (Fe3+) ions Note that some ions have a single positive or negative charge, whereas others have charges of ±2 or ±3 because they gain or lose more than one electron The charge on an ion is called its valence Ions are not always single atoms that have become charged; some are groups of atoms—phosphate (PO43–) and bicarbonate (HCO3–) ions, for example Ions with opposite charges are attracted to each other and tend to follow each other through the body Thus, when Na+ is excreted in the urine, Cl– tends to follow it The attraction of cations and anions to each other is important in maintaining the excitability of muscle and nerve cells, as we shall see in chapters 11 and 12 Electrolytes are substances that ionize in water (acids, bases, or salts) and form solutions capable of conducting electricity (table 2.2) We can detect electrical activity of the muscles, heart, and brain with electrodes on the skin because electrolytes in the body fluids conduct electrical currents from these organs to the skin surface Electrolytes are important for their chemical reactivity (as when calcium phosphate becomes incorporated into bone), osmotic effects (influence on water content and distribution in the body), and electrical effects (which are essential to nerve and muscle function) Electrolyte balance is one of the most important considerations in patient care Electrolyte imbalances have effects ranging from muscle cramps and brittle bones to coma and cardiac arrest Free radicals are chemical particles with an odd number of electrons For example, oxygen normally exists as a stable molecule composed of two oxygen atoms, O2; but if an additional electron is added, it becomes a free radical called the superoxide anion, O2–• Free radicals are represented with a dot to symbolize the odd electron Free radicals are produced by some normal metabolic reactions of the body (such as the ATP-producing oxidation reactions in mitochondria, and a reaction that some white blood cells use to kill bacteria); by radiation (such as ultraviolet radiation and X-rays); and by chemicals (such as carbon tetrachloride, once widely used as a cleaning solvent, and – TABLE 2.2 Major Electrolytes and the Ions Released by their Dissociation Electrolyte 11 protons 12 neutrons 10 electrons Sodium ion (Na+) 17 protons 18 neutrons 18 electrons Chloride ion (Cl–) Sodium chloride The charged sodium ion (Na+) and chloride ion (Cl–) that result FIGURE 2.4 Ionization sal78259_ch02_042-077.indd 47 47 Cation Anion Calcium chloride (CaCl2) → Ca Disodium phosphate (Na2HPO4) → Na+ HPO42– Magnesium chloride (MgCl2) → Mg2+ Cl– Potassium chloride (KCl) → K+ Cl– Sodium bicarbonate (NaHCO3) → Na+ Sodium chloride (NaCl) → + 2+ Na Cl– HCO3– Cl– 11/2/10 4:23 PM 48 PART ONE Organization of the Body nitrites, present as preservatives in some wine, meat, and other foods) They are short-lived and combine quickly with molecules such as fats, proteins, and DNA, converting them into free radicals and triggering chain reactions that destroy still more molecules Among the damages caused by free radicals are some forms of cancer and myocardial infarction, the death of heart tissue One theory of aging is that it results in part from lifelong cellular damage by free radicals Because free radicals are so common and destructive, we have multiple mechanisms for neutralizing them An antioxidant is a chemical that neutralizes free radicals The body produces an enzyme called superoxide dismutase (SOD), for example, that converts superoxide into oxygen and hydrogen peroxide Selenium, vitamin E (α-tocopherol), vitamin C (ascorbic acid), and carotenoids (such as β-carotene) are some antioxidants obtained from the diet Dietary deficiencies of antioxidants have been associated with increased incidence of heart attacks, sterility, muscular dystrophy, and other disorders Molecules and Chemical Bonds Molecules are chemical particles composed of two or more atoms united by a chemical bond The atoms may be identical, as in nitrogen (N2), or different, as in glucose (C6H12O6) Molecules composed of two or more elements are called compounds Oxygen (O2) and carbon dioxide (CO2) are both molecules, because they consist of at least two atoms; but only CO2 is a compound, because it has atoms of two different elements Molecules can be represented by molecular formulae that identify their constituent elements and show how many atoms of each are present Molecules with identical molecular formulae but different arrangements of their atoms are called isomers4 of each other For example, both ethanol (grain alcohol) and ethyl ether have the molecular formula C2H6O, but they are certainly not interchangeable! To show the difference between them, we use structural formulae that show the location of each atom (fig 2.5) The molecular weight (MW) of a compound is the sum of the atomic weights of its atoms Rounding the atomic mass units (amu) to whole numbers, we can calculate the approximate MW of glucose (C6H12O6), for example, as 12 C atoms × H atoms × O atoms × 12 amu each amu each 16 amu each Molecular weight (MW) = = = Ethanol H = 180 amu H H C C H H H Ethyl ether H C H OH Condensed structural formulae Molecular formulae CH3CH2OH C2H6O CH3OCH3 C2H6O H O C H H FIGURE 2.5 Structural Isomers, Ethanol and Ethyl Ether The molecular formulae are identical, but the structures and chemical properties are different bonds, covalent bonds, hydrogen bonds, and van der Waals forces (table 2.3) An ionic bond is the attraction of a cation to an anion Sodium (Na+) and chloride (Cl–) ions, for example, are attracted to each other and form the compound sodium chloride (NaCl), common table salt Ionic compounds can be composed of more than two ions Calcium has two valence electrons It can become stable by donating TABLE 2.3 Types of Chemical Bonds Bond Type Definition and Remarks Ionic bond Relatively weak attraction between an anion and a cation Easily disrupted in water, as when salt dissolves Sharing of one or more pairs of electrons between nuclei Sharing of one electron pair Sharing of two electron pairs Often occurs between carbon atoms, between carbon and oxygen, and between carbon and nitrogen Covalent bond in which electrons are equally attracted to both nuclei May be single or double Strongest type of chemical bond Covalent bond in which electrons are more attracted to one nucleus than to the other, resulting in slightly positive and negative regions in one molecule May be single or double Weak attraction between polarized molecules or between polarized regions of the same molecule Important in the three-dimensional folding and coiling of large molecules Easily disrupted by temperature and pH changes Weak, brief attraction due to random disturbances in the electron clouds of adjacent atoms Weakest of all bonds Covalent bond Single covalent Double covalent Nonpolar covalent Polar covalent 72 amu 12 amu 96 amu Molecular weight is needed to compute some measures of concentration discussed later A molecule is held together, and molecules are attracted to one another, by forces called chemical bonds The bonds of greatest physiological interest are ionic Structural formulae Hydrogen bond Van der Waals force iso = same; mer = part sal78259_ch02_042-077.indd 48 11/2/10 4:23 PM CHAPTER one electron to one chlorine atom and the other electron to another chlorine, thus producing a calcium ion (Ca2+) and two chloride ions The result is calcium chloride, CaCl2 Ionic bonds are weak and easily dissociate (break up) in the presence of something more attractive, such as water The ionic bonds of NaCl break down easily as salt dissolves in water, because both Na+ and Cl– are more attracted to water molecules than they are to each other C The Chemistry of Life 49 Nonpolar covalent C C bond C (a) Apply What You Know Do you think ionic bonds are common in the human body? Explain your answer Covalent bonds form by the sharing of electrons For example, two hydrogen atoms share valence electrons to form a hydrogen molecule, H2 (fig 2.6a) The two electrons, one donated by each atom, swarm around both nuclei in a dumbbell-shaped cloud A single covalent bond is the sharing of a single pair of electrons It is symbolized by a single line between atomic symbols, for example H–H A double covalent bond is the sharing of two pairs of electrons In carbon dioxide, for example, a central carbon atom shares two electron pairs with each oxygen atom Such bonds are symbolized by two lines— for example, O=C=O (fig 2.6b) When shared electrons spend approximately equal time around each nucleus, they form a nonpolar covalent bond (fig 2.7a), the strongest of all chemical bonds Carbon atoms bond to each other with nonpolar cova- p+ p+ + Hydrogen atom p+ p+ H H Hydrogen molecule (H2) Hydrogen atom (a) Oxygen atom Carbon atom Oxygen atom 8p+ 8n0 6p+ 6n0 8p+ 8n0 O C O Carbon dioxide molecule (CO2) (b) FIGURE 2.6 Covalent Bonding (a) Two hydrogen atoms share a single pair of electrons to form a hydrogen molecule (b) A carbon dioxide molecule, in which a carbon atom shares two pairs of electrons with each oxygen atom, forming double covalent bonds ● How is the octet rule illustrated by the CO2 molecule? sal78259_ch02_042-077.indd 49 O δ− Polar covalent O H bond H δ+ (b) FIGURE 2.7 Nonpolar and Polar Covalent Bonds (a) A nonpolar covalent bond between two carbon atoms, formed by electrons that spend an equal amount of time around each nucleus, as represented by the symmetric blue cloud (b) A polar covalent bond, in which electrons orbit one nucleus significantly more than the other, as represented by the asymmetric cloud This results in a slight negative charge (δ–) in the region where the electrons spend most of their time, and a slight positive charge (δ+) at the other pole lent bonds If shared electrons spend significantly more time orbiting one nucleus than they the other, they lend their negative charge to the region where they spend the most time, and they form a polar covalent bond (fig. 2.7b) When hydrogen bonds with oxygen, for example, the electrons are more attracted to the oxygen nucleus and orbit it more than they the hydrogen This makes the oxygen region of the molecule slightly negative and the hydrogen regions slightly positive The Greek delta (δ) is used to symbolize a charge less than that of one electron or proton A slightly negative region of a molecule is represented δ– and a slightly positive region is represented δ+ A hydrogen bond is a weak attraction between a slightly positive hydrogen atom in one molecule and a slightly negative oxygen or nitrogen atom in another Water molecules, for example, are weakly attracted to each other by hydrogen bonds (fig 2.8) Hydrogen bonds also form between different regions of the same molecule, especially in very large molecules such as proteins and DNA They cause such molecules to fold or coil into precise three-dimensional shapes Hydrogen bonds are represented by dotted or broken lines between atoms:  –C=O…H–N– Hydrogen bonds are relatively weak, but they are enormously important to physiology Van der Waals5 forces are weak, brief attractions between neutral atoms When electrons orbit an atom’s Johannes Diderik van der Waals (1837–1923), Dutch physicist 11/2/10 4:23 PM 50 PART ONE Organization of the Body δ+ H δ+ H δ+ H O O δ+ δ– H δ+ δ+ H δ– δ– Answer the following questions to test your understanding of the preceding section: Consider iron (Fe), hydrogen gas (H2 ), and ammonia (NH3 ) Which of them is or are atoms? Which of them is or are molecules? Which of them is or are compounds? Explain each answer H δ– O Why is the biological half-life of a radioisotope shorter than its physical half-life? Where free radicals come from? What harm they do? How is the body protected from free radicals? O H δ+ Covalent bond Before You Go On H δ+ Hydrogen bond How does an ionic bond differ from a covalent bond? What is a hydrogen bond? Why hydrogen bonds depend on the existence of polar covalent bonds? 2.2 δ– Expected Learning Outcomes O δ+ H δ+ Water molecule H FIGURE 2.8 Hydrogen Bonding of Water The polar covalent bonds of water molecules enable each oxygen to form a hydrogen bond with a hydrogen of a neighboring molecule Thus, the water molecules are weakly attracted to each other ● Why would this behavior raise the boiling point of water above that of a nonpolar liquid? nucleus, they not maintain a uniform distribution but show random fluctuations in density If the electrons briefly crowd toward one side of an atom, they render that side slightly negative and the other side slightly positive for a moment If another atom is close enough to this one, the second atom responds with disturbances in its own electron cloud Oppositely charged regions of the two atoms then attract each other for a very short instant in time A single van der Waals force is only about 1% as strong as a covalent bond, but when two surfaces or large molecules meet, the van der Waals forces between large numbers of atoms can create a very strong attraction This is how plastic wrap clings to food and dishes; flies and spiders walk across a ceiling; and even a 100  g lizard, the Tokay gecko, can run up a windowpane Van der Waals forces also have a significant effect on the boiling points of liquids In human structure, they are especially important in protein folding, the binding of proteins to each other and to other molecules such as hormones, and the association of lipid molecules with each other Some of these molecular behaviors are described later in this chapter sal78259_ch02_042-077.indd 50 Water and Mixtures When you have completed this section, you should be able to a define mixture and distinguish between mixtures and compounds; b describe the biologically important properties of water; c show how three kinds of mixtures differ from each other; d discuss some ways in which the concentration of a solution can be expressed, and explain why different expressions of concentration are used for different purposes; and e define acid and base and interpret the pH scale Our body fluids are complex mixtures of chemicals A mixture consists of substances that are physically blended but not chemically combined Each substance retains its own chemical properties To contrast a mixture with a compound, consider sodium chloride again Sodium is a lightweight metal that bursts into flame if exposed to water, and chlorine is a yellow-green poisonous gas that was used for chemical warfare in World War I When these elements chemically react, they form common table salt Clearly, the compound has properties much different from the properties of its elements But if you were to put a little salt on your watermelon, the watermelon would taste salty and sweet because the sugar of the melon and the salt you added would merely form a mixture in which each compound retained its individual properties Water Most mixtures in our bodies consist of chemicals dissolved or suspended in water Water constitutes 50% to 75% of your body weight, depending on age, sex, fat content, and other factors Its structure, simple as it is, has profound biological effects Two aspects of its structure are particularly important: (1) its atoms are joined by polar covalent 11/2/10 4:23 PM ... 19 93, and in 19 97 the first edition of The Unity of Form and Function was published In 2 011 the story continues with the sixth edition of Ken’s best-selling A&P textbook The first edition (19 97) The. ..Sixth Edition & The Unity of Form and Function Kenneth S Saladin Georgia College & State University TM sal78259_fm_i-xxvi.indd i 11 /19 /10 9: 31 AM TM ANATOMY & PHYSIOLOGY: THE UNITY OF FORM AND FUNCTION, ... Chapter 1. 1 The Scope of Anatomy and Physiology 1. 2 The Origins of Biomedical Science 1. 3 Scientific Method 1. 4 Human Origins and Adaptations 1. 5 Human Structure 12 1. 6 Human Function 14 1. 7 The