Mcgraw hill anatomy and physiology answers

KENNETH S. SALADIN Georgia College

Digital Authors

CHRISTINA A. GAN Highline Community College

HEATHER N. CUSHMAN Tacoma Community College

ANATOMY PHYSIOLOGY The Unity of Form and Function

Eighth Edition

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ANATOMY & PHYSIOLOGY: THE UNITY OF FORM AND FUNCTION, EIGHTH EDITION

Published by McGraw-Hill Education, 2 Penn Plaza, New York, NY 10121. Copyright © 2018 by McGraw- Hill Education. All rights reserved. Printed in the United States of America. Previous editions © 2015, 2012, and 2010. 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 McGraw-Hill Education, 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.

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Library of Congress Cataloging-in-Publication Data

Names: Saladin, Kenneth S., author. | Gan, Christina A., author. | Cushman, Heather N., author. Title: Anatomy & physiology : the unity of form and function / Kenneth S. Saladin, Georgia College & State University ; digital authors, Christian A. Gan, Highline Community College, Heather N. Cushman, Tacoma Community College. Other titles: Anatomy and physiology Description: Eighth edition. | New York, NY : McGraw-Hill Education, [2018]

Includes index. Identifiers: LCCN 2016033675 | ISBN 9781259277726 (alk. paper) Subjects: LCSH: Human physiology—Textbooks. | Human anatomy—Textbooks. Classification: LCC QP34.5 .S23 2018 | DDC 612—dc23 LC record available at https://lccn.loc.gov/2016033675

The Internet addresses listed in the text were accurate at the time of publication. The inclusion of a website does not indicate an endorsement by the authors or McGraw-Hill Education, and McGraw-Hill Education does not guarantee the accuracy of the information presented at these sites. mheducation.com/highered

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BRIEF CONTENTS

About the Authors iv

PART ONE ORGANIZATION OF THE BODY 1

1 Major Themes of Anatomy and Physiology 1

ATLAS A General Orientation to Human Anatomy 27

2 The Chemistry of Life 41 3 Cellular Form and Function 75 4 Genetics and Cellular Function 111 5 Histology 139

PART TWO SUPPORT AND MOVEMENT 175

6 The Integumentary System 175 7 Bone Tissue 201 8 The Skeletal System 228 9 Joints 273 10 The Muscular System 307 ATLAS B Regional and Surface

Anatomy 373 11 Muscular Tissue 395

PART THREE INTERNAL COORDINATION AND CONTROL 431

12 Nervous Tissue 431 13 The Spinal Cord, Spinal Nerves, and

Somatic Reflexes 471 14 The Brain and Cranial Nerves 504 15 The Autonomic Nervous System and

Visceral Reflexes 554 16 Sense Organs 575 17 The Endocrine System 626

PART FOUR CIRCULATION AND DEFENSE 669

18 The Circulatory System: Blood 669 19 The Circulatory System: Heart 705 20 The Circulatory System: Blood Vessels and

Circulation 741 21 The Lymphatic and Immune Systems 800

PART FIVE INTAKE AND OUTPUT 845

22 The Respiratory System 845 23 The Urinary System 886 24 Fluid, Electrolyte, and Acid–Base

Balance 921 25 The Digestive System 944 26 Nutrition and Metabolism 991

PART SIX REPRODUCTION AND THE LIFE CYCLE 1025

27 The Male Reproductive System 1025 28 The Female Reproductive System 1055 29 Human Development and Aging 1093

APPENDIX A: Periodic Table of the Elements A-1

APPENDIX B: Answer Keys A-2

APPENDIX C: Symbols, Weights, and Measures A-15

APPENDIX D: Biomedical Abbreviations A-18

APPENDIX E: The Genetic Code A-19

APPENDIX F: Lexicon of Biomedical Word Elements A-20

APPENDIX G: Eighth Edition Changes in Terminology A-24

Glossary G-1

Index I-1

iii

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iv

KENNETH S. SALADIN has taught since 1977 at Georgia College 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 men- tor” 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, American Physiological Society, 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 Galápagos Conservancy, and he has endowed student schol- arships, the natural history museum, and a faculty chair at his university. Ken is married to Diane Saladin, a registered nurse. They have two adult children.

CHRISTINA A. GAN, digital coauthor for Connect®, has been teaching anatomy and physiol- ogy, microbiology, and general biology at Highline Community College in Des Moines, Washington, since 2004. Before that, she taught at Rogue Community College in Medford, Oregon, for 6 years. She earned her M.A. in biology from Humboldt State University, researching the genetic variation of mitochondrial DNA in various salmonid species, and is a member of the Human Anatomy and Physiology Society. When she is not in the classroom or developing digital media, she is climbing, mountaineering, skiing, kayaking, sailing, cycling, and mountain biking throughout the Pacific Northwest.

HEATHER N. CUSHMAN, digital coauthor for Connect®, teaches anatomy and physiology at Tacoma Community College in Tacoma, Washington, and is a member of the Human Anatomy and Physiology Society. She received her Ph.D. in neuroscience from the University of Minnesota in 2002, and completed a postdoctoral fellowship at the Vollum Institute at Oregon Health & Science University in Portland, Oregon, where she studied sensory transduction and the cellular and molec- ular mechanisms of muscle pain. She currently resides in Tacoma, Washington, and enjoys climbing, camping, and hiking with her husband Ken and their daughter Annika.

ABOUT THE AUTHORS

© JC Penney Portraits/Lifetouch Portrait Studios, Inc.

© Tim Vacula

© Chris Gan/Yuen Lui Studios

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v

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 tenth-grade biology class. With his “first book,” featuring 53 original India ink drawings and photomicrographs, a true storyteller was born.

Ken in 1964

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

when I was 15.

—Ken Saladin

Ken’s “first book,” Hydra Ecology, 1965 Courtesy of Ken Saladin

One of Ken’s drawings from Hydra Ecology Courtesy of Ken Saladin

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 2017, the story continues with the eighth edition of Ken’s best-selling A&P textbook.

The first edition (1997)

The story continues (2017)

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vi

ACKNOWLEDGMENTS Peer review is a critical part of the scien- tific process, and very important to ensure the content in this book continues to meet the needs of the instructors and students who use it. We are grateful for the people who agree to participate in this process and thank them for their time, talents, and feed- back. The reviewers of this text have con- tributed significant comments that help us refine and update the print and digital components of this program.

Mervan Agovic City University of New York

Rita Bagwe GBC, Pahrump

Neda Baniasadi North Shore Community College

Joan Barber Delaware Technical Community College

Jennifer Biederman Winona State University

Carol Britson University of Mississippi

Susan Capasso St. Vincent’s College

Kwan Christenson Georgia College

Joseph Comber Villanova University

Suzanne Cooke UNH Manchester

Andrew Corless Vincennes University

Rupa De Purdue University

Elizabeth Dunphy Gateway Community College

Chelsea Edward Cleveland Community College

Lori Garrett Parkland College

Melissa Glenn SUNY Broome

Donna Harman Lubbock Christian University

Clare Hays Metropolitan State University of Denver

Jana Herron Chattanooga State Community College

Austin Hicks University of Alabama

Roxann Isch-Clifton SWOSU at Sayre

Pamela Jackson Piedmont Technical College

Paula Johnson New River Community and Technical College

Jacqueline Jordan Clayton State University

Karen Kelly Milligan College

Shadi Kilani Houston Community College

Nathaniel M. King Palm Beach State College

Jeff Kingsbury Arizona State University

Brian H. Kipp Grand Valley State University

Shelley Kirkpatrick Saint Francis University

Theresa Kong William Rainey Harper College

Mary Katherine Lockwood University of New Hampshire

Kerrie McDaniel Western Kentucky University

Melinda Melton McNeese State University

Melanie Meyer Community College of Vermont

Kathy Monroe Blue Ridge Community and Technical College

David Moore Harrisburg Area Community College

Mina Moussavi University of Central Missouri

Ellen Ott-Reeves Blinn College Bryan

Andrew Petto UW Milwaukee

James Roush WKCTC

Stephen R. Peterson Delgado Community College

Richard Pirkle Tennessee Tech University

Jackie Reynolds Richland College

Crista Royal Toccoa Falls College

Frantz Sainvil Broward College

Colin Scanes UWM

Carl Shuster Madison College

Scott Simerlein Purdue University North Central

Gehan Soliman FTCC

Sherry Stewart Navarro College

Leticia Vega Barry University

Cuc Vu St. Catherine University

Stephanie Wallace Texas Christian University

Katy Wallis State College of Florida

Janice Webster Ivy Tech Community College

John Whitlock Mount Aloysius College

Harvey Wiener Manchester Community College

Sonya J. Williams Oklahoma City Community College

Cindy Wingert Cedarville University

Theopholieus Worrell Delgado Community College

Robin Wright Houston Community College

Xiaobo Yu Kean University (Union, NJ)

David Zimmer Trocaire College

Jeff Zuiderveen Columbus State University

Board of Advisors Cheryl Christensen Palm Beach State College

Lisa Conley Milwaukee Area Tech

Thomas Kalluvila Bryant and Stratton College

AJ Petto University of Wisconsin - Milwaukee

Jason Pienaar University of Alabama Tuscaloosa

Frantz Sainvil Broward College Central

Colin Scanes University of Wisconsin - Milwaukee

Carl Shuster Madison College

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Saladin’s text is written using plain language for A&P students who may be taking this course early in their curricula. 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.

INNOVATIVE CHAPTER SEQUENCING Some chapters and topics are presented in a sequence that is more instructive than the conventional order.

Early Presentation of Heredity

Fundamental principles of heredity are presented in the last few pages of chapter 4 rather than at the back of the book to better integrate molecular and Mendelian genetics. This organization also prepares students to learn about such genetic traits and conditions as cystic fibrosis, color blindness, blood types, hemophilia, cancer genes, and sickle-cell disease by first teaching them about dominant and recessive alleles, genotype and phenotype, and sex linkage.

Muscle Anatomy and Physiology Follow Skeleton and Joints

The functional morphology of the skeleton, joints, and muscles is treated in three consecutive chapters, 8 through 10, so when students learn muscle attachments, these come only two chapters after the names of the relevant bone features. When they learn muscle actions, it is in the first chapter after learning the terms for the joint movements. This order brings another advantage: the physiology of muscle and nerve cells is treated in two consecutive chapters (11 and 12), which are thus closely integrated in their treatment of synapses, neurotransmitters, and membrane electrophysiology.

Urinary System Presented Close to Circulatory and Respiratory Systems

Most textbooks place this system near the end of the book because of its anatomical and developmental relationships with the reproductive system. However, its physiological ties to the circulatory and respiratory systems are much more important. Except for a necessary digression on lymphatics and immunity, the circulatory system is followed almost immediately with the respiratory and urinary systems, which regulate blood composition and whose functional mechanisms rely on recently covered principles of blood flow and capillary exchange.

THE STORY OF FORM AND FUNCTION

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THE STORY OF FORM AND FUNCTION

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LEARNING TOOLS Engaging Chapter Layouts • Chapters are structured around the way students learn. • Frequent subheadings and expected learning outcomes help

students plan their study time and review strategies.

Deeper Insights highlight areas of interest and career relevance for students.

Chapter Outlines provide quick previews of the content.

Each numbered section begins with Expected Learning Outcomes to help focus the reader’s attention on the larger concepts and make the course outcome-driven. This also assists instructors in structuring their courses around expected learning outcomes.

Each chapter begins with Brushing Up to emphasize the interrelatedness of concepts, and serves as an aid for instructors when teaching chapters out of order.

Tiered Assessments Based on Key Learning Outcomes • Chapters are divided into easily manageable

chunks, which help students budget study time effectively.

• Section-ending questions allow students to check their understanding before moving on.

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Questions in figure legends and Apply What You Know items prompt students to think more deeply about the implications and applications of what they have learned. This helps students practice higher order thinking skills throughout the chapter.

The end-of-chapter Study Guide offers several methods for assessment that are useful to both students and instructors.

Assess Your Learning Outcomes provides students a study outline for review, and addresses the needs of instructors whose colleges require outcome-oriented syllabi and assessment of student achievement of the expected learning outcomes.

End-of-chapter questions build on all levels of Bloom’s taxonomy in sections to

    1. assess learning outcomes 2. test simple recall and analytical thought 3. build medical vocabulary 4. apply the basic knowledge to new clinical

problems and other situations

What's Wrong with These Statements questions further address Bloom’s taxonomy by asking the student to explain why the false statements are untrue.

Testing Your Comprehension questions address Bloom’s Taxonomy in going beyond recall to application of ideas.

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THE STORY OF FORM AND FUNCTION

x

Vivid Illustrations

Rich textures and shading and bold, bright colors bring structures to life.

Muscle Tables

Muscle tables organize information and integrate stunning visuals to help students learn. They also serve as a great student reference for study.

The visual appeal of nature is immense- ly important in motivating one to study it. We certainly see this at work in human anatomy—in the countless stu- dents who describe themselves as visual learners, in the many laypeople who find anatomy atlases so intriguing, and in the enormous popularity of Body Worlds and similar exhibitions of human anatomy.

—Ken Saladin

ARTWORK THAT INSPIRES LEARNING The incredible art program in this textbook sets the standard in A&P. The stunning portfolio of art and photos was created with the aid of art focus groups, and with feedback from hundreds of accuracy reviews.

Conducive to Learning • Easy-to-understand process figures • Tools for students to easily orient themselves

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Orientation Tools

Saladin art integrates tools to help students quickly orient themselves within a figure and make connections between ideas.

CSF is secreted by choroid plexus in each lateral ventricle.

Arachnoid villus

Choroid plexus

Third ventricle

Cerebral aqueduct

Lateral aperture

Fourth ventricle

Median aperture

Central canal of spinal cord

Subarachnoid space of spinal cord

Subarachnoid space Dura mater

Arachnoid mater

Superior sagittal sinus

CSF flows through interventricular foramina into third ventricle.

Choroid plexus in third ventricle adds more CSF.

CSF flows down cerebral aqueduct to fourth ventricle.

Choroid plexus in fourth ventricle adds more CSF.

CSF flows out two lateral apertures and one median aperture.

CSF fills subarachnoid space and bathes external surfaces of brain and spinal cord.

At arachnoid villi, CSF is reabsorbed into venous blood of dural venous sinuses.

1

3

4

56

7

7

8

1

2

3

4

5

6

7

8

2

Process Figures

Saladin breaks complicated physiological processes into numbered steps for a manageable introduction to difficult concepts.

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xii

New Scientific Content Saladin’s Anatomy & Physiology, eighth edition, has about 85 updates in scientific content, keeping abreast of new literature and new interpretations of old assumptions, including: • New guidelines on cholesterol and trans fats (chapter 2) • New skin-grafting method (chapter 6) • New coverage of the genetics and evolution of lactose intolerance (chapter 25) • New federal guidelines for recommended dietary intakes (chapter 26) • Updates on papillomavirus, genital warts, and cervical cancer (chapter 27)

For a complete list, please visit www.mcgrawhillconnect.com.

New Photographs This edition contains many new photographs, including: • Figure 1.10: new brain scans • Figure 7.20: osteoporosis with kyphosis • Figure 19.22: coronary artery disease • Figure 20.1: vascular cast of thyroid gland capillary beds • Figure 29.7: embryonic and fetal developmental stages

For a complete list, please visit www.mcgrawhillconnect.com.

New Pedagogy • In each chapter Study Guide, where students were previously prompted to distinguish between five true and five false

statements, they are now prompted to analyze the fallacies of 10 false statements. • This edition deletes 21 increasingly obsolete eponymous terms that are no longer recommended by the

Terminologia Anatomica or Gray’s Anatomy (such as Skene glands, Howship lacunae, Auerbach plexus, Hassall corpuscles, and organ of Corti) and replaces them with the standard English terms for easier student comprehension and retention.

• The explanation of units of chemical concentration is moved from chapter 2 to appendix C.

Enhanced Concepts Saladin’s Anatomy & Physiology, eighth edition, also updates and enhances about 25 more major physiological concepts in response to user feedback, including: • Chapter 3: leak and gated channels • Chapter 4: functions of intron DNA, small regulatory RNAs, and cell-cycle regulators • Chapter 11: the lactate threshold • Chapter 12: the vasomotor role of astrocytes, serial and parallel processing in neural circuits, long-term depression

and forgetting • Chapter 14: the role of orexins in the sleep–wake cycle, Bell palsy • Chapter 16: tactile functions of lingual papillae, function of oblique muscles of the eye • Chapter 17: stimuli inducing secretion of individual hormones, photoperiod and pineal gland function • Chapter 18: ABO blood types in hemolytic disease of the newborn, lymphocyte selection in the thymus • Chapter 20: sympathetic effects on coronary arteries • Chapter 21: precipitation versus agglutination in antibody action • Chapter 25: membrane transport of dietary triglycerides, blood circulation of the colon • Chapter 26: fuller coverage of hepatitis, fuller coverage of core versus shell body temperature • Chapter 27: structure and function of the male prepuce

WHAT’S NEW IN THE EIGHTH EDITION?

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• Chapter 28: history of mastectomy approaches, leptin and adiposity in relation to menarche, endometriosis • Chapter 29: telomere repair and cancer

Enhanced Artwork This edition contains many pieces of enhanced artwork, including: • Figure 3.15: mechanism of osmosis • Figure 3.28: structure of the cell nucleus • Figure 11.6: organization and size principle of motor units • Figure 14.13: functions of the five cerebral lobes • Figure 15.2: somatic versus autonomic outflow pathways • Figure 19.7: cross-sectional shapes and relationships of heart ventricles • Figure 20.4: schematic of blood distribution in rest and exercise • Figure 25.18: positive feedback control of gastric secretion • Figure 25.31: pathways of nutrient digestion and assimilation • Figure 26.12: environmental temperatures versus core and shell body temperatures

For a complete list, please visit www.mcgrawhillconnect.com.

Enhanced Data-Driven Revision Thousands of students have interacted with this textbook via McGraw-Hill Education’s adaptive reading experience, SmartBook®. Data about these interactions are collected over time and visually displayed in a heat map. Heat maps direct the author’s attention to areas where students are struggling. The author then evaluates the questions and associated text content to determine if revisions are needed to more clearly ask the question or clarify explanations. Heat maps can also confirm areas that the text is successful in aiding students’ comprehension. This edition was revised using heat map data to clarify explanations, and to enhance the SmartBook® experience for all students.

New Digital Enhancements Faculty now have the ability to assign select LearnSmart® questions in Connect®. The question bank in Connect® has select probes from SmartBook® available for you to assign on assignments or quizzes as you see fit.

The 8th edition provides SmartBook® sub-section assignability. SmartBook® assignments now go beyond section level to give instructors a more granular level of content.

Four new Concept Overview Interactive animations give exploration and engagement on key concepts: Innate Immunity; Adap- tive Immunity; Blood Pressure; Endocrine System, in addition to the existing Glomerular Filtration and Its Regulation; Tubular Reab- sorption and Tubular Secretion; Neuron Physiology; Passive and Active Processes of Membrane Transport; Skeletal Muscle Contraction; Changes Associated with a Cardiac Cycle; and The Movement of Oxygen and Carbon Dioxide. This brings the total Concept Overview Interactive animations to 11. They can be used in class, as a study tool, and are assignable in modules with associ- ated questions. The animations were recently converted to html for mobile compatibility.

Anatomy and Physiology REVEALED® 3.2 cadaver dissection simulator is available with Connect® Anatomy & Physiology. Now in html for mobile compatibility, with customizable anatomical structure list, version 3.2 offers 50 new animations, and 7 added physi- ology interactives.

Enhanced focus on encouraging critical thinking. Connect® question banks now have 30% or more questions at Bloom’s level 3 (apply) or higher.

SmartBook® includes additional Learning Resources – McGraw-Hill Education, using student usage data, determined the most difficult concepts for students. Additional study tools (tutorial videos, narrated slides, interactive activities) are now available for those difficult concepts in SmartBook®, just when the student needs it!

Assignable Connect® orientation videos available in the question bank can be assigned to help students get acquainted with Connect® and best practices for use.

Assignable APR, Ph.I.L.S, diagnostic prep exams, model questions and more! Course-wide A&P content gives a much larger pool of assignable content so instructors can easily tailor the course to their needs.

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Required=Results

McGraw-Hill Connect® Learn Without Limits Connect is a teaching and learning platform that is proven to deliver better results for students and instructors.

Connect empowers students by continually adapting to deliver precisely what they need, when they need it, and how they need it, so your class time is more engaging and effective.

Mobile

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©Getty Images/iStockphoto

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SmartBook®

Proven to help students improve grades and study more efficiently, SmartBook contains the same content within the print book, but actively tailors that content to the needs of the individual. SmartBook’s adaptive technology provides precise, personalized instruction on what the student should do next, guiding the student to master and remember key concepts, targeting gaps in knowledge and offering customized feedback, and driving the student toward comprehension and retention of the subject matter. Available on tablets, SmartBook puts learning at the student’s fingertips—anywhere, anytime.

Adaptive

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50% of the country’s students are not ready for A&P

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Improve preparation for the course and increase student success with the only adaptive Prep tool available for students today. Areas of individual weaknesses are identified in order to help students improve their understanding of core course areas needed to succeed.

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About the Authors iv

PART ONE ORGANIZATION OF THE BODY

CHAPTER 1 MAJOR THEMES OF ANATOMY AND PHYSIOLOGY 1 1.1 The Scope of Anatomy and

Physiology 2 1.2 The Origins of Biomedical

Science 3 1.3 Scientific Method 6 1.4 Human Origins and

Adaptations 9 1.5 Human Structure 11 1.6 Human Function 13 1.7 The Language of Medicine 19 1.8 Review of Major Themes 21 STUDY GUIDE 24

ATLAS A GENERAL ORIENTATION TO HUMAN ANATOMY 27 A.1 General Anatomical

Terminology 28 A.2 Major Body Regions 29 A.3 Body Cavities and

Membranes 32 A.4 Organ Systems 35 STUDY GUIDE 38

CHAPTER 2 THE CHEMISTRY OF LIFE 41 2.1 Atoms, Ions, and Molecules 42 2.2 Water and Mixtures 49 2.3 Energy and Chemical

Reactions 53 2.4 Organic Compounds 56 STUDY GUIDE 72

CHAPTER 3 CELLULAR FORM AND FUNCTION 75 3.1 Concepts of Cellular Structure 76 3.2 The Cell Surface 80 3.3 Membrane Transport 88 3.4 The Cell Interior 98 STUDY GUIDE 108

CHAPTER 4 GENETICS AND CELLULAR FUNCTION 111 4.1 DNA and RNA—The Nucleic

Acids 112 4.2 Genes and Their Action 117 4.3 DNA Replication and the Cell

Cycle 126

4.4 Chromosomes and Heredity 130 STUDY GUIDE 136

CHAPTER 5 HISTOLOGY 139 5.1 The Study of Tissues 140 5.2 Epithelial Tissue 143 5.3 Connective Tissue 149 5.4 Nervous and Muscular

Tissues—Excitable Tissues 158 5.5 Cell Junctions, Glands, and

Membranes 160 5.6 Tissue Growth, Development,

Repair, and Degeneration 167 STUDY GUIDE 172

PART TWO SUPPORT AND MOVEMENT

CHAPTER 6 THE INTEGUMENTARY SYSTEM 175 6.1 The Skin and Subcutaneous

Tissue 176 6.2 Hair and Nails 184 6.3 Cutaneous Glands 189

6.4 Skin Disorders 192 CONNECTIVE ISSUES 197 STUDY GUIDE 198

CHAPTER 7 BONE TISSUE 201 7.1 Tissues and Organs of the

Skeletal System 202 7.2 Histology of Osseous Tissue 204 7.3 Bone Development 208 7.4 Physiology of Osseous Tissue 215 7.5 Bone Disorders 220 CONNECTIVE ISSUES 224 STUDY GUIDE 225

CHAPTER 8 THE SKELETAL SYSTEM 228 8.1 Overview of the Skeleton 229 8.2 The Skull 231 8.3 The Vertebral Column and

Thoracic Cage 245 8.4 The Pectoral Girdle and Upper

Limb 254 8.5 The Pelvic Girdle and

Lower Limb 258 STUDY GUIDE 270

CHAPTER 9 JOINTS 273 9.1 Joints and Their Classification 274 9.2 Synovial Joints 278 9.3 Anatomy of Selected

Diarthroses 292 STUDY GUIDE 304

CHAPTER 10 THE MUSCULAR SYSTEM 307 10.1 Structural and Functional

Organization of Muscles 308 10.2 Muscles of the Head and

Neck 317 10.3 Muscles of the Trunk 328 10.4 Muscles Acting on the Shoulder

and Upper Limb 338

CONTENTS

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10.5 Muscles Acting on the Hip and Lower Limb 354

STUDY GUIDE 370

ATLAS B REGIONAL AND SURFACE ANATOMY 373 B.1 Regional Anatomy 374 B.2 The Importance of Surface

Anatomy 374 B.3 Learning Strategy 374

CHAPTER 11 MUSCULAR TISSUE 395 11.1 Types and Characteristics of

Muscular Tissue 396 11.2 Microscopic Anatomy of Skeletal

Muscle 397 11.3 The Nerve–Muscle

Relationship 402 11.4 Behavior of Skeletal Muscle

Fibers 405 11.5 Behavior of Whole Muscles 412 11.6 Muscle Metabolism 415 11.7 Cardiac and Smooth Muscle 420 CONNECTIVE ISSUES 427 STUDY GUIDE 428

PART THREE INTERNAL COORDINATION AND CONTROL

CHAPTER 12 NERVOUS TISSUE 431 12.1 Overview of the Nervous

System 432 12.2 Properties of Neurons 433 12.3 Supportive Cells (Neuroglia) 438 12.4 Electrophysiology of Neurons 443 12.5 Synapses 451 12.6 Neural Integration 457 CONNECTIVE ISSUES 467 STUDY GUIDE 468

CHAPTER 13 THE SPINAL CORD, SPINAL NERVES, AND SOMATIC REFLEXES 471 13.1 The Spinal Cord 472

13.2 The Spinal Nerves 480 13.3 Somatic Reflexes 493 STUDY GUIDE 501

CHAPTER 14 THE BRAIN AND CRANIAL NERVES 504 14.1 Overview of the Brain 505 14.2 Meninges, Ventricles,

Cerebrospinal Fluid, and Blood Supply 509

14.3 The Hindbrain and Midbrain 514 14.4 The Forebrain 521 14.5 Integrative Functions of the

Brain 527 14.6 The Cranial Nerves 538 STUDY GUIDE 551

CHAPTER 15 THE AUTONOMIC NERVOUS SYSTEM AND VISCERAL REFLEXES 554 15.1 General Properties of the

Autonomic Nervous System 555 15.2 Anatomy of the Autonomic

Nervous System 558 15.3 Autonomic Effects on Target

Organs 565 15.4 Central Control of Autonomic

Function 569 STUDY GUIDE 572

CHAPTER 16 SENSE ORGANS 575 16.1 Properties and Types of

Sensory Receptors 576 16.2 The General Senses 578 16.3 The Chemical Senses 584 16.4 Hearing and Equilibrium 589 16.5 Vision 603 STUDY GUIDE 622

CHAPTER 17 THE ENDOCRINE SYSTEM 626 17.1 Overview of the Endocrine

System 627 17.2 The Hypothalamus and Pituitary

Gland 630 17.3 Other Endocrine Glands 637

17.4 Hormones and Their Actions 647 17.5 Stress and Adaptation 656 17.6 Eicosanoids and Other Signaling

Molecules 657 17.7 Endocrine Disorders 659 CONNECTIVE ISSUES 665 STUDY GUIDE 666

PART FOUR CIRCULATION AND DEFENSE

CHAPTER 18 THE CIRCULATORY SYSTEM: BLOOD 669 18.1 Introduction 670 18.2 Erythrocytes 675 18.3 Blood Types 682 18.4 Leukocytes 687 18.5 Platelets and Hemostasis—The

Control of Bleeding 693 STUDY GUIDE 702

CHAPTER 19 THE CIRCULATORY SYSTEM: HEART 705 19.1 Overview of the Cardiovascular

System 706 19.2 Gross Anatomy of the Heart 708 19.3 Cardiac Muscle and the Cardiac

Conduction System 717 19.4 Electrical and Contractile Activity

of the Heart 719 19.5 Blood Flow, Heart Sounds, and

the Cardiac Cycle 725 19.6 Cardiac Output 731 STUDY GUIDE 738

CHAPTER 20 THE CIRCULATORY SYSTEM: BLOOD VESSELS AND CIRCULATION 741 20.1 General Anatomy of the Blood

Vessels 742 20.2 Blood Pressure, Resistance, and

Flow 750 20.3 Capillary Exchange 756 20.4 Venous Return and Circulatory

Shock 760

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20.5 Special Circulatory Routes 763 20.6 Anatomy of the Pulmonary

Circuit 764 20.7 Systemic Vessels of the Axial

Region 765 20.8 Systemic Vessels of the

Appendicular Region 784 CONNECTIVE ISSUES 795 STUDY GUIDE 796

CHAPTER 21 THE LYMPHATIC AND IMMUNE SYSTEMS 800 21.1 The Lymphatic System 801 21.2 Innate Immunity 814 21.3 Adaptive Immunity—General

Aspects 822 21.4 Cellular Immunity 827 21.5 Humoral Immunity 830 21.6 Immune System Disorders 835 CONNECTIVE ISSUES 841 STUDY GUIDE 842

PART FIVE INTAKE AND OUTPUT

CHAPTER 22 THE RESPIRATORY SYSTEM 845 22.1 Anatomy of the Respiratory

System 846 22.2 Pulmonary Ventilation 857 22.3 Gas Exchange and Transport 868 22.4 Respiratory Disorders 878 CONNECTIVE ISSUES 882 STUDY GUIDE 883

CHAPTER 23 THE URINARY SYSTEM 886 23.1 Functions of the Urinary

System 887 23.2 Anatomy of the Kidney 889 23.3 Urine Formation I: Glomerular

Filtration 895 23.4 Urine Formation II: Tubular

Reabsorption and Secretion 901 23.5 Urine Formation III: Water

Conservation 905 23.6 Urine and Renal Function

Tests 908

23.7 Urine Storage and Elimination 911 CONNECTIVE ISSUES 917 STUDY GUIDE 918

CHAPTER 24 FLUID, ELECTROLYTE, AND ACID–BASE BALANCE 921 24.1 Fluid Balance 922 24.2 Electrolyte Balance 928 24.3 Acid–Base Balance 933 STUDY GUIDE 941

CHAPTER 25 THE DIGESTIVE SYSTEM 944 25.1 General Anatomy and Digestive

Processes 945 25.2 The Mouth Through

Esophagus 949 25.3 The Stomach 956 25.4 The Liver, Gallbladder, and

Pancreas 965 25.5 The Small Intestine 971 25.6 Chemical Digestion and

Absorption 974 25.7 The Large Intestine 981 CONNECTIVE ISSUES 987 STUDY GUIDE 988

CHAPTER 26 NUTRITION AND METABOLISM 991 26.1 Nutrition 992 26.2 Carbohydrate Metabolism 1003 26.3 Lipid and Protein Metabolism 1010 26.4 Metabolic States and

Metabolic Rate 1012 26.5 Body Heat and

Thermoregulation 1016 STUDY GUIDE 1021

PART SIX REPRODUCTION AND THE LIFE CYCLE

CHAPTER 27 THE MALE REPRODUCTIVE SYSTEM 1025 27.1 Sexual Reproduction and

Development 1026

27.2 Male Reproductive Anatomy 1031

27.3 Puberty, Hormonal Control, and Climacteric 1039

27.4 Sperm and Semen 1041 27.5 Male Sexual Response 1046 STUDY GUIDE 1052

CHAPTER 28 THE FEMALE REPRODUCTIVE SYSTEM 1055 28.1 Reproductive Anatomy 1056 28.2 Puberty and Menopause 1066 28.3 Oogenesis and the

Sexual Cycle 1068 28.4 Female Sexual Response 1076 28.5 Pregnancy and

Childbirth 1077 28.6 Lactation 1084 CONNECTIVE ISSUES 1089 STUDY GUIDE 1090

CHAPTER 29 HUMAN DEVELOPMENT AND AGING 1093 29.1 Fertilization and the

Preembryonic Stage 1094 29.2 The Embryonic and Fetal

Stages 1100 29.3 The Neonate 1109 29.4 Aging and Senescence 1114 STUDY GUIDE 1123

APPENDIX A: PERIODIC TABLE OF THE ELEMENTS A-1

APPENDIX B: ANSWER KEYS A-2

APPENDIX C: SYMBOLS, WEIGHTS, AND MEASURES A-15

APPENDIX D: BIOMEDICAL ABBREVIATIONS A-18

APPENDIX E: THE GENETIC CODE A-19

APPENDIX F: LEXICON OF BIOMEDICAL WORD ELEMENTS A-20

APPENDIX G: EIGHTH EDITION CHANGES IN TERMINOLOGY A-24

GLOSSARY G-1

INDEX I-1

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LETTER TO STUDENTS

When I was a young boy, I became interested in what I then called “nature study” for two reasons. One was the sheer beauty of nature. I reveled in children’s books with abundant, colorful drawings and photographs of animals, plants, minerals, and gems. It was this esthetic appreciation of nature that made me want to learn more about it and made me hap- pily surprised to discover I could make a career of it. At a slightly later age, another thing that drew me still deeper into biology was to discover writers who had a way with words—who could capti- vate my imagination and curiosity with their elegant prose. Once I was old enough to hold part-time jobs, I began buying zoology and anatomy books that mesmerized me with their gracefulness of writing and fascinating art and photography. I wanted to write and draw like that myself, and I began teaching myself by learning from “the masters.” I spent many late nights in my room peering into my microscope and jars of pond water, typing page after page of manuscript, and trying pen and ink as an art medium. My “first book” was a 318-page paper on some little pond animals called hydras, with 53 India ink illustrations that I wrote for my tenth- grade biology class when I was 16 (see page v). Fast-forward about 30 years, to when I became a textbook writer, and I found myself bringing that same enjoyment of writing and illustrating to the first edition of this book you are now hold- ing. Why? Not only for its intrinsic creative satisfaction, but because I’m guessing that you’re like I was—you can appreciate a book that does more than simply give you the information you need. You appreciate, I trust, a writer who makes it enjoyable for you through his scientific, storytelling prose and his concept of the way things should be illustrated to spark interest and facilitate understanding. I know from my own students, however, that you need more than captivating illustrations and enjoyable reading. Let’s face it— A&P is a complex subject and it may seem a formidable task to acquire even a basic knowledge of the human body. It was difficult even for me to learn (and the learning never ends). So in addition to simply writing this book, I’ve given a lot of thought to its

pedagogy—the art of teaching. I’ve designed my chapters to make them easier for you to study and to give you abundant opportunity to check whether you’ve understood what you read—to test your- self (as I advise my own students) before the instructor tests you. Each chapter is broken down into short, digestible bits with a set of Expected Learning Outcomes at the beginning of each sec- tion, and self-testing questions (Before You Go On) just a few pages later. Even if you have just 30 minutes to read during a lunch break or a bus ride, you can easily read or review one of these brief sections. There are also numerous self-testing questions in a Study Guide at the end of each chapter, in some of the figure legends, and the occasional Apply What You Know questions dispersed throughout each chapter. The questions cover a broad range of cognitive skills, from simple recall of a term to your ability to evaluate, analyze, and apply what you’ve learned to new clinical situations or other problems. In this era of digital publishing, how- ever, learning aids go far beyond what I write into the book itself. SmartBook®, available on smartphones and tablets, includes all of the book’s contents plus adaptive technology that can give you personalized instruction, target the unique gaps in your knowledge, and guide you in comprehension and retention of the subject matter. I hope you enjoy your study of this book, but I know there are always ways to make it even better. Indeed, what quality you may find in this edition owes a great deal to feedback I’ve received from students all over the world. If you find any typos or other errors, if you have any suggestions for improvement, if I can clarify a con- cept for you, or even if you just want to comment on something you really like about the book, I hope you’ll feel free to write to me. I correspond quite a lot with students and would enjoy hearing from you.

Ken Saladin Georgia College Milledgeville, GA 31061 (USA) ksaladin2@windstream.net

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A colorized MRI scan of the human body © Simon Fraser/Getty Images

C H

A P

T E

R

Module 1: Body Orientation

PART ONE: ORGANIZATION OF THE BODY

1 MAJOR THEMES OF ANATOMY AND PHYSIOLOGY

CHAPTER OUTLINE

1.1 The Scope of Anatomy and Physiology

• Anatomy—The Study of Form • Physiology—The Study of Function

1.2 The Origins of Biomedical Science

• The Greek and Roman Legacy • The Birth of Modern Medicine • Living in a Revolution

1.3 Scientific Method

• The Inductive Method • The Hypothetico–Deductive Method • Experimental Design • Peer Review • Facts, Laws, and Theories

1.4 Human Origins and Adaptations

• Evolution, Selection, and Adaptation • Our Basic Primate Adaptations • Walking Upright

1.5 Human Structure

• The Hierarchy of Complexity • Anatomical Variation

1.6 Human Function

• Characteristics of Life • Physiological Variation • Homeostasis and Negative Feedback • Positive Feedback and Rapid Change • Gradients and Flow

1.7 The Language of Medicine

• The History of Anatomical Terminology • Analyzing Medical Terms • Plural, Adjectival, and Possessive Forms • Pronunciation • The Importance of Precision

1.8 Review of Major Themes

Study Guide

DEEPER INSIGHTS

1.1 Evolutionary Medicine: Vestiges of Human Evolution

1.2 Clinical Application: Situs Inversus and Other Unusual Anatomy

1.3 Medical History: Men in the Oven

1.4 Medical History: Obscure Word Origins

1.5 Clinical Application: Medical Imaging

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2 PART ONE Organization of the Body

No branch of science hits as close to home as the science of our own bodies. We’re grateful for the dependability of our hearts; we’re awed by the capabilities of muscles and joints dis- played by Olympic athletes; and we ponder with philosophers the ancient mysteries of mind and emotion. We want to know how our body works, and when it malfunctions, we want to know what’s happening and what we can do about it. Even the most ancient writings of civilization include medical documents that attest to humanity’s timeless drive to know itself. You are em- barking on a subject that is as old as civilization, yet one that grows by thousands of scientific publications every week.

This book is an introduction to human structure and function, the biology of the human body. It is meant primarily to give you a foundation for advanced study in health care, exercise physi- ology, pathology, and other fields related to health and fitness. Beyond that purpose, however, it can also provide you with a deeply satisfying sense of self-understanding.

As rewarding and engrossing as this subject is, the human body is highly complex, and understanding it requires us to comprehend a great deal of detail. The details will be more manageable if we relate them to a few broad, unifying concepts. The aim of this chapter, therefore, is to introduce such concepts and put the rest of the book into perspective. We consider the historical development of anatomy and physiology, the thought processes that led to the knowledge in this book, the meaning of human life, some central concepts of physiology, and how to better understand medical terminology.

1.1 The Scope of Anatomy and Physiology

Expected Learning Outcomes When you have completed this section, you should be able to

a. define anatomy and physiology and relate them to each other;

b. describe several ways of studying human anatomy; and c. define a few subdisciplines of human physiology.

Anatomy is the study of structure, and physiology is the study of function. These approaches are complementary and never entirely separable. Together, they form the bedrock of the health sciences. When we study a structure, we want to know, What does it do? Physiology thus lends meaning to anatomy; conversely, anatomy is what makes physiology possible. This unity of form and function is an important point to bear in mind as you study the body. Many examples of it will be apparent throughout the book—some of them pointed out for you, and others you will notice for yourself.

Anatomy—The Study of Form There are several ways to examine the structure of the human body. The simplest is inspection—simply looking at the body’s appearance, as in performing a physical examination or making

a clinical diagnosis from surface appearance. Physical examina- tions also involve touching and listening to the body. Palpation1 means feeling a structure with the hands, such as palpating a swol- len lymph node or taking a pulse. Auscultation2 (AWS-cul-TAY- shun) is listening to the natural sounds made by the body, such as heart and lung sounds. In percussion, the examiner taps on the body, feels for abnormal resistance, and listens to the emitted sound for signs of abnormalities such as pockets of fluid, air, or scar tissue.

But a deeper understanding of the body depends on dissection (dis-SEC-shun)—carefully cutting and separating tissues to reveal their relationships. The very words anatomy3 and dissection4 both mean “cutting apart”; until the nineteenth century, dissection was called “anatomizing.” In many schools of health science, one of the first steps in training students is dissection of the cadaver,5 a dead human body. Many insights into human structure are ob- tained from comparative anatomy—the study of multiple spe- cies in order to examine similarities and differences and analyze evolutionary trends. Anatomy students often begin by dissecting other animals with which we share a common ancestry and many structural similarities. Many of the reasons for human structure become apparent only when we look at the structure of other animals.

Dissection, of course, is not the method of choice when studying a living person! It was once common to diagnose dis- orders through exploratory surgery—opening the body and taking a look inside to see what was wrong and what could be done about it. Any breach of the body cavities is risky, however, and most exploratory surgery has now been replaced by medical imaging techniques—methods of viewing the inside of the body without surgery, discussed at the end of this chapter (see Deeper Insight 1.5). The branch of medicine concerned with imaging is called radiology. Structure that can be seen with the naked eye— whether by surface observation, radiology, or dissection—is called gross anatomy.

Ultimately, the functions of the body result from its individ- ual cells. To see those, we usually take tissue specimens, thinly slice and stain them, and observe them under the microscope. This approach is called histology6 (microscopic anatomy). Histopathology is the microscopic examination of tissues for signs of disease. Cytology7 is the study of the structure and func- tion of individual cells. Ultrastructure refers to fine detail, down to the molecular level, revealed by the electron microscope.

Physiology—The Study of Function Physiology8 uses the methods of experimental science discussed later. It has many subdisciplines such as neurophysiology (physi- ology of the nervous system), endocrinology (physiology of

1palp = touch, feel; ation = process 2auscult = listen; ation = process 3ana = apart; tom = cut 4dis = apart; sect = cut 5from cadere = to fall down or die 6histo = tissue; logy = study of 7cyto = cell; logy = study of 8physio = nature; logy = study of

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CHAPTER 1 Major Themes of Anatomy and Physiology 3

hormones), and pathophysiology (mechanisms of disease). Partly because of limitations on experimentation with humans, much of what we know about bodily function has been gained through comparative physiology, the study of how different species have solved problems of life such as water balance, respiration, and re- production. Comparative physiology is also the basis for the de- velopment of new drugs and medical procedures. For example, a cardiac surgeon may learn animal surgery before practicing on humans, and a vaccine cannot be used on human subjects until it has been demonstrated through animal research that it confers significant benefits without unacceptable risks.

BEFORE YOU GO ON Answer the following questions to test your understanding of the preceding section:

1. What is the difference between anatomy and physiology? How do these two sciences support each other?

2. Name the method that would be used for each of the fol- lowing: listening to a patient for a heart murmur; study- ing the microscopic structure of the liver; microscopically examining liver tissue for signs of hepatitis; learning the blood vessels of a cadaver; and performing a breast self- examination.

1 .2 The Origins of Biomedical Science

Expected Learning Outcomes When you have completed this section, you should be able to

a. give examples of how modern biomedical science emerged from an era of superstition and authoritarianism; and

b. describe the contributions of some key people who helped to bring about this transformation.

Any science is more enjoyable if we consider not just the cur- rent state of knowledge, but how it compares to past under- standings of the subject and how our knowledge was gained. Of all sciences, medicine has one of the most fascinating histories. Medical science has progressed far more in the last 50 years than in the 2,500 years before that, but the field did not spring up overnight. It is built upon centuries of thought and con- troversy, triumph and defeat. We cannot fully appreciate its present state without understanding its past—people who had the curiosity to try new things, the vision to look at human form and function in new ways, and the courage to question authority.

The Greek and Roman Legacy As early as 3,000 years ago, physicians in Mesopotamia and Egypt treated patients with herbal drugs, salts, physical ther- apy, and faith healing. The “father of medicine,” however, is

usually considered to be the Greek physician Hippocrates (c. 460–c. 375 bce). He and his followers established a code of ethics for physicians, the Hippocratic Oath, which is still recited in modern form by graduating physicians at some medi- cal schools. Hippocrates urged physicians to stop attributing disease to the activities of gods and demons and to seek their natural causes, which could afford the only rational basis for therapy.

Aristotle (384–322 bce) was one of the first philosophers to write about anatomy and physiology. He believed that diseases and other natural events could have either supernatural causes, which he called theologi, or natural ones, which he called physici or phys- iologi. We derive such terms as physician and physiology from the latter. Until the nineteenth century, physicians were called “doctors of physic.” In his anatomy book, On the Parts of Animals, Aristotle tried to identify unifying themes in nature. Among other points, he argued that complex structures are built from a smaller variety of simple components—a perspective that we will find useful later in this chapter.

▶▶▶APPLY WHAT YOU KNOW When you have completed this chapter, discuss the relevance of Aristotle’s philosophy to our current thinking about human structure.

Claudius Galen (c. 130–c. 200), physician to the Roman gladiators, wrote the most influential medical textbook of the ancient era—a book worshipped to excess by medical profes- sors for centuries to follow. Cadaver dissection was banned in Galen’s time because of some horrid excesses that preceded him, including public dissection of living slaves and prisoners. Aside from what he could learn by treating gladiators’ wounds, Galen was therefore limited to dissecting pigs, monkeys, and other animals. Because he was not permitted to dissect cadav- ers, he had to guess at much of human anatomy and made some incorrect deductions from animal dissections. He described the human liver, for example, as having five fingerlike lobes, some- what like a baseball glove, because that is what he had seen in baboons. But Galen saw science as a method of discovery, not as a body of fact to be taken on faith. He warned that even his own books could be wrong and advised his followers to trust their own observations more than any book. Unfortunately, his advice was not heeded. For nearly 1,500 years, medical pro- fessors dogmatically taught what they read in Aristotle and Galen, seldom daring to question the authority of these “ancient masters.”

The Birth of Modern Medicine In the Middle Ages, the state of medical science varied greatly from one religious culture to another. Science was severely re- pressed in the Christian culture of Europe until about the six- teenth century, although some of the most famous medical schools of Europe were founded during this era. Their profes- sors, however, taught medicine primarily as a dogmatic commen- tary on Galen and Aristotle, not as a field of original research.

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4 PART ONE Organization of the Body

Medieval medical illustrations were crude representations of the body intended more to decorate a page than to depict the body re- alistically (fig. 1.1a). Some were astrological charts that showed which sign of the zodiac was thought to influence each organ of the body. From such pseudoscience came the word influenza, Italian for “influence.”

Free inquiry was less inhibited in Jewish and Muslim cul- ture during this time. Jewish physicians were the most esteemed practitioners of their art—and none more famous than Moses ben Maimon (1135–1204), known in Christendom as Maimonides. Born in Spain, he fled to Egypt at age 24 to escape antisemitic persecution. There he served the rest of his life as physician to the court of the sultan, Saladin. A highly admired rabbi, Maimonides wrote voluminously on Jewish law and theology, but also wrote 10 influential medical books and numerous treatises on specific diseases.

Among Muslims, probably the most highly regarded medical scholar was Ibn Sina (980–1037), known in the West as Avicenna or “the Galen of Islam.” He studied Galen and Aristotle, combined their findings with original discoveries, and questioned authority when the evidence demanded it. Medicine in the Mideast soon became superior to European medicine. Avicenna’s textbook, The Canon of Medicine, was the leading authority in European medical schools for over 500 years.

Chinese medicine had little influence on Western thought and practice until relatively recently; the medical arts evolved in China quite independently of European medicine. Later chapters of this book describe some of the insights of ancient China and India.

Modern Western medicine began around the sixteenth century in the innovative minds of such people as the anato- mist Andreas Vesalius and the physiologist William Harvey.

FIGURE 1.1 The Evolution of Medical Art. Two illustrations of the skeletal system made about 500 years apart. (a) From an eleventh- century work attributed to Persian physician Avicenna. (b) From De Humani Corporis Fabrica by Andreas Vesalius, 1543. a: Source: Wellcome Library, London/CC BY 4.0; b: © SPL/Science Source

(a) (b)

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CHAPTER 1 Major Themes of Anatomy and Physiology 5

Andreas Vesalius (1514–64) taught anatomy in Italy. In his time, the Catholic Church relaxed its prohibition against cadaver dissec- tion, in part to allow autopsies in cases of suspicious death. Fur- thermore, the Italian Renaissance created an environment more friendly to innovative scholarship. Dissection gradually found its way into the training of medical students throughout Europe. It was an unpleasant business, however, and most professors consid- ered it beneath their dignity. In those days before refrigeration or embalming, the odor from the decaying cadaver was unbearable. Dissections were a race against decay. Bleary medical students had to fight the urge to vomit, lest they incur the wrath of an over- bearing professor. Professors typically sat in an elevated chair, the cathedra, reading dryly in Latin from Galen or Aristotle while a lower-ranking barber–surgeon removed putrefying organs from the cadaver and held them up for the students to see. Barbering and surgery were considered to be “kindred arts of the knife”; today’s barber poles date from this era, their red and white stripes symbolizing blood and bandages.

Vesalius broke with tradition by coming down from the cathedra and doing the dissections himself. He was quick to point out that much of the anatomy in Galen’s books was wrong, and he was the first to publish accurate illustrations for teaching anatomy (fig. 1.1b). When others began to plagiarize them, Vesalius published the first atlas of anatomy, De Humani Corporis Fabrica (On the Structure of the Human Body), in 1543. This book began a rich tradition of medical illustration that has been handed down to us through such milestones as Gray’s Anatomy (1856) and the vividly illustrated atlases and textbooks of today.

Anatomy preceded physiology and was a necessary foundation for it. What Vesalius was to anatomy, the Englishman William Harvey (1578–1657) was to physiology. Harvey is remembered especially for his studies of blood circulation and a little book he published in 1628, known by its abbreviated title De Motu Cordis (On the Motion of the Heart). He and Michael Servetus (1511–53) were the first Western scientists to realize that blood must circulate continuously around the body, from the heart to the other organs and back to the heart again. This flew in the face of Galen’s belief that the liver con- verted food to blood, the heart pumped blood through the veins to all other organs, and those organs consumed it. Harvey’s colleagues, wedded to the ideas of Galen, ridiculed Harvey for his theory, though we now know he was correct (see chapter 20 prologue). Despite persecution and setbacks, Harvey lived to a ripe old age, served as physician to the kings of England, and later did important work in embryology. Most importantly, Harvey’s contributions represent the birth of experimental physiology—the method that generated most of the information in this book.

Modern medicine also owes an enormous debt to two inventors from this era, Robert Hooke and Antony van Leeuwenhoek, who extended the vision of biologists to the cel- lular level.

Robert Hooke (1635–1703), an Englishman, designed sci- entific instruments of various kinds, including the compound microscope. This is a tube with a lens at each end—an objective

lens near the specimen, which produces an initial magnified image, and an ocular lens (eyepiece) near the observer’s eye, which magnifies the first image still further. Although crude compound microscopes had existed since 1595, Hooke im- proved the optics and invented several of the helpful features found in microscopes today—a stage to hold the specimen, an illuminator, and coarse and fine focus controls. His microscopes magnified only about 30 times, but with them, he was the first to see and name cells. In 1663, he observed thin shavings of cork and observed that they “consisted of a great many little boxes,” which he called cellulae (little cells) after the cubicles of a monastery (fig. 1.2). He later observed living cells “filled with juices.” Hooke became particularly interested in microscopic ex- amination of such material as insects, plant tissues, and animal parts. He published the first comprehensive book of microscopy, Micrographia, in 1665.

Antony van Leeuwenhoek (an-TOE-nee vahn LAY-wen- hook) (1632–1723), a Dutch textile merchant, invented a simple (single-lens) microscope, originally for the purpose of examin- ing the weave of fabrics. His microscope was a beadlike lens mounted in a metal plate equipped with a movable specimen clip.

FIGURE 1.2 Hooke’s Compound Microscope. (a) The compound microscope had a lens at each end of a tubular body. (b) Hooke’s drawing of cork cells, showing the thick cell walls characteristic of plants. a: Source: National Museum of Health and Medicine, Silver Spring, MD; b: © Bettman/Corbis

(a) (b)

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6 PART ONE Organization of the Body

Even though his microscopes were simpler than Hooke’s, they achieved much greater useful magnification (up to 200×) owing to Leeuwenhoek’s superior lens-making technique. Out of cu- riosity, he examined a drop of lake water and was astonished to find a variety of microorganisms—“little animalcules,” he called them, “very prettily a-swimming.” He went on to ob- serve practically everything he could get his hands on, includ- ing blood cells, blood capillaries, sperm, muscular tissue, and bacteria from tooth scrapings. Leeuwenhoek began submitting his observations to the Royal Society of London in 1673. He was praised at first, and his observations were eagerly read by scientists, but enthusiasm for the microscope did not last. By the end of the seventeenth century, it was treated as a mere toy for the upper classes, as amusing and meaningless as a kaleido- scope. Leeuwenhoek and Hooke had even become the brunt of satire. But probably no one in history had looked at nature in such a revolutionary way. By taking biology to the cellular level, the two men had laid an entirely new foundation for the modern medicine to follow centuries later.

The Hooke and Leeuwenhoek microscopes produced poor images with blurry edges (spherical aberration) and rainbow- like distortions (chromatic aberration). These problems had to be solved before the microscope could be widely used as a bio- logical tool. In the nineteenth century, German inventors greatly improved the compound microscope, adding the condenser and developing superior optics. With improved microscopes, biolo- gists began eagerly examining a wider variety of specimens. By 1839, botanist Matthias Schleiden (1804–81) and zoologist Theodor Schwann (1810–82) concluded that all organisms were composed of cells. Although it took another century for this idea to be generally accepted, it became the first tenet of the cell theory, added to by later biologists and summarized in section 3.1. The cell theory was perhaps the most important breakthrough in bio- medical history; all functions of the body are now interpreted as the effects of cellular activity.

Although the philosophical foundation for modern medicine was largely established by the time of Leeuwenhoek, Hooke, and Harvey, clinical practice was still in a dismal state. Few doctors attended medical school or received any formal education in basic science or human anatomy. Physicians tended to be ignorant, inef- fective, and pompous. Their practice was heavily based on expel- ling imaginary toxins from the body by bleeding their patients or inducing vomiting, sweating, or diarrhea. They performed opera- tions with filthy hands and instruments, spreading lethal infections from one patient to another and refusing, in their vanity, to believe that they themselves were the carriers of disease. Countless women died of infections acquired during childbirth from their obstetri- cians. Fractured limbs often became gangrenous and had to be am- putated, and there was no anesthesia to lessen the pain. Disease was still widely attributed to demons and witches, and many people felt they would be interfering with God’s will if they tried to treat it.

Living in a Revolution This short history brings us only to the threshold of modern biomedical science; it stops short of such momentous discover- ies as the germ theory of disease, the mechanisms of heredity,

and the structure of DNA. In the twentieth century, basic biol- ogy and biochemistry yielded a much deeper understanding of how the body works. Advances in medical imaging enhanced our diagnostic ability and life-support strategies. We witnessed monumental developments in chemotherapy, immunization, an- esthesia, surgery, organ transplants, and human genetics. By the close of the twentieth century, we had discovered the chemical “base sequence” of every human gene and begun attempting gene therapy to treat children born with diseases recently considered incurable. As future historians look back on the turn of this cen- tury, they may exult about the Genetic Revolution in which you are now living.

Several discoveries of the nineteenth and twentieth centuries, and the men and women behind them, are covered in short his- torical sketches in later chapters. Yet, the stories told in this chap- ter are different in a significant way. The people discussed here were pioneers in establishing the scientific way of thinking. They helped to replace superstition with an appreciation of natural law. They bridged the chasm between mystery and medication. With- out this intellectual revolution, those who followed could not have conceived of the right questions to ask, much less a method for answering them.

BEFORE YOU GO ON Answer the following questions to test your understanding of the preceding section:

3. In what way did the followers of Galen disregard his advice? How does Galen’s advice apply to you and this book?

4. Describe two ways in which Vesalius improved medical education and set standards that remain relevant today.

5. How is our concept of human form and function today affected by inventors from the seventeenth to the nine- teenth centuries?

1.3 Scientific Method

Expected Learning Outcomes When you have completed this section, you should be able to

a. describe the inductive and hypothetico–deductive methods of obtaining scientific knowledge;

b. describe some aspects of experimental design that help to ensure objective and reliable results; and

c. explain what is meant by hypothesis, fact, law, and theory in science.

Prior to the seventeenth century, science was done in a haphazard way by a small number of isolated individuals. The philosophers Francis Bacon (1561–1626) in England and René Descartes (1596–1650) in France envisioned science as a far greater, sys- tematic enterprise with enormous possibilities for human health and welfare. They detested those who endlessly debated ancient

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CHAPTER 1 Major Themes of Anatomy and Physiology 7

philosophy without creating anything new. Bacon argued against biased thinking and for more objectivity in science. He outlined a systematic way of seeking similarities, differences, and trends in nature and drawing useful generalizations from observable facts. You will see echoes of Bacon’s philosophy in the discussion of scientific method that follows.

Though the followers of Bacon and Descartes argued bitterly with one another, both men wanted science to become a public, cooperative enterprise, supported by governments and conducted by an international community of scholars rather than a few iso- lated amateurs. Inspired by their vision, the French and English governments established academies of science that still flourish today. Bacon and Descartes are credited with putting science on the path to modernity, not by discovering anything new in nature or inventing any techniques—for neither man was a scientist—but by inventing new habits of scientific thought.

When we say “scientific,” we mean that such thinking is based on assumptions and methods that yield reliable, objective, testable information about nature. The assumptions of science are ideas that have proven fruitful in the past—for example, the idea that natural phenomena have natural causes and nature is there- fore predictable and understandable. The methods of science are highly variable. Scientific method refers less to observational procedures than to certain habits of disciplined creativity, care- ful observation, logical thinking, and honest analysis of one’s ob- servations and conclusions. It is especially important in health science to understand these habits. This field is littered with more fads and frauds than any other. We are called upon constantly to judge which claims are trustworthy and which are bogus. To make such judgments depends on an appreciation of how scien- tists think, how they set standards for truth, and why their claims are more reliable than others.

The Inductive Method The inductive method, first prescribed by Bacon, is a process of making numerous observations until one feels confident in draw- ing generalizations and predictions from them. What we know of anatomy is a product of the inductive method. We describe the normal structure of the body based on observations of many bodies.

This raises the issue of what is considered proof in science. We can never prove a claim beyond all possible refutation. We can, however, consider a statement as proven beyond reasonable doubt if it was arrived at by reliable methods of observation, tested and confirmed repeatedly, and not falsified by any credible observa- tion. In science, all truth is tentative; there is no room for dogma. We must always be prepared to abandon yesterday’s truth if tomor- row’s facts disprove it.

The Hypothetico–Deductive Method Most physiological knowledge was obtained by the hypothetico– deductive method. An investigator begins by asking a ques- tion and formulating a hypothesis—an educated speculation or possible answer to the question. A good hypothesis must be

(1) consistent with what is already known and (2) capable of being tested and possibly falsified by evidence. Falsifiability means that if we claim something is scientifically true, we must be able to specify what evidence it would take to prove it wrong. If nothing could possibly prove it wrong, then it is not scientific.

▶▶▶APPLY WHAT YOU KNOW The ancients thought that gods or invisible demons caused epilepsy. Today, epileptic seizures are attributed to bursts of abnormal electrical activity in nerve cells of the brain. Explain why one of these claims is falsifiable (and thus scientific), whereas the other claim is not.

The purpose of a hypothesis is to suggest a method for an- swering a question. From the hypothesis, a researcher makes a deduction, typically in the form of an “if–then” prediction: If my hypothesis on epilepsy is correct and I record the brain waves of patients during seizures, then I should observe abnor- mal bursts of activity. A properly conducted experiment yields observations that either support a hypothesis or require the sci- entist to modify or abandon it, formulate a better hypothesis, and test that one. Hypothesis testing operates in cycles of con- jecture and disproof until one is found that is supported by the evidence.

Experimental Design Doing an experiment properly involves several important consid- erations. What shall I measure and how can I measure it? What effects should I watch for and which ones should I ignore? How can I be sure my results are due to the variables that I manipulate and not due to something else? When working on human subjects, how can I prevent the subject’s expectations or state of mind from influencing the results? How can I eliminate my own biases and be sure that even the most skeptical critics will have as much confi- dence in my conclusions as I do? Several elements of experimental design address these issues:

• Sample size. The number of subjects (animals or people) used in a study is the sample size. An adequate sample size controls for chance events and individual variations in response and thus enables us to place more confidence in the outcome. For example, would you rather trust your health to a drug that was tested on 5 people or one tested on 5,000? Why?

• Controls. Biomedical experiments require comparison between treated and untreated individuals so that we can judge whether the treatment has any effect. A control group consists of subjects that are as much like the treatment group as possible except with respect to the variable being tested. For example, there is evidence that garlic lowers blood cholesterol levels. In one study, volunteers with high cholesterol were each given 800 mg of garlic powder daily for 4 months and exhibited an average 12% reduction in cholesterol. Was this a significant

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8 PART ONE Organization of the Body

reduction, and was it due to the garlic? It is impossible to say without comparison to a control group of similar people who received no treatment. In this study, the control group averaged only a 3% reduction in cholesterol, so garlic seems to have made a difference.

• Psychosomatic effects. Psychosomatic effects (effects of the subject’s state of mind on his or her physiology) can have an undesirable effect on experimental results if we do not control for them. In drug research, it is therefore customary to give the control group a placebo (pla-SEE- bo)—a substance with no significant physiological effect on the body. If we were testing a drug, for example, we could give the treatment group the drug and the control group identical-looking sugar tablets. Neither group must know which tablets it is receiving. If the two groups showed significantly different effects, we could feel con- fident that it did not result from a knowledge of what they were taking.

• Experimenter bias. In the competitive, high-stakes world of medical research, experimenters may want certain results so much that their biases, even subconscious ones, can affect their interpretation of the data. One way to control for this is the double-blind method. In this procedure, neither the subject to whom a treatment is given nor the person giv- ing it and recording the results knows whether that subject is receiving the experimental treatment or the placebo. A researcher may prepare identical-looking tablets, some with the drug and some with placebo; label them with code num- bers; and distribute them to participating physicians. The physicians themselves do not know whether they are admin- istering drug or placebo, so they cannot give the subjects even accidental hints of which substance they are taking. When the data are collected, the researcher can correlate them with the composition of the tablets and determine whether the drug had more effect than the placebo.

• Statistical testing. If you tossed a coin 100 times, you would expect it to come up about 50 heads and 50 tails. If it actually came up 48:52, you would probably attribute this to random error rather than bias in the coin. But what if it came up 40:60? At what point would you begin to suspect bias? This type of problem is faced routinely in research— how great a difference must there be between control and experimental groups before we feel confident that it was due to the treatment and not merely random variation? What if a treatment group exhibited a 12% reduction in cholesterol level and the placebo group a 10% reduction? Would this be enough to conclude that the treatment was effective? Scientists are well grounded in statistical tests that can be applied to the data—the chi-square test, the t test, and analysis of variance, for example. A typical outcome of a statistical test may be expressed, “We can be 99.5% sure that the difference between group A and group B was due to the experimental treatment and not to random variation.” Science is grounded not in statements of absolute truth, but in statements of probability.

Peer Review When a scientist applies for funds to support a research project or submits results for publication, the application or manuscript is submitted to peer review—a critical evaluation by other ex- perts in that field. Even after a report is published, if the results are important or unconventional, other scientists may attempt to reproduce them to see if the author was correct. At every stage from planning to postpublication, scientists are therefore subject to intense scrutiny by their colleagues. Peer review is one mechanism for ensuring honesty, objectivity, and quality in science.

Facts, Laws, and Theories The most important product of scientific research is understanding how nature works—whether it be the nature of a pond to an ecolo- gist or the nature of a liver cell to a physiologist. We express our understanding as facts, laws, and theories of nature. It is important to appreciate the differences among these.

A scientific fact is information that can be independently verified by any trained person—for example, the fact that an iron deficiency leads to anemia. A law of nature is a gener- alization about the predictable ways in which matter and en- ergy behave. It is the result of inductive reasoning based on repeated, confirmed observations. Some laws are expressed as concise verbal statements, such as the law of complementary base pairing: In the double helix of DNA, a chemical base called adenine always pairs with one called thymine, and a base called guanine always pairs with cytosine (see section 4.1). Other laws are expressed as mathematical formulae, such as Boyle’s law, used in respiratory physiology: Under specified conditions, the volume of a gas (V ) is inversely proportional to its pressure (P)—that is,

V ∝ 1/P.

A theory is an explanatory statement or set of statements derived from facts, laws, and confirmed hypotheses. Some theories have names, such as the cell theory, the fluid-mosaic theory of cell membranes, and the sliding filament theory of muscle contraction. Most, however, remain unnamed. The pur- pose of a theory is not only to concisely summarize what we already know but, moreover, to suggest directions for further study and to help predict what the findings should be if the theory is correct.

Law and theory mean something different in science than they do to most people. In common usage, a law is a rule cre- ated and enforced by people; we must obey it or risk a penalty. A law of nature, however, is a description; laws do not govern the universe—they describe it. Laypeople tend to use the word theory for what a scientist would call a hypothesis—for example, “I have a theory why my car won’t start.” The difference in meaning causes significant confusion when it leads people to think that a scien- tific theory (such as the theory of evolution) is merely a guess or conjecture, instead of recognizing it as a summary of conclusions drawn from a large body of observed facts. The concepts of grav- ity and electrons are theories, too, but this does not mean they are merely speculations.

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CHAPTER 1 Major Themes of Anatomy and Physiology 9

▶▶▶APPLY WHAT YOU KNOW Was the cell theory proposed by Schleiden and Schwann more a product of the hypothetico–deductive method or of the inductive method? Explain your answer.

BEFORE YOU GO ON Answer the following questions to test your understanding of the preceding section:

6. Describe the general process involved in the inductive method.

7. Describe some sources of potential bias in biomedical research. What are some ways of minimizing such bias?

8. Is there more information in an individual scientific fact or in a theory? Explain.

1.4 Human Origins and Adaptations

Expected Learning Outcomes When you have completed this section, you should be able to

a. explain why evolution is relevant to understanding human form and function;

b. define evolution and natural selection; c. describe some human characteristics that can be attributed

to the tree-dwelling habits of earlier primates; and

d. describe some human characteristics that evolved later in connection with upright walking.