Schematic of ascending (sensory) and descending (motor) pathways between the brain and the spinal cord.


Elaine N. Marieb Suzanne M. Keller

Essentials of Human Anatomy & Physiology




Learn the Essential What, How & Why of Human Anatomy & Physiology

With the Twelfth Edition of Essentials of Human Anatomy & Physiology, science educator Suzanne Keller joins bestselling author Elaine Marieb in helping learners focus on the What, How & Why of A&P, without getting sidetracked in details.



When most people hear the term cardio-vascular system, they immediately think of the heart. We have all felt our own heart “pound” from time to time when we are ner- vous. The crucial importance of the heart has been recognized for ages. However, the cardiovascular system is much more than just the heart, and from a scientific and medical standpoint, it is important to understand why this system is so vital to life.

Night and day, minute after minute, our tril- lions of cells take up nutrients and excrete wastes. Although the pace of these exchanges slows dur- ing sleep, they must go on continuously: when they stop, we die. Cells can make such exchanges

only with the interstitial fluid in their immediate vicinity. Thus, some means of changing and “refreshing” these fluids is necessary to renew the nutrients and prevent pollution caused by the buildup of wastes. Like a bustling factory, the body must have a transportation system to carry its various “cargoes” back and forth. Instead of roads, railway tracks, and subways, the body’s delivery routes are its hollow blood vessels.

Most simply stated, the major function of the cardiovascular system is transportation. Using blood as the transport vehicle, the system carries oxygen, nutrients, cell wastes, hormones, and many other substances vital for body homeostasis to and from the cells. The force to move the blood

The Cardiovascular System




The cardiovascular system delivers oxygen and

nutrients to the body tissues and carries away wastes such as carbon dioxide

via blood.

The heart pumps blood throughout the body in blood vessels. Blood flow

requires both the pumping action of the heart and changes in

blood pressure.

If the cardiovascular system cannot perform its

functions, wastes build up in tissues. Body organs fail to function properly,

and then, once oxygen becomes depleted, they will die.


New Building Vocabulary Coaching Activities for this chapter are assignable in

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NEW! What, How & Why chapter previews introduce key examples of anatomy and physiology concepts that will be covered in the chapter. This technique helps learners hone in on what they are studying, how it functions, and why it is important for them to learn.

NEW! Building Vocabulary Coaching Activities in Pearson Mastering A&P help students learn the essential language of A&P.

See p. 382.



Throughout every chapter, the text’s conversational writing style and straightforward explanations have been strengthened with familiar analogies and abundant mnemonic cues to help students learn and remember concepts.

UPDATED! Exceptionally clear photos and illustrations, including dozens of new and improved figures, present concepts and processes at the right level of detail. Many figures from the text are assignable as Art- Labeling Activities in Pearson Mastering A&P.

Unique Concept Links reinforce previously-learned concepts and help students make connec- tions across body systems while learning new material.

Focus on Essential A&P Concepts

Chapter 4: Skin and Body Membranes 137


Cutaneous membrane (skin)


Parietal layer

Visceral layer

Serous fluid

(a) Cutaneous membrane (the skin) covers the body surface.

(d) A fist thrust into a limp balloon demonstrates the relationship between the parietal and visceral serous membrane layers.

(c) Serous membranes line body cavities closed to exterior.

(b) Mucous membranes line body cavities open to the exterior.

Outer balloon wall (comparable to parietal serosa)

Air (comparable to serous cavity)

Inner balloon wall (comparable to visceral serosa)

Figure 4.1 Classes of epithelial membranes.

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282 Essentials of Human Anatomy and Physiology

Figure 7.21 Schematic of ascending (sensory) and descending (motor) pathways between the brain and the spinal cord.

Cerebral cortex (gray matter)


White matter

Interneuron carrying response to motor neuron

Cell body of sensory neuron in sensory ganglion



Sensory receptors

Motor output


Interneuron Motor neuron cell body

Gray matter White matter

Interneuron carrying sensory information to cerebral cortex

Interneuron carrying response to motor neurons

Integration (processing and interpretation of sensory input) occurs

Interneuron carrying sensory information to cerebral cortex

Brain stem


Cervical spinal cord

➔ConCeptLinkThe terms for the connective tissue coverings of a nerve should seem familiar: We discussed similar struc-tures in the muscle chapter (Figure 6.1, p. 209). Names of muscle structures include the root word mys, whereas the root word neuro tells you that the struc- ture relates to a nerve. For example, the endomysium covers one individual muscle fiber, whereas the endo- neurium covers one individual neuron fiber. ➔

Like neurons, nerves are classified according to the direction in which they transmit impulses. Nerves that carry impulses only toward the CNS are called sensory (afferent) nerves, whereas those that carry only motor fibers are motor (efferent) nerves. Nerves carrying both sensory and motor fibers are called mixed nerves; all spi- nal nerves are mixed nerves.

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See p. 137.

See p. 282.



UPDATED! Homeostatic Imbalance discussions are clinical examples that revisit the text’s unique theme by describing how the loss of homeostasis leads to pathology or disease. Related assessment questions are assignable in Pearson Mastering A&P, along with Clinical Case Study coaching activities.

Explore Essential Careers and Clinical Examples

To inspire and inform students who are preparing for future healthcare careers, up-to-date clinical applications are integrated in context with discussions about the human body.

Focus on Careers essays feature conversations with working professionals and explain the relevance of anatomy and physiology course topics across a wide range of allied health careers. Featured careers include:

Ch. 2 Pharmacy Technician Ch. 4 Medical Transcriptionist Ch. 5 Radiologic Technologist Ch. 8 Physical Therapy Assistant Ch. 10 Phlebotomy Technician Ch. 15 Licensed Practical Nurse

Students can visit the Pearson Mastering A&P Study Area for more information about career options that are relevant to studying anatomy and physiology.

See p. 295.

See p. 82.



Pearson Mastering A&P improves results by engaging students before, during, and after class.

Continuous Learning Before, During, and After Class

Instructors can further encourage students to prepare for class by assigning NEW! Building Vocabulary activities, reading questions, art labeling activities, and more.

Before Class

Dynamic Study Modules enable students to study more effectively on their own. With the Dynamic Study Modules mobile app, students can quickly access and learn the concepts they need to be more successful on quizzes and exams. NEW! Instructors can now select which questions to assign to students within each module.



During Class

After Class A wide variety of interactive coaching activities can be assigned to students as homework, including Art-Labeling Activities, Interactive Physiology 2.0 tutorials, Clinical Case Studies, and activities featuring A&P Flix 3-D movie- quality animations of key physiological processes.

with Pearson Mastering A&P

NEW! Learning Catalytics is a “bring your own device” (laptop, smartphone, or tablet) engagement, assessment, and classroom intelligence system. Students use their device to respond to open-ended questions and then discuss answers in groups based on their responses. Visit to learn more.



Media references in the text direct learners to digital resources in the Pearson Mastering A&P Study Area, including practice tests and quizzes, flashcards, a complete glossary, and more.

NEW! Interactive Physiology 2.0

Practice Anatomy Lab (PAL™ 3.0) is a virtual anatomy study and practice tool that gives students 24/7 access to the most widely used lab specimens, including the human cadaver, anatomical models, histology, cat, and fetal pig. PAL 3.0 is easy to use and includes built-in audio pronunciations, rotatable bones, and simulated fill-in-the- blank lab practical exams.

A&P concepts come to life with Pearson Mastering A&P

NEW! Interactive Physiology 2.0 helps students advance beyond memorization to a genuine understanding of complex physiological processes. Fun, interactive tutorials, games, and quizzes give students additional explanations to help them grasp difficult concepts. IP 2.0 features brand-new graphics, quicker navigation, and more robust interactivity.



Access the complete textbook online with the eText on Pearson Mastering A&P

Powerful interactive and customization functions include instructor and student note-taking, highlighting, bookmarking, search, and links to glossary terms.



Additional Support for Students and Instructors

The perfect companion to Essentials of Human Anatomy & Physiology, this engaging interactive workbook helps students get the most out of their study time. The Twelfth Edition includes NEW! crossword puzzles for every chapter, along with coloring activities, self-assessments, “At the Clinic” questions, and unique “Incredible Journey” visualization exercises that guide learners into memorable explorations of anatomical structures and physiological functions.

• All of the figures, photos, and tables from the text in JPEG and PowerPoint® formats, in labelled and unlabeled versions, and with customizable labels and leader lines

• Step-edit Powerpoint slides that present multi-step process figures step-by-step

• Clicker Questions and Quiz Show Game questions that encourage class interaction

• A&PFlix™ animations bring human anatomy and physiology concepts to life

• Customizable PowerPoint® lecture outlines save valuable class prep time

• A comprehensive Instructor’s Guide includes lecture outlines, classroom activities, and teaching demonstrations for each chapter.

• Test Bank provides a wide variety of customizable questions across Bloom’s taxonomy levels. Includes art labeling questions, and available in Microsoft® Word and TestGen® formats.

NEW! Anatomy & Physiology Coloring Workbook Twelfth Edition, Global Edition by Elaine N. Marieb and Simone Brito

The Instructor Resources Area in Pearson Mastering A&P includes the following downloadable tools:

NEW! IN FULL COLOR! Essentials of Human Anatomy & Physiology Laboratory Manual Seventh Edition by Elaine N. Marieb and Pamela B. Jackson

This popular lab manual provides 27 exercises for a wide range of hands-on laboratory experiences, designed especially for a short A&P Lab course. This edition, which includes a Histology Atlas with 55 photomicrographs, features NEW! full-color illustrations, photos, and page design that help students navigate and learn the material faster and easier than ever before. Each concise lab exercise includes a Pre-Lab Quiz, brief background information, integrated learning objectives, student-friendly review sheets, and more.








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Authorized adaptation from the United States edition, entitled Essentials of Human Anatomy & Physiology, 12th edition, ISBN 9780134395326, by Elaine N. Marieb and Suzanne M. Keller, published by Pearson Education © 2018.

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About the Authors

Elaine Marieb After receiving her Ph.D. in zoology from the University of Massachusetts at Amherst, Elaine N. Marieb joined the faculty of the Biological Science Division of Holyoke Community College. While teaching at Holyoke Community College, where many of her students were pursu- ing nursing degrees, she developed a desire to bet- ter understand the relationship between the scientific study of the human body and the clinical aspects of the nursing practice. To that end, while continuing to teach full time, Dr. Marieb pursued her nursing education, which culminated in a Master of Science degree with a clinical specializa- tion in gerontology from the University of Massa- chusetts. It is this experience that has informed the development of the unique perspective and acces- sibility for which her publications are known.

Dr. Marieb has given generously to provide oppor- tunities for students to further their education. She funds the E. N. Marieb Science Research Awards at Mount Holyoke College, which promotes research by undergraduate science majors, and has underwritten renovation of the biology labs in Clapp Laboratory at that college. Dr. Marieb also contributes to the Univer- sity of Massachusetts at Amherst, where she gener- ously provided funding for reconstruction and instrumentation of a cutting-edge cytology research laboratory. Recognizing the severe national shortage of nursing faculty, she underwrites the Nursing Schol- ars of the Future Grant Program at the university. In January 2012, Florida Gulf Coast University named a new health professions facility in her honor. The Dr. Elaine Nicpon Marieb Hall houses several specialized laboratories for the School of Nursing, made possible by Dr. Marieb’s generous support.

Suzanne Keller Suzanne M. Keller began her teaching career while she was still in graduate school at the University of Texas Health Science Center in San Antonio, Texas. Inspired by her life- long passion for learning, Dr. Keller quickly adopted a teaching style focused on translating challenging concepts into easily understood parts using analogies and stories from her own experi- ences. An Iowa native, Dr. Keller uses her expertise to teach microbiology and anatomy and physiol- ogy at Indian Hills Community College, where most of her students are studying nursing or other health science programs.

Dr. Keller values education as a way for students to express their values through the careers they pursue. She supports those endeavors both in and out of the classroom by participating in her local Lions Club, by donating money to the Indian Hills Foundation to fund scholarships, and by financially supporting service-learning trips for students. Dr. Keller also enjoys sponsoring children in need with gifts for the holidays.

Dr. Keller is a member of the Human Anatomy and Physiology Society (HAPS) and the Iowa Acad- emy of Science. Additionally, while engaged as an author, Dr. Keller has served on multiple advisory boards for various projects at Pearson and has authored assignments for the Pearson Mastering A&P online program. When not teaching or writ- ing, Dr. Keller enjoys reading, trav eling, family gatherings, and relaxing at home under the watch- ful eyes of her two canine children.




New to the Twelfth Edition

This edition has been thoroughly updated. New “What, How, Why” art opens each chapter, highlighting key concepts relating to the chapter topic. Other specific chapter-by-chapter changes include the following:

• New colors used in Figure 3.14 DNA images to help students track new and old strands of DNA.

• New description of each chromosome being composed of two sister chromatids.

• New explanation of protein synthesis includes the role of the large ribosomal subunit in peptide bond formation.

• New Figure 3.18 descriptions of nuclei lining up in simple columnar and not lining up in pseudostratified epithelia.

• New description of cell shapes in different layers of stratified epithelia as “squished” and variable.

• New analogy for mucus produced by goblet cells as a “sticky trap” for dust and debris.

• New Figure 3.19 labels for osteocytes, the elastic and collagen fibers in areolar connective tissue, and the fluid matrix of blood; new art for dense fibrous connective tissue.

• New analogy for reticular tissue as “cellular bleachers” where other cells rest to monitor the body.

• Updated Figure 3.21 to include the term neuroglia to describe supporting cells.

• New information added to Figure 3.22: cartilage added to the connective tissue list and two major hallmarks of each of the four tissue types.

• New example of atrophy: when a broken leg is in a cast, lack of use causes muscles to atrophy during healing.

• Revised “A Closer Look: Cancer—An Intimate Enemy” and updated art. • New “Short Answer Essay” questions on the components of the

plasma membrane and their functions and on contrasting cytokinesis, interphase, and mitosis.

• New “Critical Thinking and Clinical Application” question on IV fluids and tonicity.

• New “Did You Get It?” questions throughout the chapter.

Chapter 4: Skin and Body Membranes • New Figure 4.1 on epithelial membranes. • New description of sensory receptors as part of nervous system

including a list of the stimuli detected. • New text updates on Figure 4.4 on epidermal structure; included a

new figure question on stratum lucidum. • New analogy for epidermal dendritic cells as “sentries” guarding

the skin. • New photo of stage 2 decubitus ulcer added to Homeostatic

Imbalance 4.2. • New layout for Figure 4.7 combining scanning electron micrograph

of hair shaft with existing art of the hair root and follicle. • New discussion of fourth-degree burns. • New criteria for determining whether a burn is critical, including

circumferential burns, burns of the airway, and burns to the genital area.

• New images of basal cell and squamous cell carcinoma in Figure 4.11.

• New component added to ABCDE rule: now includes “Evolution,” changes in a skin lesion over time.

• New “Short Answer Essay” questions on the risks of full-thickness burns, contrasting eccrine and apocrine sweat glands, and the relative severity of different skin infections.

• New “Critical Thinking and Clinical Application” question on burns. • New “Did You Get It?” questions throughout the chapter.

Chapter 5: The Skeletal System • Updated description of long bones. • New analogy comparing lubrication over articular cartilage at

joints to a slick marble floor.

Chapter 1: The Human Body: An Orientation • Updated description of the integumentary system to include

vitamin D production in the presence of sunlight. • Updated definition of the term crural to specify the anterior leg,

or shin. • New “Critical Thinking and Clinical Application” question on blood

clotting and feedback regulation. • New “Critical Thinking and Clinical Application” question on using

anatomical language to describe the location of a spinal injury and identifying the best medical imaging technique to diagnose a spinal problem.

• Updated “A Closer Look: Medical Imaging” with new discussion and images of mammogram and bone densitometry.

• New “Did You Get It?” questions throughout the chapter.

Chapter 2: Basic Chemistry • New example of atomic symbol and Latin derivative for potassium. • Revised discussion of hydrogen bonds to clarify that electrons are

not involved in this type of bond as they are in covalent and ionic bonds.

• New example of importance of hydrogen bond in holding DNA strands together.

• All references to hydroxyl ion have been corrected to hydroxide ion. • New sports analogies for acids and bases: putting electrons “in the

game,” to represent free protons versus taking electrons “out of the game,” to represent binding a proton so it cannot contribute to a shift in pH.

• New “Did You Get It?” question part on the difference in pH between solutions at pH 11 and pH 5.

• Introduced concepts of hydrophilic and hydrophobic in discussion of phospholipids to help explain the functions of the polar head and fatty acid tails in cell membranes.

• Updated “Did You Get It?” question on lipids to include both phospholipids and cholesterol as cell membrane components.

• New analogy comparing the alpha (α)-helix to a metal spring. • New analogy comparing a beta (β)-sheet to a pleated skirt, or

paper folded into a fan. • New analogy comparing enzymes and substrates to scissors and

paper, respectively. • New description of RNA function as DNA’s “molecular assistant.” • New shorthand symbols for messenger (mRNA), transfer (tRNA)

and ribosomal (rRNA) added. • New analogy comparing glucose and ATP to crude oil and gasoline;

energy must be in the proper form before it can be used by cells. • New explanation of why the terminal phosphate bonds in ATP are

high energy. • New “Critical Thinking and Clinical Application” question on sickle

cell anemia.

Chapter 3: Cells and Tissues • New description of the principle of complementarity. • New information about how mitochondria divide. • New “cargo” in the form of a membrane-bound receptor protein

added to pathway 2 of Figure 3.6. • New analogy for lysosomes as “cellular stomachs.” • New art of plasma membrane and new detail of mitochondrial

function including aerobic respiration in Table 3.1. • New analogy of dust “crowd surfing” on the mucus that cilia carry

from the lungs. • New description of neuron function includes production of




• Updated descriptions of red and yellow bone marrow. • Updated descriptions of sagittal and coronal sutures. • Updated description of the capitulum of the humerus. • New analogy comparing the trochlea meeting the trochlear notch

to a curved “tongue-in-groove” joint. • Updated description of buttock injections to include the

consequences of hitting a nerve. • Updated description of a synovial membrane to include areolar

connective tissue. • Updated description of cartilaginous joints. • New description of saddle joints including a reference to

opposable thumbs. • Updated list of triggers for rheumatoid arthritis. • Discussion of the fetal skull and fontanels moved to the

Developmental Aspects section. • New analogy likening skulls of small children to “bobble heads.” • Updated review question on bones that articulate with the

sphenoid to reflect only bones shown in the figures of Chapter 5. • Updated “Short Answer Essay” question on synovial joints to

include osteoarthritis. • New “Short Answer Essay” question contrasting the foramen

magnum and obturator foramen. • New “Critical Thinking and Clinical Application” question on gouty

arthritis. • New statistics, information, and images added to “A Closer Look:

Joint Ventures.” • Updated description of comminuted fractures on Table 5.2. • Updated Figure 5.6 to include osteoblasts and osteoclasts in the

descriptions of bone addition and resorption, respectively. • Updated Systems In Sync with respect to the descriptions of

relationships of cardiovascular and muscular systems to the skeletal system.

Chapter 6: The Muscular System • Updated descriptions of tendons and aponeuroses. • New analogy about running to explain the difference between the

contraction of skeletal muscle (fast) versus smooth muscle (slow). • Updated description of a sarcomere to include its role as the

structural and functional unit of muscle. • Added discussion of titin to the description of a sarcomere as the

elastic filament that attaches myosin to the Z disc. • New Homeostatic Imbalance on ALS (amyotropic lateral sclerosis,

or Lou Gehrig’s disease). • New “Did You Get It?” question on the roles of calcium in muscle

contraction. • Updated descriptions of cross-bridge formation and the sliding

filament theory, including the role of ATP. • New link to IP Essentials for the sliding filament theory. • New description of flaccid versus spastic paralysis. • New mnemonic device for adduction: “add” back to the body by

moving toward the trunk (midline). • New descriptions of dorsiflexion and plantar flexion with …

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This contains 100% correct material for UMUC Biology 103 LAB01. However, this is an Answer Key, which means, you should put it in your own words. Here is a sample….