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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
- Veröffentlichungsjahr: 2017
Learn about the human body from the inside out Some people think that knowing about what goes on inside the human body can sap life of its mystery--which is too bad for them. Anybody who's ever taken a peak under the hood knows that the human body, and all its various structures and functions, is a realm of awe-inspiring complexity and countless wonders. The dizzying dance of molecule, cell, tissue, organ, muscle, sinew, and bone that we call life can be a thing of breathtaking beauty and humbling perfection. Anatomy & Physiology For Dummies combines anatomical terminology and function so you'll learn not only names and terms but also gain an understanding of how the human body works. Whether you're a student, an aspiring medical, healthcare or fitness professional, or just someone who's curious about the human body and how it works, this book offers you a fun, easy way to get a handle on the basics of anatomy and physiology. * Understand the meaning of terms in anatomy and physiology * Get to know the body's anatomical structures--from head to toe * Explore the body's systems and how they interact to keep us alive * Gain insight into how the structures and systems function in sickness and health Written in plain English and packed with beautiful illustrations, Anatomy & Physiology For Dummies is your guide to a fantastic voyage of the human body.
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Anatomy & Physiology For Dummies®, 3rd Edition
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Copyright © 2017 by John Wiley & Sons, Inc., Hoboken, New Jersey
Published simultaneously in Canada
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Anatomy & Physiology For Dummies®
To view this book's Cheat Sheet, simply go to www.dummies.com and search for “Anatomy & Physiology For Dummies Cheat Sheet” in the Search box.
Table of Contents
Cover
Introduction
About This Book
Foolish Assumptions
Icons Used in This Book
Beyond the Book
Where to Go from Here
Part 1: Locating Physiology on the Web of Knowledge
Chapter 1: Anatomy and Physiology: The Big Picture
Scientifically Speaking
A Little Chat about Jargon
Looking at the Body from the Proper Perspective
Organizing Yourself on Many Levels
Chapter 2: What Your Body Does All Day
Transferring Energy: A Body’s Place in the World
Building Up and Breaking Down: Metabolism
Staying in Range: Homeostasis
Growing, Replacing, and Renewing
Chapter 3: A Bit about Cell Biology
The Functions of Cells
Seeing the Inside of Eukaryotic Cells
Building Blocks That Build You
Genes and Genetic Material
The Cell Cycle
Organizing Cells into Tissues
Part 2: Sizing Up the Structural Layers
Chapter 4: Getting the Skinny on Skin, Hair, and Nails
Functions of the Integument
Structure of the Integument
Accessorizing Your Skin
Your Skin Saving You
Pathophysiology of the Integument
Chapter 5: Scrutinizing the Skeletal System
Reporting for Duty: The Jobs of Your Skeleton
Checking Out the Skeleton’s Makeup
Bone Growth and Remodeling
The Axial Skeleton
The Appendicular Skeleton
Joints and the Movements They Allow
Pathophysiology of the Skeletal System
Chapter 6: Muscles: Setting You in Motion
Functions of the Muscular System
Talking about Tissue Types
Getting a Grip on the Sliding Filament
Naming the Skeletal Muscles
Pathophysiology of the Muscular System
Part 3: Talking to Yourself
Chapter 7: The Nervous System: Your Body’s Circuit Board
Integrating the Input with the Output
Integrated Networks
Thinking about Your Brain
Transmitting the Impulse
Making Sense of Your Senses
Pathophysiology of the Nervous System
Chapter 8: The Endocrine System: Releasing Chemical Messages
Homing In on Hormones
Grouping the Glands
Pathophysiology of the Endocrine System
Part 4: Exploring the Inner Workings of the Body
Chapter 9: The Cardiovascular System: Getting Your Blood Pumping
Getting Substances from Here to There
Carrying Cargo: Your Blood and What’s in It
Looking at Your Blood Vessels
Cardiac Anatomy
Cardiac Cycle
Physiology of Circulation
Pathophysiology of the Cardiovascular System
Chapter 10: The Respiratory System: Breathing Life into Your Body
Functions of the Respiratory System
Nosing around Your Respiratory Anatomy
Breathing: Everybody’s Doing It
Gas Exchange
Pathophysiology of the Respiratory System
Chapter 11: The Digestive System: Beginning the Breakdown
Functions of the Digestive System
The Alimentary Canal
Accessory Organs
Pathophysiology of the Digestive System
Chapter 12: The Urinary System: Cleaning Up the Act
Functions of the Urinary System
Structures of the Urinary System
The Yellow River
Maintaining Homeostasis
Pathophysiology of the Urinary System
Chapter 13: The Lymphatic System: Living in a Microbe Jungle
Functions of the Lymphatic System
Loving Your Lymphatic System
Identifying Immune System Cells
Examining Immune System Molecules
Immune System Mechanisms
Adaptive Immunity
Pathophysiology of the Immune System
Part 5: Life’s Rich Pageant: Reproduction and Development
Chapter 14: The Reproductive System
Functions of the Reproductive System
Producing Gametes
The Female Reproductive System
The Male Reproductive System
Pausing for Pregnancy
Pathophysiology of the Reproductive System
Chapter 15: Change and Development over the Life Span
Programming Development
Development before Birth
The Human Life Span
Part 6: The Part of Tens
Chapter 16: Ten (Or So) Chemistry Concepts Related to Anatomy and Physiology
Energy Can Neither Be Created Nor Destroyed
Everything Falls Apart
Everything’s in Motion
Probability Rules
Polarity Charges Life
Water Is Special
Fluids and Solids
Under Pressure
Redox Reactions Transfer Electrons
Chapter 17: Ten Phabulous Physiology Phacts
Unique to You: Hands, Fingers, Thumbs
Nothing’s Better than Mother’s Milk
It’s Apparent: Your Hair Is Different
The Only Thing You Have to Fear Is …
You Smell Well!
Microbes: We Are Their World
The Pesky Appendix
Talkin’ about Breath Control
Taking Your First Breath
Is Blood Really Blue?
About the Authors
Supplemental Images
Connect with Dummies
End User License Agreement
Guide
Cover
Table of Contents
Begin Reading
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Introduction
Congratulations on your decision to study human anatomy and physiology. The knowledge you gain from your study is of value in many aspects of your life.
Begin with the most obvious: the social value of this knowledge. Human anatomy and physiology is always a suitable topic of discussion in social situations because it allows people to talk about their favorite subject (themselves) in a not-too-personal way. Thus, some particularly interesting detail of anatomy and physiology is an ideal conversation opener with attractive strangers or horrifying shirt-tail relatives. (First, though, be completely clear in your mind about the boundary between scientific anatomy and physiology on the one hand and personal clinical details on the other.) Choose the specific topic carefully to be sure of having your intended effect. For example, telling a young boy that he has the same density of hair follicles on his body as a chimp does will probably please him. Telling his teenage sister the same thing may alienate her. Use this power carefully!
A little background in anatomy and physiology should be considered a valuable part of anyone’s education. Health and medical matters are part of world events and people’s daily lives. Basic knowledge of anatomy and physiology gets you started when trying to make sense of the news about epidemics, novel drugs and medical devices, and purported environmental hazards, to name just a few examples. Anatomy and physiology prepare you to be a more well-rounded, knowledgeable person and will help you be a better parent, spouse, care-giver, neighbor, friend, or colleague.
Knowledge of anatomy and physiology may also benefit your own health. Sometimes, comprehension of a particular fact or concept can help drive a good decision about long-term health matters, like the demonstrated benefits of exercise, or it may help you take appropriate action in the context of a specific medical problem, like an infection, an infarction, a cut, or a muscle strain. You may understand your doctors’ instructions better during a course of treatment, which may give you a better medical outcome.
About This Book
This book guides you on a quick walk-through of human anatomy and physiology. It doesn’t have the same degree of technical detail as a textbook. It contains relatively little in the way of lists of important anatomical structures, for instance.
We expect that most readers are using this book as a complementary resource for course work in anatomy and physiology at the high-school, college, or career-training level. Most of the information overlaps with the information available in your other resources. However, sometimes a slightly different presentation of a fact or of the relationship between facts can lead to a small “aha!” Some technical details in your more comprehensive resources may become easier to master after that. Consider reading the relevant chapter prior to class. That way, when your instructor covers the content, it’ll be more likely to stick!
The goals of this book are to be informal but not unscientific; brief but not sketchy; and information-rich but accessible to readers at many levels. We’ve tried to present a light but serious survey of human anatomy and physiology that you can enjoy for the sake of the information it imparts and that will help you perform well on your tests. As always, the reader is the judge of its success.
You won’t find clinical information in this book. Chapters 4 through 15 have a pathophysiology section that uses disorders and disease states to explore the details of some physiological processes, but this book contains nothing related to patient care or self-care. It’s also not a health and wellness manual or any kind of lifestyle book.
Within this book, you may note that some web addresses break across two lines of text. If you’re reading this book in print and want to visit one of these web pages, simply key in the web address exactly as it’s noted in the text, pretending as though the line break doesn’t exist. If you’re reading this as an e-book, you’ve got it easy — just click the web address to be taken directly to the web page.
Foolish Assumptions
When we wrote this book, we tried to keep you in mind. We’re guessing that you fall into one of these categories:
Formal student:
You’re a high-school or college student enrolled in a basic anatomy and physiology course for credit, or a student in a career-training program for a certification or credential. You need to pass an exam or otherwise demonstrate understanding and retention of data, terminology, and concepts in human anatomy and physiology.
Informal student:
You’re not enrolled in a credit course, but gaining some background in human anatomy and physiology is important to you for personal or professional reasons.
Casual reader:
Here you are with a book on your hands and a little time to spend reading it. And it’s all about you!
Icons Used in This Book
The little round pictures that you see in the margins throughout this book are icons that alert you to several different kinds of information.
The Tip icon lets you know what you can do to improve your understanding of an anatomical structure.
The Remember icon serves to jog your memory. Sometimes, the text is information that we think you should permanently store in your anatomy and physiology file. Other times, the info here makes a connection between what you’re reading and related information elsewhere in the book.
The Technical Stuff icon flags extra information that takes your understanding of anatomy or physiology to a slightly deeper level, but the text isn’t essential for understanding the organ system under discussion.
Beyond the Book
In addition to the material in the print or e-book you’re reading right now, this product also comes with some access-anywhere goodies on the web. Check out the free Cheat Sheet for more on everything from anatomical terms to the anatomical planes of the body and more. To get this Cheat Sheet, simply go to www.dummies.com and type Anatomy & Physiology For Dummies Cheat Sheet in the Search box.
Where to Go from Here
If you’re a formal student (that is, one who’s enrolled or planning to enroll in a formal course in human anatomy and physiology), you may get the most benefit by becoming familiar with this book a week or two before your course begins. Flip to the color plates in the center of the book to get started. The illustrations, charming as well as scientific, are arranged to follow the flow of the text, and the callouts indicate important technical terminology.
Then peruse the book as you would any science book; look at the table of contents and the index. Read the Introduction. (See, you’ve started already!) Then start reading chapters. Look at the figures, especially the color plates, as you read. You’ll probably be able to get through the entire book in just a couple of sittings. Then go back and reread chapters you found particularly interesting, relevant, or puzzling. Study the illustrations carefully. The line drawings as well as the color plates are keyed closely to the text and often clarify important facts. Pay attention to technical terminology; your instructors will use it and expect you to use it, too.
If you’re a casual reader (you’re not enrolled in a formal course in anatomy and physiology and have little or no background in biology), the following approach may work well. Take some time with the color plates at the center of the book. They give you a good feel for the flow of information (and a good feeling about the human body). Then read the book straight through, beginning to end. Look at the figures, especially the color plates, as you read. After you’ve been through it all quickly once, go back and reread chapters you found particularly interesting, relevant, or puzzling. Make a habit of studying the illustrations while reading the related text. Don’t sweat too much over terminology; for your purposes, saying “of my lungs” communicates as well as “pulmonary.” (If you also enjoy word games, though, you can get started on a whole new vocabulary.) Keep the book handy for future reference the next time you wonder what the heck they’re talking about in a TV drug ad. The color plates alone make it worth space on your bookshelf.
Part 1
Locating Physiology on the Web of Knowledge
IN THIS PART …
Get acquainted with the basics of anatomy and physiology.
Find out about metabolism — all the chemical reactions that keep you alive.
Learn how we keep everything in check — maintaining balance in our bodies.
Brush up on biochemistry.
Find the fundamentals of cell biology.
See how cells organize into tissues.
Chapter 1
Anatomy and Physiology: The Big Picture
IN THIS CHAPTER
Placing anatomy and physiology in a scientific framework
Jawing about jargon
Looking at anatomy: planes, regions, and cavities
Delineating life’s levels of organization
Human anatomy is the study of the human body’s structures — all the parts that make up the physical body itself. Physiology is the study of how the human body works; how all the anatomical parts function together to keep an individual alive. Anatomy and physiology are bound together. As such, this book abandons the old technique of learning all the anatomy and then the physiology as though the two were independent. Here, we examine each body system, identify the structures within that system, and then discuss their functions.
Scientifically Speaking
Human anatomy and physiology are closely related to biology, which is the study of living things and their relationship with the rest of the universe, including all other living things. If you’ve studied biology, you understand the basics of how organisms operate. Anatomy and physiology narrow the science of biology by looking at the specifics of one species: Homo sapiens.
Anatomy is form; physiology is function. You can’t talk about one without talking about the other.
THE ANATOMY AND PHYSIOLOGY OF EVERYTHING ELSE
Scientifically speaking, human biology isn’t more or less complex, specialized, or cosmically significant than the biology of any other species, and all are interdependent. Every species of animal, plant, and fungus on the planet has both anatomy and physiology. So does each species of protist (one-celled creatures, like amoebae) and bacteria. At the cellular level (see Chapter 3), all these groups are astoundingly similar. At the levels of tissues, organs, and organ systems, plants are very different from animals, and both plants and animals are equally dissimilar to fungi.
Each of these major groups, called a kingdom, has its own characteristic anatomy and physiology. It’s evident at a glance to everyone at the beach that a starfish and a human are both animals, while the seaweed in the tide pool and the cedar tree on the shoreline are both plants. Obvious details of anatomy (the presence or absence of bright green tissue) and physiology (the presence or absence of movement) tell that story. The different forms within each kingdom have obvious differences as well: The cedar must stand on the shore, but the seaweed would die there. The starfish can move from one place to another within a limited range, while humans can (theoretically) go anywhere on the planet and survive there for at least a while. Scientists use these differences to classify organisms into smaller and smaller groups within the kingdom, until each organism is classified into its own special group.
Not that human anatomy and physiology aren’t special. Humans’ bipedal posture and style of locomotion are very special . There’s nothing like a human hand anywhere except at the end of a human arm. Perhaps most special of all is the anatomy and physiology that allows (or maybe compels) humans to engage in science: our highly developed brain and nervous system. It’s entirely within the norms of evolutionary theory that people would be most interested in their own species, so more humans find human anatomy and physiology more interesting than the anatomy and physiology of the tree. From here on, we’re restricting our discussion to the anatomy and physiology of our own species.
How anatomy and physiology fit into science
Biologists base their work on the assumption that every structure and process, no matter how tiny in scope, must somehow contribute to the survival of the individual. So each process — and the chemistry and physics that drive it — must help keep the individual alive and meeting the relentless challenges of a continually changing environment. Although anatomy and physiology combined are classified as a subsection of biology, it’s truly an interdisciplinary science.
Human pathophysiology is the study of “human anatomy and physiology gone wrong.” (The prefix path- is Greek for “suffering.”) It’s the interface of human biology and medical science. Clinical medicine is the application of medical science to alleviate an anatomical or physiological problem in an individual human.
Pathophysiology and clinical medicine aren’t the subject of this book, but we discuss applications of them when they’re particularly relevant to the physiology. You’re probably using this book to supplement instructional material in career training for a clinical environment, so the information throughout the book is slightly slanted in that direction. We chose the conditions that we briefly examine to demonstrate some characteristic of the system, especially its interaction with other systems, but we don’t discuss diagnosis or treatment.
TAXONOMY OF HOMO SAPIENS
Taxonomy is the science that seeks to classify and organize living things, expressed as a series of mutually exclusive categories. The highest (most inclusive) category is domain, of which there are three: Archea, Eubacteria, Eukaryota. Each of these domains is split into kingdoms, which are further divided until each individual organism is its own unique species. Outside of bacteria, all living things fall under the Eukaryota domain; the kingdoms are: Protista, Fungi, Plantae, and Animalia. Within each kingdom, the system classifies each organism into the hierarchical subgroups (and sometimes sub-subgroups) of phylum, class, order, family, genus, and species. Here’s the breakdown of humankind:
Kingdom Animalia: All animals.
Phylum Chordata: Animals that have a number of structures in common, particularly the notochord, a rodlike structure that forms the body’s supporting axis.
Subphylum Vertebrata: Animals with backbones.
Superclass Tetrapoda: Four-footed vertebrates.
Class Mammalia: Tetrapods with hair. Other classes of the vertebrata are Pisces (fish), Amphibia (frogs), Aves (birds), and Reptilia (scaly things).
Order Primates: Mammals with more highly developed brains, flexible hips and shoulders, and prehensile hands and feet (able to grasp).
Superfamily Hominoidea: Apes (chimpanzees, gorillas, orangutans, humans).
Family Hominidae: Great apes, including humans.
Genus Homo: The human species is the only surviving species of our genus, though this genus included several species in the evolutionary past.
Species Sapiens: All species are given a two-part Latin name, in which the genus name comes first and a species epithet comes second. The biologists who name species sometimes try to use a descriptor in the epithet. For humans, they could have chosen “bipedal” or “talking” or “hairless,” but they chose “thinker.”
Variety Sapiens: Some species get a “varietal” name, usually indicating a difference that’s obvious but not necessarily important from an evolutionary point of view. The human species has one other variety, Homo sapiens neanderthalensis, which has been extinct for tens of thousands of years. All humans living since then are of one species variety, Homo sapiens sapiens. In the evolutionary classification of humans, there’s no biologically valid category below species variety.
Anatomy, gross and otherwise
Some biologists specialize in the anatomy and physiology of animals at various hierarchical levels (horses, fish, frogs) or particular organs (mammalian circulatory systems, olfaction in fish, insect hormones). Some focus solely on humans, others concentrate on other species, and still others examine the areas of overlap between humans and other animal species. These various areas of study contribute to our knowledge of biology in general and have important applications in clinical medicine. The work of anatomists contributes to medical advances, such as improved surgical techniques and the development of bioengineered prostheses.
Throughout this book, you encounter some information from each major subset of anatomy, including
Gross anatomy:
The study of the large parts of an animal body — any animal body — that can be seen with the unaided eye. That’s the aspect of anatomy we concentrate on in this book.
Histologic anatomy:
The study of different tissue types and the cells that comprise them. Histologic anatomists use a variety of microscopes to study the cells and tissues that make up the body.
Developmental anatomy:
The study of the life cycle of the individual, from fertilized egg through adulthood, senescence (aging), and death. Body parts change throughout the life span. For information about human developmental anatomy, see
Chapter 15
.
Comparative anatomy:
The study of the similarities and differences among the anatomical structures of different species, including extinct species. Information from comparative anatomy can help scientists understand the human body’s structures and processes. For example, comparing the anatomy of apes to that of humans shows us what particular structures allow for our ability to walk upright on two legs.
A Little Chat about Jargon
Why does science have so many funny words? Why can’t scientists just say what they mean, in plain English? Good question, with a two-part answer.
Creating better communication
Scientists need to be able to communicate with others in their field. They say what they mean (most of them, most of the time, to the best of their ability), but what they mean can’t be said in the English language that people use to talk about routine daily matters.
Like people working in every field, scientists develop vocabularies of technical terminology and other forms of jargon so they can better communicate with other scientists. It’s important that the scientist sending the information and the scientist receiving it both use the same words to refer to the same phenomenon. To understand anatomy and physiology, you must know and use the same terminology, too. The jargon can be overwhelming at first, but understanding the reason for it and taking the time to learn it before diving into the complicated content will make your learning experience less painful.
Establishing precise terminology
The second part of the answer starts with a little chat about jargon. Contrary to the belief of some, jargon is a good thing. Jargon is a set of words and phrases that people who know a lot about a particular subject use to talk together. There’s jargon in every field (scientific or not), every workplace, every town, even every home. Families and close friends almost always use jargon in conversations with one another. Plumbers use jargon to communicate about plumbing. Anatomists and physiologists use jargon, much of which is shared with medicine and other fields of biology, especially human biology.
Scientists try to create terminology that’s precise and easy to understand by developing it systematically. That is, they create new words by putting together existing and known elements. They use certain syllables or word fragments over and over to build new terms. With a little help from this book, you’ll soon start to recognize some of these fragments. Then you can put the meanings of different fragments together and accurately guess the meaning of a term you’ve never seen before, just as you can understand a sentence you’ve never read before. Table 1-1 gets you started, listing some word fragments related to the organ systems we cover in this book.
TABLE 1-1 Technical Anatomical Word Fragments
Body System
Root or Word Fragment
Meaning
Skeletal system
os-, oste-; arth-
bone; joint
Muscular system
myo-, sarco-
muscle, striated muscle
Integument
derm-
skin
Nervous system
neur-
nerve
Endocrine system
aden-, estr-
gland, steroid
Cardiovascular system
card-, angi-, hema-, vaso-
heart (muscle), vessel, blood vessels
Respiratory system
pulmon-, bronch-
lung, windpipe
Digestive system
gastr-, enter-, dent-, hepat-
stomach, intestine, teeth, liver
Urinary system
ren-, neph-; ur-
kidney; urinary
Lymphatic system
lymph-, leuk-, -itis
lymph, white, inflammation
Reproductive system
andr-, uter-
male, uterine
But why do these terms have to be Latin and Greek syllables and word fragments? Why should you have to dissect and put back together a term like iliohypogastric? Well, the terms that people use in common speech are understood slightly differently by different people, and the meanings are always undergoing change. Not so long ago, for example, no one speaking plain English used the term laptop to refer to a computer or hybrid to talk about a car. It’s possible that, not many years from now, almost no one will understand what people mean by those words. Scientists, however, require consistency and preciseness to describe the things they talk about in a scientific context. The relative vagueness and changeability of terms in plain English makes this impossible. In contrast, Greek and Latin stopped changing centuries ago: ilio, hypo, and gastro have the same meaning now as they did 200 years ago.
Every time you come across an anatomical or physiological term that’s new to you, see if you recognize any parts of it. Using this knowledge, go as far as you can in guessing the meaning of the whole term. After studying Table 1-1 and the other vocabulary lists in this chapter, you should be able to make some pretty good guesses.
Looking at the Body from the Proper Perspective
Remember that story about a friend of a friend that went in to have a foot amputated only to awaken from surgery to find they removed the wrong one? This story highlights the need for a consistent perspective to go with the jargon. Terms that indicate direction make no sense if you’re looking at the body the wrong way. You likely know your right from your left, but ignoring perspective can get you all mixed up. This section shows you the anatomical position, planes, regions, and cavities, as well as the main membranes that line the body and divide it into major sections.
Getting in position
Stop reading for a minute and do the following: Stand up straight. Look forward. Let your arms hang down at your sides and turn your palms so they’re facing forward. You are now in anatomical position (see Figure 1-1). Unless you are told otherwise, any reference to location (diagram or description) assumes this position. Using anatomical position as the standard removes confusion.
Illustration by Kathryn Born, MA
FIGURE 1-1: The standard anatomical position.
The following list of common anatomical descriptive terms (direction words) that appear throughout this and every other anatomy book may come in handy:
Right:
Toward the patient’s right
Left:
Toward the patient’s left
Anterior/ventral:
Front, or toward the front of the body
Posterior/dorsal:
Back, or toward the back of the body
Medial:
Toward the middle of the body
Lateral:
On the side or toward the side of the body
Proximal:
Nearer to the point of attachment or the trunk of the body
Distal:
Farther from the point of attachment or the trunk of the body (think “distance”)
Superficial:
Nearer to the surface of the body
Deep:
Farther from the surface of the body
Superior:
Above or higher than another part
Inferior:
Below or lower than another part
Notice that this list of terms is actually a series of pairs. Learning them as pairs is more effective and useful.
Dividing the anatomy
If you’ve taken geometry, you know that a plane is a flat surface and that a straight line can run between two points on that flat surface. Geometric planes can be positioned at any angle. In anatomy, generally three planes are used to separate the body into sections. Figure 1-2 shows you what each plane looks like. The reason for separating the body with imaginary lines — or making actual cuts referred to as sections — is so that you know which half or portion of the body or organ is being discussed. When identifying or comparing structures, you need to know your frame of reference. The anatomical planes are as follows:
Frontal plane:
Divides the body or organ into anterior and posterior portions — think front and back.
Sagittal plane:
Divides the body or organ lengthwise into right and left sections. If the vertical plane runs exactly down the middle of the body, it’s referred to as the
midsagittal plane.
Transverse plane:
Divides the body or organ horizontally, into superior and inferior portions — think top and bottom. Diagrams from this perspective can be quite disorienting. You can think of the body like a music box that has a top that opens on a hinge. The transverse plane is where the music box top separates from the bottom of the box. Imagine that you open the box by lifting the lid and are looking down at the contents.
Illustration by Kathryn Born, MA
FIGURE 1-2: Planes of the body: frontal, sagittal, and transverse.
Anatomical planes do not always create two equal portions and can “pass through” the body at any angle. The three planes provide an important reference but don’t expect the structures of the body, and especially the joints, to line up or move along the standard planes and axes.
Mapping out your regions
The anatomical planes orient you to the human body, but regions (shown in Figure 1-3) compartmentalize it. Just like on a map, a region refers to a certain area. The body is divided into two major portions: axial and appendicular. The axial body runs right down the center (axis) and consists of everything except the limbs, meaning the head, neck, thorax (chest and back), abdomen, and pelvis. The appendicular body consists of appendages, otherwise known as upper and lower extremities (which you call arms and legs).
Illustration by Kathryn Born, MA
FIGURE 1-3: The body’s regions: Anterior view (a), Posterior view (b).
Here’s a list of the axial body’s main regions:
Head and neck
Cephalic (head)
Cervical (neck)
Cranial (skull)
Frontal (forehead)
Nasal (nose)
Occipital (base of skull)
Oral (mouth)
Orbital/ocular (eyes)
Thorax
Axillary (armpit)
Costal (ribs)
Deltoid (shoulder)
Mammary (breast)
Pectoral (chest)
Scapular (shoulder blade)
Sternal (breastbone)
Vertebral (backbone)
Abdomen
Abdominal (abdomen)
Gluteal (buttocks)
Inguinal (bend of hip)
Lumbar (lower back)
Pelvic (area between hipbones)
Perineal (area between anus and external genitalia)
Pubic (genitals)
Sacral (end of vertebral column)
Here’s a list of the appendicular body’s main regions:
Upper extremity
Antebrachial (forearm)
Antecubital (inner elbow)
Brachial (upper arm)
Carpal (wrist)
Cubital (elbow)
Digital (fingers/toes)
Manual (hand)
Palmar (palm)
Lower extremity
Crural (shin, front of lower leg)
Femoral (thigh)
Patellar (front of knee)
Pedal (foot)
Plantar (arch of foot)
Popliteal (back of knee)
Sural (calf, back of lower leg)
Tarsal (ankle)
Casing your cavities
If you remove all the internal organs, the body is empty except for the bones and other tissues that form the space where the organs were. Just as a dental cavity is a hole in a tooth, the body’s cavities are “holes” where organs are held (see Figure 1-4). The two main cavities are the dorsal cavity and the ventral cavity.
Illustration by Kathryn Born, MA
FIGURE 1-4: The body’s cavities.
The dorsal cavity consists of two cavities that contain the central nervous system. The first is the cranial cavity, the space within the skull that holds your brain. The second is the spinal cavity (or vertebral cavity), the space within the vertebrae where the spinal cord runs through your body.
The ventral cavity is much larger and contains all the organs not contained in the dorsal cavity. The ventral cavity is divided by the diaphragm into smaller cavities: the thoracic cavity, which contains the heart and lungs, and the abdominopelvic cavity, which contains the organs of the abdomen and the pelvis. The thoracic cavity is divided into the right and left pleural cavities (lungs) and the pericardial cavity (heart). The abdominopelvic cavity is also subdivided. The abdominal cavity contains organs such as the stomach, liver, spleen, and most of the intestines. The pelvic cavity contains the reproductive organs, the bladder, the rectum, and the lower portion of the intestines.
Additionally, the abdomen is divided into quadrants and regions. The mid-sagittal plane and a transverse plane intersect at an imaginary axis passing through the body at the umbilicus (navel or belly button). This axis divides the abdomen into quadrants (four sections). Putting an imaginary cross on the abdomen creates the right upper quadrant, left upper quadrant, right lower quadrant, and left lower quadrant. Physicians take note of these areas when a patient describes symptoms of abdominal pain.
The regions of the abdominopelvic cavity include the following:
Epigastric:
The central part of the abdomen, just above the navel
Hypochondriac:
Doesn’t moan about every little ache and illness but lies to the right and left of the epigastric region and just below the cartilage of the rib cage (
chondral
means “cartilage,” and
hypo-
means “below”)
Umbilical:
The area around the umbilicus
Lumbar:
Forms the region of the lower back to the right and left of the umbilical region
Hypogastric:
Below the stomach and in the central part of the abdomen, just below the navel
Iliac:
Lies to the right and left of the hypogastric regions near the hipbones
Organizing Yourself on Many Levels
Anatomy and physiology are concerned with the level of the individual body, what scientists call the organism. However, you can’t merely focus on the whole and ignore the role of the parts. The life processes of the organism are built and maintained at several physical levels, which biologists call levels of organization: the cellular level, the tissue level, the organ level, the organ system level, and the organism level (see Figure 1-5). In this section, we review these levels, starting at the bottom.
Illustration by Kathryn Born, MA
FIGURE 1-5: Levels of organization in the human body.
Level I: The cellular level
If you examine a sample of any human tissue under a microscope, you see cells, possibly millions of them. All living things are made of cells. In fact, “having a cellular level of organization” is inherent in any definition of “organism.” The work of the body actually occurs in the cells; for example, your whole heart beats to push blood around your body because of what happens inside the cells that create its walls.
Level II: The tissue level
A tissue is a structure made of many cells — usually several different kinds of cells — that performs a specific function. Tissues are divided into four categories:
Connective tissue
serves to support body parts and bind them together. Tissues as different as bone and blood are classified as connective tissue.
Epithelial tissue (epithelium)
functions to line and cover organs as well as carry out absorption and secretion. The outer layer of the skin is made up of epithelial tissue.
Muscle tissue
— surprise! — is found in the muscles, which allow your body parts to move; in the walls of hollow organs (such as intestines and blood vessels) to help move their contents along; and in the heart to move blood along via the acts of contraction and relaxation. (Find out more about muscles in
Chapter 6
.)
Nervous tissue
transmits impulses and forms nerves. Brain tissue is nervous tissue. (We talk about the nervous system in
Chapter 7
.)
Level III: The organ level
An organ is a group of tissues assembled to perform a specialized physiological function. For example, the stomach is an organ that has the specific physiological function of breaking down food. By definition, an organ is made up of at least two different tissue types; many organs contain tissues of all four types. Although we can name and describe all four tissue types that make up all organs, as we do in the preceding section, listing all the organs in the body wouldn’t be so easy.
Level IV: The organ system level
Human anatomists and physiologists have divided the human body into organ systems, groups of organs that work together to meet a major physiological need. For example, the digestive system is one of the organ systems responsible for obtaining energy from the environment. Realize, though, that this is not a classification system for your organs. The organs that “belong” to one system can have functions integral to another system. The pancreas, for example, produces enzymes vital to the breakdown of our food (digestion), as well as hormones for the maintenance of our homeostasis (endocrine).
The chapter structure of this book is based on the definition of organ systems.
Level V: The organism level
The whole enchilada. The real “you.” As we study organ systems, organs, tissues, and cells, we’re always looking at how they support you on the organism level.
TAKING PICTURES OF YOUR INSIDES
For early anatomists like Hippocrates and da Vinci, the images they had were the sketches they made for themselves. The drawings made by Andreas Vesalius were compiled into the first anatomical atlas and the accuracy, considering it was the 16th century, is impressive. However, it is a German physicist named Wilhelm Conrad Roentgen who’s remembered as “the father of medical imaging.” In 1895, Roentgen changed the game by recording the first image of the internal parts of a living human: an X-ray image of his wife’s hand. By 1900, X-rays were in widespread use for the early detection of tuberculosis, at that time a common cause of death. X-rays are beams of radiation emitted from a machine toward the patient’s body, and X-ray images show details only of hard tissues, like bone, that reflect the radiation. In this way, they’re similar to photographs. Refinements and enhancements of X-ray techniques were developed all through the 20th century, with extensive use and major advances during World War II. The X-ray is still a widely used method for medical diagnosis, not just for bone breaks but for screening for signs of disease, especially tumors.
In the 1970s, computer technology took off, taking medical imaging technology with it. Digital imaging techniques began to be applied to convert multiple flat-slice images into one three-dimensional image. The first technology of this sort was called computed axial tomography (commonly called a CAT or CT scan). The technique combines multiple X-ray images of varying depths into images of whole structures inside the body. Contrast dye can be used to highlight particular areas, which is especially useful for a quick assessment (for example, after a trauma).
Another class of imaging technology utilizing radiation is positron emission tomography (PET). A radioactive isotope can be attached to a specific molecule — a drug, for example. After administering the drug to the patient, the isotope emits radiation, which can be traced and followed with radiation detectors. This is especially useful for testing the efficacy of drugs in a clinical research setting. It’s unique in that the scan provides information of organ function on a cellular level.
Ultrasound imaging technology uses the echoes of sound waves sent into the body to generate a signal that a computer turns into a real-time image of anatomy and physiology. Ultrasound can also produce audible sounds, so the anatomist or physiologist can, for example, watch the pulsations of an artery while hearing the sound of the blood flowing through it. Although all these technologies are considered noninvasive, ultrasound is the least invasive of all (no radiation) so it’s used more freely, especially in sensitive situations like pregnancy.
Magnetic resonance imaging (MRI) utilizes magnetic fields and radio pulses to create an image of the interior. Soft tissue structures are more difficult to scan using other methods, especially those found underneath bone. The resulting 3D image can pinpoint anomalies within an organ, often in great detail. Since the early 1990s, neuroscientists have been using a type of specialized MRI scan, called functional MRI (fMRI), to acquire images of the brain. Images can be recorded over time, and the active areas of the brain “light up” on the scan, showing which parts are active during specific tasks. Basically, fMRI enables scientists to watch a patient’s or research subject’s thoughts as he or she is thinking them!
Digital imaging technologies produce images that are extremely clear and detailed. The images can be produced much more quickly and cheaply than older technologies allowed for, and the images can be easily duplicated, transmitted, and stored. The amount of anatomical and physiological knowledge that digital imaging technologies have helped generate over the past 30 years has transformed biological and medical science. As the techniques are continually researched and developed, our understanding of physiology and accuracy in diagnostics will continue to improve.
Chapter 2
What Your Body Does All Day
IN THIS CHAPTER
Seeing what your body does automatically every day
Finding out what goes on inside of every cell
Discovering the importance of homeostasis
Building and maintaining your parts
This chapter is about your life as an organism. As Chapter 1 explains, organism is the fifth of five levels of organization in living things. Although the word organism has many possible definitions, for the purposes of this chapter, an organism is a living unit that metabolizes and maintains its own existence.
In this chapter, you see why your to-do list, crowded as it is, doesn’t include items such as Take ten breaths every minute or At 11:30 a.m., open sweat glands. The processes that your body must carry out minute by minute to sustain life, not to mention the biochemical reactions that happen millions of times a second, can’t be left to the distractible frontal lobes (the conscious, planning part of your brain). Instead, your organs and organ systems function together smoothly to carry out these processes and reactions automatically, without the activity ever coming to your conscious attention. All day and all night, year in and year out, your body builds, maintains, and sustains every part of you; keeps your temperature and your fluid content within some fairly precisely defined ranges; and transfers substances from outside itself to inside, and then back out again. These are the processes of metabolism and homeostasis.
Transferring Energy: A Body’s Place in the World
The laws of thermodynamics are the foundation of how the physics and chemistry of the universe are understood. They’re at the “we hold these truths to be self-evident” level for chemists and physicists of all specialties, including all biologists. The first law of thermodynamics states that energy can be neither created nor destroyed — it can only change form. (Turn to Chapter 16 for a brief look at the first law and other basic laws of chemistry and physics.) Energy changes form continuously — within stars, within engines of all kinds, and, in some very special ways, within organisms.
The most basic function of the organism that is you on this planet is to take part in this continuous flow of energy. As a heterotroph (an organism that doesn’t photosynthesize), you ingest (take in) energy in the form of matter — that is, you eat the bodies of other organisms. You use the energy stored in the chemical bonds of that matter to fuel the processes of your metabolism and homeostasis. That energy is thereby transformed into matter called “you” (the material in your cells), matter that’s “not you” (the material in your exhaled breath and in your urine), and some heat radiated from your body to the environment.
Hetero means “other,” and tropho means “nourishment.” A heterotroph gets its nourishment from others, as opposed to an autotroph, which makes its own nourishment, as a plant does.
Plants convert light energy from the sun into the chemical energy in carbohydrates, which comprise most of the matter of the plant bodies, recycling the waste matter (carbon dioxide) of your metabolic processes. Energy goes around and around, and some of it is always flowing through your body, being transformed constantly as it does so. You, my friend, are part of a cycle of cosmic dimensions!
Building Up and Breaking Down: Metabolism
The word metabolism describes all the chemical reactions that happen in the body. These reactions are of two kinds — anabolic reactions make things (molecules), and catabolic reactions break things down.
To keep the meanings of anabolic and catabolic clear in your mind, associate the word catabolic with the word catastrophic to remember that catabolic reactions break down products. Then you’ll know that anabolic reactions create products.
Your body performs both anabolic and catabolic reactions at the same time, around the clock, to keep you alive and functioning. Even when you’re sleeping, your cells are busy. You just never get to rest (until you’re dead).
Chapter 11 gives you the details on how the digestive system breaks down food into nutrients and gets them into your bloodstream. Chapter 9 explains how the bloodstream carries nutrients around the body to every cell and carries waste products to the urinary system. Chapter 12 shows you how the urinary system filters the blood and removes waste from the body. This chapter describes the reactions that your cells undergo to convert fuel to usable energy. Ready?
Why your cells metabolize
Even when your outside is staying still, your insides are moving. Day and night, your muscles twitch and contract and maintain “tone.” Your heart beats. Your blood circulates. Your diaphragm moves up and down with every breath. Nervous impulses travel. Your brain keeps tabs on everything. You think. Even when you’re asleep, you dream (a form of thinking). Your intestines push the food you ate hours ago along your alimentary canal. Your kidneys filter your blood and make urine. Your sweat glands open and close. Your eyes blink, and even during sleep, they move. Men produce sperm. Women move through the menstrual cycle. The processes that keep you alive are always active.
Every cell in your body is like a tiny factory, converting raw materials to useful molecules such as proteins and thousands of other products, many of which we discuss throughout this book. The raw materials (nutrients) come from the food you eat, and the cells use the nutrients in metabolic reactions. During these reactions, some of the energy from catabolized nutrients is used to generate a compound called adenosine triphosphate (ATP). This molecule is the one your cells can actually use to power all those chemical reactions.
So, nutrients are catabolized (broken down), ATP is formed (anabolized), and when needed, ATP is catabolized (for energy). This principle of linked anabolic and catabolic reactions is one of the cornerstones of human physiology and is required to maintain life. Cellular metabolism also makes waste products that must be removed (exported) from the cell and ultimately from the body.
ATP works like a rechargeable battery. It contains three phosphates aligned in a row (see Figure 2-1). Breaking one of them off accesses the energy, leaving behind adenosine diphosphate (ADP) and a phosphate (P) by itself. However, just like you can plug in your phone to recharge its battery, the energy in the bonds of glucose is used to reattach the P — re-creating ATP (albeit in an incredibly complicated way).
© John Wiley & Sons, Inc.
FIGURE 2-1: The chemical structure of ADP and ATP.
How your cells metabolize
The reactions that convert fuel (specifically glucose) to usable energy (ATP molecules) include glycolysis, the Krebs cycle (aerobic respiration) and anaerobic respiration, and oxidative phosphorylation. Together, these reactions are referred to as cellular respiration. These are complex pathways, so expect to take some time to understand them. See Figure 2-2 and refer to it as many times as necessary to understand what happens in cellular respiration. (Note: Alcohol fermentation is included for reference but does not occur in the human body.)
© John Wiley & Sons, Inc.
FIGURE 2-2: Cellular respiration: glycolysis, aerobic (Krebs cycle) and anaerobic respiration, and oxidative phosphorylation, all of which convert energy from fuel into ATP.
Here, we focus on the ins and outs of the three main components of cellular respiration.
Glycolytic pathway (glycolysis)
Starting at the top of Figure 2-2, you can see that glucose — the smallest molecule that a carbohydrate can be broken into during digestion — goes through the process of glycolysis, which starts cellular respiration and uses some energy (ATP) itself. Glycolysis occurs in the cytoplasm and doesn’t require oxygen. Two molecules of ATP are required to start each molecule of glucose rolling down the glycolytic pathway; although four molecules of ATP are generated during glycolysis, the net production of ATP is two molecules. In addition to the two ATPs, two molecules of pyruvic acid (also called pyruvate) are generated. They move into a mitochondrion and enter the Krebs cycle.
Krebs cycle
The Krebs cycle is a major biological pathway in the metabolism of every multicellular organism. It’s an aerobic pathway, requiring oxygen.
As the pyruvate enters the mitochondrion, a molecule called nicotinamide adenine dinucleotide (NAD+) joins it. NAD+ is an electron carrier (that is, it carries energy), and it gets the process moving by bringing some energy into the pathway. The NAD+ provides enough energy that when it joins with pyruvate, carbon dioxide is released, and the high-energy molecule NADH is formed. Flavin adenine dinucleotide (FAD) works in much the same way, becoming FADH2. The product of the overall reaction is acetyl coenzyme A (acetyl CoA), which is a carbohydrate molecule that puts the Krebs cycle in motion.
Cycles are endless. Products of some reactions in the cycle are used to keep the cycle going. An example is acetyl CoA: It’s a product of the Krebs cycle, yet it also helps initiate the cycle. With the addition of water and acetyl CoA, oxaloacetic acid (OAA) is converted to citric acid. Then, a series of reactions proceeds throughout the cycle.
Oxidative phosphorylation
Oxidative phosphorylation, also called the electron transport chain (ETC), takes place in the inner membrane of the mitochondria. The electron carriers produced during the Krebs cycle — NADH and FADH2 — are created when NAD+ and FAD, respectively, are “reduced.” When a substance is reduced, it gains electrons; when it’s oxidized, it loses electrons. (Turn to Chapter 16 for more information about such “redox reactions.”) So NADH and FADH2 are compounds that have gained electrons, and therefore, energy. In the ETC, oxidation and reduction reactions occur repeatedly as a way of transporting energy. At the end of the chain, oxygen atoms accept the electrons, producing water. (Water from metabolic reactions isn’t a significant contributor to the water needs of the body.)
As NADH and FADH2 pass down the respiratory (or electron transport) chain, they lose energy as they become oxidized and reduced, oxidized and reduced, oxidized and … . It sounds exhausting, doesn’t it? Well, their energy supplies become exhausted for a good cause. The energy that these electron carriers lose is used to add a molecule of phosphate to adenosine diphosphate (ADP) to make it adenosine triphosphate — the coveted ATP. For each NADH molecule that’s produced in the Krebs cycle, three molecules of ATP can be generated. For each molecule of FADH2 that’s produced in the Krebs cycle, two molecules of ATP are made.
Theoretically, the entire process of aerobic cellular respiration — glycolysis, Krebs cycle, and oxidative phosphorylation — generates a total of 38 ATP molecules from the energy in one molecule of glucose: 2 from glycolysis, 2 from the Krebs cycle, and 34 from oxidative phosphorylation. However, this theoretical yield is never quite reached because processes, especially biological processes, are never 100 percent efficient. In the real world, usually around 29 to 30 ATP molecules per glucose molecule are expected.
Anaerobic respiration
Sometimes oxygen isn’t present, but your body still needs energy. During these times, a backup system, an anaerobic pathway (called anaerobic because it proceeds in the absence of oxygen) exists. Lactic acid fermentation generates NAD+ so that glycolysis, which results in the net production of two molecules of ATP, can continue. However, if the supply of NAD+ runs out, glycolysis can’t occur, and ATP can’t be generated.
This occurs most often in muscle cells during periods of intense exercise. The byproduct of this reaction, lactic acid, builds up in the muscle, contributing to muscle fatigue
