Anatomy & Physiology For Dummies®, 3rd Edition
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Library of Congress Control Number: 2017932045
ISBN 978-1-119-34523-7 (pbk); ISBN 978-1-119-34530-5 (ebk); ISBN 978-1-119-34536-7 (ebk)
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.
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.
When we wrote this book, we tried to keep you in mind. We’re guessing that you fall into one of these categories:
The little round pictures that you see in the margins throughout this book are icons that alert you to several different kinds of information.
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.
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
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
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.
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.
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.
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
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.
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.
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.
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.
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.
The following list of common anatomical descriptive terms (direction words) that appear throughout this and every other anatomy book may come in handy:
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:
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).
Here’s a list of the axial body’s main regions:
Here’s a list of the appendicular body’s main regions:
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.
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:
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.
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.
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:
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.
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.
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.
Chapter 2
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.
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.
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!