STUDENT LEARNING OBJECTIVES

At the completion of this chapter, you should be able to do the following:

1.Describe what is meant by levels of organization.

2.Describe a person standing in the correct anatomical position.

3.Describe the appearance of the body using the three different body planes.

4.Identify the major body cavities and the major organs lying within each cavity.

5.Describe the four abdominopelvic quadrants and the nine abdominopelvic regions.

6.Use directional terms to describe the relative positions of different body structures.

7.Describe the relationship between structure and function.

8.Describe the process of homeostasis and its importance.

9.Compare a negative feedback mechanism with a positive feedback mechanism.

LANGUAGE OF SCIENCE AND MEDICINE

Before reading the chapter, say each of these terms out loud. This will help you avoid stumbling over them as you read.

abdominopelvic cavity (ab-DOM-i-no-PEL-vik KAV-ih-tee)

[abdomin- belly, -pelv- basin, cav- hollow, -ity state]

afferent (AF-fer-ent)

[a[d]- toward, -fer- carry, -ent relating to]

anatomical position (an-ah-TOM-i-kal po-ZISH-un)

[ana- apart, -tom- cut, -ical- relating to, posit- place, -tion state]

anatomy (ah-NAT-o-mee)

[ana- apart, -tom- cut, -y action]

anterior (an-TEER-ee-or)

[ante- front, -er- more, -or quality]

apical (AY-pik-al)

[apic- tip, -al relating to]

appendicular (ah-pen-DIK-yoo-lar)

[append- hang upon, -ic- relating to, -ul- little, -ar relating to]

atrophy (AT-ro-fee)

[a- without, -troph- nourishment, -y state]

axial (AK-see-al)

[axi- axis, -al relating to]

basal (BAY-sal)

[bas- base, -al relating to]

bilateral symmetry (bye-LAT-er-al SIM-e-tree)

[bi- two, -later- side, -al relating to, sym- together, -metr- measure, -ry condition of]

body plane

(BOD-ee playn)

cell (sell)

[cell storeroom]

central (SEN-tral)

[centr- center, -al relating to]

coronal plane (ko-RO-nal playn)

[corona- crown, -al relating to]

cortical (KOR-tik-al)

[cortic- bark, -al relating to]

deep

dissection (dis-SEK-shun)

[dissect- cut apart, -tion process]

distal (DIS-tal)

[dist- distance, -al relating to]

dorsal cavity (DOR-sal KAV-ih-tee)

[dors- back, -al relating to, cav- hollow, -ity state]

efferent (EF-fer-ent)

[e- away, -fer- carry, -ent relating to]

feedback control loop

homeostasis (ho-mee-o-STAY-sis)

[homeo- same or equal, -stasis standing still]

hypothesis (hye-POTH-eh-sis)

[hypo- under or below, -thesis placing or proposition]; pl., hypotheses (hye-POTH-eh-seez)

inferior (in-FEER-ee-or)

[infer- lower, -or quality]

lateral

(LAT-er-al)

lumen (LOO-men)

[lumen light]; pl., lumina (LOO-min-ah)

macromolecule (mak-roh-MOL-eh-kyool)

[macro- large, molec- mass, -ule small]

medial (MEE-dee-al)

[media- middle, -al relating to]

mediastinum (mee-dee-ah-STY-num)

[mediastinus- midway]

medullary (MED-oo-lar-ee)

[medulla- middle, -ry state]

metabolism (me-TAB-o-liz-em)

[metabol- change, -ism condition]

microscopic anatomy (my-kroh-SKOP-ik ah-NAT-o-mee)

[micro- small, -scop- see, -ic relating to, ana- apart, -tom- cut, -y action]

molecule (MOL-eh-kyool)

[mole- mass, -cule small]

negative feedback

[negative opposing or prohibitive]

organ (OR-gan)

[organ instrument]

organ system (OR-gan SIS-tem)

[organ instrument, system organized whole]

organelle (or-gah-NELL)

[organ- tool or instrument, -elle small]

organism (OR-gah-niz-im)

[organ- instrument, -ism condition]

parietal (pah-RYE-ih-tal)

[pariet- wall, -al relating to]

peripheral (pe-RIF-er-al)

[peri- around, -phera- boundary, -al relating to]

physiology (fiz-ee-OL-o-jee)

[physio- nature (function), -o- combining form, -log- words (study of), -y activity]

positive feedback

[positive place or amplify]

posterior (pos-TEER-ee-or)

[poster- behind, -or quality]

proximal (PROK-si-mal)

[proxima- near, -al relating to]

sagittal plane (SAJ-i-tal playn)

[sagitta- arrow, -al relating to]

scientific method (sye-en-TIFF-ik METH-od)

[scienti- knowledge, -ic relating to]

set point

superficial (soo-per-FISH-al)

[super- over or above, -fici- face, -al relating to]

superior (soo-PEER-ee-or)

[super- over or above, -or quality]

theory (THEE-o-ree)

[theor- look at, -y act of]

thoracic cavity (thoh-RASS-ik KAV-ih-tee)

[thorac- chest (thorax), -ic relating to]

tissue (TISH-yoo)

[tissue fabric]

transverse plane (TRANS-vers playn)

[trans- across or through, -vers turn]

ventral cavity (VEN-tral KAV-ih-tee)

[ventr- belly, -al relating to, cav- hollow, -ity state]

viscera, visceral (VISS-er-ah) (VISS-er-al)

[visc- internal organ, -al relating to]; sing., viscus

NOTE: Table 1-4 lists additional key terms in this chapter.

SAM was just starting his first year in college, and he had been thinking about going into the medical field—maybe nursing. To find out what nursing was really like, Sam signed up for a “shadow a nurse” day at the local hospital. He was scheduled to follow a nurse in the emergency department to see what the job involved.

Everything seemed rather boring and quiet for the first hour. Then suddenly, an ambulance pulled into the bay and a paramedic rushed a patient in on a stretcher. The paramedic gave a quick patient report, and Sam overheard, “Stab wound to the right upper quadrant … additional cuts to his right brachial region … there's a large contusion on his right thigh, just proximal to the knee.”

Sam felt like he was listening to a foreign language! You may feel likewise, but after reading this chapter, you should be able to interpret the paramedic's report and answer questions we pose at the end of this chapter.

Now that you have read this chapter, see if you can answer these questions about Sam's experience in the emergency department from the Introductory Story.

1. The patient was stabbed in the right upper quadrant; where is that exactly?

a. In his thoracic cavity

b. In his abdominopelvic cavity

c. In his pericardial cavity

d. In his pleural cavity

2. What organ is most likely to have been damaged by the stabbing attack?

a. His heart

b. His lungs

c. His liver

d. His spleen

3. Where is the bruise (contusion) on the patient's leg, which was said to be just proximal to the knee?

a. His femoral region

b. His crural region

c. His humoral region

d. His popliteal region

4. Where is the patient's brachial region?

a. His armpit

b. His lower leg

c. His cheek

d. His upper arm

To solve these questions, you may have to refer to the glossary or index, other chapters in this textbook, A&P Connect, Mechanisms of Disease, and other resources.

HUMAN ANATOMY AND PHYSIOLOGY

What could be more fascinating and personally empowering than understanding our own bodies? To do so requires that we know the structures, or anatomy, of the human body as well as understand how the functions of these structures, or physiology, are integrated. We tend to separate these two fields of study, but in reality they are intimately connected: As you will see, structure determines function. Understanding this basic concept takes on great significance as you enter into one of the many fascinating health careers available to students today.

Sometimes anatomists use the phrase “gross anatomy” to describe the study of body parts visible to the naked eye. In contrast, we use the phrase “microscopic anatomy” to describe the study of cells. Microscopic anatomy includes the study of cells, cytology, and tissues, histology.

Our understanding of human anatomy and physiology is the result of thousands of years of human inquiry into the causes of human illness. Today, modern researchers use the scientific method to study nature in a rational, logical manner. This means scientists must conduct rigorous experiments under controlled conditions to explore a hypothesis—a statement used as a proposed explanation for a scientific problem. Through the scientific method, a reasonable conclusion can be obtained. If the results of experiments are repeatable, they may support the hypothesis. If the data are not supportive, the hypothesis is disproven. However, sometimes the original hypothesis needs to be “tweaked,” sending the investigators in a more refined direction. Eventually, through rigorous and controlled testing, enough support may build for the hypothesis to elevate it to the level of a theory.

You should note that a hypothesis is not a theory and that hypotheses must always be testable in a valid, scientific manner. You also should understand that a theory in science is very rare, and most important, a theory is a well-tested statement that has never been disproved. This is because science depends on disproof, not proof. Also note that it is not “cheating” to return to your original hypothesis and change it when new evidence arises. This is the power of science—we are always improving our understanding of nature, but may never actually reach a complete understanding. Nonetheless, major scientific breakthroughs are constantly changing our lives.

Using the scientific method, anatomists learn about the structures of the human body by the process of dissection—literally cutting the body apart. Physiologists use many complex technologies as they attempt to discover and understand the intricate control systems that permit the body to operate and survive, often in changing, even hostile, environments.

Both anatomy and physiology are typically studied by examining specific organ systems. We will begin in this chapter with an overview of the body as a whole. Later chapters will examine the body both structurally and functionally, system by system. Our ultimate goal, of course, is the basic understanding of the whole body.

Such an understanding requires learning many scientific terms—often derived from Greek and Latin roots—that are standardized throughout the world. The study of anatomy and physiology, therefore, requires you to learn the definitions and uses of these terms, just as if you were learning a foreign language—and to be truthful, you are!

To help you learn the vocabulary of anatomy and physiology, we have provided several helpful tools. Within each chapter, a section entitled Language of Science and Medicine provides you with a list of boldface key terms. Each term in the list has a pronunciation guide, the Latin or Greek word parts that make up the term, and the meaning of the word parts. Each term also appears in boldface within the chapter text where it is defined. Spending the time to learn these terms will help you tremendously throughout your studies.

Scientific language evolves like any other language. This evolution of the language of science helps us understand changes that are constantly taking place in science, and it also allows us to accommodate the description of new discoveries. The International Federation of Associations of Anatomists (IFAA) now adheres to a list of “universal” anatomical terminology called the Terminologia Anatomica (TA), which has become a useful, standard reference.

One purpose of the Terminologia Anatomica is to avoid eponyms, or terms that are based on a person's name. For this reason, a more descriptive Latin-based term is always preferred. For example, the term Eustachian tube (named after Eustachius) has been replaced by the more descriptive term auditory tube. Likewise, the islets of Langerhans are now called pancreatic islets. However, we should note here that a few eponyms continue to be used.

In 2007 the Terminologia Histologica (TH) was published for microscopic anatomy, such as the study of cells and tissues.

In this textbook, we use the English terms from the published lists as our standard reference, but we do occasionally refer to the pure Latin form or an alternate term when appropriate.

Unfortunately, there are currently no standard lists of physiological terms.

Now, before we begin our tour of the human body, let's first discuss what we mean by “life.”

1. Define anatomy and physiology. How do they differ?

2. Why is the Big Picture of anatomy and physiology important to your studies?

3. What is the difference between a hypothesis and a theory?

4. What is the value of the Terminologia Anatomica and Terminologia Histologica?

CHARACTERISTICS OF HUMAN LIFE

Before we begin, you should understand that there is no one “perfect” definition for life. Life, as defined by modern researchers, exhibits self-sustaining, biological processes, which include many of the characteristics that we list below as properties of being “alive.”

Human life, like all life, shares a number of basic characteristics not associated with inorganic matter. Taken together, these characteristics define life and separate life from nonlife. They all illustrate the self-organization needed to live. In this book, we are interested in characteristics of human life, and you are probably familiar with at least a few of these characteristics: responsiveness, conductivity, growth, respiration, circulation, digestion, absorption, secretion, excretion, and reproduction. These characteristics of human life are listed and described briefly for you in Table 1-1.

TABLE 1-1 Characteristics of Human Life

CHARACTERISTIC

DESCRIPTION

Responsiveness

Ability of an organism to sense, monitor, and respond to changes in both its external and internal environments

Conductivity

Capacity of living cells to transmit a wave of electrical disturbance from one point to another within the body

Growth

Organized increase in the size and number of cells, and therefore an increase in size of the individual or a particular organ or part

Respiration

Exchange of respiratory gases (oxygen and carbon dioxide) between an organism and its environment

Circulation

Movement of body fluids containing many substances from one body area to another in a continuous, complete route through hollow vessels

Digestion

Process by which complex food products are broken down into simpler substances that can be absorbed and used by individual body cells

Absorption

Movement of molecules, such as respiratory gases or digested nutrients, through a membrane and into the body fluids for transport to cells for use

Secretion

Production and release of important substances, such as digestive juices and hormones, for diverse body functions

Excretion

Removal of waste products

Reproduction

Formation of new individual offspring

Each characteristic of life is a part of all the physical and chemical processes that take place in our bodies. The sum total of all of life's chemical processes is called metabolism.

We mention these important characteristics of human life because we will study each characteristic of life and its integration with other life functions throughout this book.

LEVELS OF STRUCTURAL ORGANIZATION

Before you begin the study of the structures and functions of the human body, it's important to think about how the various parts fit together to function effectively. Figure 1-1 illustrates the hierarchy of our human organization. Refer to the illustration and note that chemical reactions form the base, followed by organelles making up cells, cells making up tissues, tissues making up organs, and organs making up organ systems. The sum of all these integrated levels working together as a coordinated whole is the human body. Let's look briefly at each level so you can better understand the stepwise increase of complexity from chemistry to organisms.

All of life is based on chemistry. As we will see in Chapter 2, there are more than 100 different chemical building blocks called elements making up all of nature. Each element is made of atoms consisting of varying numbers of subatomic particles: protons, electrons, and neutrons. If you took a very narrow “chemical” viewpoint of life, you could say that we are nothing more than organized protons, electrons, and neutrons that make up atoms, which then bond together to make molecules. In turn, these molecules combine in specific ways to make even larger, more complex molecules called macromolecules.

These enormous macromolecules form organelles—subcellular structures or packages of gel-like fluids surrounded by membranes. Organelles are the “tiny organs” that allow each cell to live. They are to cells

FIGURE 1-1 Levels of organization. The smallest parts of the body are the atoms that make up our molecules. In turn, molecules make up microscopic parts called organelles that fit together to form each cell of the body. Groups of similar cells are called tissues, which combine with other tissues to form organs. Groups of organs that work together are called systems. All the systems of the body together make up an individual organism. Knowledge of the different levels of organization will help you understand the basic concepts of human anatomy and physiology.

what organs are to our bodies. Organelles cannot survive outside the cell, but without organelles a cell could not survive either. Dozens of different kinds of organelles have been identified. A few examples include mitochondria, the so-called powerhouses of the cell, and cilia, tiny whiplike extensions of specialized cells. Unique and complex relationships exist between atoms, molecules, macromolecules, and organelles to make up the cytoplasm of our cells. You will find a complete discussion of organelles and their functions in Chapter 3.

Cells are the foundation and basic building blocks of our bodies. They are the smallest structural units that possess and exhibit the basic characteristics of living matter. The specific characteristics of each of our many kinds of cells result from a hierarchy of structure and function that begins with the organization of atoms, molecules, macromolecules, and organelles. Incredibly, a 68-kg (150-pound) adult is composed of nearly one hundred trillion (100,000,000,000,000) cells—an almost unimaginable number! Each cell is surrounded by a membrane enclosing its cytoplasm and organelles, and has one or more nuclei whose DNA controls the cell's activities. Although all cells have certain features in common, they specialize or differentiate to perform specific functions. Fat cells, for example, are structurally modified to store fat; cardiac muscle cells contract rhythmically; and sperm cells are rapidly moving cells that deliver genetic material from a father to the egg of a mother.

There are over 200 different kinds of cells in the human body. (Body cells differ from one another because specific genes are active in some cells and not in others.) Cells are organized into tissues—groups of many related cells that develop together (from the same part of a human embryo) and perform certain functions. The cells of tissues are surrounded by a matrix of nonliving substances that holds them together. There are four major tissue types: epithelial, connective, muscle, and nervous, and a number of different subtypes within each major type. For example, cardiac muscle is a specific type of muscle found only in the heart. Chapters 3, 4, and 5 will give you a more complete understanding of the types and functions of cells and tissues making up our bodies.

As we continue up the ladder of organization, you can see that organs are structures made up of several different kinds of tissues arranged to perform specific functions. The heart is an example of an organ: it is made of specialized cardiac muscle, connective tissue, and nervous tissue. Organs are the operational units of our bodies. The lungs, heart, brain, kidneys, liver, and spleen are all examples of organs.

Next we have organ systems, the most complex of the organizational units of the body. Each organ system, such as the digestive system, comprises varying numbers and kinds of organs arranged so that they can perform complex functions of the body. As you can see in Figure 1-1, 11 major systems make up the human body: integumentary, skeletal, muscular, nervous, endocrine, cardiovascular, lymphatic/immune, respiratory, digestive, urinary, and reproductive. Take a few minutes to look at the organ systems highlighted in the human bodies of Figure 1-1. Different systems often work together to accomplish some larger goal. For example, the first three systems shown (integumentary, skeletal, muscular) make up the framework of the body and provide support and movement. These body systems correspond to the organization of this book and serve as a broad outline for how we will study the organ system components of the human body (Table 1-2).

TABLE 1-2 Body Systems (with Unit and Chapter References)

FUNCTIONAL CATEGORY

SYSTEM

PRINCIPAL ORGANS

PRIMARY FUNCTIONS

Support and movement (Unit 2)

Integumentary (Chapter 7)

Skin

Protection, temperature regulation, sensation

Skeletal (Chapters 8-9)

Bones, ligaments

Support, protection, movement, mineral and fat storage, blood production

Muscular (Chapter 10)

Skeletal muscles, tendons

Movement, posture, heat production

Communication, control, and integration (Unit3)

Nervous (Chapter 11–14)

Brain, spinal cord, nerves, sensory organs

Control, regulation, and coordination of other systems; sensation; memory

Endocrine (Chapter 15)

Pituitary gland, adrenals, pancreas, thyroid, parathyroids, and other glands

Control and regulation of other systems

Transportation and defense (Unit 4)

Cardiovascular (Chapter 16–18)

Heart, arteries, veins, capillaries

Exchange and transport of materials

Lymphatic and immune (Chapter 19)

Lymph nodes, lymphatic vessels, spleen, thymus, tonsils

Immunity, fluid balance

Respiration, nutrition, and excretion (Unit 5)

Respiratory (Chapter 20)

Lungs, bronchial tree, trachea, larynx, nasal cavity

Gas exchange, acid-base balance

Digestive (Chapters 21–22)

Stomach, small and large intestines, esophagus, liver, mouth, pancreas

Breakdown and absorption of nutrients, elimination ofwaste

Urinary (Chapter 23)

Kidneys, ureters, bladder, urethra

Excretion of waste, fluid and electrolyte balance, acid-base balance

Reproduction and development (Unit 6)

Reproductive (Chapter 24–27)

Male: Testes, vas deferens, prostate, seminal vesicles, penis

Reproduction, continuity of genetic information, nurturing of offspring

Female: Ovaries, fallopian tubes, uterus, vagina, breasts

Finally, we have the organism level—the incredibly unique human organism of our studies. Although composed of the 11 organ systems, you can readily see that the human body is certainly more complex than the sum of all its parts. As organisms, our bodies are marvelously coordinated teams of interactive and self-regulating structures capable of surviving in often very hostile environments. The human body reproduces itself (and its genetic information) and maintains ongoing repair and replacement of worn or damaged parts. It can also control—in a constant and predictable way—an incredible number of variables required to lead healthy, productive lives. We should always remember that the various systems of the human body are interdependent—they do not operate in isolation! For that reason alone, you should not just memorize facts. Instead, you should try to visualize in your mind what is being said in the text, and then put together the factual information presented so that you understand the human body as a complete biological system.

5. What are the characteristics of life?

6. Try to recall the various levels of life.

7. Without looking, try to list the 11 major organ systems.

LANGUAGE OF BODY ORGANIZATION

Anatomical Position

Our discussion of the human body requires that we pick a standard position as a reference point of view. This is called the anatomical position. This position allows us to discuss the body's structures relative to one another without confusion—as when we always hold a map in the same orientation. In this reference position the body is viewed in a standing posture with the feet and head facing forward and the arms at the sides with the palms facing forward (Figure 1-2). All body directions and the location of structures relative to one another require reference to this standard anatomical position. This reference frame works well because the body (for the most part) exhibits bilateral symmetry—the external right and left sides of the body are roughly mirror images of one another. This fact is important in describing injury to parts of the body. For example, injuries to an arm or leg require careful comparison of the injured side with the noninjured side.

Body Cavities

The human body may appear solid but it is not. In fact, it contains two major cavities, the ventral and dorsal cavities. In turn these major cavities are subdivided and contain compact

FIGURE 1-2 Anatomical position and bilateral symmetry. In the anatomical position, the body is in an erect, or standing, posture with the arms at the sides and palms facing forward. The head and feet are also pointing forward. The dotted line shows the axis of the body's bilateral symmetry. As a result of this organizational feature, the right and left external sides of the body are roughly mirror images of each other.

arrangements of internal organs. As you read through the next few paragraphs, refer to Figure 1-3 and Table 1-3 to help you visualize the content.

The ventral cavities include the thoracic (chest) cavity and the abdominopelvic (abdomen and pelvis) cavity.

The thoracic cavity includes a right and a left pleural cavity and a middle portion called the mediastinum. As you might suspect, the left lung lies in the left pleural cavity and the right lung lies in the right pleural cavity. All the other organs of the thoracic cavity are located in the mediastinum. Here you will find the heart, trachea, esophagus, and thymus, as well as several major nerves, blood vessels, and lymph nodes and their ducts.

The lower abdominopelvic cavity is divided into an upper abdominal cavity and a lower pelvic cavity. The abdominal cavity contains the liver, gallbladder, stomach, pancreas, intestines, spleen, and kidneys and their ducts, whereas the pelvic cavity contains the reproductive organs and part of the large intestine.

FIGURE 1-3 Major body cavities. The dorsal body cavities are in the dorsal (back) part of the body. They include a cranial cavity above and a spinal cavity below. The ventral body cavities are on the ventral (front) side of the trunk. They include the thoracic cavity above the diaphragm and the abdominopelvic cavity below the diaphragm. The thoracic cavity is subdivided into the mediastinum in the center and pleural cavities to the sides. The abdominopelvic cavity is subdivided into the abdominal cavity above the pelvis and the pelvic cavity within the pelvis.

The dorsal cavities include the cranial and spinal cavities. The cranial cavity lies in the skull and houses the brain. The head also has smaller cavities: the oral cavity (teeth and tongue), the nasal cavity (the nose and sinuses), the orbital cavity (eyes and associated muscles and nerves), and the middle ear cavities (housing the bones of the middle ear). The spinal cavity lies in the spinal column and houses the spinal cord.

There are thin membranes that line the body cavities or cover the surfaces of organs within the body cavities. These membranes also have special names. The term parietal refers to the inside wall of a body cavity or the membrane that covers this wall. In contrast, the term visceral refers to the internal organs, or viscera), that reside within the cavity, o