Introduction to Human Anatomy PDF

1 AN INTRODUCTION TO THE HUMAN BODY I N T R O D U C T I O N You are about to begin a study of the human body to learn how it is organized and how it functions. In order to understand wh...

1 AN INTRODUCTION TO THE HUMAN BODY I N T R O D U C T I O N You are about to begin a study of the human body to learn how it is organized and how it functions. In order to understand what happens when the body is injured, diseased, or placed under stress, you must know how it is put together and how its different parts work. Just as an auto mechanic must be familiar with the details of the structure and function of a car, health-care professionals and others who work in human performance and care professions must have intimate knowledge of the structures and functions of the human body. This knowledge can be one of your most effective tools. Much of what you study in this chapter will help you under- stand how anatomists visualize the body, and the basic anatomical vocabulary presented here will help you describe the body in a language common to both scientists and professionals. Did you ever wonder why an autopsy is performed? You can find out on page 19. Mark Nielsen 1 CONTENTS AT A GLANCE 1.1 Anatomy Defined 2 1.5 Body Cavities 14 1.2 Levels of Body Organization and Body Systems 3 Thoracic and Abdominal Cavity Membranes 15 1.3 Life Processes 9 1.6 Abdominopelvic Regions and Quadrants 18 1.4 Basic Anatomical Terminology 9 1.7 The Human Body and Disease 19 Anatomical Position 9 1.8 Aging 20 Regional Names 9 1.9 Medical Imaging 20 Planes and Sections 10 1.10 Measuring the Human Body 23 Exhibit 1.A Directional Terms 12 1.1 ANATOMY DEFINED structure, you will learn how the structure of the body often reflects its functions. Some of the structure–function relation- OBJECTIVE ships are visibly obvious, such as the tight connections between the Define anatomy and physiology, and name several bones of the skull, which protect the brain. In contrast, the bones branches of anatomy. of the fingers are more loosely joined to permit movements such as playing an instrument, grasping a baseball bat, or retrieving a small Anatomy (a-NAT-ō-mē; ana-=up; =-tomy=process of cutting) object from the floor. The shape of the external ear assists in the is primarily the study of structure and the relationships among collection and localization of sound waves, which facilitates hear- structures. It was first studied by dissection (dis-SEK-shun; dis-= ing. Other relationships are not as visibly obvious; for example, the apart; -section=act of cutting), the careful cutting apart of body passageways that carry air into the lungs branch extensively when structures to study their relationships. Today, a variety of imag- they reach the lungs. Tiny air sacs—about 300 million—cluster at ing techniques also contribute to the advancement of anatomical the ends of the large number of airway branches. Similarly, the ves- knowledge. We will describe and compare some common imag- sels carrying blood into the lungs branch extensively to form tiny ing techniques in Table 1.3, which appears later in this chapter tubes that surround the small air sacs. Because of these anatomical (see Section 1.8). The anatomy of the human body can be studied features, the total surface area within the lungs is about the size of at various levels of structural organization, ranging from micro- a handball court. This large surface area is the key to the primary scopic (visible only with the aid of a microscope) to macroscopic function of the lungs: the efficient exchange of oxygen and carbon (visible without the use of a microscope). These levels and the dioxide between the air and the blood. different methods used to study them provide the basis for the branches of anatomy, several of which are described in Table 1.1. CHECKPOINT Anatomy deals mostly with structures of the body. A related 1. Which branches of anatomy would be used when discipline, physiology (fiz′-e-OL-o-je; physio-=nature; -logy= dissecting a cadaver? study of), deals with functions of body parts—that is, how they 2. Give several examples of connections between structure work. Because function cannot be separated completely from and function in the human body. TABLE 1.1 Selected Branches of Anatomy BRANCH STUDY OF Embryology (em′-brē-OL-ō-jē; In humans, the first eight weeks of development after fertilization of the egg embry-=embryo; -logy=study of) Developmental biology The complete developmental history of an individual from fertilization to death Cell biology Cellular structure and function Histology Microscopic structure of tissues (his′-TOL-ō-jē-; hist-=tissue) Sectional anatomy Internal structure and relationships of the body through the use of sections Gross anatomy Structures that can be examined without using a microscope Systemic anatomy Structure of specific systems of the body such as the nervous or respiratory systems Regional anatomy Specific regions of the body such as the head or chest Surface anatomy Surface markings of the body to understand the relationships of deep or internal anatomy through visualization and palpation (gentle touch) Imaging anatomy Internal body structures that can be visualized with x-rays, CT scans, MRI, and other technologies Pathological anatomy Structural changes (from gross to microscopic) associated with disease (path′-ō-LOJ-i-kal; path-=disease) 2  1.2 LEVELS OF BODY ORGANIZATION AND BODY SYSTEMS 3 C L INIC AL C ON N E C T ION | Noninvasive Diagnostic Techniques Several noninvasive diagnostic techniques are commonly used by stethoscope to amplify the sounds (Figure C). An example is auscul- health-care professionals and students to assess certain aspects tation of the lungs during breathing to check for crackling sounds of body structure and function. A noninvasive diagnostic associated with abnormal fluid accumulation in the air spaces of the technique is one that does not involve insertion of an instrument lungs. In percussion (pur-KUSH-un; percus-=to beat) the examiner or device through the skin or into a body opening. In inspection, taps on the body surface with the fingertips and listens to the result- the first noninvasive diagnostic technique, the examiner observes ing sound. Hollow cavities or spaces produce a different sound than the body for any changes that deviate from normal (Figure A). For solid organs do (Figure D). For example, percussion may reveal the ab- example, a physician may examine the mouth cavity for evidence of normal presence of fluid in the lungs or air in the intestines. It is also disease. In palpation (pal-PĀ-shun; palpa-=to touch) the examiner used to reveal the size, consistency, and position of an underlying feels body surfaces with the hands (Figure B). An example is palpating structure. An understanding of anatomy is important for the effec- the neck to detect enlarged or tender lymph nodes. In auscultation tive application of most of these techniques. Also, clinicians use these (aus′-cul-TĀ-shun; ausculta-=to listen to) the examiner listens to body terms and others covered in this chapter to annotate their findings sounds to evaluate the functioning of certain organs, often using a following a clinical examination. Gary Conner/Phototake ©La/Bc.Aigo/Phototake Jose Luis Pelaez/Getty Images, Inc. Malvina Mendil/Science Source Inc (A) Inspection of oral (mouth) cavity (B) Palpation of lymph nodes in neck (C) Auscultation of lungs (D) Percussion of lungs 1.2 LEVELS smallest building blocks of language, cells are the smallest living units in the human body. Among the many kinds of OF BODY ORGANIZATION cells in your body are muscle cells, nerve cells, and blood AND BODY SYSTEMS cells. Figure 1.1 shows a smooth muscle cell, one of three types of muscle cells in the body. The cellular level of organi- OBJECTIVES zation is the focus of Chapter 2. Describe the levels of structural organization that make ➌ The next level of structural organization is the tissue level. up the human body. Tissues are groups of cells and the materials surrounding Outline the 11 systems of the human body, list the organs them that work together to perform a particular function, present in each, and explain their general functions. similar to the way words are put together to form sentences. The levels of organization of a language—letters of the alphabet, There are just four basic types of tissue in your body: epithe- words, sentences, paragraphs, and so on—can be compared to the lial tissue, connective tissue, muscular tissue, and nervous tis- levels of organization of the human body. Your exploration of the sue. Epithelial tissue covers body surfaces, lines hollow organs human body will extend from some of the smallest body structures and cavities, and forms glands. Connective tissue connects, and their functions to the largest structure—an entire person. Or- supports, and protects body organs while distributing blood ganized from smallest to largest, six levels of organization will help vessels to other tissues. Muscular tissue contracts (shortens) you to understand anatomy: the chemical, cellular, tissue, organ, to make body parts move and generates heat. Nervous tissue system, and organismal levels of organization (Figure 1.1). carries information from one part of the body to another. Chapter 3 describes the tissue level of organization in greater ➊ The chemical level, which can be compared to the letters of detail. Shown in Figure 1.1 is smooth muscle tissue, which the alphabet, includes atoms, the smallest units of matter that consists of tightly packed smooth muscle cells. participate in chemical reactions, and molecules, two or ➍ At the organ level, different types of tissues are joined together. more atoms joined together. Certain atoms, such as carbon Similar to the relationship between sentences and paragraphs, (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus organs are structures that are composed of two or more dif- (P), and calcium (Ca), are essential for life. Two familiar ferent types of tissues; they have specific functions and usually molecules found in the body are deoxyribonucleic acid have recognizable shapes. Examples of organs are the stomach, (DNA), the genetic material passed from one generation to heart, liver, lungs, and brain. Figure 1.1 shows how several tis- the next, and glucose, commonly known as blood sugar. sues make up the stomach. The stomach’s outer covering is ➋ At the cellular level, molecules combine to form cells, which a layer of epithelial and connective tissues that reduces fric- can be compared to assembling letters into words. Cells are tion when the stomach moves and rubs against other organs. structures composed of chemicals and are the basic structural Underneath these layers is a type of muscular tissue called and functional units of an organism. Just as words are the smooth muscle tissue, which contracts to churn and mix food and 4 CHAPTER 1 AN INTRODUCTION TO THE HUMAN BODY push it on to the next digestive organ, the small intestine. The ➏ The largest organizational level is the organismal level. An innermost lining, the epithelial tissue layer, produces fluid and organism (OR-ga-nizm), any living individual, can be com- chemicals responsible for digestion in the stomach. pared to a book in our analogy. All the parts of the human ➎ The next level of structural organization in the body is the body functioning together constitute the total organism. system level, also called the organ-system level. A system (or In the following chapters, you will study the anatomy and chapter in our language analogy) consists of related organs some physiology of the body systems. Table 1.2 introduces the (paragraphs) with a common function. An example is the components and functions of these systems in the order they are digestive system, which breaks down and absorbs food. Its discussed in the book. organs include the mouth, salivary glands, pharynx (throat), esophagus (tube that carries food from the throat to the stom- CHECKPOINT ach), stomach, small intestine, large intestine, liver, gallblad- 3. Define the following terms: atom, molecule, cell, tissue, der, and pancreas. Sometimes an organ is part of more than organ, system, and organism. one system. For example, the pancreas, which has multiple 4. Which body systems help eliminate wastes? (Hint: Refer functions, is included in the digestive and endocrine systems. to Table 1.2.) Figure 1.1 Levels of structural organization in the human body. The levels of structural organization are chemical, cellular, tissue, organ, system, and organismal. T 2 CELLULAR LEVEL 1 CHEMICAL LEVEL 3 TISSUE LEVEL Smooth muscle cell Atoms (C, H, O, N, P) Smooth muscle tissue Molecule (DNA) 5 SYSTEM LEVEL Epithelial and connective tissues 4 ORGAN LEVEL Salivary glands Mouth Pharynx (throat) Smooth muscle Esophagus tissue layers Epithelial tissue Stomach Stomach Liver Pancreas Gallbladder (behind stomach) Large intestine Small intestine Mark Nielsen 6 ORGANISMAL LEVEL Digestive system Which level of structural organization is composed of two or more different types of tissues that work together to perform a specific function?  1.2 LEVELS OF BODY ORGANIZATION AND BODY SYSTEMS 5 TABLE 1.2 The Eleven Systems of the Human Body Bone C rtilage Ca Jo oint Hair Skeletal muscle Skin and associated d T Tendon glands SKELETAL SYSTEM (CHAPTERS 6–9) Components: Bones and joints of the body and their associated cartilages. Fingernails Functions: Supports and protects the body; provides a surface area for muscle attachments; aids body movements; houses cells that produce blood cells; stores minerals and lipids (fats). T Toenails INTEGUMENTARY SYSTEM (CHAPTER 5) MUSCULAR SYSTEM (CHAPTERS 10, 11) Components: Skin, and structures associated with it, Components: Specifically refers to skeletal such as hair, fingernails and toenails, sweat glands, muscle tissue, which is muscle usually and oil glands and the subcutaneous layer. attached to bones (other muscle tissues include smooth and cardiac). Functions: Protects the body; helps regulate body temperature; eliminates some wastes; helps make Functions: Participates in bringing about vitamin D; detects sensations such as touch, body movements, such as walking; maintains pain, warmth, and cold; stores fat; provides posture; and produces heat. insulation. T A B L E 1. 2 C O N T I N U E S 6 CHAPTER 1 AN INTRODUCTION TO THE HUMAN BODY TABLE 1.2 CONTINUED The Eleven Systems of the Human Body Pharyngeal tonsil Palatine tonsil Thym mus Lingual tonsil Thoracic duct Spleen Red bone Lymph marrow n node Brain Lymp y pha p atic vess sel Blood vessels s: V Vein Heart Spinal cord Artery r LYMPHATIC SYSTEM AND IMMUNITY (CHAPTER 15) Components: Lymphatic fluid, lymphatic vessels, spleen, thymus, lymph nodes, and tonsils; cells that carry out immune responses (B cells, T cells, and others). Nerve Functions: Returns proteins and fluid to blood; carries lipids from gastrointestinal tract to blood; contains sites of maturation and proliferation of B cells and T cells that protect against disease-causing microbes. CARDIOVASCULAR SYSTEM NERVOUS SYSTEM (CHAPTERS 12–14) (CHAPTERS 16–21) Components: Blood, heart, and blood vessels. Components: Brain, spinal cord, nerves, and special sense organs, such as the eyes and ears. Functions: Heart pumps blood through blood vessels; blood carries oxygen and nutrients to Functions: Generates action potentials (nerve cells and carbon dioxide and wastes away from impulses) to regulate body activities; detects cells and helps regulate acid–base balance, changes in the body’s internal and external temperature, and water content of body fluids; environments, interprets the changes, and blood components help defend against disease responds by causing muscular contractions or and repair damaged blood vessels. glandular secretions.  1.2 LEVELS OF BODY ORGANIZATION AND BODY SYSTEMS 7 RESPIRATORY SYSTEM (CHAPTER 23) Components: Lungs and air passageways such as the pharynx (throat), larynx (voice box), trachea (windpipe), and bronchial tubes within the lungs. Functions: Transfers oxygen from inhaled air to blood and carbon dioxide from blood to exhaled air; helps regulate acid–base balance of body fluids; air flowing out of lungs through vocal cords produces sounds. Nasal cavity Pharynx Oral cavity Larynx Pharr ynx Trachea Lar ynx x Bronchus DIGESTIVE SYSTEM (CHAPTER 24) ENDOCRINE SYSTEM (CHAPTER 22) Lung Components: Organs of gastrointestinal Components: Hormone-producing glands tract—a long tube that includes the (pineal gland, hypothalamus, pituitary mouth, pharynx (throat), esophagus, gland, thymus, thyroid gland, parathyroid stomach, small and large intestines, glands, adrenal glands, pancreas, ovaries, and anus; also includes accessory and testes) and hormone-producing cells in organs that assist in digestive processes, several other organs. such as the salivary glands, liver, Functions: Regulates body activities by gallbladder, and pancreas. releasing hormones, which are chemical Functions: Achieves physical and messengers transported in blood from an chemical breakdown of food; absorbs endocrine gland or tissue to a target organ. nutrients; eliminates solid wastes. Hyp pothalam mus Saliv alivar ary r Mouth Pine eal glan nd gland Pitu uitary gla and Phar ynxx Thyroid d gland Esophagus Thyyroid glan nd Parrathyroid d Adrenaal glan nds gland Liver Posterior view Stomach Pancreas Gallbla adder (behind Pancreas e s omach) st Small intestine Large Rectum intestine Anus Testis T (male) Ovary (female) T A B L E 1. 2 C O N T I N U E S 8 CHAPTER 1 AN INTRODUCTION TO THE HUMAN BODY TABLE 1.2 CONTINUED The Eleven Systems of the Human Body Ductus d erens def Seminal vesicle Penis Prostate T Testis Ductus deferens Seminal vesicle Prostate Penis Epididymis T Testis Mammary Kidney gland Ureter Uterine tube Urinary bladder Ovary Uterus V Vagina Uterine Urethra tube Uterus Ovary Vagina URINARY SYSTEM (CHAPTER 25) REPRODUCTIVE SYSTEMS (CHAPTER 26) Components: Kidneys, ureters, urinary bladder, Components: Gonads (testes in males and ovaries in females) and associated organs and urethra. (such as the uterine (fallopian) tubes, uterus, and vagina in females and epididymides, seminal vesicles, prostate, ductus (vas) deferenses, and penis in males). Functions: Produces, stores, and eliminates urine; eliminates wastes and regulates volume and chemical Functions: Gonads produce gametes (sperm or oocytes) that unite to form a new composition of blood; helps maintain the acid–base organism; gonads also release hormones that regulate reproduction and other body balance of body fluids; maintains body’s mineral processes; associated organs transport and store gametes; mammary glands produce balance; helps regulate production of red blood cells. milk.  1.4 BASIC ANATOMICAL TERMINOLOGY 9 1.3 LIFE PROCESSES This might be true if your upper limbs (described shortly) are at your sides. But if you held your hands up above your OBJECTIVE head, your fingers would be above your wrists. To prevent Define the important life processes of humans. this kind of confusion, anatomists use a standard anatomical position and a special vocabulary for relating body parts to All living organisms have certain characteristics that set them one another. apart from nonliving things. The following are six important life processes of humans: Anatomical Position 1. Metabolism (me-TAB-oˉ-lizm) is the sum of all the chemical processes that occur in the body. It includes the breakdown In anatomy, the anatomical position (an′-a-TOM-i-kal) is the of large, complex molecules into smaller, simpler ones and standard position of reference for the description of anatomical the building up of complex molecules from smaller, simpler structures. In the anatomical position, the subject stands erect ones. facing the observer, with the head level and the eyes facing 2. Responsiveness is the body’s ability to detect and re- directly forward. The lower limbs are parallel and the feet are spond to changes in its environment. Nerve cells respond flat on the floor and directed forward. The upper limbs are at the to changes in the environment by generating electrical sides with the palms facing forward (Figure 1.2). With the body signals, known as nerve impulses. Muscle cells respond to in the anatomical position, it is easier to visualize and understand nerve impulses by contracting, which generates force to its organization into various regions and describe relationships move body parts. of various structures. 3. Movement includes motion of the whole body, individual As just described, in the anatomical position, the body is up- organs, single cells, and even tiny organelles inside cells. right. There are two terms used to describe a reclining body. If 4. Growth is an increase in body size. It may be due to an in- the body is lying face down, it is in the prone position. If the crease in (1) the size of existing cells, (2) the number of cells, or body is lying face up, it is in the supine position. (3) the amount of material surrounding cells. 5. Differentiation (dif′-er-en-sheˉ-A ˉ -shun) is the process whereby Regional Names unspecialized cells become specialized cells. Specialized cells differ in structure and function from the unspecialized cells The human body is divided into several major regions that that gave rise to them. For example, a single fertilized egg cell can be identified externally. These are the head, neck, trunk, undergoes tremendous differentiation to develop into a unique upper limbs, and lower limbs. The head consists of the skull individual who is similar to, yet quite different from, either of and face. The skull encloses and protects the brain, while the the parents. face is the front portion of the head that includes the eyes, 6. Reproduction (rē-prō-DUK-shun) refers to either (1) the nose, mouth, forehead, cheeks, and chin. The neck, a modi- formation of new cells for growth, repair, or replacement or fied portion of the trunk, supports the head and attaches it to (2) the production of a new individual. the remainder of the trunk. The trunk consists of the neck, thorax, abdomen, and pelvis. Each upper limb (extremity) is Although not all of these processes are occurring in cells attached to the trunk and consists of the shoulder, armpit, arm throughout the body all of the time, when they cease to occur (portion of the limb from the shoulder to the elbow), forearm properly cell death may occur. When cell death is extensive and (portion of the limb from the elbow to the wrist), wrist, and leads to organ failure, the result is death of the organism. hand. Each lower limb (extremity) is also attached to the trunk CHECKPOINT and consists of the buttock, thigh (portion of the limb from the 5. What are the different meanings for growth? buttock to the knee), leg (portion of the limb from the knee to the ankle), ankle, and foot. The groin is the area on the front surface of the body marked by a crease on each side, where the trunk attaches to the thighs. Understanding the precise mean- ing of arm and forearm in the upper limb and thigh and leg in 1.4 BASIC ANATOMICAL the lower limb is very important when reading or describing a TERMINOLOGY clinical assessment. Figure 1.2 shows the anatomical and common names of OBJECTIVES major parts of the body. The anatomical term appears first Describe the orientation of the human body in the followed by the corresponding common name (in parentheses). anatomical position. For example, if you receive a tetanus shot in your gluteal region, Relate the common names to the corresponding it is in the buttock. Why is the anatomical term for a body part anatomical descriptive terms for various regions of the different from its common name? The anatomical term is based human body. on a Greek or Latin word or “root.” For example, the Latin Define the anatomical planes, the anatomical sections, and word axilla (ak-SIL-a) is the armpit region. Thus, the axillary the directional terms used to describe the human body. nerve is one of the nerves passing within the armpit region. Scientists and health-care professionals use a common language Understanding the word roots of anatomical terms can help of special terms when referring to body structures and their you learn the terms more easily. The word roots will become functions. The language of anatomy has precisely defined mean- more familiar as you read this book, so by the time you finish ings that allow us to communicate clearly and unambiguously. the course you’ll be able to tell your roommate with confidence For example, take the statement “The wrist is above the fingers.” that the funnybone she just hit on the door jamb is the olecranon 10 CHAPTER 1 AN INTRODUCTION TO THE HUMAN BODY Figure 1.2 The anatomical position. The anatomical names and corresponding common names (in parentheses) are indicated for specific body regions. For example, the cephalic region is the head. In the anatomical position, the subject stands erect facing the observer with the head level and the eyes facing forward. The lower limbs are parallel and the feet are flat on the floor and directed forward, and the upper limbs are at the sides with the T palms facing forward. Frontal (forehead) Temporal (temple) Cranial Orbital or ocular (eye) Cephalic (skull) Otic (ear) (Head) Facial Buccal (cheek) (face) Cephalic Nasal (nose) (Head) Cervical Occipital Oral (mouth) (base of skull) (Neck) Mental (chin) Cervical (Neck) Axillary Thoracic Sternal (breastbone) (armpit) (chest) Scapular Brachial Mammary (breast) (shoulder blade) (arm) Umbilical Vertebral Abdominal (spinal column) Antecubital (navel) (abdomen) Dorsal Trunk (front of elbow) Coxal (hip) Olecranal or (back) Inguinal Antebrachial (groin) cubital Upper (forearm) (back of elbow) limb Pelvic Sacral Lumbar (loin) Carpal (pelvis) (between (wrist) hips) Pollex Palmar (thumb) or volar (palm) Gluteal Manual (buttock) Digital or (hand) Perineal (region phalangeal of anus and (fingers) Femoral external genitals) Pubic Dorsum (thigh) (pubis) (back of hand) Patellar Popliteal Lower (anterior surface of knee) (hollow behind knee) limb Crural (leg) Sural Tarsal (calf) (ankle) Pedal (foot) Digital or phalangeal Dorsum (toes) Plantar (top of foot) (sole) Hallux Calcaneal (a) Anterior view (great toe) (b) Posterior view (heel) Why is it important to define one standard anatomical position? region (elbow) of her brachium (arm) (not that it will help pass through the body (Figure 1.3). A sagittal plane (SAJ-i- much with the pain). tal; sagitta-=arrow) is a vertical plane that divides the body or organ into right and left sides. More specifically, when such a plane passes through the midline of the body and divides it Planes and Sections into equal right and left sides, it is called a midsagittal plane, As you have just seen, referencing various body regions enables or a median plane. The midline is an imaginary vertical line that you to study the surface anatomy of the body. It is also possible divides the body into equal left and right sides. If the sagittal to study the internal structure of the body by slicing the body plane does not pass through the midline but instead divides the in different ways and examining the sections. The terms that body into unequal right and left sides, it is called a parasagittal follow describe the different planes and sections you will en- plane (para-=beside, near). A frontal, or coronal, plane (kō- counter in your anatomical studies; they are also used in many RŌ-nal; corona=crown) divides the body or an organ into front medical procedures. Planes are imaginary flat surfaces that and back portions. A transverse plane divides the body or an  1.4 BASIC ANATOMICAL TERMINOLOGY 11 Figure 1.3 Planes through the human body. Figure 1.4 Planes and sections through different parts of the brain. The diagrams (left) show the planes, M Midsagittal, parasagittal, frontal, transverse, and oblique and the photographs (right) show the resulting planes divide the body in specific ways. p sections. Note: The “view” arrows in the diagrams indicate the direction from which each section is viewed. This aid is used throughout the book to indicate viewing perspective. Frontal P Planes divide the body in various ways and the resulting plane ccuts made along a plane are called sections. Midsagittal plane Parasagittal plane View Midsagittal section Transverse (a) plane Midsagittal plane (through Frontal plane midline) Oblique plane View Frontal section (b) Anterolateral view View Transverse plane Which plane divides the heart into anterior and posterior portions? Posterior Anterior Transverse section organ into upper and lower portions. A transverse plane may also be termed a cross-sectional plane or horizontal plane. Sag- (c) ittal, frontal, and transverse planes are all at right angles to one another. An oblique plane (ō-BLĒK), by contrast, passes Which plane divides the brain into equal right and left through the body or organ at an oblique angle (any angle other sides? than a 90° angle). When you study a body region, you often view it in section. Sections are cuts of the body or one of its organs made along one of the planes just described. A section produces a flat two- CHECKPOINT dimensional surface of the original three-dimensional struc- 6. Describe the anatomical position and explain why it is used. ture. It is important to know the plane of the section so you 7. Locate each region shown in Figure 1.2 on your own can understand the anatomical relationship of one part to body, and then identify it by its anatomical descriptive another. Figure 1.4 indicates how three different sections— form and corresponding common name. a midsagittal section, a frontal section, and a transverse (cross) 8. Which of the planes that divide the body are vertical? section—provide different views of the brain. 9. What is the difference between a plane and a section? 12 CHAPTER 1 AN INTRODUCTION TO THE HUMAN BODY E X HIBIT 1.A Directional Terms (Figure 1.5) OBJECTIVE lower part of the body. It is important to understand that direc- Define each directional term used to describe the human tional terms have relative meanings; they make sense only when body. used to describe the position of one structure relative to another. For example, your knee is superior to your ankle, even though both Overview are located in the inferior half of the body. Study the directional terms below and the example of how each is used. As you read the To help improve communication when discussing the basic parts examples, look at Figure 1.5 to see the location of each structure. of the body and the relationships those parts have to one another, anatomists and health-care professionals use specific directional terms, words that describe the position of one body part rela- CHECKPOINT tive to another. Most of the directional terms used to describe the 10. Which directional terms can be used to specify the relationship of one part of the body to another can be grouped into relationships between (1) the elbow and the shoulder, pairs that have opposite meanings. For example, superior means (2) the left and right shoulders, (3) the sternum and the toward the upper part of the body, and inferior means toward the humerus, and (4) the heart and the diaphragm? DIRECTIONAL TERM DEFINITION EXAMPLE OF USE Superior (soo′-PĒR-ē-or) Above or higher in position; toward the head. The heart is superior to the liver. (Not used in reference to the limbs.) Cranial (KRĀN-ē-al) or Relating to the skull or head; toward the head. The stomach is more cranial than the urinary cephalic (se-FAL-ik) (This is a more flexible term than superior because bladder. it can be applied to all animals, whether they stand upright on two limbs or on all four limbs.) Inferior (in′-FĒR-ē-or) Below or lower in position; toward the feet. (Not The stomach is inferior to the lungs. used in reference to the limbs.) Rostral (ROS′-tral) Relating to the nose and mouth region; toward The frontal lobe of the brain is rostral to the the face. (Used only in references within the head). occipital lobe (see Figure 18.12b). Caudal (KAWD-al) Relating to the tail; at or near the tail or posterior The lumbar vertebrae are caudal to the cervical part of the body. (Used only in references within the vertebrae (see Figure 7.15a). trunk). Anterior (an-TĒR-ē-or) Nearer to or at the front of the body. The sternum (breastbone) is anterior to the heart. Posterior (pos-TĒR-ē-or) Nearer to or at the back of the body. The esophagus (food tube) is posterior to the trachea (windpipe). Ventral (VEN-tral) Relating to the belly side of the body; toward the The intestines are ventral to the vertebral belly. (Used synonymously with anterior in human column. anatomy.) Dorsal (DORS-al) Relating to the back side of the body; toward the The kidneys are dorsal to the stomach. back. (Used synonymously with posterior in human anatomy.) Medial (MĒ-dē-al) Nearer to the midline (an imaginary vertical line The ulna is medial to the radius. that divides the body into equal right and left sides). Lateral (LAT-er-al) Farther from the midline. The lungs are lateral to the heart. Intermediate (in′-ter-MĒ-dē-at) Between two structures. The transverse colon is intermediate to the ascending colon and descending colon. Ipsilateral (ip-si-LAT-er-al) On the same side of the body’s midline as another The gallbladder and ascending colon are structure. ipsilateral. Contralateral On the opposite side of the body’s midline from The ascending and descending colons are (CON-tra-lat-er-al) another structure. contralateral. Proximal (PROK-si-mal) Nearer to the attachment of a limb to the trunk; The humerus (arm bone) is proximal to the nearer to the origination of a structure. radius. Distal (DIS-tal) Farther from the attachment of a limb to the trunk; The phalanges (finger bones) are distal to the farther from the origination of a structure. carpals (wrist bones). Superficial (soo′-per-FISH-al) Toward or on the surface of the body. The ribs are superficial to the lungs. Deep Away from the surface of the body. The ribs are deep to the skin of the chest and back.  1.4 BASIC ANATOMICAL TERMINOLOGY 13 DIRECTIONAL TERM DEFINITION EXAMPLE OF USE External (ex-STERN-al) Toward the outside of a structure. (Is typically used The visceral pleura is on the external surface of when describing relationships of individual organs.) the lungs (see Figure 1.7a). Internal (in-TERN-al) Toward the inside of a structure. (Is typically used The mucosa forms the internal lining of the when describing relationships of individual organs.) stomach (see Figure 24.11a). Figure 1.5 Directional terms. Directional terms precisely locate various parts of the body relative to one another. D LATERAL MEDIAL LATERAL SUPERIOR Midline Esophagus (food tube) Trachea (windpipe) PROXIMAL Rib Right lung Left lung Sternum (breastbone) Heart Humerus Stomach Liver Transverse colon Radius Small intestine Ulna Gallbladder Descending colon Ascending colon Carpals Metacarpals Phalanges DISTAL INFERIOR Anterior view of trunk and right upper limb Is the radius proximal to the humerus? Is the esophagus anterior to the trachea? Are the ribs superficial to the lungs? Is the urinary bladder medial to the ascending colon? Is the sternum lateral to the descending colon?  1.5 BODY CAVITIES 15 system. Organs inside the thoracic and abdominopelvic cavities of the lungs (the part of the balloon touching your fist); the are termed the viscera (VIS-er-a). parietal pleura lines the chest wall and covers the superior sur- face of the diaphragm. In between is the serous cavity called the pleural cavity (analogous to the inside of the balloon). The Thoracic and Abdominal Cavity Membranes serous membrane of the heart is the pericardium (per′-i-KAR- A membrane is a thin pliable tissue that covers, lines, partitions, dē-um) (see Figure 1.7a, c, d). The visceral pericardium covers or connects structures. One example is a slippery double-layered the surface of the heart, and the parietal pericardium lines the membrane associated with body cavities that does not open directly fibrous pericardium that surrounds the heart. Between them is to the exterior called a serous membrane. It covers the viscera the serous cavity called the pericardial cavity. The peritoneum within the thoracic and abdominal cavities and also lines the walls (per′-i-to-NE-um) is the serous membrane of the abdomi- of the thorax and abdomen. The parts of a serous membrane are nal cavity (see Figure 24.3a). The visceral peritoneum covers (1) the parietal layer (pa-RĪ-e-tal=wall of a cavity), a thin epithe- the abdominal viscera, and the parietal peritoneum lines the ab- lium that lines the walls of the body cavities, and (2) the visceral dominal wall and covers the inferior surface of the diaphragm. layer (VIS-er-al), a thin epithelium that covers and adheres to the Between them is the serous cavity called the peritoneal cavity. viscera within the body cavities. Because the parietal and visceral Most abdominal organs are surrounded by the peritoneum and membranes are continuous with one another, they form a serous are referred to as intraperitoneal (in′-tra-per′-i-tō-NĒ-al; intra- sac. The organs of the body cavity push into this serous sac, simi- =within). These include the stomach, spleen, liver, gallblad- lar to pushing your hand into a balloon (Figure 1.7e). Between der, jejunum and ileum of the small intestine, and the cecum, the parietal and visceral layers is a potential space called the serous appendix, and tranverse colon of the large intestine. However, cavity. It contains a small amount of lubricating fluid called serous some are not surrounded by the peritoneum or are only par- fluid that reduces friction between the two layers, allowing the tially covered by peritoneum and lie behind the peritoneum. viscera to slide freely during movements such as the pumping of Such organs are said to be retroperitoneal (re-trō-per′-i-tō- the heart or the inflation and deflation of your lungs when you NĒ-al; retro=behind). The kidneys, adrenal glands, pancreas, breathe in and out. duodenum of the small intestine, ascending and descending The serous membrane associated with the lungs is called the colons of the large intestine, and the abdominal aorta and inferior pleura (Figure 1.7a, c, d). The visceral pleura clings to the surface vena cava are retroperitoneal organs. Brain in cranial cavity Spinal cord in vertebral canal Lung Thoracic Heart in Heart cavity thoracic cavity Diaphragm Vertebral column Diaphragm Liver and intestines in abdominal cavity Liver Abdominopelvic cavity Urinary bladder Intestines in pelvic cavity Dissection Shawn Miller; Photograph Mark Nielsen Dissection Shawn Miller; Photograph Mark Nielsen (c) Sagittal section (d) Anterior view In which cavities are the following organs located: urinary bladder, stomach, heart, small intestine, lungs, internal female reproductive organs, thymus, spleen, liver? Use the following symbols for your responses: T = thoracic cavity, A = abdominal cavity, or P = pelvic cavity. 16 CHAPTER 1 AN INTRODUCTION TO THE HUMAN BODY In addition to the major body cavities just described, you movable joints and contain synovial fluid (see Figure 9.3a). A will learn about other regional cavities in later chapters. These summary of the major body cavities and their membranes is include the oral (mouth) cavity, which contains the tongue presented in the table in Figure 1.6. and teeth (see Figure 24.4); the nasal cavity in the nose (see Figure 23.1a); the orbital cavities (orbits), which contain the CHECKPOINT eyeballs (see Figure 7.2a); the middle ear cavities (middle ears), 11. What structures separate the various body cavities from which contain small bones and muscles in the middle ear one another? (Figure 21.11a); and synovial cavities, which are found in freely 12. Describe the contents of the mediastinum. Figure 1.7 The thoracic cavity. The black dashed lines in (a) and (b) indicate the borders of the mediastinum. Notice that the pericardium surrounds the heart, and that the pleurae surround the lungs. Note: When transverse sections such as those shown in (b) and (c) are viewed inferiorly (from below), the anterior aspect of the body appears on the top of the illustration and the left side of the body appears on the right side of the illustration. T mediastinum is an anatomical region that is between the lungs and extends from the sternum to the vertebral column The and from the first rib to the diaphragm. a Mediastinum Right pleural cavity Parietal pericardium Pleura Pericardial cavity Pericardium Parietal pleura Visceral pericardium Visceral pleura Diaphragm Left pleural cavity (a) Anterior view of thoracic cavity Transverse plane ANTERIOR View Sternum (breastbone) Muscle Thymus Heart Pericardial cavity Left lung Right lung Esophagus Aorta (food tube) Right pleural Vertebral column cavity (backbone) Left pleural Rib cavity (b) Inferior view of transverse section of thoracic cavity  1.5 BODY CAVITIES 17 ANTERIOR Sternum Parietal pericardium Parietal pleura Pericardial Pericardium cavity Right pleural Visceral Pleura cavity pericardium Heart View Visceral pleura Skin Esophagus Aorta Right lung Vertebral column (backbone) Rib Spinal cord MEDIAL Mark Nielsen (c) Inferior view of transverse section of thoracic cavity Parietal pericardium Pericardial Right Pericardium cavity lung Visceral pericardium Heart Visceral pleura (covering lung) Parietal pleura (covering fibrous pericardium) Diaphragm Pleura Parietal pleura (lining rib cage) Pleural cavity Parietal pleura Dissection Shawn Miller; Photograph Mark Nielsen (covering diaphragm) (d) Layers of the pericardium and pleura Parietal layer (outer wall of balloon) Serous cavity (containing small Organ amount of lubricating serous fluid) Visceral layer (inner wall of balloon) (e) The concept of a serous sac Which of the following structures are contained in the mediastinum: right lung, heart, esophagus, spinal cord, trachea, rib, thymus, left pleural cavity? 18 CHAPTER 1 AN INTRODUCTION TO THE HUMAN BODY 1.6 ABDOMINOPELVIC REGIONS dividing the abdominopelvic cavity into smaller areas. In the first method, two transverse and two vertical lines, aligned like a tick- AND QUADRANTS tack-toe grid, partition this cavity into nine abdominopelvic regions (Figure 1.8). The superior horizontal line, the subcostal OBJECTIVE line (sub-=below; costal=rib), passes across the lowest level of the Name and describe the abdominopelvic regions and the 10th costal cartilages (see also Figure 7.23c); the inferior hori- abdominopelvic quadrants. zontal line, the transtubercular line (trans-too-BER-kū-lar), passes To describe the location of the many abdominal and pelvic or- across the superior margins of the iliac crests of the right and left gans more easily, anatomists and clinicians use two methods of hip bones (see also Figure 8.7). Two vertical lines, the left and Figure 1.8 Abdominopelvic regions. (a) The nine regions in surface view. (b) The nine regions with the greater omentum removed. The greater omentum is a double fold of the serous membrane that contains fatty tissue and covers some of the abdominal organs (see Figure 24.3). (c) Organs or parts of organs in the nine regions. The internal reproductive organs in the pelvic cavity are shown in Figures 26.1 and 26.11. The nine-region designation is used for anatomical studies. T Clavicles Midclavicular lines Right Left Left Epigastric hypochondriac Right region region hypochondriac region Subcostal line Left lumbar Right Umbilical region lumbar region region Transtubercular line Pubic Right inguinal Left inguinal region region region Andy Washnik (a) Anterior view showing abdominopelvic regions Clavicles Midclavicular lines Right Left Right Left Right lobe Spleen Epigastric of liver Left lobe of liver hypochondriac hypochondriac region region region Stomach Gallbladder 10th costal Transverse colon cartilage of large intestine Ascending colon Right Umbilical Left of large intestine Descending colon lumbar region lumbar region region of large intestine Small intestine Cecum Pubic Appendix Right inguinal region Left inguinal region region Urinary bladder (b) Anterior view showing location of abdominopelvic regions (c) Anterior superficial view of organs in abdominopelvic regions In which abdominopelvic region is each of the following found: most of the liver, transverse colon, urinary bladder, spleen?  1.7 THE HUMAN BODY AND DISEASE 19 right midclavicular lines (mid-kla-VIK-ū-lar), are drawn through CLIN ICA L CON N ECTI O N | Autopsy the midpoints of the clavicles (collar bones), just medial to the nipples. The four lines divide the abdominopelvic cavity into a An autopsy (AW-top-seˉ; auto-=self; -opsy=to see) or necropsy is larger middle section and smaller left and right sections. The a postmortem (after-death) examination of the body and dissec- names of the nine abdominopelvic regions are right hypochon- tion of its internal organs to confirm or determine the cause of driac (hı̄′-pō-KON-drē-ak), epigastric (ep-i-GAS-trik), left death. An autopsy can uncover the existence of diseases not detected hypochondriac, right lumbar, umbilical (um-BIL-i-kal), left during life, determine the extent of injuries, and explain how those lumbar, right inguinal (iliac) (IN-gwi-nal), hypogastric (pubic), injuries may have contributed to a person's death. It also may support and left inguinal (iliac). Note which organs and parts of organs the accuracy of diagnostic tests, establish the beneficial and adverse are in the different regions by carefully examining Figure 1.8c. effects of drugs, reveal the effects of environmental influences on the body, provide more information about a disease, assist in the accumu- The organs of the abdominopelvic cavity will be discussed in de- lation of statistical data, and educate health-care students. Moreover, tail in later chapters. an autopsy can reveal conditions that may affect offspring or siblings The second method is simpler and divides the abdominopel- (such as congenital heart defects). An autopsy may be legally required, vic cavity into quadrants (KWOD-rantz; quad-=one-fourth), as such as in the course of a criminal investigation, or may be used to re- shown in Figure 1.9. In this method, a transverse line, the trans- solve disputes between beneficiaries and insurance companies about umbilical line, and a midsagittal line, the median line, are passed the cause of death. Because it is so important for the clinician perform- through the umbilicus (um-BIL-i-kus or um-bi-LĪ–kus; umbilic- ing the autopsy to record and detail the findings accurately, complete =navel) or belly button. The names of the abdominopelvic quad- knowledge of the terms outlined in this chapter is essential. rants are right upper quadrant (RUQ), left upper quadrant (LUQ), right lower quadrant (RLQ), and left lower quadrant (LLQ). The nine-region division is widely used for anatomical studies to determine organ location; quadrants are more com- CHECKPOINT monly used by clinicians for describing the site of abdominopel- 13. Locate the abdominopelvic regions and the abdomi- vic pain, tumor, injury, or other abnormality. nopelvi