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Essential Clinical Anatomy relates the structure and function of the body to what is commonly required in the general practice of medicine, dentistry, and the allied health sciences. Because the number of details in anatomy overwhelms many beginning students, Essential Clinical Anatomy simplifies, correlates, and integrates the information so that it is easier to understand. The clinical correlation boxes (blue boxes) illustrate the clinical applications of anatomy. The surface anatomy boxes (orange boxes) provide an understanding of what lies under the skin, and the medical imaging techniques (green boxes), included throughout and at the end of each chapter, illustrate how anatomy is visualized clinically.

APPROACHES TO STUDYING ANATOMY

There are three main approaches to studying human gross anatomy: regional, systemic, and clinical (applied).

Regional anatomy is based on the organization of the body into parts, which are further subdivided into regions (Fig. 1.1). Emphasis is placed on the relationships of systemic structures (e.g., muscles, nerves, and arteries) within the region. Each region is not an isolated part and must be put into the context of adjacent regions and of the body as a whole. Surface anatomy is an essential part of the regional approach, providing a knowledge of what structures are visible and/or palpable (perceptible to touch) in the living body at rest and in action. The physical examination of patients is the clinical extension of surface anatomy.

FIGURE 1.1. Anatomical position, parts of body, and regions of lower limb.

Systemic anatomy is an approach to anatomical study organized by organ systems that work together to carry out complex functions. None of the organ systems functions in isolation. For example, much of the skeletal, articular, and muscular systems constitute the locomotor system. And although the structures directly responsible for locomotion are the muscles, bones, joints, and ligaments, other systems are involved as well. The arteries and veins of the circulatory system supply oxygen to them and remove waste from them, and the nerves of the nervous system stimulate them to act. Brief descriptions of the systems of the body and their fields of study (in parentheses) follow:

• Integumentary system (dermatology) consists of the skin (integument) and its appendages, such as the hair and nails. The skin, an extensive sensory organ, forms a protective covering for the body.

• Skeletal system (osteology, orthopedics) consists of bones and cartilage. It provides support for the body and protects vital organs. The muscular system acts on the skeletal system to produce movements.

• Articular system (arthrology) consists of joints and their associated ligaments. It connects the bony parts of the skeletal system and provides the sites at which movements occur.

• Muscular system (myology) consists of muscles that act (contract) to move or position parts of the body (e.g., the bones that articulate at joints).

• Nervous system (neurology) consists of the central nervous system (brain and spinal cord) and the peripheral nervous system (nerves and ganglia, together with their motor and sensory endings). The nervous system controls and coordinates the functions of the organ systems.

• Circulatory system (angiology) consists of the cardiovascular and lymphatic systems, which function in parallel to distribute fluids within the body.

• Cardiovascular system (cardiology) consists of the heart and blood vessels that propel and conduct blood through the body.

• Lymphatic system consists of a network of lymphatic vessels that withdraws excess tissue fluid (lymph) from the body’s interstitial (intercellular) fluid compartment, filters it through lymph nodes, and returns it to the bloodstream.

• Digestive or alimentary system (gastroenterology) consists of the organs and glands associated with the ingestion, mastication (chewing), deglutition (swallowing), digestion and absorption of food, and the elimination of feces (solid wastes) after the nutrients have been absorbed.

• Respiratory system (pulmonology) consists of the air passages and lungs that supply oxygen and eliminate carbon dioxide. The control of airflow through the system produces tone, which is further modified into speech.

• Urinary system (urology) consists of the kidneys, ureters, urinary bladder, and urethra, which filter blood and subsequently produce, transport, store, and intermittently excrete liquid waste (urine).

• Genital (reproductive) systems (obstetrics and gynecology for females, andrology for males) consist of the gonads (ovaries and testes) and the other genital organs concerned with reproduction.

• Endocrine system (endocrinology) consists of discrete ductless glands (e.g., thyroid gland) as well as cells of the intestine and blood vessel walls and specialized nerve endings that secrete hormones. Hormones are distributed by the cardiovascular system to reach receptor organs in all parts of the body. These glands influence metabolism and coordinate and regulate other processes (e.g., the menstrual cycle).

Clinical (applied) anatomy emphasizes aspects of the structure and function of the body important to clinical practice. It encompasses both the regional and the systemic approaches and stresses clinical application. Case studies, demonstrating the application of anatomy in clinical practice, are integral parts of the clinical approach.

SEX AND GENDER

Sex, male or female, is assigned genetically. Females have 46 chromosomes including 2 X chromosomes and males have 46 chromosomes including an X and a Y chromosome. There are also uncommon genetically based conditions where the chromosome number varies, such as Klinefelter syndrome (47 chromosomes [XXY]) and Jacob syndrome (47 chromosomes [XYY]).

Gender identity is an individual’s intrinsic sense of their own gender, which may or may not be consistent with their sex assigned chromosomally (or genetic sex). Gender is not a binary but a spectrum that may be expressed through appearance, personality, behaviors, and relationships or not be outwardly expressed at all.

The difference between sex and gender is important for clinical practice to be able to understand and form a trusting relationship with your patients. Clinically, gender dysphoria is the significant distress an individual may undergo due to a mismatch between their gender identity and their genetic sex. Although some children see their anatomy as having a different meaning to the way society sees it, many may not express feelings and behaviors until puberty or much later.

ANATOMICOMEDICAL TERMINOLOGY

Anatomy has an international vocabulary that is the foundation of medical terminology. This nomenclature enables communication worldwide. Although eponyms (names of structures derived from the names of people) are not used in official anatomical terminology, those commonly used by clinicians appear in parentheses to aid students in their clinical years. Similarly, formerly used terms appear in parentheses on first mention. The terminology in this book conforms to the second edition of the Terminologia Anatomica (Federative International Programme for Anatomical Terminology [FIPAT], 2019).

Anatomical Position

All anatomical descriptions are expressed in relation to the anatomical position (Fig. 1.1) to ensure that the descriptions are not ambiguous. The anatomical position refers to people—regardless of the actual position they may be in—as if they were standing erect, with their

• head, eyes (gaze), and toes directed anteriorly (forward).

• upper limbs by the sides with the palms facing anteriorly.

• lower limbs close together with the feet parallel and the toes directed anteriorly.

Anatomical Planes and Sections

Anatomical descriptions relating to sectional anatomy and planar medical imaging (e.g., CT or MRI—see “Medical Imaging” at the end of this chapter) are based on conceptual planes that intersect the body in the anatomical position (Fig. 1.2). There are unlimited sagittal, frontal, transverse, and oblique planes, but there is only one median plane.

• Median (median sagittal) plane is the vertical plane passing longitudinally through the center of the body, dividing it into right and left halves.

• Sagittal planes are vertical planes passing through the body parallel to the median plane. It is helpful to give a point of reference to indicate the position of a specific plane—for example, a sagittal plane through the midpoint of the clavicle. A plane parallel to and near the median plane may be referred to as a paramedian plane.

• Frontal (coronal) planes are vertical planes passing through the body at right angles to the median plane, dividing it into anterior (front) and posterior (back) portions—for example, a frontal plane through the heads of the mandible.

• Transverse planes are planes passing through the body at right angles to the median and frontal planes. A transverse plane divides the body into superior (upper) and inferior (lower) parts—for example, a transverse plane through the umbilicus. Radiologists refer to transverse planes as transaxial planes or simply axial planes.

• Oblique planes or sections are planes or sections that do not align with the preceding planes.

FIGURE 1.2. Anatomical position and anatomical planes of body.

Terms of Relationship and Comparison

Various adjectives, arranged as pairs of opposites, describe the relationship of parts of the body in the anatomical position and compare the position of two structures relative to each other. These pairs of adjectives are explained and illustrated in Figure 1.3. For example, the eyes are superior to the nose, whereas the nose is inferior to the eyes.