1 Introduction to Anatomic Systems and Terminology
Anatomy of the human body can be studied by inspection of all the systems that occupy a specific region or by considering the global aspects of a particular system throughout the entire body. The first approach tends to focus on anatomic relationships while the second is better suited to studying physiologic influences. Most systems, however, are conveniently confined to one or two regions, and in this text are discussed in the units devoted to those regions. Some systems, however, (those included in this chapter) are more pervasive throughout the body, and a fundamental under-standing of their basic organization is important before undertak-ing the study of the systems they support.
1.1 Structural Design of the Human Body
The most preliminary inspection of the human body reveals that it is structurally divided into a head and neck region, a trunk, and paired upper and lower extremities (limbs). Each is further divided into smaller regions (Fig. 1.1; Table 1.1). These house the structures that make up the functional organ systems that perform the basic bodily functions (Table 1.2). Although the pri-mary organ of a system is often confined to a single anatomic region (e.g., the brains resides in the head), systems extend beyond regional borders, both anatomically and physiologically, to inte-grate their influences on normal function and growth.
Table 1.1 Regional Subdivisions of the Body
| Trunk •Thorax (chest) •Abdomen •Pelvis |
| Upper limb •Shoulder girdle •Free upper limb |
| Lower limb •Pelvic girdle •Free lower limb |
Table 1.2 Functional Subdivisions by Organ Systems
| Locomotor system (musculoskeletal system) •Skeleton and skeletal connections (passive part) •Striated skeletal musculature (active part) |
| Viscera •Cardiovascular system •Hemolymphatic system •Endocrine system •Respiratory system •Digestive system •Urinary system •Male and female reproductive system |
| Nervous system •Central and peripheral nervous system •Sensory organs |
| The skin and its appendages |
Fig. 1.1 Structural design of the human body: location of the internal organs.
(From Schuenke M, Schulte E, Schumacher U. THIEME Atlas of Anatomy, Vol 1. Illustrations by Voll M and Wesker K. 3rd ed. New York: Thieme Publishers; 2020.)
1.2 Terms of Location and Direction, Cardinal Planes, and Axes
—All locational and directional terms used in anatomy, and in medical practice, refer to the human body in the anatomic position, in which the body is upright, arms at the side, with the eyes, palms of the hands, and feet directed forward (Fig. 1.2, Table 1.3).
—Three perpendicular cardinal planes and three axes based on the three spatial coordinates can be drawn through the body (Fig. 1.3).
•The sagittal plane passes through the body from front to back, dividing it into right and left sides.
Fig. 1.2 Anatomic position.
Anterior view. (From Schuenke M, Schulte E, Schumacher U. THIEME Atlas of Anatomy, Vol 1. Illustrations by Voll M and Wesker K. 3rd ed. New York: Thieme Publishers; 2020.)
Table 1.3 General Terms of Location and Direction
| Upper Body (Head, Neck, and Trunk) |
| Cranial | Pertaining to, or located toward, the head |
| Caudal | Pertaining to, or located toward, the tail |
| Anterior | Pertaining to, or located toward, the front; synonym: ventral (used for all animals) |
| Posterior | Pertaining to, or located toward, the back; synonym: dorsal (used for all animals) |
| Axial | Pertaining to the axis of a structure |
| Transverse | Situated at right angles to the long axis of a structure |
| Longitudinal | Parallel to the long axis of a structure |
| Horizontal | Parallel to the plane of the horizon |
| Vertical | Perpendicular to the plane of the horizon |
| Medial | Toward the median plane |
| Lateral | Away from the median plane (toward the side) |
| Median | Situated in the median plane or midline |
| Peripheral | Situated away from the center |
| Superficial | Situated near the surface |
| Deep | Situated deep beneath the surface |
| External | Outer or lateral |
| Apical | Pertaining to the top or apex |
| Basal | Pertaining to the bottom or base |
| Sagittal | Situated parallel to the sagittal suture |
| Coronal | Situated parallel to the coronal suture (pertaining to the crown of the head) |
| Proximal | Close to, or toward, the trunk, or toward the point of origin |
| Distal | Away from the trunk (toward the end of the limb), or away from the point of origin |
| Radial | Pertaining to the radius or the lateral side of the forearm |
| Ulnar | Pertaining to the ulna or the medial side of the forearm |
| Tibial | Pertaining to the tibia or the medial side of the leg |
| Fibular | Pertaining to the fibula or the lateral side of the leg |
| Palmar (volar) | Pertaining to the palm of the hand |
| Plantar | Pertaining to the sole of the foot |
| Dorsal | Pertaining to the back of the hand or top of the foot |
Fig. 1.3 Cardinal planes and axes.
Neutral position, left anterolateral view. (From Schuenke M, Schulte E, Schumacher U. THIEME Atlas of Anatomy, Vol 1. Illustrations by Voll M and Wesker K. 3rd ed. New York: Thieme Publishers; 2020.)
•The coronal plane passes through the body from side to side, dividing it into front (anterior) and back (posterior) parts.
•The transverse (axial, horizontal, cross-sectional) plane divides the body into upper and lower parts. A particular transverse section is often given the designation of the corresponding vertebral level, such as T4, which passes through the fourth thoracic vertebra.
•The longitudinal axis passes along the height of the body in a craniocaudal direction.
•The sagittal axis passes from the front to the back (or the back to the front) of the body in an anteroposterior direction.
•The transverse (horizontal) axis passes through the body from side to side.
1.3 Landmarks and Reference Lines
—In surface anatomy, palpable structures or visible markings on the surface of the body are used to identify the location of underlying structures. Reference lines are vertical or transverse planes that connect palpable structures or markings (Tables 1.4, 1.5, and 1.6; see also Fig. 1.5).
Table 1.4 Anterior and Lateral Reference Lines on the Trunk
(From Schuenke M, Schulte E, Schumacher U. THIEME Atlas of Anatomy, Vol 1. Illustrations by Voll M and Wesker K. 3rd ed. New York: Thieme Publishers; 2020.)
| Anterior midline | Passes through the center of the sternum |
| Sternal line | Passes along the lateral border of the sternum |
| Midclavicular line | Passes through the midpoint of the clavicle |
| Parasternal line | Passes through a point midway between the sternal and midcla- vicular lines |
| Anterior axillary line | Marks the anterior axillary fold formed by the pectoralis major... |
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