Terms of Relationship and Comparison

  1. Various adjectives, arranged as pairs of opposites, describe the relationship of parts of the body or compare the position of two structures relative to each other.Some of these terms are specific for comparisons made in the anatomical position, or with reference to the anatomical planes:

  2. Superior refers to a structure that is nearer the vertex, the topmost point of the cranium (Mediev. L., skull). Cranial relates to the cranium and is a useful directional term, meaning toward the head or cranium. Inferior refers to a structure that is situated nearer the sole of the foot. Caudal (L. cauda, tail) is a useful directional term that means toward the feet or tail region, represented in humans by the coccyx (tail bone), the small bone at the inferior (caudal) end of the vertebral column.

  3. Posterior (dorsal) denotes the back surface of the body or nearer to the back.Anterior (ventral) denotes the front surface of the body. Rostral is often used instead of anterior when describing parts of the brain; it means toward the rostrum (L. for beak); however, in humans, it denotes nearer the anterior part of the head (e.g.,the frontal lobe of the brain is rostral to the cerebellum).

  4. Medial is used to indicate that a structure is nearer to the median plane of the body. For example, the 5th digit of the hand (little finger) is medial to the other digits. Conversely, lateral stipulates that a structure is farther away from the median plane. The 1st digit of the hand (thumb) is lateral to the other digits.

  5. Dorsum usually refers to the superior aspect of any part that protrudes anteriorly from the body, such as the dorsum of the tongue, nose, penis, or foot.It is also used to describe the posterior surface of the hand, opposite the palm.Because the term dorsum may refer to both superior and posterior surfaces in humans, the term is easier to understand if one thinks of a quadrupedal plantigrade animal that walks on its palms and soles, such as a bear. The sole is the inferior aspect or bottom of the foot, opposite the dorsum, much of which is in contact with the ground when standing barefoot. The surface of the hands, the feet, and the digits of both corresponding to the dorsum is the dorsal surface, the surface of the hand and fingers corresponding to the palm is the palmar surface, and the surface of the foot and toes corresponding to the sole is the plantar surface.

  6. Combined terms describe intermediate positional arrangements: inferomedial means nearer to the feet and median plane—for example, the anterior parts of the ribs run inferomedially; superolateral means nearer to the head and farther from the median plane.

  7. Other terms of relationship and comparisons are independent of the anatomical position or the anatomical planes, relating primarily to the body’s surface or its central core:

a) Superficial, intermediate, and deep describe the position of structures relative to the surface of the body or the relationship of one structure to another underlying or overlying structure.

b) External means outside of or farther from the center of an organ or cavity, while internal means inside or closer to the center, independent of direction.

c) Proximal and distal are used when contrasting positions nearer to or farther from the attachment of a limb or the central aspect of a linear structure, respectively.

Terms of Laterality

Ø Paired structures having right and left members (e.g., the kidneys) are bilateral, whereas those occurring on one side only (e.g., the spleen) are unilateral.

Ø Designating whether you are referring specifically to the right or left member of bilateral structures can be critical and is a good habit to begin at the outset of one’s training to become a health professional.

Ø Something occurring on the same side of the body as another structure is ipsilateral; the right thumb and right great (big) toe are ipsilateral, for example.

Ø Contralateral means occurring on the opposite side of the body relative to another structure; the right hand iscontralateral to the left hand.