Comparative Animal Anatomy

Topographical terms

(A) TERMS USED TO INDICATE THE PRECISE POSITION AND DIRECTION

OF PARTS OF THE BODY

N.B. It is to be assumed that the terms listed below apply to a quadruped

(four-legged) animal in an ordinary standing position.

PLANE: A flat surface, real or imaginary, passing through the animal, or part of it.

TYPES OF PLANES: (See Figs. 1-A and 1-B)

1. MEDIAN OR LONGITUDINAL: (divides the body into similar halves)

divides the head, body of the limb longitudinally into equal right and left

halves.

2. SAGITTAL: passes through the head, body or limb parallel to the median

plane.

3. TRANSVERSE OR SEGMENTAL: cuts perpendicular to the median

plane, or at right angles to its long axis or an organ or limb.

4. FRONTAL (OR CORONAL): perpendicular to the median and transverse

planes.

SURFACES: The outer or external aspects of an object or body.

TYPES OF SURFACES: (see Figs. 1-C and 1-D)

1. VENTRAL: the surface directed towards the ground. Towards or relatively

near to the underside of the head or body.

2. DORSAL: the opposite surface to the preceding (i.e. towards or relatively

near to the top of the head, back of the neck, trunk or tail). On the limbs, it

applies to the upper or front surfaces of the carpus (knee),, tarsus (hock),

metapodium (homologous to the hand and foot), and digits.

3. MEDIAL OR INTERNAL: a surface or structure which is nearer than

another to the median plane (i.e. towards or relatively near to the median

plane).

4. LATERAL OR EXTERNAL: a surface which is further than another

from the median plane (i.e. away from or relatively further from the median

plane).

5. CRANIAL: is the head-end of the body. A surface towards or relatively

near to the head. On the limbs, it only applies to structures above the

carpus and tarsus. You may also encounter the term CEPHALIC which

means the same thing.

Figure 1-A: Terms of planes and of decirtion( Redrawn from Sisson and

Grossman)

6. CAUDAL: is the tail-end of the body. A surface towards or relatively near

the tail. On the limbs, again it applies to structures above the carpus and

tarsus.

7. ROSTRAL: applies to the head region only. A surface towards or relatively

near to the nose.

8. ORAL: applies to the mouth region only. A surface towards or relatively

near to the mouth.

9. ABORAL: applies to the surface opposite to or away from the mouth

region.

(B) TERMS APPLIED TO THE LIMBS (see Fig. 1-D)

1. PROXIMAL: refers to relative distances of different parts from the long

axis of the body; viz., those parts of the limb or limb structures that are

nearest to the body or main mass. Thus, we have the proximal extremity of

limb bones being the upper extremity and the proximal part of bone structures

being mostly the upper parts.

2. DISTAL: refers to that part of a structure that is furthest away from the

main mass of tissue. In the appendages, it applies to the lower end of say a

limb bone or even the free end of the limb.

With reference to the thoracic limb (pectoral limb) or forelimb (see Fig. 1-D)

3. DORSAL: refers to the cranial face of the distal part of the forelimb. In

addition, it can refer to the dorsum of the manus (homologue of the hand).

4. PALMAR: (the older term is VOLAR) refers to the face opposite the

dorsal face.

5. RADIAL (EQUIVALENT TO MEDIAL): that side of the forearm in

which the radius is located.

6. ULNAR (EQUIVALENT TO LATERAL): that side of the forearm in

which the ulna is located.

7. BRACHIUM (OR ARM): specifically the region from the shoulder to

the elbow. Also, a general term used to designate an arm-like process or

structure.

8. AXILLA: is the space between the thoracic limb and the thoracic wall.

With reference to the pelvic limb or hindlimb (see Fig. 1-D)

9. DORSAL: the anterior face of the distal part of the pelvic limb. In

addition, it can refer to the dorsum of the pes (foot).

10. PLANTAR: refers to the face opposite the dorsal face.

11. TIBIAL (EQUIVALENT TO MEDIAL): that side of the leg on which

the tibia is located (medial).

12. FIBULAR (EQUIVALENT TO LATERAL): that side of the leg on

which the fibula is located (lateral

(C) TERMS TO INDICATE RELATIVE DISTANCES FROM THE CENTRE OF

THE LIMB (see Fig. 1-E)

AXIS: is the centre line of the body or any of its parts.

In ARTIODACTYLA (RUMINANTS and PIGS) and in CARNIVORA

(DOGS AND CATS), the functional axis of the limb passes between the

3rd and 4th digits. In PERISSODACTYLA (HORSE), the functional axis

of the limb passes along the centre line of the only digit present.

1. AXIAL and 2. ABAXIAL

are terms meaning pertaining to or being relative to the axis. e.g. the

AXIAL SURFACE of a digit faces the axis while the ABAXIAL SURFACE

faces away from the axis.

(D) TERMS TO INDICATE RELATIVE DISTANCES FROM THE SURFACE

OF THE BODY

1. SUPERFICIAL: relatively near to the surface of the body, or to the

surface of a solid organ.

2. DEEP: relatively near to the centre of the body or the centre of a solid

organ.

3. EXTERNAL OR OUTER: away from the centre of a hollow organ.

4. INTERNAL OR INNER: close to, or in the direction of the centre of a

hollow organ

Figure 1-E: Axis of the limbs in diffeenrt orders of animal

(E) TERMS WHICH APPLY TO THE BASIC MOVEMENT OF THE PARTS OF

THE BODY (see and complete Fig. 1-F)

1. PROTRACTION: taking the whole limb forward.

2. RETRACTION: taking the whole limb backward.

3. EXTENSION: the movement of one bone upon another in such a way

that the angle formed at their joint is increased. Thus, the limb reaches out

or is extended; the digits are straightened. Referring to the back it means

that it is straightened.

4. FLEXION: the movement of one bone in relation to another in such a

way that the angle formed at their joint is reduced. Thus, the limb may be

retracted or folded; the digits are bent. Referring to the back it is arched.

5. PRONATION: as applied to the manus (hand or paw), the act of turning

the palm backward (posteriorly) or downward, performed by medial

rotation of the forearm. This is the normal position of the manus in

quadripeds.

6. SUPINATION: as applied to the manus (hand), the act of turning the

palm forward (anteriorly) or upward, performed by lateral rotation of the

forearm. Dogs have some limited ability to supinate the manus; horse

forelimbs are fixed in pronation and the manus cannot be supinated at all.

7. ABDUCTION: the movement of a part away from the median plane.

8. ADDUCTION: the movement of a part towards the median plane.

Figure 1-F: Terms applied to basic mveoments