User talk:Valentino jems

Table 3: Equivalent directional terms used in vertebrate zoology and human anatomy Vertebrate zootomy 	Human torso 	Human head Direction 	Synonyms 	Direction 	Synonyms 	Direction 	Synonyms Anterior 	Rostral, Cranial, Cephalic1 	Anterior 	Ventral, Front 	Anterior 	Rostral, Front Posterior 	Caudal 	Posterior 	Dorsal, Back 	Posterior 	Caudal, Back Dorsal 	— 	Superior 	Same1, Up 	Superior 	Dorsal, Up Ventral 	— 	Inferior 	Caudal1, Down 	Inferior 	Ventral, Down lateral 	Away from the middle 	Same 	— 	Same 	— Left (lateral) 	Sinister1 	Same 	— 	Same 	— Right (lateral) 	Dexter1 	Same 	— 	Same 	— Medial 	Middle 	Same 	— 	Same 	— Proximal 	Away from extremity 	Same 	— 	Same 	— Distal 	Toward extremity 	Same 	— 	Same 	— Intermediate2 	— 	Same 	— 	Same 	— Ipsilateral2 	Same side 	Same 	— 	Same 	— Contralateral2 	Opposite side 	Same 	— 	Same 	— Superficial2 	— 	Same 	— 	Same 	— Deep2 	— 	Same 	— 	Same 	— Notes: (1) Rarely used. (2) Strictly relative term, used with other locational descriptors. Sources of confusion Figure 3: Directional axes in the tetrapod vertebrate Equus caballus (a horse). The axis between cranial and caudal is the Cr-Cd axis, and between the dorsal and ventral is the D-V axis. (Left-right axis not shown; image shows the right side of the organism.) Figure 4: Different directional AP axes in three body segments of a horse). Axis (A) (in red) shows the AP axis of the tail, (B) shows the AP axis of the neck, and (C) shows the AP axis of the head. Both images have been rendered with the same height, and a total width of 320px

Together, the AP, DV and LR (or ML) axes allow for precise three-dimensional descriptions of location within any bilaterally symmetrical organism, whether vertebrate or invertebrate. In practice, the terms can cause some confusion when, unlike the fish shown in Fig. 2, the organism in question is not strictly linear in form, which includes most tetrapods (see Figs. 3 and 4). For example, the AP axis in Fig. 3 does not appear to be at right angles to the DV axis. Rather, it is a depiction of the approximate average AP axis, when all body segments are included.

When considering any one segment, the dorsoventral axis is perpendicular to the AP axis. Thus, in Fig. 4, the DV axis of the tail would run from the "back" of the tail (posterior end of the trunk), to the "underside" of the tail (near the legs) — nearly parallel to the AP axis of the main body.

As a rule of thumb, if the body is included in consideration, the AP axis of the main body would be used, as would the DV and ML axes perpendicular to it. However, if considering only one segment, the AP axis would shift to reflect the axes shown in Fig. 4, with the DV and ML axes shifting correspondingly. In alternative manner, to avoid confusion, AP, DV, and ML terms are used strictly in relation to the main body, and the terms proximal and distal are used for body segments such as the head, neck, and tail (see below).

To avoid this confusion, in veterinary medicine, the terms anterior, posterior, superior, and inferior are in general avoided except for certain structures within the head.[18] By using the terms cranial, caudal, dorsal and ventral, all tetrapod