Some Basic Terms:

In describing bones and portions of bones, a series of standard terms of orientation are used. Most of these are pairs of terms that describe contrasting aspects of the skeleton or a bone. Some of the more common term-pairs you will be using include:

cranial - postcranial: The cranial portion of the skeleton consist of the cranium, the mandibles, and the hyoids The postcranial skeleton is everything else — the vertebrae, ribs, and limb bones.

axial-appendicular: Axial is used to describe the portions of the post-cranial skeleton that comprise the main axial or trunk of the body. This includes the vertebrae, ribs, and sternabrae. The appendicular skeleton is composed of the bones of the appendages or limbs.

medial-lateral: Medial refers to surfaces or parts of the body that are closest to the sagittal midline of the skeleton (in the direction of the middle of the animal). Lateral refers to parts or surfaces that are away from the midline. Each limb bone has a medial and a lateral surface.

proximal-distal: Proximal refers to the parts of a limb bone that are upward, or nearer the back of the animal when in normal anatomical position. Distal is used to describe the portion of a limb bone that is downward, or farthest away from the back. Each limb bone and rib has a proximal and a distal end.

cranial-caudal: Surfaces or parts of a bone that are toward the head (anterior) are called cranial. Portions or surfaces that are toward the tail (posterior) are called caudal. All bones have a cranial and a caudal aspect.

dorsal-ventral: These two terms are used to describe the vertebrae. Dorsal refers to the uppermost portions of a vertebra (e.g., the dorsal spine). Ventral is used to describe those portions of a vertebra that are closest to the abdomen (e.g., the centrum or body).