The axial skeleton is divided into three sections: the skull, the vertebral_column (spinal_column), and the thorax.

The vertebral column extends from the skull to the pelvis, and creates a central support system for the body. The bones of the vertebral column are called the vertebrae (sing: vertebra). There are 24 single vertebral bones (7 cervical, 12 thoracic, and 5 lumbar), and 9 fused bones (the sacrum has 5; the coccyx has 4).

The vertebral column is flexible because of pads of fibrocartilage that lie between each bone. These pads are called intervertebral_discs. Each disc has a fluid center called the nucleus_pulposus and an outer ring of fibrous tissue called the annulus_fibrosus.

The basic structure of a vertebra consists of:

centrum (body),

vertebral_arch,

vertebral_foramen,

transverse_process,

spinous_process,

superior and inferior_articular_processes, and the

intervertebral_foramina.

C-1 is called the atlas bone, because it holds up the skull (like the legendary Atlas, who is reputed to have supported the world). C-1 lacks a centrum and its transverse processes have large concave depressions to support the skull.

C-2 is the axis bone and it acts as a pivot for the atlas. It has a large vertical process known as the odontoid_process (dens) that serves as the pivot point.