A Vertebra

A typical vertebra has a drum-shaped "body" (centrum) that forms a thick, anterior portion of the bone. A longitudinal row of the bodies supports the weight of the head and trunk. The intervertebral disks, which separate joining vertebrae, are fastened to the roughened upper and lower surfaces of the bodies. These disks cushion and soften the forces created by walking and jumping, which might otherwise fracture the vertebrae or jar the brain. Each intervertebral disk is composed of a band of fibrous fibrocartilage (anulus fibrosus) that surrounds a gelatinous core, called the "nucleus pulposus." The bodies of adjacent vertebrae are joined on the front surfaces by "anterior ligaments" and on the back by "posterior ligaments." Projecting from the back of each body are two short stalks called "pedicles." They form the sides of the "vertebral foramen." Two plates (laminae) arise from the pedicles and fuse in the back to become "spinous process." The pedicles, laminae, and spinous process together complete a bony vertebral arch around the vertebral opening, through which the spinal cord passes. Between the pedicles and laminae of a typical vertebra is a "transverse process" that projects laterally and toward the back. Various ligaments and muscles are attached to the spinal process and the transverse process. Projecting upward and downward from each vertebral arch are "superior" and "inferior articulating processes." These processes bear cartilage-covered facets by which each vertebra is joined to the one above and the one below it. On the surfaces of the vertebral pedicles are notches that align to create openings, called "intervertebral foramina." These openings provide passageways for spinal nerves that proceed between joining vertebrae and connect to the spinal cord.