The anatomy of a vertebra

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Each vertebra has several parts. The most important are:

Body
The largest part of the vertebra, this is a cylindrical column of spongy bone, padded by cartilaginous discs above and below.
Vertebral foramen
The hole in the center of the vertebra, through which passes the spinal cord.
Spinous process
A projection on the posterior aspect of the bone, together these form the ``spine'' that can be felt from outside the skin.
Transverse processes
Left and right, these project from the vertebra allowing muscular and ligamentous attachments.

Additionally, the first two vertebrae below the head are special in their anatomy. The first, called the atlas, holds up the head and lacks any vertebral body. Its anatomy is like a simple ring of bone. The second, the axis has a large projection from its superior surface, called the dens, or odontoid process, which stabilizes rotation of the neck.

The rest of the vertebrae are slightly different from each other, depending on the part of the spine. The transverse processes of the cervical vertebrae tend to be split, or bifid, as are the spinous processes of C3-C6. The thoracic vertebrae have articular surfaces for the ribs, called rib facets, and their spinous processes are long and directed downward (caudally). The lumbar vertebrae have very large and thick vertebral bodies and stout spinous processes.

Anatomy of the vertebral column