The spinal cord parenchyma consists of both gray (neurons and supporting glial cells) and white matter (axonal) and tracts that transmit electrical impulses between the brain and the body.

The brain and spinal cord together make up the central nervous system (CNS).

The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the medulla oblongata.

The spinal cord begins at the occipital bone and extends down to the space between the first and second lumbar vertebrae; it does not extend the entire length of the vertebral column. It is around 45 cm (18 in) in men and around 43 cm (17 in) long in women. Also, the spinal cord has a varying width, ranging from 1/2 inch thick in the cervical and lumbar regions to 1/4 inch thick in the thoracic area. The enclosing bony vertebral column protects the relatively shorter spinal cord.