The major column of nerve tissue that is connected to the brain and that lies within the vertebral canal and from which the spinal nerves emerge.

Thirty-one pairs of spinal nerves originate in the spinal cord: eight cervical , twelve thoracic, 5 lumbar, five sacral, and one coccygeal.

The spinal cord and the brain constitute the central nervous system (CNS). The spinal cord consists of nerve fibers that transmit impulses to and from the brain.

Like the brain, the spinal cord is covered by three connective-tissue envelopes called the meninges. The space between the outer and middle envelopes is filled with cerebrospinal fluid (CSF), a clear colorless fluid that cushions the spinal cord against strong and sudden shocks.