The Spinal Cord

The spinal cord is a thick cylinder of nervous tissue that comprises part of the central nervous system, communicating afferent sensory information from the periphery to the brain, and efferent motor information from the brain to the periphery.

In cross-section the gray matter on the interior of the spinal cord appears butterfly-shaped. The ventral horn of the gray matter contains motor neurons. It is surrounded by white matter with groups of axons of both ascending and descending tracts. In the center is a central canal which contains cerebrospinal fluid that nourishes the nervous tissue. The cord itself is surrounded by membranes, the spinal meninges, that include dura mater.

Connected at the brain stem the spinal cord runs through the foramen magnum and the series of bones of the vertebral column until it terminates at the lumbar level of L1-2, and forms a long bundle of nerves called the cauda equina. It's subdivided into levels or regions determined by the position of the vertebrae with paired spinal nerves.

For instance, the cervical spine, regions C2 to C7, correspond to the nerves innervating the neck, shoulders, arms and hands. Within each vertebra nerve root pairs exit through the vertebral foramen into separate branches. The ventral nerve root targets muscles to control movement whereas the dorsal nerve root innervates the skin to convey sensation. Each area of the skin innervated by a specific spinal nerve is called a dermatome and portrayed by dermatome maps. These maps are designed to help clinicians identify where a particular pain or a skin condition may be originating.