spinal cord (SPY-nul kord)
A column of nerve tissue that runs from the base of the skull down the center of the back. It is covered by three thin layers of protective tissue called membranes. The spinal cord and membranes are surrounded by the vertebrae (back bones). The spinal cord and the brain make up the central nervous system (CNS). Spinal cord nerves carry messages between the brain and the rest of the body.