Spinal Cord and Nerves
Spinal Regions, side view
The spinal cord is a column of nerve cells and bundles of nerve fibers which connects the brain to all parts of the body. The spinal cord itself does not descend the entire length of the spinal canal. It ends at about the level of the second lumbar vertebra. Below this level, the remaining spinal nerves descend as a group of nerves resembling a horses mane, hence their name the "cauda equina". The spinal cord gives off spinal nerves in pairs: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. The spinal cord and nerves are surrounded by a sac called the dura mater which contains them in a bath of spinal fluid. Outside the dura, between it and the bony and ligamentous walls of the spinal canal, is the epidural space. It is in this space that epidural injections are given, including cortisone (steroid) injections to treat spinal disorders or novocaine for regional anesthesia for surgery or to deliver a baby.