Components of the human spinal cord include the cervical, thoracic, lumbar and sacral regions, as well as three layers of meningeal tissue that encase the cord. Two continuous rows of nerve roots extend on each side of the spinal cord, and come together to form 31 pairs of spinal nerves, while the anterior and posterior vertebral arteries provide the spinal cord's blood supply.
The spinal cord is a cylindrical, noodle-like structure of nerve tissue that is composed of both white and gray brain matter. It is approximately 40 to 50 centimeters long, and about 1 to 1.5 centimeters in diameter. The nerves and nerve impulses that enter and leave the spinal cord control motor and sensory functions to and from the entire body.
The layers of meningeal tissue that encase the spinal cord are known as the pia, arachnoid and dura. These are the same three layers that cover the brain, and not only protect both the brain and the spinal cord, but also serve as conductors of nerve impulses and synapses. The pia adheres to the surface of the spinal cord, while the arachnoid layer lies on top of it, followed by the tough, outer covering of the dura.