Spinal Cord

The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. The brain and spinal cord make up the central nervous system (CNS). The main function of the spinal cord is to carry nerve impulses between the brain and the rest of the body.

The adult human spinal cord is about 45 cm (18 in) long and about 1 cm (0.39 in) in diameter. It is surrounded by three layers of connective tissue: an outer dura mater, a middle arachnoid mater, and an inner pia mater. The dura mater is a tough, fibrous membrane that encloses the entire CNS. The arachnoid mater is a delicate, spider-web like membrane that covers most of the CNS. The pia mater is a thin layer of tissue that closely covers the surface of each individual nerve cell within the CNS.

Within these three layers are numerous blood vessels and cerebrospinal fluid (CSF). CSF surrounds and protects the brain and spinal cord from impact or infection. It also provides nutrients to these tissues. Blood vessels supply oxygen and nutrients to all parts of the CNS.

The spinal cord begins at what is known as the foramen magnum, which is a large hole at the base of your skull through which your spinal cord passes. It then descends through your vertebral column until it reaches your lower back where it ends near your waistline. Your spinal cord does not extend into your extremities (arms and legs). That job falls to nerves that branch off from your spine throughout your body. There are 31 pairs of these nerves, called roots, which exit from between your vertebrae; 8 cervical nerves (C1-C8), 12 thoracic nerves (T1-T12), 5 lumbar nerves (L1-L5), 5 sacral nerves (S1-S5), 1 coccygeal nerve (#1). These exiting roots come together again to form mixed nerves which innervate different areas throughout your body depending on where they are located along your spine; i