The |spinal cord| is one of the primary portions of the central nervous system, serving as a sort of telegraph cable which allows signals to be sent from the |brain| to the structures of the body, and received from them in return. Extending from the |medulla| oblongata, through the |foramen magnum| in the base of the |skull|, to the base of the |vertebral column|, the |spinal cord| is about a fourth of an inch (or a half of a centimeter) in diameter, and is slightly flattened. The |spinal cord| itself passes through the |vertebral canal| created by the vertebral arches, and sends out roots and branches much as does a tree. These structures contain bundles of |nerve fibers| which extend all the way down the body, innervating even the skin of the tips of the toes. The |spinal cord| features both efferent and afferent ~nerve~ pathways, so that ~nerves~ may be transmitted to the body's structures as well as received from them. Paired sets of ~nerves~ branch out from the |spinal cord| along the |vertebral column|, with the lowest of these forming the |sacral plexus| of ~nerves~. The sympathetic ~nerves~ travel alongside the |spinal cord| in the sympathetic ~nerve~ trunk, which features periodic clusters of ~nerves~, called ganglia, which deal with specific organ groups. The |spinal cord| floats in a spinal fluid which protects and nourishes it and, as with the |brain|, is covered by a meningeal membrane composed of three layers: the |pia mater|, the |arachnoid|, and the |dura mater|. Damage to the |spinal cord| results in inability to transmit and receive ~nerve~ impulses to and from the specific area supplied by the damaged section of the |spinal cord|, and all sections below it, resulting in |paralysis| and numbness. Inflammation of the spinal covering is a condition called spinal ~meningitis~.
