The spinal cord is a long structure, approximately as thick as our little finger. The principal function of the spinal cord is to distribute motor axons to the effector organs of the body (glands and muscles) and to collect somatosensory information to be passed on to brain. The spinal cord also has a certain degree of autonomy from the brain, various reflexive control circuits are located there.
The spinal cord is protected by the verbal column, which is composed of twenty-four individual vertebrae of the cervical (neck), thoracic (chest), and lumbar (Lower back) regions and the fused vertebrae making up the sacral and coccygeal portions of the column (located in the pelvic region). The spinal cord passes through a hole in each of the vertebrae (the spinal foramens). The spinal cord is only about two thirds as long as the vertebral column; the rest of the space is filled by a mass of spinal roots composing the Caudal Equina (horse a tail).
Early in embryological development the vertebral column and spinal cord are the same length. As development progress the vertebral column grows faster than the spinal cord. To produced the Caudal Block that is sometimes used in pelvic surgery, a local anesthetic can be injected into the CSF contained within the sac of durra mater surrounding the cauda equina. The drug blocks conduction in the axons of the cauda equina which produces temporary anesthesia (and paralysis) of the lower part of the body. Small bundles of axons emerge from each side of the spinal cord in two straight lines along its dorsolateral and ventrolateral surfaces. Groups of these bundles fuse together and become the Thirty-one paired sets of dorsal roots and ventral roots. The dorsal and ventral roots join together as they pass through gaps between the vertebrae and become Spinal Nerves.
The spinal cord consists of white matter and gray matter. In the spinal cord the white matter is on the outside and the gray matter is on the inside. The white matter consists of ascending and descending bundles of myelinated axons, and the gray matter consists mostly of neural cell bodies and short, unmyelinated axons.
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