It is a white nervous cord, cylinder shaped and slightly leveled. It is born in the brain stem and runs along the spine through the spinal canal, until it gets to the upper part of the lumbar region (vertebra Image 1). Below this zone it is transformed into a kind of nervous fiber crest, called ponytail. Next to the later lies the filum terminale, which anchors the marrow in the coccyx bone. The spinal cord is formed by 31 pairs of spinal nerves. Among their main functions are:
– Transport information from the body to the brain.
– Control automatic or reflex reactions (for example, sensation of fear).
– Transmit, through the spinal nerves, nerve impulses to the muscles, blood vessels and glands.
Internal composition
Same as the brain, the spinal cord is composed by a gray substance that is found in the center, and a white one that surrounds it. The gray matter contains nerve cell bodies and is organized into four shafts or roots: two dorsal, that receive information by means of the sensitive neurons distributed in the body, and two ventral shafts, which contain the cell bodies of the Motor neurons that send signals to the skeletal muscles. The white matter is formed by neuron axons that are grouped into two types of ways: the ascending, that transmit perception signals from the body to the brain, and the descending ways, that emit nerve impulses from the brain toward the spinal cord, to then go to the skeletal muscles, producing voluntary movements.
Protection of the spinal cord
It is protected by the vertebrae (cervical, thoracic and lumbar) of the backbone and its support ligaments and the meninges. It is also protected by the Cerebrospinal fluid (transparent substance that travels through the brain and the brain stem), which acts like a shock absorber, and the epidural space, filled by a layer of grease and conjunctive tissue located between the periosteum (thin layer that covers the bone) and the dura mater (exterior layer of the meninges).
