Peripheral nervous system
The spinal cord is a massive nerve column contiguous with the brain stem, emerging through the foramen magnum and terminating at the upper border of the second lumbar vertebra. It is much shorter than the vertebral canal in which it rests, measuring about 18 inches. It is also covered by the three membranes or meninges - the outermost duramater, the middle arachnoid and the innermost piamater. The cerebrospinal fluid is present in the space between the arachnoid and piamater. The cylindrical spinal cord has a dorsal septum and a deep ventral fissure. There are two swellings, the first one is known as cervical swelling, at the level of the 6th spinal nerve; and the other is lumbar swelling, at the level of the third lumbar spinal nerve. The spinal cord is divided into 5 regions: cervical, thoracic, lumbar, sacral and coccygeal regions. A cross section of the spinal cord at any level reveals the following structures: the gray matter of the spinal cord is internally located and is arranged in the form of a letter -H-, surrounded by the white matter. The upper arms of the -H- are called dorsal horns, and the lower ones, the ventral horns. The central bar of gray matter of the spinal cord is pierced by the central canal. The posterior part of the spinal cord with nerves is called cauda equina, and the slender terminal part is called filum terminale.
Functions of the spinal cord
Spinal cord carries stimuli to the brain and also conveys impulses from the brain to various parts of the body. It also carries out reflex actions.
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