vocal cord

Either of two folds of mucous membrane that extend across the interior cavity of the larynx and are primarily responsible for voice production. Sound is produced by the vibration of the folds in response to the passage between them of air exhaled from the lungs. The pitch of sound varies with the degree of vocal-cord tension. Sounds are then modified by the tongue, palate, and lips to produce speech. When at rest, the vocal cords lie apart, forming a V-shaped opening (glottis) through which air is breathed. The folds located just above the vocal cords are termed the vestibular or false vocal cords because they are not involved in voice production. Inflammation (as from excessive use) limits the normal contraction of the vocal cords, resulting in hoarseness.

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Section of a spinal cord. The anterior horn of the gray matter contains cell bodies from which the elipsis

In vertebrates, the body's major nerve tract. In humans it is about 18 in. (45 cm) long, running from the base of the brain through the vertebral column. It is covered by the meninges and cushioned by cerebrospinal fluid. It connects the peripheral nervous system (outside the brain and spinal cord) to the brain. The spinal cord and the brain constitute the central nervous system. Sensory impulses reach the brain via the spinal cord, and impulses from the brain travel down the spinal cord to motor neurons, which reach the body's muscles and glands via the peripheral nerves. The peripheral nerves are connected to the spinal cord via the spinal nerves. In humans there are 31 pairs of spinal nerves containing both sensory and motor fibres, which originate in the spinal cord and pass out between the vertebrae. These nerves branch and relay motor impulses to all parts of the body. Injury to the spinal cord may result in loss of communication between the brain and outlying parts and cause paralysis, loss of sensation, or weakness in the parts of the body served by areas below the injured region. Because nerve cells and fibres are unable to regenerate themselves, the effects are usually permanent.

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In optical communications, zip-cord is a two-fiber cable consisting essentially of two single-fiber cables having their jackets conjoined by a strip of jacket material. The name is borrowed from electrical terminology referring to lamp cord. As with lamp cord, optical zip-cord may be easily furcated by slitting or tearing the two jackets apart, permitting the installation of optical connectors. Zip-cord cables include both loose-buffer and tight-buffer designs.


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