nerve root defined in 1951 yearnerve root - nerve root;
nerve root - In vertebrates, each spinal nerve arises from the spinal cord by two roots; a dorsal (posterior in human anatomy) and a ventral (anterior in human anatomy) which join to form the spinal nerve as they pass through the wall of the vertebral column. The dorsal roots contain all the sensory nerve fibres, their cell-bodies being in a ganglion on the course of each root; in some vertebrates they may also contain a few motor fibres. Through the ventral roots pass the motor fibres, their cell-bodies being in the spinal cord. Cranial nerves can also be classified into dorsal and ventral roots, which do not however join, remaining separate nerves; cranial dorsal roots have ganglia and contain, besides sensory, numerous motor fibres running to face, jaw, and gill muscles, and motor fibres of the parasympathetic system; cranial ventral roots contain some sensory (proprioceptor) fibres. Dorsal and ventral roots are a characteristic feature of all vertebrates, and occur in amphioxus, though in this chordate motor fibres to the viscera go through dorsal roots, and (as also in some Cyclostomes) the two roots do not join to form spinal nerves.
near nerve root in Knolik
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