anterior root of spinal nerve the anterior, or motor, division of each spinal nerve, attached centrally to the spinal cord and joining peripherally with the posterior root to form the nerve before it emerges from the intervertebral foramen.
Diagram of a horizontal section of the spinal cord, with posterior and anterior roots and a spinal nerve.dorsal root of spinal nerve posterior r. of spinal nerve.
motor root of spinal nerve anterior r. of spinal nerve.
nerve roots the series of paired bundles of nerve fibers that emerge at each side of the spinal cord, termed posterior ( or dorsal) or anterior ( or ventral) according to their position. There are 31 pairs ( 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal) , each corresponding posterior and anterior root joining to form a spinal nerve. Certain cranial nerves, e.g., the trigeminal, also have nerve roots.
posterior root of spinal nerve the posterior, or sensory, division of each spinal nerve, attached centrally to the spinal cord and joining peripherally with the anterior root to form the nerve before it emerges from the intervertebral foramen.