radix

1. the descending and subterranean part of a plant.

2. that portion of an organ, such as a tooth, hair, or nail, that is buried in the tissues, or by which it arises from another structure, or the part of a nerve that is adjacent to the center to which it is connected.

anterior root 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; it conveys motor fibers to skeletal muscle and contains preganglionic autonomic fibers at the thoracolumbar and sacral levels. Called also ventral root.

dorsal root posterior root.

motor root anterior root.

nerve r's the series of paired bundles of nerve fibers which emerge at each side of the spinal cord, termed dorsal (or posterior) or ventral (or anterior) according to their position. There are 31 pairs (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal), each corresponding dorsal and ventral root joining to form a spinal nerve. Certain cranial nerves, e.g., the trigeminal, also have nerve roots.

posterior root 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; each posterior root bears a spinal ganglion that conveys sensory fibers to the spinal cord. Called also dorsal root.

sensory root posterior root.

ventral root anterior root.