What is in the anterior roots of the spinal cord?

Each ventral root (also called anterior root) attaches to the spinal cord by a series of roots that emerge from the ventrolateral groove of the spinal cord at the exit of the anterior root. The ventral roots are composed predominantly of efferent somatic motor fibers (thick axons of alpha-motor neurons and medium-sized axons of gamma motor neurons). In the thoracic and upper lumbar segments, alpha and gamma axons are supplemented by thin autonomic preganglionic motor fibers derived from the intermediate colic column.