Posterior Roots of Sacral Nerves (Left)

Description

The posterior (dorsal or sensory) roots of the sacral nerves arise bilaterally from the posterior aspect of the spinal cord as a series of smaller rootlets that merge to form the posterior root. Their axons generally run from peripheral sensory organs all the way into the dorsal horn of the spinal cord. A swelling of the posterior root, located just medial to the spinal nerve, is called the spinal (dorsal root) ganglion. It is the site at which cell bodies for these sensory axons reside.

The posterior roots contain only information traveling towards the spinal cord. This consists of sensory axons carrying signals such as touch, temperature, and pain. In addition, autonomic afferents enter the spinal cord via the posterior roots.

Posterior sacral roots run inferiorly in a bundle of nerve roots called the cauda equina. They continue down the vertebral canal to the appropriate level in the sacrum at which they will exit. Here, they merge with the corresponding anterior (ventral) root to form a sacral nerve, just prior to exiting the sacral foramen.