The fifth lumbar dorsal nerve root consists of the processes of spinal ganglia.  The medial and lateral fascicles split into rootlets, which enter to spinal cord along the postero-lateral sulcus.  Rootlets of adjacent dorsal roots may communicate via thin branches.  The root is ensheathed in pia mater and a loose layer of arachnoid mater.

The roots pass infero-laterally to their exit through the intervertebral foramina between the pedicles of L5 and S1.  They are larger in diameter, obliquity and length than the dorsal roots above.  They pass over the superior surfaces of the pedicles of S1 to join with the fifth lumbar ventral roots to form the fifth lumbar spinal nerves.  On each side, the fifth lumbar dorsal roots possess an ovoid spinal ganglion (dorsal root ganglion) proximal to where they join the fifth dorsal ventral roots.  They are covered by a sleeve of pia mater, which is continuous with that of the spinal cord, and loosely invested by a prolongation of dura and arachnoid mater (the dural sleeve) almost as far as the spinal nerves.

Cauda Equina
The cauda equina is formed from the most caudal spinal roots.  As the spinal cord terminates before the vertebral column, the lower spinal roots descend inferior to the cord, as a divergent sheath, to reach their corresponding foramina.