The fifth sacral dorsal nerve roots contain afferent somatic nerve fibers corresponding to the fifth sacral spinal cord segment.  They enter as two or three rows of rootlets from the postero-lateral sulci of the spinal cord.

The roots pass obliquely infero-laterally as part of the cauda equina to their exit.  They are larger in obliquity and length than the dorsal roots above.  They join with the fifth sacral ventral roots to form the fifth sacral spinal nerves.  Each of the fifth sacral dorsal roots possesses an ovoid spinal ganglion (dorsal root ganglion) proximal to joining the fifth sacral 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.