Sacral spinal nerve 4

The sacral spinal nerve 4 (S4) is a spinal nerve of the sacral segment.

It originates from the spinal column from below the 4th body of the sacrum

Muscles
S4 supplies many muscles, either directly or through nerves originating from S4. They are not innervated with S4 as single origin, but partly by S4 and partly by other spinal nerves. The muscles are:
 * iliococcygeus
 * puborectalis
 * coccygeus
 * sphincter ani externus muscle
 * sphincter urethrae membranaceae