Sacral nerves

The sacral nerves and coccygeal nerve (S1-S5, C0) emerge respectively below the sacral vertebrae and the Coccyx.

The anterior divisions of the sacral and coccygeal nerves (rami anteriores) form the sacral and pudendal plexuses. The anterior divisions of the upper four sacral nerves enter the pelvis through the anterior sacral foramina, that of the fifth between the sacrum and coccyx, while that of the coccygeal nerve curves forward below the rudimentary transverse process of the first piece of the coccyx. The first and second sacral nerves are large; the third, fourth, and fifth diminish progressively from above downward. Each receives a gray ramus communicans from the corresponding ganglion of the sympathetic trunk, while from the third and frequently from the second and the fourth sacral nerves, a white ramus communicans is given to the pelvic plexuses of the sympathetic.

The posterior divisions of the sacral nerves (rami posteriores) are small, and diminish in size from above downward; they emerge, except the last, through the posterior sacral foramina. The upper three are covered at their points of exit by the Multifidus, and divide into medial and lateral branches. The posterior divisions of the lower two sacral nerves are small and lie below the Multifidus. They do not divide into medial and lateral branches, but unite with each other and with the posterior division of the coccygeal nerve to form loops on the back of the sacrum; filaments from these loops supply the skin over the coccyx. The posterior division of the coccygeal nerve(ramus posterior) does not divide into a medial and a lateral branch, but receives, as already stated, a communicating branch from the last sacral; it is distributed to the skin over the back of the coccyx.