Pudendal nerve

Gray's Fig. 837 - Sacral plexus of the right side.

The pudendal nerve (S2,S3,S4) is responsible for urination, defecation and orgasm in both sexes.

Physiology

The pudendal nerve innervates the penis and clitoris, bulbospongiosus and ischiocavernosus muscles, and areas around the scrotum, perineum, and anus. At sexual climax, the spasms in the bulbospongiosus and ischiocavernous results in ejaculation in the male and most of the feelings of orgasm in both sexes. These muscles pulse at 0.8Hz at orgasm in both sexes.

Role in disease

Difficult childbirth or bicycling can compress or stretch the pudendal nerve but permanent injury is rare. Entrapment of the nerve is very rare but can happen. Pudendal Nerve Entrapment (PNE) is akin to Carpal Tunnel syndrome.

Details from Gray's anatomy

The Pudendal Nerve (internal pudic nerve) derives its fibers from the ventral branches of the second, third, and fourth sacral nerves. It passes between the Piriformis and Coccygeus muscles and leaves the pelvis through the lower part of the greater sciatic foramen. It then crosses the spine of the ischium, and reënters the pelvis through the lesser sciatic foramen. It accompanies the internal pudendal vessels upward and forward along the lateral wall of the ischiorectal fossa, being contained in a sheath of the obturator fascia termed Alcock's canal, and divides into two terminal branches, viz., the perineal nerve, and the dorsal nerve of the penis or clitoris. Before its division it gives off the inferior hemorrhoidal nerve.
* The inferior hemorrhoidal nerve (n. hæmorrhoidalis inferior) occasionally arises directly from the sacral plexus; it crosses the ischiorectal fossa, with the inferior hemorrhoidal vessels, toward the anal canal and the lower end of the rectum, and is distributed to the Sphincter ani externus and to the integument around the anus. Branches of this nerve communicate with the perineal branch of the posterior femoral cutaneous and with the posterior scrotal nerves at the forepart of the perineum.
* The perineal nerve (n. perinei), the inferior and larger of the two terminal branches of the pudendal, is situated below the internal pudendal artery. It accompanies the perineal artery and divides into posterior scrotal (or labial) and muscular branches.
** The posterior scrotal (or labial) branches (nn. scrotales (or labiales) posteriores; superficial peroneal nerves) are two in number, medial and lateral. They pierce the fascia of the urogenital diaphragm, and run forward along the lateral part of the urethral triangle in company with the posterior scrotal branches of the perineal artery; they are distributed to the skin of the scrotum and communicate with the perineal branch of the posterior femoral cutaneous nerve. These nerves supply the labium majus in the female.
** The muscular branches are distributed to the Transversus perinæi superficialis, Bulbocavernous, Ischiocavernosus, and Constrictor urethræ. A branch, the nerve to the bulb, given off from the nerve to the Bulbocavernosus, pierces this muscle, and supplies the corpus cavernosum urethræ, ending in the mucous membrane of the urethra.
* The dorsal nerve of the penis (n. dorsalis penis) is the deepest division of the pudendal nerve; it accompanies the internal pudendal artery along the ramus of the ischium; it then runs forward along the margin of the inferior ramus of the pubis, between the superior and inferior layers of the fascia of the urogenital diaphragm. Piercing the inferior layer it gives a branch to the corpus cavernosum penis, and passes forward, in company with the dorsal artery of the penis, between the layers of the suspensory ligament, on to the dorsum of the penis, and ends on the glans penis. In the female this nerve is very small, and supplies the clitoris (n. dorsalis clitoridis).

External links

* Pudendal nerve entrapment