Nerve · Pelvis

Pudendal nerve

Nervus pudendus

The main nerve of the perineum, and one of the few that leave the pelvis only to turn straight back into it — the nerve to obturator internus makes the same journey beside it. It forms from S2, S3 and S4 on the front of piriformis, escapes through the greater sciatic foramen below that muscle, hooks round the back of the ischial spine between the sacrospinous and sacrotuberous ligaments, and re-enters through the lesser sciatic foramen to run forward in a fascial tunnel — the pudendal canal — in the side wall of the ischiorectal fossa. From there it gives the inferior rectal nerve, the perineal nerve and the dorsal nerve of the penis or clitoris. Between them those branches control the outlet muscles of the pelvic floor and carry sensation from the entire perineum.