Perineum - LO 11

11. Diagram the branches of the pudendal nerve, and understand the distribution of other nerves that provide afferent innervation to the perineum.

The pudendal n. arises from VPR of S2-4 and follows the internal pudendal a. out the greater sciatic foramen, back through the lesser sciatic foramen (where there is a close relationship with the ischial spine), and through the pudendal (Alcock’s) canal to serve as the primary nerve of the perineum.

The pudendal n. has several major brs., including the:

• • Inferior rectal (anal) nn.

    • • Branching point: proximal portion of pudendal (Alcock’s) canal

      • Efferent to external anal sphincter

      • Afferent from peri-anal skin, and potentially inferior vagina

  • Perineal nn. - two branches:

    • • Deep perineal nn. - efferent to mm. of perineum (ischiocavernosus, bulbospongiosus, etc.)

        • • Sometimes a direct branch of pudendal n.

      • Posterior labial/scrotal nn. - afferent from skin of posterior labia majora/ scrotum & inferior vagina

  • Dorsal nn. of the clitoris/penis - afferent from the skin of the shaft of clitoris / penis; sympathetic motor to skin of shaft of clitoris/penis

Nerves that also provide afferent innervation from the perineum:

• • Anterior labial/scrotal brs. (from ilio-inguinal n., L1) - mons pubis/anterior scrotum, and

  • Perineal br. of posterior femoral cutaneous nn. (S1-3) - lateral perineum.