Perineum LO11

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.