Sensory Innervation of Pelvis and Perineum
In addition to the sacral and coccygeal nerves, the following nerves participate: the ilioinguinal nerve and the genitofemoral nerve (C15), the iliohypogastric nerve (C16),the obturator nerve (C17), the posterior cu-taneous nerve of the thigh (C18), the inferior cluneal nerves (C19), and the medial cluneal nerves (C20).
External openings of genitals, bladder, and rectum are border areas between involun-tary smooth intestinal muscles and volun-tary striated muscles. Accordingly, auto-nomic and somatomotor fibers are here in-tertwined. The pudendal nerve contains, apart from sensory, somatomotor, and sym pathetic fibers, also parasympathetic fibers from the sacral spinal cord. Sympathetic fibers also originate as pelvic splanchnic nerves from the second to fourth sacral nerves.