Neurophysiologic maps of cutaneous innervation of the external genitalia of the ram.

The area of skin innervated by the afferent fibers in a peripheral nerve is called the cutaneous area (CA) of that nerve. Mapping of those areas that were responsive to movement of wool/hairs in the genital region of 18 anesthetized rams, combined with subsequent identification of spinal nerves and dissection of the pudendal nerve plexus, indicated considerable differences in the extent of the CA and the origins of cutaneous branches from the pudendal plexus. The CA of the proximal and distal cutaneous branches of the pudendal nerve (or plexus) overlapped craniocaudally by approximately one-half, and the latter included most of the skin of the ipsilateral half of the scrotum. The CA of the deep perineal and caudal rectal nerves lay immediately adjacent to the anus. The CA of the scrotal branches of the pudendal nerve were restricted primarily to the scrotum. Fascicles in the dorsal nerve of the penis irregularly supplied CA along the length of the prepuce and consistently supplied the cranial free end of the prepuce. The CA of the ventral cutaneous branches of the caudal thoracic spinal nerves, the first 2 or 3 lumbar spinal nerves, and the genitofemoral nerve extended to the midline of the prepuce. Overlapping of CA was extensive, especially on the prepuce.