Pudendal nerve arises from the sacral plexus in the pelvis. It is the chief nerve of the perineum and external genitalia. It derives from S2, S3, and S4. Several branches of the pudendal nerve innervate the penis, including the dorsal nerve of the penis. The pudendal nerve carries axons responsible for sensation and motor responses for defecation, micturition, and procreation. It relays information from the external genitalia as well as the skin around the anus and perineum. It also carries motor axons to various pelvic muscles as well as the external urethral sphincter, the external anal sphincter, and bulbospongiosus muscle.
Inside the pudendal canal, the pudendal nerve divides into several branches. It first gives off the inferior rectal nerve followed by the perineal nerve and, finally, the dorsal nerve of the penis. The dorsal nerve of the penis or clitoris is a smaller terminal branch of the pudendal nerve. It runs forward first in the pudendal canal above the internal pudendal vessels and then in the deep perineal space between these vessels and the pubic arch. After branching off of the pudendal nerve, the dorsal nerve of the penis runs along the inferior ischial ramus; then, it is joined by the deep dorsal vein at the base of the penis. Then it passes through the lateral part of the oval gap between the apex of the perineal membrane and arcuate pubic ligament, and runs on the dorsum of the penis and clitoris and ends in the glans penis and glans clitoris.
In addition to the efferent fibers of the dorsal nerve of the penis, this nerve includes afferent fibers that innervate the penile skin, clitoris in females, and also the glans penis. These afferents propagate sensory signals to the central nervous system that are critical to achieving an erection and sexual function.