The pudendal nerve is a significant nerve in the pelvic region that plays a crucial role in the sensory and motor supply to the pelvic floor, including the genitalia and perineum. It is derived from the sacral plexus, with roots from the ventral rami of the second, third, and fourth sacral nerves (S2-S4).
Location
The pudendal nerve travels from the sacral plexus, exiting the pelvis through the greater sciatic foramen. It then curves around the ischial spine, re-entering the pelvis through the lesser sciatic foramen. This unique course causes the nerve to lie close to the sacrospinous ligament and the pudendal canal (also known as Alcock’s canal), which is located on the lateral wall of the ischiorectal fossa.
Structure
The pudendal nerve is composed of both motor and sensory fibers. It has several branches:
- Inferior rectal nerves: These branches supply the muscles and skin surrounding the anus, contributing to anal sphincter control and providing sensation to the perianal area.
- Perineal nerves: These divide into superficial and deep branches. The superficial branches provide sensory innervation to the perineum and parts of the external genitalia, such as the labia in women and the scrotum in men. The deep branches supply the muscles of the urogenital triangle, including the bulbospongiosus and ischiocavernosus muscles, playing a role in erectile function.
- Dorsal nerve of the penis or clitoris: This is the terminal branch of the pudendal nerve, providing sensory innervation to the penis in males and the clitoris in females. It is essential for the sensory aspect of sexual function.
Function
The pudendal nerve has several main functions, primarily related to the sensory and motor innervation of the pelvic region:
- Sensory Functions: The pudendal nerve provides sensation to the external genitalia and surrounding skin. In females, this includes the clitoris, labia, and part of the vulva; in males, it includes the penis and scrotum. It also provides sensory innervation to the perineum (the area between the genitals and anus) and the anal canal. This sensory input is crucial for sexual function and for the sensation related to urination and defecation.
- Motor Functions: The nerve supplies motor innervation to various muscles of the pelvic floor, including the external anal sphincter and the urethral sphincter. This helps control bowel and bladder functions, enabling the retention and release of feces and urine. The pudendal nerve also innervates muscles involved in sexual activity, such as the bulbospongiosus and ischiocavernosus, which contribute to erection in males and clitoral engorgement in females.
- Sympathetic and Parasympathetic Functions: Though primarily a somatic nerve, the pudendal nerve also carries autonomic (sympathetic and parasympathetic) fibers that contribute to the function of the internal organs in the pelvis. These autonomic functions are involved in the physiological processes of sexual arousal, such as vasodilation for erectile tissue in both sexes.
Clinical significance
The pudendal nerve holds significant clinical importance due to its critical roles in pelvic floor functions and its involvement in various medical conditions. One of the primary concerns in clinical practice is pudendal neuralgia, a condition characterized by chronic, painful sensations in the areas innervated by the pudendal nerve, such as the genitals, perineum, and anus. This condition can result from nerve entrapment, injury during childbirth, surgery, or repetitive strain activities. Pudendal neuralgia can severely impact quality of life, causing discomfort during sitting, sexual dysfunction, and problems with urination and defecation.
In childbirth, the pudendal nerve is also of particular interest. It can be subjected to stretching or compression, leading to temporary or, less frequently, permanent dysfunction. This can result in postpartum issues such as incontinence, sexual dysfunction, or pelvic pain. In obstetrics, pudendal nerve blocks are a common procedure used to alleviate pain during childbirth by numbing the lower vagina and perineum, demonstrating the nerve’s importance in managing labor pain.
