Overview
The pudendal nerve is a major peripheral nerve of the pelvis that supplies motor, sensory, and autonomic fibers to the perineum. It is the primary nerve responsible for innervation of the external genitalia and the sphincters of the anus and urethra.
Anatomical Origin
- Spinal Roots: Ventral rami of the second, third, and fourth sacral spinal nerves (S2‑S4).
- Formation: The nerve arises within the pelvis from a common pudendal plexus formed by contributions of these sacral roots.
Course
- Exit from Pelvis: Travels laterally and posteriorly, exiting the pelvic cavity through the greater sciatic foramen, inferior to the piriformis muscle.
- Loop Around Ischial Spine: Crosses the sacrospinous ligament and re‑enters the pelvis via the lesser sciatic foramen.
- Alcock’s Canal: Enters the pudendal (Alcock’s) canal, a fascial sheath formed by the obturator internus fascia, running along the lateral wall of the ischioanal fossa.
- Distribution: Within the canal, it gives off several branches before exiting to innervate superficial perineal structures.
Major Branches
- Inferior Rectal (Hemorrhoidal) Nerve: Provides motor innervation to the external anal sphincter and sensory innervation to the lower anal canal and perianal skin.
- Perineal Nerve: Divides into superficial and deep branches; supplies the muscles of the urogenital diaphragm (including the bulbospongiosus and ischiocavernosus) and provides sensory fibers to the posterior scrotum or labia majora.
- Dorsal Nerve of the Penis (or Clitoris): A terminal branch that runs along the dorsum of the penis or clitoris, delivering sensory innervation to these structures.
Functions
| Domain | Role |
|---|---|
| Motor | Controls voluntary contraction of the external urethral sphincter and external anal sphincter, contributing to continence. |
| Sensory | Conveys somatic sensation from the perineum, external genitalia, and anal region. |
| Autonomic (Visceral) | Carries some parasympathetic fibers that assist in genital vascular engorgement and erectile function. |
Clinical Relevance
- Pudendal Neuralgia: Chronic pain in the distribution of the pudendal nerve, often related to entrapment, prolonged sitting, or postoperative scarring. Diagnosis is clinical, sometimes aided by nerve block.
- Nerve Blocks: Image‑guided pudendal nerve blocks are employed for analgesia in childbirth, urological procedures, and chronic pelvic pain management.
- Obstetric Injury: Stretch or laceration of the nerve can occur during vaginal delivery, potentially leading to transient or permanent sensory deficits.
- Surgical Considerations: Preservation of the pudendal nerve is a priority in procedures such as radical prostatectomy, colorectal resections, and reconstructive pelvic surgeries.
Anatomical Variations
While the typical origin is S2‑S4, variations can include contributions from adjacent sacral roots or a more medial course. Rarely, the nerve may bifurcate earlier or have accessory branches.
References
- Standring, S. (Ed.). Gray's Anatomy: The Anatomical Basis of Clinical Practice (42nd ed.). Elsevier.
- Moore, K. L., Dalley, A. F., & Agur, A. M. R. Clinically Oriented Anatomy (8th ed.). Lippincott Williams & Wilkins.
- DeLancey, J. O. (1993). "Anatomy and biomechanics of pelvic support." Clinical Obstetrics and Gynecology, 36(4), 897‑915.
This entry provides a concise, factual overview of the pudendal nerve, its anatomy, functions, and clinical significance.
