During a difficult forceps delivery, the pudendal nerve can be stretched. The pudendal nerve (S2, S3, S4) exits the greater sciatic foramen, hooks around the ischial spine/sacrospinous ligament, and re-enters via the lesser sciatic foramen into the pudendal canal (Alcock's canal). Which structure forms the medial wall of the pudendal canal?
- A Levator ani muscle
- B Sacrotuberous ligament
- C Obturator internus fascia (obturator fascia) ✓
- D Ischiorectal fossa fat
Correct answer: C. Obturator internus fascia (obturator fascia)
Explanation
Alcock's canal (pudendal canal) is a fascial tunnel formed by a split in the obturator internus fascia on the lateral wall of the ischiorectal (ischioanal) fossa. The medial wall of this canal is the obturator internus fascia itself. The pudendal nerve, internal pudendal artery, and vein pass through this canal to reach the perineum. Understanding this anatomy is important for pudendal nerve block, given at the ischial spine, and for recognizing pudendal nerve entrapment syndrome.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.