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Dissection of anal triangle and ischiorectal fossae

Posterior recesses of ischiorectal fossae; sacrotuberous ligaments

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Image #173-6
Diagram Image
Legend Image
Dissection of anal triangle and ischiorectal fossae
Posterior recesses of ischiorectal fossae; sacrotuberous ligaments
Both gluteus maximus muscles have been cut off close to their origins from the sacrotuberous ligaments, coccyx and sacrum. In the left ischiorectal fossa the inferior fascia of the pelvic diaphragm has been resected. On the right the inferior rectal vessels and nerves have been cut off but the fascia has been left intact. Blending with the inferior fascia of the pelvic diaphragm on the right is the lunate fascia which covers the pudendal canal (21).
  1. Coccyx (terminal piece)
  2. Gluteus maximus muscle (fibers cut off at origin from sacrotuberous ligament)
  3. Coccygeus muscle
  4. Piriform muscle
  5. Levator ani muscle
  6. Sacrotuberous ligament
  7. Upper pointer: Infrapiriform foramen (part of greater sciatic foramen through which inferior gluteal vessels and nerves emerge) Lower pointer: Posterior femoral cutaneous nerve
  8. Inferior rectal nerves
  9. Inferior rectal artery
  10. Ischial tuberosity
  11. Lunate fascia (covering pudendal canal and obscuring obturator fascia)
  12. Obturator externus muscle
  13. Ramus of ischium
  14. Ischiocavernosus muscle (visible through deep perineal fascia)
  15. Posterior scrotal nerve (exposed by removal of membranous layer of superficial perineal fascia to the left of midline)
  16. Perineal branch of inferior rectal nerve
  17. Bulb of penis
  18. Anococcygeal ligament
  19. Middle cluneal nerve
  20. Inferior fascia of pelvic diaphragm
  21. Lunate fascia covering pudendal canal
  22. Upper pointer: Anus Lower pointer: External anal sphincter muscle
  23. Posterior margin of urogenital triangle (membranous layer of superficial perineal fascia intact to right of midline in this area)