Guided Dissection Week 9 - Lower limb
1. Make some transverse incisions across the gluteal region and reflect the skin and superficial fascia laterally. a. On the gluteal region clean:
i. The surface of gluteus maximus
ii. Above gluteus maximus you can see parts of gluteus medius iii. Look for cutaneous nerves supplying this region.
b. Below gluteus maximus expose the fascia lata of the posterior thigh but leave it in place. 2. Reflect gluteus maximus:
a. Characterise thoroughly the edges of the muscle and mobilise it as much as possible. Detach it from the sacrum and ilium by using a scalpel to shave the muscle from the bone, and then reflect it laterally. Be careful in how far down you shave the sacrum. b. Be careful not to cut:
i. The sacrotuberous ligament that lies deep the inferior edge of gluteus maximus ii. The posterior cutaneous nerve of the thigh.
3. Identify the newly uncovered structures, from above down: a. gluteus medius
b. superior gluteal vessels
c. piriformis muscle
d. inferior gluteal nerve and vessels
e. sciatic nerve
f. the gemelli and the tendon of obturator internus
g. quadratus femoris.
4. Locate the ischial spine and sacrospinous ligament, then find the internal pudendal vessels and pudendal nerve that cross the sacrospinous ligament to enter the lesser sciatic notch and the perineum. 5. Remove the perianal skin and then take the fat out of the ischiorectal (ischioanal) fossa to expose the levator ani muscle and the inferior rectal nerves and vessels heading towards the anus. 6. The pudendal nerve and vessels run in a fascial (pudendal) canal on the lateral wall of the fossa. 7. You should be able to push your finger forwards, above the urogenital diaphragm into the anterior recess of the ischiorectal fossa.
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