The sciatic nerve has two major components: the tibial nerve from the anterior division of L4–S3 and the common peroneal nerve from the posterior division of L4–S2. It forms in front of the piriformis muscle in the pelvis and exits the greater sciatic foramen usually below the piriformis, occasionally within the muscle, and then enters the thigh between the ischial tuberosity and the greater trochanter. Structures deep to the sciatic nerve from cranial to caudal are the gemellus superior , obturator internus , gemellus inferior , quadratus femoris , and adductor magnus . Structures superficial to the sciatic nerveinclude, in the buttock: gluteus maximus , and in the thigh: the long head of biceps femoris crosses the nerve from medial to lateral. The nerve supplies the hamstrings—biceps femoris, semimembranosus , and semitendinosus —as well as the ischial part of adductor magnus. The nerve ends by splitting into tibial and common peroneal (common fibular) components in the lower thigh.
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