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sciatic nerve[sī′ad·ik ′nərv]
the largest nerve trunk in vertebrate animals and man. It is formed from projections of spinal-cord motor neurons and sensory cells of the spinal ganglia; in man, it is formed from the fourth and fifth pairs of the lumbar nerves and the first to third pairs of the sacral nerves. It emerges through the foramen infrapiriforme as a long branch of the sacral plexus.
The sciatic nerve consists of two nerves, the tibial nerve (pre-axial component) and the common peroneal nerve (postaxial component), enclosed in a common connective-tissue membrane. Branches emerging from the sciatic nerve in the femur extend from the musculus gluteus maximus to the popliteal fossa, reaching the posterior muscles and the knee joint; the tibial and common peroneal nerves are separated here as well. The tibial nerve innervates the posterior muscles of the leg and the muscles of the sole; it gives off the medial cutaneous nerve in the leg and innervates the skin of the sole. The common peroneal nerve bifurcates into the deep and superficial peroneal nerves which terminate in the anterior and lateral muscles of the leg, the muscles of the back of the foot, and the skin of the lateral surface of the leg and of the back of the foot.
V. V. KUPRIIANOV