Sciatic Nerve: The sciatic nerve is a long nerve in humans. Sciatic nerve begins in the lower back and travels through the buttock and down the lower limb. The sciatic nerve provides the connection to the nervous system for nearly the whole of the skin of the leg, the muscles of the back of the thigh, and those of the leg and foot. It originates from spinal nerves L4 to S3. It receives fibers from both the anterior and posterior divisions of the lumbosacral plexus.
Nerve Roots: L4-S3.
Sciatic Nerve Course: The sciatic nerve originated from the lumbosacral plexus. After its formation, it transmits the pelvis and penetrates the gluteal region via greater sciatic foramen. It begins inferiorly to the piriformis muscle and drops in an inferolateral direction.
As the nerve moves within the gluteal region, it passes the posterior surface of the obturator internus, superior gemellus, inferior gemellus and quadratus femoris muscles. It next enters the posterior thigh by passing deep to the long head of the biceps femoris muscle.
Inside the posterior thigh, the nerve gives rise to branches to the hamstring and adductor Magnus muscles. When the sciatic nerve enters the apex of the popliteal fossa, it terminates by bifurcating within the tibial and common fibular nerves.
While the sciatic nerve crosses within the gluteal region, it does not innervate any muscles within the gluteal region. However, the sciatic nerve innervates the muscles in the posterior compartment of the thigh muscles, and the hamstring portion of the Adductor Magnus.
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Sciatic Nerve Branches: The sciatic nerve innervates several other muscles, via its terminal branches:
Common fibular nerve – the muscles of the lateral leg, anterior leg, and the remaining intrinsic foot muscles.
Tibial nerve – the muscles of the calf in the posterior leg, and some of the intrinsic muscles of the foot.
The sciatic nerve does not hold any primary cutaneous functions. It does give secondary sensory innervation via its terminal branches:
Common fibular nerve – Innervates the lateral leg and the dorsal surface of the foot.
Tibial nerve – Innervates the posterolateral and anterolateral sides of the leg and the plantar surface of the foot.