Sciatic Nerve
Definition
It is the longest and widest nerve of the leg which begins in the lower back and runs through the buttock and down the lower limb to the foot.
Origin
It is derived from spinal nerves L4 to S3
Contains fibers from both the anterior and posterior divisions of the lumbosacral plexus.
Structure & Course
Formed in front of the piriformis muscle by the union of fibers that emerge from the sacral partof the spinal cord.
Passes beneath piriformis and through the greater sciatic foramen, exiting the pelvis.
Travels down the posterior thigh to the poplital fossa
It is situated in the posterior compartment of the thigh behind (superficial to ) the adductor magnus muscle.
At the popliteal fossa it divides into its two branches : Tibial nerve which travels down the posterior compartment of the leg into the foot; the common peroneal nerve which travels down the anterior and lateral compartments of the leg into te foot.
Supply and Functions
supplies sensation to the skin of the foot and the entire lower leg
Skin of the sole of the foot is provided with sensation by the tibial nerve
Skin of the lower leg and upper surface of the foot by the common peroneal nerve
Muscles of the posterior compartment of the leg and sole of the foot are supplied by the tibial nerve
Muscles in the anterior and lateral compartments of the leg are supplied by the common peroneal nerve
Applied anatomy
Sciatica : pain caused by a comptession or irritation of the sciatic nerve. Common causes : spinal disc herniation, degenerative disc disease, lummbar spinal stenosis, spondylolisthesis and piriformis syndrome
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