The sciatic nerve is a large nerve that runs down the lower limb. It is the longest single nerve in the body. Pain caused by a compressed or damaged sciatic nerve is called sciatica.

Arising from the lower part of the sacral plexus, the sciatic nerve enters the gluteal region by the greater sciatic foramen of the hip bone. It continues down the posterior compartment of the thigh, until it separates into the tibial nerve and the common peroneal nerve. The location of this division varies between people.

Sciatic nerves from frogs and rats are often used in physiology experiments on nerve conduction because this nerve is large, and easily dissected and manipulated.

In the Jewish dietary laws (Kashrut), the hindquarters of a mammal are not kosher unless the sciatic nerve and the fat surrounding it are removed (Genesis 32, last verse).

Anatomical details (from Gray's)

The Sciatic (n. ischiadicus; great sciatic nerve) nerve is the largest and broadest nerve in the body and is formed by the anterior rami of L4 to S3 that converge on the anterior surface of the piriformis. The Sciatic supplies 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 is the largest nerve in the body, measuring 2 cm. in breadth, and is the continuation of the flattened band of the sacral plexus. It passes out of the pelvis through the greater sciatic foramen, below the Piriformis muscle. It descends between the greater trochanter of the femur and the tuberosity of the ischium, and along the back of the thigh to about its lower third, where it divides into two large branches, the tibial and common peroneal nerves. This division may take place at any point between the sacral plexus and the lower third of the thigh. When it occurs at the plexus, the common peroneal nerve usually pierces the Piriformis.

In the upper part of its course the nerve rests upon the posterior surface of the ischium, the nerve to the Quadratus femoris, the Obturator internus and Gemelli, and the Quadratus femoris; it is accompanied by the posterior femoral cutaneous nerve and the inferior gluteal artery, and is covered by the Glutæus maximus. Lower down, it lies upon the Adductor magnus, and is crossed obliquely by the long head of the Biceps femoris.

The nerve gives off articular and muscular branches.

• The articular branches (rami articulares) arise from the upper part of the nerve and supply the hip-joint, perforating the posterior part of its capsule; they are sometimes derived from the sacral plexus.

• The muscular branches (rami musculares) are distributed to the Biceps femoris, Semitendinosus, Semimembranosus, and Adductor magnus. The nerve to the short head of the Biceps femoris comes from the common peroneal part of the sciatic, while the other muscular branches arise from the tibial portion, as may be seen in those cases where there is a high division of the sciatic nerve.

External links

Peripheral nervous system | Lower limb anatomy

Ишиас | Nervus ischiadicus | Nerf ischiatique