Sciatic nerve

The sciatic nerve ([' ɪʃias ] also [' ɪsçias ] ), fachsprachlich sciatic nerve (also called " ischial nerve" or " sciatic nerve ", ischium = " ischium " ), is a peripheral nerve of the lumbosacral plexus ( lumbar Cross - shield). He is the most powerful nerve in the body. It has its origin in humans from the last lumbar and the first three sacral spinal cord segments ( lumbar segment 4 to 3 cross segment of the spinal cord, L4 - S3). In the domestic mammals it springs from L6 -S2 lumbosacral as a direct continuation of the so-called trunk.

Course

The sciatic nerve passes through the greater sciatic notch and the greater sciatic foramen (more precisely, by the infrapiriforme foramen ) on the extensor surfaces of the hip joint and then on the dorsal side of the thigh, covered by the Kniebeugern ( hamstring ) in the direction of the knee. On his way, he dispatched for the individual mammals somewhat varying, branches to the motor innervation to some thigh muscles:

• Musculi gemelli,
• Musculus quadratus femoris,
• Musculus obturator internus,
• Biceps femoris,
• Semitendinosus and
• Musculus semimembranosus.

At the thigh divides the sciatic nerve in:

• Fibular nerve (also common peroneal nerve ) and
• Tibial nerve.

In some mammals above muscular branches go only from these bifurcations.

A closer look at the sciatic nerve exists (at least in humans) not really, but is a relic of the past anatomical- morphological research. The peroneal nerve and the tibial nerve occur separately from the plexus of the sacral. Shortly before passage through the foramen infrapiriforme they are surrounded in most people by a thin connective tissue from which they emerge again in the popliteal fossa (low pitch) at the latest. In some people 's nerves come earlier from the connective tissue of (high pitch) and still others it does not exist. Within this connective tissue is no exchange of nerve fibers takes place, so that all flexors (with the exception of the short head of the biceps femoris ) of the knee and ankle from the tibial nerve and the extensor and pronator muscles of the ankle from the peroneal nerve supplies. The sciatic nerve is therefore " only connective tissue ." This can easily be demonstrated in sections by the connective tissue ( sciatic nerve ) can be cleaved with the fingers of the knee upwards without any effort. This is not possible with "real" nervous. Similarly, for example, with the vestibulocochlear nerve.

Diseases

Paralysis of the sciatic nerve often occur in the context of pelvic fractures, femoral fractures or dislocations of the sacroiliac joint. In small animals, a violation may occur by an intramuscular injection into the posterior thigh muscles. In case of damage to the sciatic nerve is absent in triggering of the flexor reflex flexion in the knee joint.

A neuralgia of the sciatic nerve is usually referred to simply as sciatica. This occurs when the nerve strain ( stretched knee, bent hip) on a characteristic pain. The so-called Lasègue test, the patient feet but is supine, legs straight in a neutral position. The passive lifting a leg causes pain in the affected side sciatica.

In herniated discs can cause damage to the sciatic nerve pain, called sciatica.