Sciatic nerve
Encyclopedia
The sciatic nerve is a large nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...

 fiber in humans and other animals. It begins in the lower back and runs through the buttock and down the lower limb
Lower limb
The lower limb is a limb of the body.According to Terminologia Anatomica, it includes the pelvic girdle, buttocks, hip, and thigh, as well as the components distal to the knee.-References:...

. It is the longest and widest single nerve in the human body going from the top of the leg to the foot on the posterior aspect.

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 derived from spinal nerves L4 through S3. It contains fibres from both the anterior and posterior divisions of the lumbosacral plexus.

Branches

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
    Sacral plexus
    -External links:*...

    .

  • The muscular branches (rami musculares) are distributed to the following muscles of the lower limb: biceps femoris, semitendinosus, semimembranosus, and adductor magnus. The nerve to the short head of the biceps femoris comes from the common fibular part of the sciatic (see below), 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.


The muscular branch eventually gives off the tibial nerve
Tibial nerve
The tibial nerve is a branch of the sciatic nerve. The tibial nerve passes through the popliteal fossa to pass below the arch of soleus.In the popliteal fossa the nerve gives off branches to gastrocnemius, popliteus, soleus and plantaris muscles, an articular branch to the knee joint, and a...

 and common fibular nerve
Common fibular nerve
The common fibular nerve , about one-half the size of the tibial nerve, is derived from the dorsal branches of the fourth and fifth lumbar and the first and second sacral nerves.It descends obliquely along the lateral side of the popliteal fossa to the head of the fibula,...

, which innervates the muscles of the (lower) leg. The tibial nerve goes on to innervate all muscles of the foot except the extensor digitorum brevis (which is innervated by the common fibular nerve).

Sensory Supply

The sciatic nerve innervates the skin on the posterior aspect of the thigh and gluteal regions, as well as the entire lower leg (except for its medial aspect).

Pathology

Pain caused by a compression or irritation of the sciatic nerve by a problem in the lower back is called sciatica
Sciatica
Sciatica is a set of symptoms including pain that may be caused by general compression or irritation of one of five spinal nerve roots that give rise to each sciatic nerve, or by compression or irritation of the left or right or both sciatic nerves. The pain is felt in the lower back, buttock, or...

. Common causes of sciatica include the following low back and hip conditions: spinal disc herniation
Spinal disc herniation
A spinal disc herniation , informally and misleadingly called a "slipped disc", is a medical condition affecting the spine due to trauma, lifting injuries, or idiopathic, in which a tear in the outer, fibrous ring of an intervertebral disc allows the soft, central portion A spinal disc herniation...

, degenerative disc disease
Degenerative disc disease
Degeneration of the intervertebral disc, often called "degenerative disc disease" of the spine, is a condition that can be painful and can greatly affect the quality of one's life...

, lumbar spinal stenosis, spondylolisthesis
Spondylolisthesis
Spondylolisthesis describes the anterior or posterior displacement of a vertebra or the vertebral column in relation to the vertebrae below. It was first described in 1782 by Belgian obstetrician, Dr. Herbinaux. He reported a bony prominence anterior to the sacrum that obstructed the vagina of a...

 and piriformis syndrome
Piriformis syndrome
Piriformis syndrome is a neuromuscular disorder that occurs when the sciatic nerve is compressed or otherwise irritated by the piriformis muscle causing pain, tingling and numbness in the buttocks and along the path of the sciatic nerve descending down the lower thigh and into the leg...

.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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