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in vertebrate animals and man, an aggregation of nerve fibers that make up somatic and autonomic nerves; these nerves innervate the skin, musculature, and viscera.
Nerve plexuses can be classified as somatic or autonomic. A somatic nerve plexus is further classed according to which division of the vertebral column it is located in. The cervical plexus consists of the anterior rami of the upper four cervical spinal nerves. This plexus lies on the anterior surface of the deep muscles of the neck, supplying the diaphragm and the skin and muscles of the neck with sensory and motor conduction pathways. The brachial plexus comprises the anterior rami of the first thoracic and the lower four cervical spinal nerves; it passes behind the clavicle and descends into the axillary area. The muscles of the spine, shoulder girdle, and chest, as well as the skin and musculature of the upper extremities, are innervated by the brachial plexus.
The lumbar plexus includes the anterior rami of the first through third and part of the fourth lumbar spinal nerves; the 12th thoracic spinal nerve is also included. The lumbar plexus is located in the posterior wall of the abdomen, innervating the skin and musculature of the abdominal wall, of the external genitalia, and of the anterior and lateral surface of the thigh and leg. The sacral plexus is the largest plexus, comprising the anterior rami of the sacral, coccygeal, and fourth and fifth lumbar spinal nerves. This plexus lies on the lateral surface of the true pelvis and descends into the gluteal region, supplying the gluteal region, perineum, thigh, leg, and foot with sensory and motor innervation.
When a nerve plexus is injured, the sensory and motor functions of the corresponding body parts are impaired.
IA. L. KARAGANOV