A nerve plexus is a system of connected nerve fibers that link spinal nerves with specific areas of the body. Fibers in a plexus connect the spinal cord and the body by grouping themselves into one larger nerve. The human body consists of several nerve plexuses, including the brachial plexus, the cervical plexus, the coccygeal plexus, the lumbar plexus, the sacral plexus, and the solar plexus.
The main function of a nerve plexus is to ensure that all areas of the body are innervated, thereby equipping each region with the ability to send and receive messages from the peripheral nervous system. The different plexuses are charged with innervating different portions of the body and help to control the functions unique to each portion. A nerve plexus is formed during development, when disparate muscles of the skeleton fuse together and result in large muscles requiring innervation.
The brachial nerve plexus supplies nerves to the arms, chest, hands, and shoulders. It runs from the spinal cord through the chest and shoulders before reaching the armpit; from there, it descends down the arm and into the hand. The brachial nerve is comprised of a series of branches, cords, divisions, roots, and trunks.
Areas of the head, neck, and shoulders are innervated by the cervical plexus. The cervical nerve plexus is primarily located in the neck, linking the spinal column with the rest of the head and down into the shoulder region. There are two types of branches in this plexus: cutaneous nerves, which provide innervation to the skin, and muscular nerves that provide sensation to and from the muscles.
The coccygeal nerve supplies nerves to a limited area near the coccyx bone. Rooted in this nerve is the anococcygeal nerve. This important nerve transmits sensation to and from the skin over the coccyx area.
The lumbar plexus is responsible for nerves in the abdomen, calves, back, knees, groin, and thighs. It contains several smaller nerve systems that handle such tasks as muscular contraction of the abdomen, the raising and lowering of testes in males, and the external rotation of the hip joint. The lumbar plexus is interwoven with the sacral plexus.
Some of the same areas are served by the sacral plexus, namely the calves and thighs. The sacral system also sends nerves to and from the buttocks, feet, and pelvis. One of the main responsibilities of this plexus is the transmission of sensory and motor stimuli from the spinal cord. Given its relationship with the lumbar plexus, both regions are sometimes lumped together under the term lumbosacral plexus.
One of the most important nerve plexuses in the body is the solar plexus, sometimes known as the celiac plexus. This region innervates the body's internal organs. A few of the areas served by the solar plexus include the stomach, pancreas, and specific areas of the heart.