Nerves are fibers that run throughout the body, carrying electrical impulses to and from the spinal cord. They detect sensation, control movement, and allow the body to regulate itself. A posterior nerve, or dorsal nerve, is a nerve that runs along the back side of the body, such as through the back and buttocks, or the back parts of internal organs. The nerves that run along the front side of the body are called anterior nerves.
The nervous system of human beings and other animals with backbones consists of a central nervous system and a peripheral nervous system. The central nervous system is made up of the spinal cord and the brain. The peripheral nervous system, on the other hand, is made up of the 31 pairs of nerves that branch off from the spinal cord and extend throughout the rest of the body. These spinal nerves exist in pairs — one half of the pair connects to the left side of the body while its counterpart connects to the matching right side of the body.
Spinal nerves have a posterior nerve root and an anterior nerve root. The posterior nerve root, often called the dorsal root, is where the sensory information from the body is transmitted to the spinal cord, sending sensation to the central nervous system. The anterior nerve root is where the nerves that transmit motor signals link to the spinal cord.
There are many posterior nerves throughout the body. Any nerve that detects sensation in the skin on the back of the body is a posterior cutaneous nerve. The posterior interosseous nerve supplies the muscles in the back and side of the forearm where the radial bone sits. The posterior cord is part of a large group of nerve fibers near the top of the spinal cord called the brachial plexus; nerves that branch from the posterior cord help control and stabilize the shoulder, arm and hand.
The sciatic nerve, the largest nerve in the peripheral nervous system, is a posterior nerve, running through the buttocks and down the back of the thigh through the leg. For much of that distance, it is joined by the posterior cutaneous femoral nerve, which gives sensation to skin on the back of the thigh and other areas. The posterior tibial nerve branches off the sciatic nerve above the knee and runs through the calf of the leg to the foot.
