Lateral nerve is a general term describing nerves located at the lateral parts of the body. The term lateral means pertaining to the side, for instance the side of the knee facing away from the body is lateral, while the side facing the other knee is medial. An example of a lateral nerve is the lateral femoral cutaneous nerve - this nerve innervates the skin on the outer (lateral) side of the thigh.
Cutaneous nerves innervate, or provide nervous communication with, the skin. They are often sensory-only nerves, that is they do not function in muscle control, although some provide innervation to structures in the skin such as sweat glands. Nerves that innervate the skin on lateral sides of body parts are called lateral cutaneous nerves, for example the the lateral cutaneous nerve of the forearm provides for sensation in the skin of the lateral forearm. There is also a medial cutaneous nerve of the forearm, which provides sensation to the skin on the inner part of the forearm.
A lateral nerve need not innervate the skin, however. Some lateral nerves control muscle contraction, such as the lateral pectoral nerve. This nerve innervates the pectoralis major - the thick, fan-shaped muscle of the chest. Nerves innervating the abdomen and body appendages trace back to the spinal cord, and the lateral pectoral nerve is no exception. It arises from the lateral cord of the brachial plexus, which is composed of nerve fibers located beneath the clavicle bone that run from the spinal cord. The brachial plexus provides muscular and cutaneous innervation of a large part of the upper limb.
As with the lateral cutaneous nerve of the forearm, the lateral pectoral nerve has a medial counterpart. The medial pectoral nerve innervates the pectoralis minor muscle - the thin, triangular muscle situated in the upper chest behind the pectoralis major. A nerve is called a lateral nerve or medial nerve based more on the location of the nerve itself, rather than the location of the muscle it innervates.
