The arm is divided into two muscle compartments:

• The anterior compartment, which contains the biceps, the brachialis, and coracobrachialis, all innervated by the musculocutaneous nerve.

• The posterior compartment, which contains the triceps, which is innervated by the radial nerve.

The forearm is divided into three muscle compartments:

• The anterior or flexor compartment, which contains the muscles responsible for wrist flexion and pronation of the forearm. These muscles are innervated by the median and ulnar nerves and receive blood supply mainly from the ulnar artery.

• The posterior or extensor compartment, which contains the muscles responsible for wrist extension. They are innervated by the radial nerve and the blood supply is provided mainly by the radial artery.

• The mobile wad is a group of three muscles on the radial aspect of the forearm that act as flexors at the elbow joint. These muscles are often grouped together with the dorsal compartment. The blood supply is provided by the radial artery and the innervation by branches of the radial nerve.

The hand includes ten separate osteofascial compartments:

• The transverse carpal ligament, over the carpal tunnel, is a strong and broad ligament. The tunnel contains the median nerve and the finger flexor tendons.