The Triceps Brachii is the
primary extensor of the forearm. It arises from three separate origins: a long
head from the infraglenoid tubercle of the scapula; a lateral head from the
humerus above the radial groove; and a medial head from the humerus below the
The deep tendon reflex of the triceps is utilized to determine the integritiy of C7 and C8 spinal cord segments. The radial nerve innervates the triceps muscle. Other muscles supplied by the same root but different nerves include pronator, teres (median) and wrist flexors (median and ulnar).