triceps

Three headed muscle of the posterior compartment of the arm, crossing 2 joints, the shoulder & elbow.. Origin: 1) long or scapular head: lateral border or the scapula below the glenoid fossa 2) lateral head: lateral & posterior surface of the humerus below the greater tubercle 3) medial head: posterior surface of the humerus below the radial groove Insertion: olecranon of ulna Action: extends elbow Innervation: radial nerve

References

Stedman's Medical Dictionary 27th ed, Williams & Wilkins, Baltimore, 1999