How many heads does the triceps brachii have?

• A. Four
• B. One
• C. Two
• D. Three

Answer: (D)

The triceps brachii is a three-headed muscle on the back of the upper arm, and that arrangement lets it extend the elbow. It has three heads: the long head, the lateral head, and the medial head. Each head has a distinct origin but they all share a common insertion on the olecranon of the ulna. The long head comes from the infraglenoid tubercle of the scapula; the lateral head from the posterior surface of the humerus above the radial groove; and the medial head from the posterior surface below the radial groove. When they contract together, they produce elbow extension, with the long head also assisting in shoulder movements when the arm is overhead. That’s why the correct count is three—no four, two, or one; there are three distinct heads.