The triceps brachii inserts at which structure?

• A. Coracoid process
• B. Intertubercular groove of the humerus
• C. Deltoid tuberosity
• D. Olecranon process of ulna

Answer: (D)

The triceps brachii inserts on the olecranon process of the ulna. This tendon attachment lets the muscle pull the ulna and straighten the elbow, which is its primary action. The triceps has three heads that originate on the scapula and humerus, but they all converge to insert at the olecranon, providing a strong distal anchor for elbow extension. The other structures are attachment sites for different muscles: the coracoid process is where parts of the biceps and coracobrachialis attach; the intertubercular groove houses the tendon of the long head of the biceps; and the deltoid tuberosity is where the deltoid attaches.