Which muscle inserts on the tuberosity and coronoid process of the ulna?

• A. Brachialis
• B. Brachioradialis
• C. Flexor digitorum profundus
• D. Pronator teres

Answer: (A)

Understanding insertion helps explain the action at a joint. Brachialis attaches from the front of the humerus to the ulna at the tuberosity and the coronoid process, so when it contracts it pulls the ulna toward the humerus to bend the elbow. This makes it the primary pure elbow flexor, active regardless of how the forearm is rotated. The other muscles don’t attach to both the ulna tuberosity and the coronoid process in their distal attachments, or they attach to different bones (like the radius or the digits), so they don’t fit this specific insertion pattern.