What action does the pronator teres perform?

What action does the pronator teres perform?

• A. Supination of Forearm
• B. Flexion of Elbow
• C. Extension of Wrist
• D. Abduction of Shoulder

Answer: (B)

The pronator teres mainly acts to pronate the forearm, turning the palm downward, because it crosses the elbow and rotates the radius over the ulna. It also crosses the elbow, so when it contracts it can assist in bending the elbow, though this is a weaker, secondary action. Among the given options, elbow flexion best reflects a true action of this muscle, since pronation is its primary role and the other actions are performed by different muscles (supination by the supinator or biceps brachii; wrist extension by wrist extensors; shoulder abduction by shoulder girdle muscles).

The pronator teres mainly acts to pronate the forearm, turning the palm downward, because it crosses the elbow and rotates the radius over the ulna. It also crosses the elbow, so when it contracts it can assist in bending the elbow, though this is a weaker, secondary action. Among the given options, elbow flexion best reflects a true action of this muscle, since pronation is its primary role and the other actions are performed by different muscles (supination by the supinator or biceps brachii; wrist extension by wrist extensors; shoulder abduction by shoulder girdle muscles).