Which movement is described as turning the palm so the ventral surface faces downward?

• A. Pronation
• B. Rotation
• C. Extension
• D. Supination

Answer: (D)

Turning the palm so the ventral (palmar) surface faces downward is pronation. In the forelimb, pronation rotates the radius over the ulna, so the palm ends up facing the ground (posteriorly in many views). Supination is the opposite: the palm faces upward or forward, with the radius and ulna parallel. Extension, by contrast, is about increasing the angle of a joint (like straightening the elbow) and is not the movement that reorients the hand. Muscles like pronator teres and pronator quadratus drive pronation, while supination is produced by the supinator and, when the elbow is flexed, the biceps brachii.