List the muscles that pronate the elbow.
The correct answer and explanation is:
The muscles that pronate the elbow are the pronator teres and pronator quadratus.
- Pronator Teres: This muscle originates from the medial epicondyle of the humerus and the coronoid process of the ulna. It inserts into the lateral surface of the radius, about halfway along its length. The pronator teres is primarily responsible for initiating the pronation of the forearm, where the palm turns downward or backward. Its action is most prominent when the forearm is in a neutral or supinated position.
- Pronator Quadratus: The pronator quadratus is a deeper muscle located in the distal part of the forearm. It originates from the anterior surface of the ulna and inserts into the anterior surface of the radius. Unlike the pronator teres, which primarily affects the upper part of the radius, the pronator quadratus acts on the lower portion of the radius to complete pronation, especially during more forceful movements.
Both muscles work together to rotate the radius over the ulna, causing the palm to face down. The pronation process involves the twisting of the forearm bones. The pronator teres is more active during weaker or slower pronation motions, while the pronator quadratus is involved during stronger or more sustained efforts. In normal daily activities, these muscles allow for functions such as turning a doorknob, typing on a keyboard, or any action where the palm faces downward.
Both muscles are innervated by the median nerve. The pronator teres is supplied by a branch of the median nerve, while the pronator quadratus receives innervation directly from the anterior interosseous nerve, a branch of the median nerve. This collaboration ensures efficient and smooth pronation during various tasks.