Final answer:
The pronator quadratus muscle is a key forearm muscle responsible for pronation, innervated by the median nerve, and supplied blood by the anterior interosseous artery.
Step-by-step explanation:
Pronator Quadratus Muscle
The pronator quadratus is a square-shaped muscle on the distal forearm that acts to pronate (turn so the palm faces downwards) the forearm. It arises from the anterior distal portion of the ulna and inserts into the anterior distal surface of the radius. Innervation of the pronator quadratus is through the median nerve (specifically, the anterior interosseous branch). Its blood supply comes from the anterior interosseous artery, a branch of the ulnar artery. This muscle works with the pronator teres to achieve pronation of the forearm. When the arm is in a supinated position, with the palm facing anteriorly, contraction of the pronator quadratus will turn the forearm so the palm faces posteriorly, thus pronating the forearm.