Final answer:
The pronator muscles (pronator teres and pronator quadratus) and the supinator muscle insert onto the radius bone of the forearm. The biceps brachii also contributes to supination by inserting on the radial tuberosity. These muscles work together to pronate and supinate the forearm and wrist.
Step-by-step explanation:
The muscles that pronate and supinate the forearm all share a common insertion point. The pronator muscles, which include the pronator teres and the pronator quadratus, as well as the supinator muscle, insert onto the radius bone of the forearm. When these muscles contract, they cause the radius to rotate over the ulna, which results in pronation or supination of the forearm and wrist.
The biceps brachii also plays a role in supinating the forearm due to its insertion on the radial tuberosity. It works in conjunction with the supinator muscle when the elbow is flexed. The biceps brachii, alongside the brachialis and brachioradialis, flexes the forearm as well. On the other hand, the triceps brachii and anconeus are involved in extending the forearm.
It is important to note that the muscles originating in the forearm move the wrists, hands, and fingers, and their tendons extend into these areas, wrapped by fibrous bands called retinacula. The flexor retinaculum and the extensor retinaculum are structures that are particularly significant as they sheath the tendons at the wrist.