A test yourself image of the anterior view of the forearm showing the bony elements and the attachment of the Pronator Teres muscle. Origin of the humeral head at the medial epicondyle of the humerus and the distal supracondylar ridge and of the ulnar head at the medial side of coronoid process of ulna are marked by red ovals. The insertion at the middle of lateral surface of the radius is marked by a blue oval. Transparent Pronator Teres muscle connects the two attachment sites.