Radius (bone) in the grooves on the lower end of the bone. The lateral surface ("facies lateralis; external surface") is convex throughout its entire extent and is known as the convexity of the radius, curving outwards to be convex at the side. Its upper third gives insertion to the supinator muscle. About its center is a rough ridge, for the insertion of the pronator teres muscle. Its lower part is narrow, and covered by the tendons of the abductor pollicis longus muscle and extensor pollicis brevis muscle. The upper extremity of the radius (or proximal extremity) presents a head, neck, and tuberosity.
Second metacarpal bone Second metacarpal bone The second metacarpal bone (metacarpal bone of the index finger) is the longest, and its base the largest, of all the metacarpal bones. Its base is prolonged upward and medialward, forming a prominent ridge. It presents four articular facets, three on the upper surface and one on the ulnar side: The extensor carpi radialis longus muscle is inserted on the dorsal surface and the flexor carpi radialis muscle on the volar surface of the base. The shaft gives origin to the first palmar interosseus and the first and second dorsal interossei. This bone is often the most