Upper extremity of radius
Encyclopedia
The upper extremity of the radius
(or proximal extremity) presents a head, neck, and tuberosity.
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
(or proximal extremity) presents a head, neck, and tuberosity.
- The radial head has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulumCapitulum of the humerusIn human anatomy of the arm, the lateral portion of the articular surface of the humerus consists of a smooth, rounded eminence, named the capitulum of the humerus....
(or capitellum) of the humerusHumerusThe humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
. The circumference of the head is smooth; it is broad medially where it articulates with the radial notch of the ulna, narrow in the rest of its extent, which is embraced by the annular ligamentAnnular ligamentThe anular ligament is a strong band of fibers, which encircles the head of the radius , and retains it in contact with the radial notch of the ulna....
. The deepest point in the fovea is not axi-symmetric with the long axis of the radius, creating a cam effect during pronation and supination. - The head is supported on a round, smooth, and constricted portion called the neck, on the back of which is a slight ridge for the insertion of part of the supinator muscleSupinator muscleIn human anatomy, the supinator is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius. Its function is to supinate the forearm.-Terminology:...
. - Beneath the neck, on the medial side, is an eminence, the radial tuberosity; its surface is divided into a posterior, rough portion, for the insertion of the tendon of the biceps brachii muscle, and an anterior, smooth portion, on which a bursa is interposed between the tendonTendonA tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
and the bone.