Upper extremity of radius

Infobox Bone
Name = Upper extremity of radius
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GraySubject = 52
GrayPage = 219

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Caption = The "radius" and ulna of the left forearm, posterior surface. The top is proximal (elbow) and bottom is distal (wrist).


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The upper extremity of the radius (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 capitulum (or capitellum) of the humerus. 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 ligament. 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 muscle.

* 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 tendon and the bone.

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