Head of radius
Encyclopedia
The head of the radius
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
.
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...
has a cylindrical form, and on its upper surface is a shallow cup or fovea for articulation with the capitulum
Capitulum of the humerus
In 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 humerus
Humerus
The 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 ligament
Annular ligament
The 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
Cam
A cam is a rotating or sliding piece in a mechanical linkage used especially in transforming rotary motion into linear motion or vice-versa. It is often a part of a rotating wheel or shaft that strikes a lever at one or more points on its circular path...
effect during pronation
Pronation
In anatomy, pronation is a rotational movement of the forearm at the radioulnar joint, or of the foot at the subtalar and talocalcaneonavicular joints. For the forearm, when standing in the anatomical position, pronation will move the palm of the hand from an anterior-facing position to a...
and supination
Supination
Supination is a position of either the forearm or foot; in the forearm when the palm faces anteriorly, or faces up . Supination in the foot occurs when a person appears "bow-legged" with their weight supported primarily on the anterior of their feet.The hand is supine in the anatomical position...
.