Radius

In anatomy, the radius is the smaller of the two bones on the thumb side of the forearm. (The bigger one is the ulna). The word "radius" comes unchanged from the Latin meaning a spoke in a wheel which this bone was thought to resemble. The word "radiation" is derived from the same Latin word — "radius."

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1. [NA] The lateral and shorter of the two bones of the forearm. 2. A straight line passing from the center to the periphery of a circle. SYN: radio- (3). [L. spoke of a wheel, rod, ray]

- r. fixus a line passing from the hormion to the inion.

- radii of lens [TA] 9–12 faint lines on the anterior and posterior surfaces of the lens that radiate from the poles toward the equator; they mark the lines along which the ends of lens fibers abut. SYN: radii lentis [TA], lens stars (1), lens sutures.

- radii lentis [TA] SYN: radii of lens.

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Routine Antenatal Diagnostic Imaging with Ultrasound [trial]

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ra·di·us 'rād-ē-əs n, pl ra·dii -ē-.ī also ra·di·us·es the bone on the thumb side of the human forearm or on the corresponding part of the forelimb of vertebrates above fishes that in humans is movably articulated with the ulna at both ends so as to permit partial rotation about that bone, that bears on its inner aspect somewhat distal to the head a prominence for the insertion of the biceps tendon, and that has the lower end broadened for articulation with the proximal bones of the carpus so that rotation of the radius involves also that of the hand

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n.

the outer and shorter bone of the forearm (compare ulna). It partially revolves about the ulna, permitting pronation and supination of the hand. The head of the radius articulates with the humerus. The lower end articulates both with the scaphoid and lunate bones of the carpus (wrist) and with the ulna (via the ulnar notch on the side of the bone).

• radial adj.

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ra·di·us (raґde-əs) gen. and pl. raґdii [L. “spoke” (of a wheel)] a line segment from the center to the circumference of a circle or the surface of a sphere; the length of such a segment. Symbol r. [TA] the bone on the outer or thumb side of the forearm, articulating proximally with the humerus and ulna and distally with the ulna and carpus. See illustration and Plate 40.

Radius and ulna. (A), Anterior view; (B), posterior view.