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The radius or radial bone (pl.: radii or radiuses) 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. The ulna is longer than the radius, but the radius is thicker. The radius is a long bone, prism-shaped and slightly ...
The ulna or ulnar bone (pl.: ulnae or ulnas) [3] is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the radius, the forearm's other long bone. Longer and thinner than the radius, the ulna is considered to be the smaller long bone of the lower arm.
During pronation the radius is rotated so that the head's major axis reaches the radial notch on the ulna. This causes a small but significant lateral displacement of the radius' main axis — equal to half the difference between the two axes of the head (2 mm (0.079 in)) — just enough space to accommodate the radial tuberosity as it being ...
The radial notch of the ulna (lesser sigmoid cavity) is a narrow, oblong, articular depression on the lateral side of the coronoid process; it receives the circumferential articular surface of the head of the radius. It is concave from before backward, and its prominent extremities serve for the attachment of the annular ligament.
Structures closer to the radius are radial, structures closer to the ulna are ulnar, and structures relating to both bones are referred to as radioulnar. Similarly, in the lower leg, structures near the tibia (shinbone) are tibial and structures near the fibula are fibular (or peroneal ).
It is distinguished by its deep concavity and crescentic outline. It is situated in the center of the proximal row carpal bones, which lie between the ulna and radius and the hand. The lunate carpal bone is situated between the lateral scaphoid bone and medial triquetral bone.
[1]: 6 It, along with the lunate bone, articulates with the radius and ulna to form the major bones involved in movement of the wrist. [5] The scaphoid serves as a link between the two rows of carpal bones. With wrist movement, the scaphoid may flex from its position in the same plane as the forearm to perpendicular. [1]: 176–177
At the junction of this surface with the front of the body is a rough eminence, the tuberosity of the ulna, which gives insertion to a part of the brachialis; to the lateral border of this tuberosity the oblique cord is attached. Its lateral surface presents a narrow, oblong, articular depression, the radial notch.