Ulna

The ulna (along with the radius) is one of the two bones in the forearm. In the anatomical position, it is medial to the radius.

Related Topics:
Radius - Bone - Forearm - Anatomical position

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The ulna articulates with:

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• the humerus, at the elbow as a hinge joint.
• the radius, near the elbow as a pivot joint, this allows the radius to cross over the ulna in pronation.
• the distal radius, where it fits into the ulna notch.

The ulna is broader proximally, and narrower distally.

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Proximally, the ulna has a bony process, the olecranon process, a hook-like structure that fits into the olecranon fossa of the humerus. This prevents hyperextension and forms a hinge joint with the trochlea of the humerus.

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There is also a radial notch for the head of the radius, and the ulna tuberosity to which muscles can attach.

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Distally (near the hand), there is a styloid process.

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The ulna (Elbow Bone) is a long bone, prismatic in form, placed at the medial side of the forearm, parallel with the radius. It is divisible into a body and two extremities. Its upper extremity, of great thickness and strength, forms a large part of the elbow-joint; the bone diminishes in size from above downward, its lower extremity being very small, and excluded from the wrist-joint by the interposition of an articular disk.

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Ulna: The upper extremity ►