Ulna

The elbow bone ( ulna ) is located on the medial side of the forearm ( ulnar direction ). On the proximal part, there is an articular surface, forming a fossa of the medial ulnar and proximal radioulnar joints. The body of the bone ( corpus ulnae ) has a triangular cross-section. The distal end of the ulna ( caput ulnae ) is indirectly articulated with the carpus and directly with the radius.

Proximal part

 * It creates a notch, incisura trochlearis, in the anatomical position it is open ventrally, into which the trochlea humeri fits , and is bordered by the following formations:
 * olecranon – the most proximal part of the bone, when the joint is flexed it forms the tip of the elbow;
 * processus coronoideus – distal border of the notch;
 * incisura radialis – a small depression covered by cartilage, connected to the articular surface, into which the caput radii fits.

The body of the ulna

 * The body has a triangular cross-section, the edges are reversed ventrally, dorsally and laterally ( margo anterior, posterior et interosseus ).
 * Margo interosseus faces the radius and is connected to it by an interosseous ligamentous membrane.
 * The foramen nutricum is directed proximally.

The head of the ulna

 * The head of the ulna is formed by the cylindrical articular surface of the circumferential articularis, which laterally attaches to the radius and proximally to the discus articularis.
 * From the mediodorsal side, the processus styloideus ulnae emerges, which is easily palpable.

Clinical contexts
See Forearm Fractures for more detailed information .

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