Trochlear notch

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Semilunar notch
Upper extremity of left ulna. Lateral aspect. (Semilunar notch visible at center top.)
Latin Incisura trochlearis ulnae,
incisura semilunaris ulnae
Gray's p.215
TA A02.4.06.006
FMA 23619
Anatomical terms of bone

The semilunar notch of the ulna (trochlear notch of ulna, greater sigmoid cavity) is a large depression, formed by the olecranon and the coronoid process, and serving for articulation with the trochlea of the humerus.

About the middle of either side of this notch is an indentation, which contracts it somewhat, and indicates the junction of the olecranon and the coronoid process.

The notch is concave from above downward, and divided into a medial and a lateral portion by a smooth ridge running from the summit of the olecranon to the tip of the coronoid process.

The medial portion is the larger, and is slightly concave transversely; the lateral is convex above, slightly concave below.

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This article incorporates text from a public domain edition of Gray's Anatomy.