Trapezoid bone

Trapezoid bone
Left hand anterior view (palmar view). Trapezoid bone shown in red.
The left trapezoid bone.
Details
Articulations	articulates with four bones: scaphoid proximally second metacarpal distally trapezium bone laterally capitate medially
Identifiers
Latin	os trapezoideum, os multangulum minus
MeSH	A02.835.232.087.319.150.805
Dorlands /Elsevier	o_07/12598807
TA	A02.4.08.010
FMA	23724
Anatomical terms of bone [edit on Wikidata]

The trapezoid bone (lesser multangular bone) is a carpal bone in tetrapods, including humans. It is the smallest bone in the distal row. It may be known by its wedge-shaped form, the broad end of the wedge constituting the dorsal, the narrow end the palmar surface; and by its having four articular facets touching each other, and separated by sharp edges. It is homologous with the "second distal carpal" of reptiles and amphibians.

Structure

The trapezoid is a four-sided carpal bone found within the hand. The trapezoid is found within the distal row of carpal bones.^{[1] :708}

Surfaces

The superior surface, quadrilateral, smooth, and slightly concave, articulates with the scaphoid.

The inferior surface articulates with the proximal end of the second metacarpal bone; it is convex from side to side, concave from before backward and subdivided by an elevated ridge into two unequal facets.

The dorsal and palmar surfaces are rough for the attachment of ligaments, the former being the larger of the two.

The lateral surface, convex and smooth, articulates with the trapezium.

The medial surface is concave and smooth in front, for articulation with the capitate; rough behind, for the attachment of an interosseous ligament.

Function

The carpal bones function as a unit to provide a bony superstructure for the hand.^{[1] :708}

History

The etymology derives from the Greek trapezion which means "irregular quadrilateral," from tra- "four" and peza "foot" or "edge." Literally, "a little table" from trapeza meaning "table" and -oeides "shaped."

Additional images

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  Position of trapezoid bone (shown in red). Left hand. Animation.

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  Trapezoid bone of the left hand. Close up. Animation.

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  Trapezoid bone.

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  Right hand posterior view (dorsal view). Thumb on bottom.

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  Trapezoid shown in yellow. Left hand. Dorsal surface.

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  Trapezoid shown in yellow. Left hand. Palmar surface.

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  Transverse section across the wrist (palm on top, thumb on left). Trapezoid bone shown in yellow (labelled as "Lesser Multang").

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  Cross section of wrist (thumb on left). Trapezoid shown in red (labelled as "Lesser Multang").

See also

• Carpal bone

References

This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)

1. Drake, Richard L.; Vogl, Wayne; Tibbitts, Adam W.M. Mitchell; illustrations by Richard; Richardson, Paul (2005). Gray's anatomy for students. Philadelphia: Elsevier/Churchill Livingstone. ISBN 978-0-8089-2306-0.