Trapezoid bone
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.
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."
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.
See also
Additional images
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Bones of upper limbs |
| Pectoral girdle, clavicle |
conoid tubercle - trapezoid line - costal tuberosity - subclavian groove |
| Scapula |
spine of scapula - suprascapular notch - acromion - glenoid cavity - glenoidal labrum - coracoid process - fossae (subscapular, supraspinatous, infraspinatous) - borders (superior, lateral/axillary, medial/vertebral) - angles (superior, inferior, lateral) - tubercles (infraglenoid, supraglenoid) |
| Humerus |
upper extremity: necks (anatomical, surgical) - tubercles (greater, lesser) - intertubercular sulcus
body: radial sulcus - deltoid tuberosity
lower extremity: capitulum - trochlea - epicondyles (lateral, medial) - supracondylar ridges (lateral, medial) - fossae (radial, coronoid, olecranon) |
| Forearm |
ulna: upper extremity (olecranon, coronoid process, tuberosity, radial notch, semilunar notch) - body of ulna - lower extremity (styloid process)
radius: upper extremity (tuberosity) - body - lower extremity (ulnar notch, styloid process) |
| Hand |
carpus: scaphoid - lunate - triquetral - pisiform - trapezium - trapezoid - capitate - hamate (hamulus) - metacarpus: 1st metacarpal - 2nd - 3rd - 4th - 5th - phalanges of the hand |
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant.
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