Trapezoid bone

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Bone: Trapezoid bone
BONES OF HAND Proximal: A=Scaphoid, B=Lunate, C=Triquetral, D=Pisiform Distal: E=Trapezium, F=Trapezoid, G=Capitate, H=Hamate
The left lesser multangular bone.
Latin	os trapezoideum, os multangulum minus
Gray's	subject #54 225
Articulations	articulates with four bones: scaphoid proximally second metacarpal distally trapezium bone laterally capitate medially
MeSH	Trapezoid+Bone
Dorlands / Elsevier	o_07/12598807

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."

[edit] 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.

[edit] See also

• Bone terminology
• Terms for anatomical location
• Trapezoid distinguishing meanings of trapezoid and trapezium in American English and British English

[edit] Additional images

Bones of the left hand. Dorsal surface.

Transverse section across the wrist and digits.

v • d • e Bones of upper limbs Pectoral girdle, clavicle conoid tubercle - trapezoid line - costal tuberosity - subclavian groove Scapula fossae (subscapular, supraspinatous, infraspinatous) - suprascapular notch - glenoid cavity tubercles (infraglenoid, supraglenoid) - spine of scapula - acromion - coracoid process borders (superior, lateral/axillary, medial/vertebral) - angles (superior, inferior, lateral) 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 radius: upper extremity (head, tuberosity) - body - lower extremity (ulnar notch, styloid process) ulna: upper extremity (tuberosity, olecranon, coronoid process, radial notch, trochlear notch) - body - lower extremity (head, styloid process) Hand carpus: scaphoid - lunate - triquetral - pisiform - trapezium - trapezoid - capitate - hamate (hamulus) metacarpus: 1st metacarpal - 2nd - 3rd - 4th - 5th phalanges of the hand: proximal - intermediate - distal

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.