Editing Trapezium (bone) (section)

==Structure==
The trapezium is distinguished by a deep groove on its anterior surface. It is situated at the radial side of the [[Carpal bones|carpus]], between the [[scaphoid]] and the first [[metacarpal]] bone (the metacarpal bone of the thumb). It is [[homology (biology)|homologous]] with the '''first distal carpal''' of reptiles and amphibians.

===Surfaces===
The trapezium is an irregular-shaped [[carpal bone]] found within the [[hand]]. The trapezium is found within the distal row of carpal bones, and is directly adjacent to the [[metacarpal]] bone of the [[thumb]]. On its ulnar surface are found the [[Trapezoid bone|trapezoid]] and [[scaphoid]] bones.<ref name=GRAYS2005>{{cite book|last=Drake|first=Richard L.|title=Gray's anatomy for students|year=2005|publisher=Elsevier/Churchill Livingstone|location=Philadelphia|isbn=978-0-8089-2306-0|author2=Vogl, Wayne |author3=Tibbitts, Adam W.M. Mitchell  |author4=illustrations by Richard |author5= Richardson, Paul }}</ref>{{rp|708}}

The ''[[Anatomical terms of location|superior surface]]'' is directed upward and medialward; medially it is smooth, and articulates with the [[scaphoid]]; laterally it is rough and continuous with the lateral surface.

The ''[[Anatomical terms of location|inferior surface]]'' is oval, concave from side to side, convex from before backward, so as to form a saddle-shaped surface for articulation with the base of the [[first metacarpal bone]]. This saddle-shaped articulation is partially responsible for the [[Carpometacarpal joint#Thumb|thumb]]'s opposable motion.

The ''dorsal surface'' is smooth.

The ''palmar surface'' is narrow and rough. At its upper part is a deep groove, running from above obliquely downward and medialward; it transmits the tendon of the [[Flexor carpi radialis]], and is bounded laterally by an oblique ridge. This surface gives origin to the [[Opponens pollicis]] and to the [[Abductor pollicis brevis muscle|Abductor]] and [[Flexor pollicis brevis]]; it also affords attachment to the [[transverse carpal ligament]].

The ''lateral surface'' is broad and rough, for the attachment of ligaments.

The ''medial surface'' presents two facets; the upper, large and concave, articulates with the [[trapezoid bone]]; the lower, small and oval, with the base of the [[second metacarpal]].

===Tubercle of trapezium===
The tubercle of trapezium is a [[tubercle]] found on the anterior surface of the bone.<ref name=GRAYS2005 />{{rp|708}} It is where sometimes [[abductor pollicis brevis muscle]] attaches.