THE CARPUS 



159 



THE CARPUS 



The carpus (figs. 188, 189) consists of eight bones, arranged in two rows, four 

 bones in each row. Enumerated from the radial to the ulnar side, the bones of 

 the proximal row are named navicular (scaphoid), lunate (semilunar), triquetral 

 (cuneiform), and pisiform; those of the distal row, greater multangular (trape- 

 zium), lesser multangular (trapezoid), capitate (os magnum), and hamate 

 (unciform) . 



When the bones of the carpus are articulated, they form a mass somewhat quad- 

 rangular in outline, wider below than above, and with the long diameter trans- 

 verse. The dorsal surface is convex and the volar surface concave from side to 

 side. The concavity is increased by four prominences, which project forward, one 



Fig. 188. — Bones of the Left Hand. (Dorsal surface.) 



Lunate 



Navicular 



Pisiform 



lUETRAL 



Greater multangular 



Extensor carpi 

 radialis longus 

 Extensor carpi 

 radialis brevis 



Metacarpal 



Extensor pollicis 

 brevis 



Extensor carpi 

 ulnaris 



Est. pollicis 

 longus 



Extensor digitorum commums 

 Second phalanx 



Extensor digitorum communis 

 Third, ungual, or terminal phalanx 



from each extremity of each row. On the radial side are the tuberosity of the 

 navicular and the ridge of the greater multangular; on the ulnar side, the pisiform 

 and the hook of the hamate. Stretched transversely between these prominences, 

 in the recent state, is the transverse carpal ligament forming a canal for the passage 

 of the flexor tendons and the median nerve into the palm of the hand. The proxi- 

 mal border of the carpus is convex and articulates with the distal end of the 

 radius and the articular disc. The pisiform, however, takes no share in this ar- 

 ticulation, being attached to the volar surface of the triquetral. The distal border 

 forms an undulating articular surface for the bases of the metacarpal bones. The 



