230 OSTEOLOGY 



The Phalanges of the Hand (Phalanges Digitorum Manus). 



The phalanges are fourteen in number, three for each finger, and two for the 

 thumb. Each consists of a body and two extremities. The body tapers from above 

 downward, is convex posteriorly, concave in front from above downward, flat 

 from side to side; its sides are marked by rough ridges which give attachment 

 to the fibrous sheaths of the Flexor tendons. The proximal extremities of the bones 

 of the first row present oval, concave articular surfaces, broader from side to side 

 than from before backward. The proximal extremity of each of the bones of the 

 second and third rows presents a double concavity separated by a median ridge. 

 The distal extremities are smaller than the proximal, and each ends in two condyles 

 separated by a shallow groove; the articular surface extends farther on the volar 

 than on the dorsal surface, a condition best marked in the bones of the first row. 



The ungual phalanges are convex on their dorsal and flat on their volar surfaces; 

 they are recognized by their small size, and by a roughened, elevated surface of 

 a horseshoe form on the volar surface of the distal extremity of each which serves 

 to support the sensitive pulp of the finger. 



One center for each bone : 

 All cartilaginous at birth 



METACARPALS OF FINGERS 



Two centers for each bone 

 One for body 

 One for head 



PHALANGES 



Two centers for each bone : 

 One for body 

 One for proximal 

 extremity 



FIG. 234. Plan of ossification of the hand. 



Articulations. In the four fingers the phalanges of the first row articulate with those of the 

 second row and with the metacarpals; the phalanges of the second row with those of the first 

 and third rows, and the ungual phalanges with those of the second row. In the thumb, which 

 has only two phalanges, the first phalanx articulates by its proximal extremity with the meta- 

 carpal bone and by its distal with the ungual phalanx. 



Ossification of the Bones of the Hand. The carpal bones are each ossified from a single center, 

 and ossification proceeds in the following order (Fig. 234) : in the capitate and hamate, during 



