100 



Bones of the Upper Extremity. 



Fovea capituli radii 



Capitulum radii_. 



_Circumferentia 

 articularis 



Collum radii 



Tuberositas radii 



Crista interossea 



I Fades \olaris 



Margo v olaris _ _ 





Processus styloideus 



125. Right radius, 



radius, from in front. 



The radius (spoke) (see also 

 Figs. 126 129, 146) is a long 

 cylindrical bone, thickened at its lower 

 end which occupies the side of the 

 forearm corresponding to the thumb. 

 It articulates above with the upper arm, 

 below enters into the joint between the 

 bones of the forearm and those of the 

 wrist and rotates above and below on 

 the ulna. 



It is divisible into a shaft or 

 corpus and two extremities. 



The corpus radii or shaft is 

 bent so as to be somewhat convex 

 toward the thumb side and is triangu- 

 larly prismatic. The narrowest of its 

 three surfaces, fades later alls (0. T. 

 external surface) is directed toward the 

 thumb side; it adjoins at the rounded 

 margo dorsalis (0. T. posterior border) 

 behind and the margo volaris (0. T. 

 anterior border) in front, the broader 

 fades dorsalis (0. T. posterior surface) 

 and fades volaris (0. T. anterior sur- 

 face). The ulnar angle formed by these 

 two surfaces is especially sharp and is 

 called the crista interossea (0. T. 

 internal or interosseous border). A 

 foramen nutridum is often visible at 

 a spot corresponding to that on the 

 ulna; the canalis nutridus is directed 

 proximalward. 



