Bones of the Upper Extremity. 



99 



124. Right ulna, ulna, 



from the radial side. 



The upper extremity of the 

 ulna is thickened and ends with a 

 rough strong process , the olecranon ; 

 beneath it, projecting from the volar 

 surface, is the strong processus coro- 

 noideus. Between these two processes 

 lies a deep notch, covered with carti- 

 lage, the incisura semilunaris (0. T. 

 greater sigmoid cavity), in which the 

 trochlea humeri is received. On the 

 radial side of the proc. coronoideus the 

 smaller, slightly concave, incisura ra- 

 dialis (0. T. lesser sigmoid cavity) (for 

 the capitulum radii) is visible. Passing 

 obliquely backward and downward from 

 this is a sharp bony ridge, the crista 

 m. supinatoris (for the origin of the 

 m. supinator). Somewhat below the 

 proc. coronoideus lies a broad rough 

 surface for the attachment of the m. 

 brachialis, the tuberositas ulnae. 



The lower extremity is nar- 

 rower and forms a small rounded head, 

 capitulum ulnae. This is covered with 

 fibro - cartilage not only on its distal 

 surface but also in the largest part of its 

 circumference, the circumferentia arti- 

 cularis (for the incisura ulnaris radii). 

 On the side corresponding to the little 

 finger, the small blunt processus 

 styloideus projects distalward. 



Olecranon 



/ 



Margo dorsalis 



Facies dorsalis 



I 



- Incisura semilunaris 



Processus 



coronoideus 

 "Incisura radialis 



Crista m. supinatoris 

 ---Tuberositas ulnae 



Crista interossea 



-Capitulum ulnae 

 " Circumferentia articularis 



\, 



Processus styloideus 



