06 



ELEMENTS OF MAMMALIAN ANATOMY 



articular surface of the distal extremity consists of the capitidiim 

 for articulation with the head of the radius, and the trochlea 

 for articulation with the semilunar notch of the ulna. On 

 the cranial side of the proximal third of the 

 bone is the rough deltoid ridge for the inser- 

 tion of the deltoid muscle which arises 

 from the shoulder girdle. 



The ulna is the longest bone of the fore- 

 arm or antchrachium, and is caudad of the 

 radius. It articulates in the semilunar 

 notch with the trochlea of the humerus and 

 in the radial notch with the head of the 

 radius. The distal articulation is with the 

 radius, triquetral and pisiform (Fig. 22). 

 The olecranon process forms the proximal 

 termination of the bone and serves for the 

 insertion of the triceps muscle. Distad of 

 the semilunar notch is a projection known 

 as the coronoid process. The styloid process 

 forms a small projection on the distal 

 extremity of the bone. 



The radius is the preaxial or cranial bone 

 of the antebrachium. It articulates prox- 

 „ *^^ ^ imally with the capitulum of the humerus 



Fig. 34. — Lateral -^ . i r i i i j* n 



OR Outer Aspect of and the radial notch of the ulna, and distally 

 "Z.^lr"Iu^Z'-tcet with the scapholunar and ulna. It bears 

 for radius; cr. coro- but two proccsscs, the tiihercU and the styloid 



noid process; gs, , rr^i . 7 7 /-r-- \ • r 1,4- 



semihinar notch; Is, proccss. The tiihercle (Fig. 35) IS a slight 

 radial notch; on, oie- ^^^^ ^^^^ ^^^ proximal end in the ulnar 



cranon process; st, ^ 



styloid process. side. Proximal from the tubercle is the 



neck which supports the head bearing a 

 concave crown for articulation with the capitulum of the 

 humerus. The styloid process projects from the distal end 

 parallel with the process of the same name on the ulna. 



ar 



