208 



OSTEOLOGY. 



LESSER TUBERCLE 



HEAD ... 



INTER-TUBERCULAR 

 GROOVE 



CAPITULUM 



TROCHLEA 



OLECRANON FOSSA GROOVE FOR ULNAR NEKV: 



FIG. 199. DISTAL ASPECT OP THE DISTAL EX- 

 TREMITY OF THE EIGHT HUMERUS. 



The posterior surface of the distal half of the body is smooth and rounded fror 



side to side ; somewhat flattene* 

 dis tally, where the whole bod; 

 tends to incline forwards, it be 

 comes continuous on either sid 

 .with the posterior surfaces of th] 

 epicondyles, the medial of whicl 

 .GREATER i s grooved for the passage of th 



TUBERCLE , & , ., * 



MEDIAL / | \ m \ T ulnar nerve, whilst the latera 



;' I ' ji mMi^Hf ' LATERAL -.. . . 1 



;~X I \ X" /"EPICONDYLE supplies an origin for the an] 



con 83us muscle. The medial heat 

 of the triceps muscle has an exten 

 sive attachment from the posterio 



FIG. 198. PROXIMAL ASPECT OF THE HEAD OF THE EIGHT surface of the distal two- thirds 0| 



the body, medial to and distal t<j 

 the groove for the radial nerve. 

 The distal extremity of the humerus is furnished with two articular surface 



(the condyles proper), the lateral of which, 



called the capitulum, for articulation with 



the proximal surface of the head of the 



radius, is a rounded eminence, placed on 



the anterior surface and distal border, but 



not extending on to the posterior surface 



of the distal end of the bone. Proximal to 



it, in front, there is a shallow depression 



(fossa radialis), into which the margin of the 



head of the radius sinks when the elbow 



is strongly flexed. A shallow groove separ- 

 ates the capitulum medially from the 



trochlea, which is a grooved articular surface, with prominent edges winding spiralljj 



round the distal extremity of the body. The' 

 spiral curves from behind forwards and medially 

 and its axis is slightly oblique to the long axis oil 

 the shaft. The medial lip is the more salient! 

 of the two, and forms a sharp and well-defined | 

 margin to the articular area ; its cartilage-covered I 

 surface is slightly convex. The lateral lip, much less ( 

 prominent, is rounded off into the articular groove! 

 which separates it from the capitulum, posterior to 

 which, however, it is carried up as a more or lessj 

 definite crest. It is by means of the trochlea that the 

 humerus articulates with the semilunar notch of the 

 ulna. On the anterior surface of the bone, imme- ! 

 diately proximal to the trochlea, is a depression 

 the fossa coronoidea (coronoid fossa) into which the ; 

 coronoid process of the ulna slips in flexion of the ; 

 joint, whilst in a corresponding position on the! 

 posterior aspect of the distal end of the body there 

 is a hollow, called the fossa olecrani (olecranon 

 fossa), just proximal to the trochlea posteriorly. 

 Into this the olecranon process sinks when the 

 elbow is extended. The two fossse are separated 

 by a thin translucent layer of bone which may be 

 deficient, thus leading to the formation of a ; 



200. THE DISTAL END OF THE foramen between the two hollows in the macerated 



5 bone. The anterior part of the capsule of the elbow- 

 joint is attached to the proximal margins of the 



radial and coronoid fossse in front, whilst the posterior ligament is connected with j 



the proximal border and lateral edges of the olecranon fossa behind. The strong 



LATERAL EPICONDYLIC 

 RIDGE (lateral margin) 



CAPITULUM 



RADIAL 



COLLATERAL 



LIGAMENT 



TROCHLEA 



FIG. 



