Bones of the Upper Extremity. 



95 



118. Right humerus, 



from behind. 



The lower extremity of the 



humerus is somewhat thinner but 

 broader than the shaft. From each 

 side of it projects a rough eminence, 

 the epicondylus medialis (0. T. internal 

 condyle) and the epicondylus lateralis 

 (0. T. external condyle). These lie in 

 the lines of continuation of the margo 

 medialis and the margo lateralis and 

 give attachment to muscles and liga- 

 ments of the elbow joint. The epi- 

 condylus medialis is the larger and 

 presents on its posterior surface a 

 shallow groove, sulcus nervi ulnaris 

 (for the n. ulnaris). 



Between the two epicon&yles lies 

 a joint surface, covered with cartilage, 

 for articulation with the bones of the 

 forearm. It consists of a medial, roller- 

 shaped surface, trochlea humeri (for 

 articulation with the ulna), which extends 

 also upon the posterior surface, and of 

 a lateral , smaller capitulum humeri 

 (0. T. capitellum or radial head) (for 

 articulation with the radius), shaped like 

 the segment of a sphere, which is not con- 

 tinued upon the posterior surface. Above 

 the trochlea, both in front and behind, 

 is a deep depression; that in front is 

 called the fossa coronoidea, that behind, 

 the fossa olecrani; between the two 

 the bone is very thin and may be 

 absent. On the anterior surface, above 

 the capitulum humeri, lies the smaller 

 fossa radialis. These three depressions 

 are not covered with cartilage. 



;Caput humeri 



^ Collum anatomicuiu 



[ _ - Tuberculum ma jus 

 Collum chirurgicuin 



Sulcus n. radialis 



Facies posterior 



Fossa olecraui 



Epicondylus 

 lateralis 



Trochlea humeri 



x Sulcus n. ulnaris 

 I Epicondylus medialis 



