196 



A MANUAL OF ANATOMY 



Articulations. — Superiorly with the capitellum of the humerus 

 and small sigmoid cavity of the ulna, and inferiorly with the head 

 of the ulna, scaphoid, and semilunar. 



For Posterior Ligament 



Groove for Ext. Longus Pollicis 



Radial Tubercle 1 



Groove for Ext. Carpi Rad. Brev, 



Groove for Ext. Carpi 



Radial is Longior j 



Groove for Ext. Oss 

 Metacarp. Poll, and^^ 

 Ext. Brev. Pollicis 



Groove for Ext. Com. Dig. and Ext. Indicis 

 I Groove for Ext. Minimi Digiti 



! 



I Groove for Ext. Carpi Ulnaris 



Ulnar Styloid Process 



For Scaphoid | 



For Anterior Ligament 



For Apex of Triangular 

 Fibro-Cartilage 



For Upper Surface of Triangular 

 For Semilunar Fibro-Cartilage 



Fig. 109. — The Lower Ends of the Left Radius and Ulna 

 AS seen from below in Pronation. 



(The Dorsal Aspect is upwards. ) 



Structure. — ^This is similar to that of long bones. At the lower 

 extremity the cancellated tissue extends upwards for about i| inches 

 above the styloid process, this level being the site of Colles' fracture. 



Ossification. — The radius ossifies in cartilage from one primary, and two 

 secondary, centres. The primary centre appears at the middle of the shaft in 

 the eighth week of intra-uterine life. At birth the shaft is ossified, but the 

 extremities are cartilaginous. The secondary centre for the lower extremity 

 appears in the second year, and that for the head in the fifth year. The 



rZS> - - Appears in the 5th Year, 

 I 7 and joins about i3 



Appears in the 8th Week 

 (intra-uterine) 



I Appears in the 2nd Year, 



' and joins about 20 



Fig. 110. — Ossification of the Radius. 



upper epiphysis joins the shaft about the eighteenth year, and the lower 

 epiphysis about the twentieth year. Sometimes the rough part of the bicipital 

 tuberosity forms an epiphysis, in which cases there is a special secondary centre 

 for it, appearing about the fourteenth year, and joining the rest of the shaft 

 very soon thereafter. 



