APPLIED ANATOMY. 



The radius is small above and gradually increases in size until its lower extremity 

 is reached, where it is largest. Its upper portion is composed mainly of compact 

 bone with a medullary cavity; lower down as the bone becomes larger it becomes 

 more cancellous. Hence it does not follow that it is strongest where it is largest; on 

 the contrary it is most often fractured at its lower extremity. About two centimetres 

 below the head of the radius is a tubercle. The biceps tendon is inserted into its 

 posterior portion and a bursa covers its anterior part, over which the tendon of the 

 biceps plays. The radius is the movable bone and to jt is attached the hand. 



Stretched across from one bone to the other is the interosseous membrane. Most 

 of its fibres run from the ulna upward and outward, so that the shocks received on the 



Flexor carpi ulnaris 



Flexor sublimis digitorum 

 Pronator radii teres 



Brachialis anticus 

 Supinator (brevis) 



Flexor sublimis digitorum 



Flexor profundus digitorum 



Pronator quadratus 



Biceps 

 Supinator (brevis) 



Pronator radii teres 

 Flexor sublimis digitorum 



Flexor longus pollicis 



Pronator quadratus 

 Brachioradialis 



FIG. 318. Anterior view of radius and ulna with areas of muscular attachments. 



hand are transmitted somewhat to the ulna. On its anterior surface run the anterior 

 interosseous artery and nerve. About 2.5 cm. (i in.) above its lower end the artery 

 pierces the membrane to go to the back of the wrist. 



MOVEMENTS OF PRONATION AND SUPINATION. 



The radius revolves on the ulna about an axis which passes through the centre 

 of the head of the radius above and the styloid process of the ulna below, which line 

 if prolonged would pass through the ring finger (Fig. 319). In pronation, the hand 

 lies with the palm down and the radius is crossed diagonally over the ulna; the bones 

 are close together (Fig. 320). In supination the hand lies with the pa!m up, the 



