JOIN rs 



the outer Mile. The upper end of the ulna forms the bony 

 prominence at the elbow. Just below this, on the front of the 

 ulna, is ,i large, deep, smooth notch. Into this notch the inner 

 half of the rounded lower edge of the humerus tits. The 

 upper end of the radius has a round disc-like head atta lied 

 by a neck to the shaft. The 

 top of the head is smooth and 

 .concave, and into this the outer 

 half of the articular surface of 

 the humerus fits. Movement 

 at the elbow joint consists of 

 flexion and extension only, the 

 ulna and radius both gliding on 

 the rounded lower edge of the 

 humerus. The joint is enclosed 

 by capsular and band-like liga- 

 ments, the strongest of which is 

 in front of the joint, and this 

 prevents the arm being bent 

 backwards at the elbow joint. 

 The forearm cannot be bent 

 quite down on the arm because 

 the fleshy parts of the two 

 come together. 



Pronation and Supina- 

 tion of the Forearm. The 

 ulna is capable of no other FlG - ao - 

 movement than flexion and ex- 

 tension at the elbow joint, but 

 the radius can also turn on the 

 ulna. The edge of the disc-like 

 head of the radius is smooth, 

 and touches a concave smooth 

 surface on the outer side of the 

 ulna, the head being held in place by a ring-like ligament 

 going round it. The lower end of the radius is broad, and it 

 alone articulates with the carpal bones at the wrist, and thereby 

 (anies the hand, the ulna not entering into the wrist joint. On 

 the inner side of the lower end of the radius there is a shallow 

 depression into which fits the small rounded lower end of the 



The elbow joint - longitudinal 



section. 



humerus ; Ul, ulna ; Tr, the triceps 

 muscle behind straightens the arm ; 

 Hi, the biceps muscle in front bends 

 the arm. The white line round the 

 joint, in this position thrown into a 

 fold behind the joint, represents the 

 capsular ligament. 



