MUSCLES AND FASCIA OF UPPER EXTREMITY 151 



The aponeurosis of the forearm (deep fascia) is 

 composed largely of transverse fibers, strengthened 

 by expansions from the condyles of the humerus, 

 olecranon, and fascia over the biceps and triceps. It 

 sends in a thin layer between the superficial and deep 

 muscles; this anterior portion of the fascia forms at 

 the wrist the anterior annular ligament, which binds 

 down the tendons of the flexor muscles. The posterior 

 portion sends off septa between the muscles and forms 

 the posterior annular ligament, which firmly holds in 

 position the tendons of the extensor muscles. The 

 tendon of the palmaris longus muscle is the only one 

 passing in front of the anterior annular ligament. 



The Anterior Radioulnar Region. These muscles are 

 described as a superficial set, consisting of five; and a 

 deep group, of three. 



SUPERFICIAL LAYER. All from a common tendon 

 in the following order from without in: 



Pronator teres arises by two heads, the larger from 

 the upper part of the inner condyle above the common 

 tendon and from the common tendon, fascia, and inter- 

 muscular septum; second head, thin and deep, from 

 the inner margin of the coronoid process; insertion, 

 by a flat tendon on the middle of the outer surface of 

 the radius. The ulnar artery is beneath this muscle, 

 and the median nerve between its heads. 



Flexor carpi radialis arises from the common tendon, 

 fascia of the forearm, and septa between it and the 

 pronator teres, palmaris longus, and flexor sublimis; 

 tendon begins below the middle of the forearm, passes 

 through a special compartment of the anterior annular 

 ligament through a groove in the trapezium; inserted 

 into the base of the second metacarpal bone, anterior 

 surface, and usually by a small slip to the base of 

 the third. 



Palmaris longus is placed between the ulnar and radial 

 flexors of the carpus, resting upon the flexor sublimis; 

 arises from the common tendon, fascia, and septa, 



