286 



APPLIED ANATOMY. 



The extensor carpi radialis longior arises from the lateral condyle and lower third 

 of the supracondyloid ridge and inserts into the base of the second metacarpal bone. 



The brachioradialis or supinator longus arises from the upper two-thirds of the 

 lateral (external) supracondyloid ridge above the preceding muscle and as high as the 

 insertion of the deltoid. It inserts into the base of the styloid process of the radius. 



These two muscles, owing to their high attachment, so much above the axis of 

 motion of the joint, both act as flexors. The brachioradialis also supinates the hand. 



The Posterior or Extensor Muscles. These comprise the triceps and 

 anconeiis muscles (Fig. 298). 



The triceps arises by its long head from the lower part of the rim of the glenoid 

 cavity and adjoining border of the scapula; by its external or lateral head from the 



Triceps 



Olecranon process 



Brachioradialis 



Extensor carpi radialis longior 



External condyle 



Fascial continuation of the triceps 

 inserting into the shaft of the ulna 



Anconeus muscle under the fascia 



FIG. 298. Extensor muscles of the back of the elbow. 



upper outer portion of the humerus from the greater tuberosity above to the radial 

 (musculospiral) groove below; by its internal or medial head from the posterior 

 surface of the humerus below the radial groove. It inserts into the posterior part of 

 the upper surface of the olecranon. Just above its insertion it is separated from the 

 bone by a bursa. It is continuous from the outer edge of the olecranon as a firm fascia 

 which passes down over the anconeus to be attached to the upper fourth of the ulna 

 and the deep fascia. This is an important structure in fractures of the olecranon. 



The anconeus passes downward and backward from the lateral (external) condyle 

 to insert into the side of the olecranon and upper fourth of the ulna. Its fibres are 

 practically continuous with the lower fibres of the triceps and it may be considered 

 as a fourth head of that muscle. It covers the posterior portion of the head of the 

 radius and overlaps somewhat the supinator (brevis) muscle. 



