THE DORSAL ANTIBRACHIAL MUSCLES 



451 



Flexor pollicis longus is a flexor of the phalanges of the thumb; when the thumb is fixed, it assists 

 in flexing the wrist. The Pronator quadratus rotates the radius upon the ulna, rendering the 

 hand prone. 



Flexor carpi radialis M. 



Antibrachial inter os- 

 seous membrane 



Lateral antibrachial \ 

 cutaneous neroe\ \ 



Radial artery 

 and nerve\ 



Median nerve 



Palmaris longus M. 



Medial antibrachial 

 / cutaneous nerve 



^volar branch] 



Flexor digitorum 

 sublimis M. 



Cephalic vein-. 

 Brachioradialis - 



Flexor pollicis 

 longus M.' 



Radius - 



Tendo m. pronatoris, 

 teretis 



Vxtensores carpi radiales/ 

 longus and brevis Mm. 



Extensor digitorum.- 

 communis M. 



_. Ulnar artery and nerve 



Flexor digitorum 

 profundus M. 



tf\.-Flexor carpi ulnaris 



Basilic vein 



'*' Ulna 



Abductor pollicis 



longus M. : 



Volar interosseous artery 

 and volar antibrachial 

 interosseous nerve 



Extensor carpi 

 \ ulnaris M. 



\ 



Extensor pollicis 

 longus M. 



Extensor digiti quinti 

 proprius M. and dor- 

 sal interosseous artery 



FIG. 417. Cross-section through the middle of the forearm. (Eycleshymer and Schoemaker.) 



2. The Dorsal Antibrachial Muscles. 



These muscles are divided for convenience of description into two groups, 

 superficial and deep. 



The Superficial Group (Fig. 418). 



Brachioradialis. Extensor digitorum communis. 



Extensor carpi radialis longus. Extensor digiti quinti proprius. 



Extensor carpi radialis brevis. Extensor carpi ulnaris. 



Anconseus. 



The Brachioradialis (Supinator longus) is the most superficial muscle on the 

 radial side of the forearm. It arises from the upper two-thirds of the lateral 

 supracondylar ridge of the humerus, and from the lateral intermuscular septum, 

 being limited above by the groove for the radial nerve. Interposed between it 

 and the Brachialis are the radial nerve and the anastomosis between the anterior 

 branch of the profunda artery and the radial recurrent. The fibers end above 

 the middle of the forearm in a flat tendon, which is inserted into the lateral side 

 of the base of the styloid process of the radius. The tendon is crossed near its 

 insertion by the tendons of the Abductor pollicis longus and Extensor pollicis 

 brevis; on its ulnar side is the radial artery. 



Variations. Fusion with the Brachialis; tendon of insertion may be divided into two or three 

 slips; insertion partial or complete into the middle of the radius, fasciculi to the tendon of the 

 Biceps, the tuberosity or oblique line of the radius; slips to the Extensor carpi radialis longus or 

 Abductor pollicis longus; absence; rarely doubled. 



