38 THE POCKET ANATOMY 



Extensor carpi ulnaris: common extensor tendon from 

 external condyle of humerus(T), intermuscular septum (F) by 

 aponeurosis from upper of posterior border of ulna(A) 

 prominence on ulnar side of base of 5th metacarpal bone 

 (T) (Posterior interosseous). [Extends wrist, carpal joints 

 and 5th metacarpo-phalangeal joint, adducts hand.] Has 

 separate sheath in posterior annular ligament. 



Anconeus : posterior surface of external condyle of humerus 

 (T) and deep fascia(F) outer side of olecranon, impression on 

 upper J of posterior surface of ulna limited by oblique line(p) 

 (Musculo-spiral). [Extends elbow.] The recurrent interosseous 

 vessels lie beneath this muscle. 



(b) Deep Layer. 



Supinator brevis : external condyle, external lateraf liga- 

 ment of elbow-joint, orbicular ligament of radius, depression 

 below lesser sigmoid cavity, external edge of ulna for 2 inches 

 (F) surrounds upper of radius, is attached to all the neck, 

 except at inner side, to the upper of posterior, and upper 

 of external surfaces(F) (Posterior interosseous). [Extends 

 elbow, supinates radius.] 



Extensor ossis metacarpi ppllicis : middle of posterior 

 surface of shaft of radius, special impression on superior and 

 external part of posterior surface of ulna for same length, 

 intervening interosseous membrane(F) dorsal aspect of base 

 of ist metacarpal (Posterior interosseous). [Extends ist 

 carpo-metacarpal joint abducts hand.] The radial artery 

 winds backwards beneath tendon near carpus. 



Extensor brevis pollicis : posterior surface of radius and 

 interosseous membrane below preceding muscle for about 

 i inches(F) dorsal aspect of base of ist phalanx of thumb 

 (T) (Posterior interosseous). [As preceding ; also extends 

 ist metacarpo-phalangeal joint ] Goes through groove under 

 posterior annular ligament with extensor ossis metacarpi 

 pollicis. 



Extensor longus pollicis : posterior surface of ulna, on 

 inner side and below extensor ossis metacarpi pollicis for 

 4 inches, interosseous membrane(F) dorsal aspect of base 

 of last phalanx of thumb(x) (Posterior interosseous). [Ex- 

 tends wrist and all joints of thumb.] Tendon goes through 

 separate sheath of posterior annular ligament, and below is separated 

 from other extensors of thumb by a triangular interval, which con- 

 tains the radial artery. 



Extensor indicis : internal part of posterior surface of shaft 

 of ulna for about 3 inches just below middle, and interosseous 



