ANATOMY IX A NUTSHELL. '.'1 



Origin. — Posterior surface of shaft of radius, below Extensor ossis meta- 

 carpi pollicis and from the int< -- - membrane. (Plate XXH . 



Insertion. — Base of first phalanx of thumb. (Plate XW 1. 



Ai tion. — Extends the proximal phalanx of thumb. 



Xerye Supply. — Seventh cervical through the posterior inter ss 



Blood Supply. — Posterior interosseous artery. 



Extensor longus pollicis. — Description. — (Plate XXXIII.) — The Ex- 

 tensor longus pollicis (Extensor secundi internodii pollicis) is much larger 

 than the preceding muscle, the origin of which it parti}' covers in. It termi- 

 nates in a tendon which passes through a separate compartment in the annu- 

 lar ligament, lying in a narrow, oblique groove at the back part of the lower end 

 of the radius. It then crosses obliquely the tendons of the Extensor carpi 

 radialis longior and brevior. being separated from the other extensor tendons of 

 the thumb by a triangular interval in which the radial artery is found. 



Origin. — Outer part of posterior surface of shaft of ulna distally from 

 origin of Extensor ossi< metacarpi pollicis and from interosseous membrane. 

 (Plate XXIV.) 



Insertion. — Base of last phalanx of thumb. (Plate XX\ I. 



Action. — Extends thumb. 



Nerve Supply. — Seventh cervical through posterior interosseous. 



Blood Supply. — Posterior interosseous artery. 



Extensor indicis. — Description. — Plate XXXIII.) — This is a narrow, 

 elongated muscle placed on the inner side of. and parallel with the preceding. 

 Its tendon passes with the Exten.-or communis digitorum through the same 

 canal in the posterior annular ligament and subsequently joins the tendon 

 the Extensor communis digitorum which belongs to the index finger, opposite 

 the lower end of the corresponding metacarpal bone, lying to the ulnar side of 

 the tendon from the common extensor. 



Origin. — Shaft of ulna posteriorly, and distally from Extensor longus 

 pollicis and from interosseous membrane. (Plate XXIV. 



Insertion. — Second and third phalanges of index finger with tendon 

 common extensor. (Plate XXVI.) 



A' tion. — Extends index ring 



Nerve Supply. — Seventh cervical through posterior inter ss 



Blood Supply. — Posterior inter — 3 artery. 



LESSON XXII. 



Radial artery. — The radial artery extends from the bifurcation of thebrach- 

 ial and ends in the deep palmar arch. It- course i- shown by a line from a 

 point about half an inch below the middle of the bend of the elbow to the inner 

 side of the base of the styloid process of the radius. Tin- artery is more a con- 

 tinuation of the brachial than the ulnar, which is more of a branch. It is ac- 

 companied by venae comites. It- branches in the forearm an- radial recurrent, 

 muscular, superficialis volae, and anterior carpal. 



