784 



HUMAN ANATOMY, 



9. The Digital Arteries. — The digital branches (aa. digitales volares com- 

 munes) arise from the portion of the ulnar artery which passes transversely across 

 the palm of the hand and is termed the superficial palmar arch (arcus volaris 

 superficialis). They are four in number; the first of the four, starting from the 

 ulnar border of the hand, passes obliquely downward and inward across the hypoth- 

 enar muscles and continues distally along the ulnar border of the little finger. The 



Radial artery 

 Superficial volar artery 



Abductor pollicis 

 Opponens pollicis 



Flexor brevis pollicis 



Flexor longus 



pollicis tendon 



Princeps pollicis 



Radialis indicis 



Ulnar nerve 



Ulnar artery 

 Pisiform bone 



Anterior annular ligament 

 Deep branch of ulnar artery 

 Dij,'ital branches of median nerve 



Abductor minimi digitj 

 Flexor brevis minimi Sigiti 



Digital arteries 



Superficial palmar arch and its branches. 



remaining three pass downward in the second, third, and fourth intermetacarpal 

 spaces resting upon the lumbrical muscles, and, *just before reaching the clefts of the 

 fingers, each receives the corresponding palmar interosseous artery and then divides 

 into two branches, the collateral digital branches (aa. digitales volares propriae), 

 which extend distally upon the adjacent sides of the neighboring digits. These col- 

 lateral branches make numerous transverse anastomoses with one another, especially 

 in the neighborhood of the interphalangeal joints, and terminate in fine branches 

 which supply the bulb of the finger and the bed of the nail. 



Variations. — The variations of the digital arteries depend principally (i) upon their pro- 

 portional development with reg:ard to the palmar interosseous vessels from the deep palmar 

 arch, and (2) upon variations in the mode of formation of the superficial palmar arch. 



The palmar interosseous branches of the radial anastomose with the digitals just before 

 the division of the latter into their collateral branches, and if the interosseae are strongly devel- 

 oped, the digitals are apt to be of small calibre, and may be so much reduced in size that the 

 collaterals of one or more of them may be regarded as continuations of the corresponding 

 palmar interosseae Conversely, although normally the supply for the radial side of the index- 

 finrer and the thumb is from the deep palmar arch, yet occasionally it is derived from the 

 superficial arch, the princeps pollicis and the radialis indicis, the branches from the deep 

 palmar arch, being much reduced in size. 



