604 THE ARTERIES. 



The posterior carpal arises immediately above the pisiform bone, and winds 

 backward beneath the tendon of the Flexor carpi ulnaris : it passes across the 

 dorsal surface of the carpus beneath the extensor tendons, anastomosing with a 

 corresponding branch of the radial artery, and forming the posterior carpal arch. 

 Immediately after its origin it gives off a small branch which runs along the 

 ulnar side of the metacarpal bone of the little finger, forming one of the meta- 

 carpal arteries, and supplies the ulnar side of the dorsal surface of the little 

 finger. (See also page 600.) 



The deep palmar or communicating branch (Fig. 365) passes deeply inward 

 between the Abductor minimi digiti and Flexor brevis minimi digiti near their 

 origins ; it anastomoses with the termination of the radial artery, completing the 

 deep palmar arch. 



The Superficial Palmar Arch. The superficial palmar arch passes outward 

 across the palm of the hand, describing a curve, with its convexity forward to the 

 space between the ball of the thumb and the index finger, where the arch is com- 

 pleted by its anastomosing with a branch from the radialis indicis, though some- 

 times the arch is completed by its anastomosing with the superficialis volge 

 branch of the radial artery. 



Relations. The superficial palmar arch is covered by the skin, the Palmaris 

 brevis, and the palmar fascia. It lies upon the annular ligament, origin of the 

 muscles of the little finger, the tendons of the superficial flexor of the fingers, 

 and, the divisions of the median and ulnar nerves. 



RELATIONS OF THE SUPERFICIAL PALMAR ARCH. 



In front. 

 Skin. 



Palmaris brevis. 

 Palmar fascia. 



Behind. 



Annular ligament. 

 Origin of muscles of little finger. 

 Superficial flexor tendons. 

 Divisions of median and ulnar nerves. 



BRANCHES OF THE SUPERFICIAL PALMAR ARCH. 

 Digital. 



The digital branches (Fig. 364), four in number, are given off from the con- 

 vexity of the superficial palmar arch. They supply the ulnar side of the little 

 finger and the adjoining sides of the little, ring, middle, and index fingers, the 

 radial side of the index finger and thumb being supplied from the radial artery. 

 The digital arteries at first lie superficial to the flexor tendons, but as they pass 

 forward with the digital nerves to the clefts between the fingers they lie between 

 them, and are there joined by the interosseous branches from the deep palmar 

 arch. The digital arteries on the sides of the fingers lie behind the digital 

 nerves ; and about the middle of the last phalanx the two branches for each 

 finger form an arch, from the convexity of which branches pass to supply the 

 pulp of the finger. 



Surface Marking. The superficial palmar arch is represented by a curved line, starting 

 from the outer side of the pisiform bone and carried downward as far as the middle third of 

 the palm, and then curved outward on a level with the upper end of the cleft between the 

 thumb and index finger. 



The deep palmar arch is situated about half an inch nearer to the carpus. 



