582 THE BLOOD-VASCULAR SYSTEM 



The Ulnar Artery in the Palm (Superficial Volar Arch) 



The ulnar arterj^, on entering the palm, divides into two branches, the super- 

 ficial and deep. 



The superficial branch (fig. 472), the direct continuation of the vessel, anasto- 

 moses with the superficial volar, a branch of the radial, forming what is then 

 known as the superficial volar arch. After descending a short distance toward the 

 cleft between the fourth and fifth fingers, it turns toward the thumb, forming a 

 curve with its convexity toward the fingers and its concavity toward the muscles 

 of the thumb, and anastomoses opposite the cleft between the index and middle 

 fingers, at the junction of the upper with the middle third of the palm, with the 

 superficial volar branch of the radial artery to complete the arch. A line drawn 

 transversely across the palm on a level with the metacarpo-phalangeal joint of the 

 thumb will roughly indicate the situation of the arch. 



Relations.— In front: in addition to the skin and superficial fascia, the vessel is crossed 

 successively, by the palmaris bevis, the palmar branch of the ulnar nerve, the palmar aponeuro- 

 sis and the palmar branch of the median nerve. 



Behind, it rests successively upon the short muscles of the little finger, the digital branches 

 of the ulnar nerve, the flexor tendons, and the digital branches of the median nerve. 



The branches of the superficial volar arch. In addition to small muscular 

 and cutaneous branches the superficial volar supplies: — 



The common digital arteries [aa. digitales volares communes]. These, usually four in 

 number, arise from the convexity of the superficial arch and, running downward through the 

 palm, give off the digital arteries proper to both sides of the httle, ring, and middle fingers, 

 and the ulnar side of the index finger. The radial side of the index finger and the thumb are 

 supplied by the first volar metacarpal branch of the radial artery. 



The most ulnar of the common digital arteries passes distally over the muscles in the ulnar 

 border of the palm, and thence along the ulnar border of the little finger. The remaining 

 arteries pass distally in the three ulnar intermetacarpal spaces to within about 6 mm. (j in.) of 

 the clefts between the fingers, where they divide into branches, the digital arteries proper 

 [aa. digitales volares proprise], which supply the sides of contiguous fingers. 



As the common digital arteries pass through the palm, they lie between the flexor tendons, 

 on the digital nerves and lumbrical muscles, and beneath the palmar aponeurosis. Just before 

 bifurcating they pass under the transverse fasciculi, and are joined by the volar metacarpal 

 branches from the deep volar arch (fig. 472). At this spot they also receive the volar perforating 

 branches from the dorsal metacarpal vessels. On the sides of the fingers the proper digital 

 arteries lie between the palmar and dorsal digital nerves. They anastomose by small branches, 

 forming an arch across the front of the bones on the proximal side of each interphalangeal joint. 

 They supply the flexor tendons and the integuments, and terminate in a plexiform manner 

 Vjeneath the pulp of the finger and around the matrix of the nail. A dorsal digital branch is 

 given off to the back of the fingers about the level of the middle of the first phalanx, and a 

 second but smaller dorsal digital branch about the level of the middle of the second phalanx. 



The deep branch of the ulnar artery, also called the communicating artery, 

 sinks deeply into the palm between the abductor and flexor quinti digiti brevis, 

 and joins the radial to form the deep volar arch. (See The Radial Artery.) 



THE RADIAL ARTERY 



The radial artery — the smaller of the two arteries into which the brachial 

 divides at the bend of the elbow — appears as the direct continuation of the 

 brachial. It runs, at first curving laterally, along th(^ radial side of the forearm 

 as far as the styloid process, then, coiling over the radial collateral ligament and 

 the lateral and l^ick part of the wrist, enters the palm of the hand from behind be- 

 tween the first and second metacarpal bones, and ends by anastomosing with the 

 deep branch of the ulnar to form the deep volar arch. Hence the artery is divisible 

 into three parts: that in the forearm, that at the wrist, and that in the palm of the 

 hand. The course of the artery is indicated by a line drawn from a point 2.5 

 cm. (1 in.) below the centre of the; elbow to a point situated just medial to the 

 .styloid process of the radius. 



I. The Radial Artery in the Forearm 



In its course through the forearm (fig. 470) the radial artery is found in the 

 most lateral of the intermuscular spaces, and it is only necessary to divide the 



