Reference > Anatomy of the Human Body > Page 595
  The first dorsal metacarpal arises just before the radial artery passes between the two heads of the first Interosseous dorsalis and divides almost immediately into two branches which supply the adjacent sides of the thumb and index finger; the radial side of the thumb receives a branch directly from the radial artery.
  The arteria princeps pollicis arises from the radial just as it turns medialward to the deep part of the hand; it descends between the first Interosseous dorsalis and Adductor pollicis obliquus, along the ulnar side of the metacarpal bone of the thumb to the base of the first phalanx, where it lies beneath the tendon of the Flexor pollicis longus and divides into two branches. These make their appearance between the medial and lateral insertions of the Adductor pollicis obliquus, and run along the sides of the thumb, forming on the volar surface of the last phalanx an arch, from which branches are distributed to the integument and subcutaneous tissue of the thumb.
  The arteria volaris indicis radialis (radialis indicis artery) arises close to the preceding, descends between the first Interosseus dorsalis and Adductor pollicis transversus, and runs along the radial side of the index finger to its extremity, where it anastomoses with the proper digital artery, supplying the ulnar side of the finger. At the lower border of the Adductor pollicis transversus this vessel anastomoses with the princeps pollicis, and gives a communicating branch to the superficial volar arch. The a. princeps pollicis and a. volaris indicis radialis may spring from a common trunk termed the first volar metacarpal artery.
  The deep volar arch (arcus volaris profundus; deep palmar arch) (Fig. 528) is formed by the anastomosis of the terminal part of the radial artery with the deep volar branch of the ulnar. It lies upon the carpal extremities of the metacarpal bones and on the Interossei, being covered by the Adductor pollicis obliquus, the Flexor tendons of the fingers, and the Lumbricales. Alongside of it, but running in the opposite direction—that is to say, toward the radial side of the hand—is the deep branch of the ulnar nerve.
  The volar metacarpal arteries (aa. metacarpeæ volares; palmar interosseous arteries), three or four in number, arise from the convexity of the deep volar arch; they run distally upon the Interossei, and anastomose at the clefts of the fingers with the common digital branches of the superficial volar arch.
  The perforating branches (rami perforantes), three in number, pass backward from the deep volar arch, through the second, third, and fourth interosseous spaces and between the heads of the corresponding Interossei dorsalis, to anastomose with the dorsal metacarpal arteries.
  The recurrent branches arise from the concavity of the deep volar arch. They ascend in front of the wrist, supply the intercarpal articulations, and end in the volar carpal network.
4b. 4. The Ulnar Artery
(A. Ulnaris)

The ulnar artery (Fig. 528), the larger of the two terminal branches of the brachial, begins a little below the bend of the elbow, and, passing obliquely downward, reaches the ulnar side of the forearm at a point about midway between the elbow and the wrist. It then runs along the ulnar border to the wrist, crosses the transverse carpal ligament on the radial side of the pisiform bone, and immediately beyond this bone divides into two branches, which enter into the formation of the superficial and deep volar arches.

Relations.—(a) In the forearm.—In its upper half, it is deeply seated, being covered by the Pronator teres, Flexor carpi radialis, Palmaris longus, and Flexor digitorum sublimis; it lies upon the Brachialis and Flexor digitorum profundus. The median nerve is in relation with the medial side of the artery for about 2.5 cm. and then crosses the vessel, being separated from it by the ulnar head of the Pronator teres. In the lower half of the forearm it lies upon the Flexor digitorum profundus, being covered by the integument and the superficial and deep fasciæ,


