The branches of the radial artery may be arranged according as they are given off in the fore-arm, on the wrist, and in the hand. The branches which arise from the radial in the fore-arm, are the radial recurrent, the muscular branches, the anterior carpal, and the superficial volar.
The radial recurrent artery, [a. recurrens radialis,] which varies much in size, arches upwards from the radial soon after its origin, running between the branches of the musculo-spiral nerve. It first lies on the supinator brevis, and then on the brachialis anticus, being covered by the supinator longus. In front of the outer condyle, and in the interval between the last two muscles, it anastomoses with the terminal branches of the superior profunda. From the lower or convex side of this artery are given off several branches; one, of considerable size, to the supinator and extensor muscles, and some beneath the latter to anastomose with the posterior interosseous branches. It also supplies the supinator brevis and brachialis anticus in part.
Several unnamed muscular branches are given to the muscles on the fore part of the arm.
The anterior carpal is a small branch which arises from the radial artery near the lower border of the pronator quadratus, and runs inwards in front of the radius. It is usually called the anterior radial carpal, to distinguish it from a similar branch from the ulnar artery, with which it anastomoses so as to form an arch above and in front of the radio-carpal articulation, from which branches descend to supply the joints of the wrist.
The superficial volar, (ramus superficialis volee) proceeds directly forwards from the radial artery, where it is about to turn backwards, following the direction of that vessel in the fore-arm. In its size this branch is subject to many varieties. Most commonly it is very small, and ends in the muscles of the thumb. When it attains considerable size, this artery runs over the small muscles of the thumb at their origin, lying upon the annular ligament, to which it is bound down by a thin process of fascia, and is usually described as inosculating with the radial ex tremity of the superficial palmar arch, which it thus completes.
The branches which arise from the second or carpal portion of the radial artery are the following: — the posterior carpal, the metacarpal, the dorsal arteries of the thumb, and the dorsal artery of the index-finger.
The posterior carpal (ar. dorsalis carpi radialis) is small but constant. It arises opposite the carpal articulations, beneath the extensor tendons of the thumb, and near the tendons of the radial extensor muscles, beneath which it runs inwards on the back of the carpus. Here it anastomoses with a similar branch from the ulnar artery, and with the terminations of the anterior interosseous artery, which, it will be remembered, perforates the interosseous ligament, and becomes dorsal in the lower part of the fore-arm. Branches descending from the carpal artery to the metacarpal spaces become the dorsal interosseous arteries, for the third and fourth interosseous spaces of the hand, after anastomosing, at the upper end of those spaces, with the posterior perforating branches from the deep palmar arch.
The first dorsal interosseous branch (metacarpal: ramus dorsalis interosseus primus, — Haller,) arises from beneath the extensors of the thumb, frequently with the posterior carpal, and descends obliquely towards the interval between the second and third metacarpal bones ; it there becomes interosseous, and, after communicating with the corresponding perforating branch of the deep palmar arch, descends upon the second dorsal interosseous muscle, as far as the cleft of the index and middle fingers, where it gives off dorsal superficial arteries to those fingers, and ends by communicating with the palmar digital branch at its point of division between the fingers.
The dorsal arteries of the thumb (dorsales pollicis), small, and two in number sometimes arise separately opposite the head of the metacarpal bone, and at others by a common trunk, which divides into two branches. They run upon the dorsal aspect of the bones of the thumb, one at its radial, the other at its ulnar border.
The dorsal artery of the index-finger (dorsalis indicis), a very small branch, arises lower down than the preceding, and after sending branches to the abductor indicis, runs along the radial side of the back of the index-finger.
From Quain's Anatomy.