In the fore-arm and on the wrist, the ulnar artery gives off several branches, which have received particular names. The branches in the fore-arm are the anterior and posterior recurrent, the interosseous, and several muscular branches. Those given at the wrist are named carpal branches (anterior and posterior).

Recurrent branches

The anterior ulnar recurrent artery, [a. recurrens ulnaris ant.], arches inwards from the upper part of the ulnar artery, running on the brachialis anticus muscle, and covered by the pronator teres, both which muscles it partly supplies.

On reaching the front of the inner condyle, it anastomoses with the inferior profunda and anastomotic arteries, derived from the brachial.

The posterior ulnar recurrent [a. recurrens ulnaris post.] is larger than the preceding, and comes off lower down; though not unfrequently the two arise by a short common trunk. The posterior recurrent runs inwards and backwards beneath the flexor sublimis, and then ascends behind the inner condyle. In the interval between that process and the olecranon it lies beneath the flexor carpi ulnaris, and passing between the heads of that muscle along the ulnar nerve, supplies branches to the muscles, to the elbow-joint, and to the nerve itself. This branch communicates with the inferior profunda, the anastomotic, and over the olecranon, with the interosseous recurrent likewise. 

Interosseous artery

The interosseous artery, [a. interossea antibrachii communis,] the next and largest branch of the ulnar, is of considerable size, and is sometimes called the common interosseous artery, from the circumstance of its forming a common trunk to two vessels named the anterior and posterior interosseous. It is a short trunk, about an inch in length, which arises below the bicipital tuberosity of the radius, beneath the flexor sublimis, and passes backwards to reach the upper border of the interosseous ligament, where its division takes place.

The anterior interosseous [a. interossea ant. s. int.] descends upon the anterior surface of the interosseous ligament, held down to it by a layer of fibro-cellular tissue, accompanied by the interosseous branch of the median nerve, and overlapped by the contiguous borders of the flexor profundus digitorum and flexor longus pollicis. Thus placed, it gives off some muscular branches, and also the nutrient arteries of the radius and ulna, which incline to either side and enter the oblique foramina in those bones to be distributed to the medullary membrane in their interior. The artery continues its course directly downwards until it reaches the upper border of the pronator quadratus muscle, where it gives off some small branches to supply that muscle, one of which descends to join upon the front of the carpus with the branches of the anterior carpal arteries. The larger branch of the artery, however, passes from before backwards, through an opening in the interosseous ligament; and, on reaching the dorsal surface of this structure, descends behind it to the carpus, where it maintains communications with the posterior carpal branches of the radial and ulnar arteries. The anterior interosseous artery gives off a long slender branch, which accompanies the median nerve and sends offsets into its substance. This artery of the median nerve, or median artery, is sometimes much enlarged, and in this case it presents several peculiarities to be hereafter noticed.

The posterior interosseous artery [a. interossea post. s. ext.] passes backward*, through the interval left between the oblique ligament and the upper border of the interosseous ligament. Continuing its course downwards, along the arm, covered by the superficial layer of extensor muscles, it gives several branches to them and the deep-seated muscles, and reaches the carpus considerably diminished in size, where its terminal branches anastomose with the posterior or terminal branch of the anterior interosseous artery, and with the carpal branches of the radial and ulnar arteries.

In addition to numerous muscular branches, which require no special notice, this artery gives off close to its origin, or as soon as it passes behind the ligament, a recurrent branch, the posterior interosseous recurrent [a. interossea recurrens] , which is nearly as large as the continuation of the vessel. This branch passes directly upwards, covered by the supinator brevis and anconeus, to reach the interval between the olecranon and external condyle, where it divides into several offsets which anastomose with the superior profunda and the posterior ulnar recurrent,

Several muscular branches of the ulnar artery are distributed to the muscles in its course along the fore-arm : some of these perforate the interosseous ligament to reach the extensor muscles.

Carpal branches

The posterior or dorsal carpal [ramus dorsalis] , a branch of variable size, inclines

backwards from the ulnar artery a little above the pisiform bone. It winds back under the tendon of the flexor carpi ulnaris, and reaches the dorsal surface of the carpus beneath the extensor tendons, where it gives a branch, which anastomoses with the posterior carpal artery derived from the radial, so as to form the posterior air [Mil arch; after which it runs along the metacarpal bone of the little finger, and forms its dorsal branch. Sometimes this metacarpal branch arises as a separate vessel, the posterior carpal being then very small. From the posterior carpal arch of anastomosis just referred to, the second and third dorsal interosseous branches are derived.

The anterior or palmar carpal branch is a very small artery, which runs on the anterior surface of the carpus, beneath the flexor profundus, anastomoses with a similar offset from the radial artery, and supplies the carpal bones and articulations.

Peculiarities in the branches of the ulnar artery

The transverse communications which sometimes exist between the ulnar and radial arteries have been already referred to.

Of the branches of the ulnar in the fore-arm, the anterior and. posterior ulnar recurrents frequently arise by a common trunk. When the ulnar artery has a high place of origin, its recurrent branches are derived from the common interosseous; one or both have been seen, but more rarely, to arise from the brachial.

The anterior and posterior interosseous arteries are occasionally given singly from the ulnar. But the common interosseous trunk is liable to much greater deviations from its ordinary course. Thus, when the ulnar arises high up, the interosseous is associated with the radial artery, and separates from that vessel at the bend of the elbow ; the trunk common to the two vessels represents the brachial in these cases. Again, the interosseous itself has been found to arise above its ordinary situation, taking origin from the brachial, and even (but more rarely) from the axillary. The anterior interosseous presents some striking varieties of excess in its branches, usually connected with a deficiency in the radial or ulnar arteries. These cases are referred to in noticing the arteries which are thus reinforced.

Median artery

The branch accompanying the median nerve is sometimes much enlarged, and in such case may be regarded as a reinforcing vessel. It is generally a branch of the anterior interosseous, but sometimes of the ulnar ; and more rarely a median branch has been met with descending from the brachial artery. Accompanying the median nerve beneath the annular ligament into the palm of the hand, the median artery ends most frequently by joining the superficial palmar arch, sometimes by forming digital branches, or by joining digital branches given from other sources.

Superficial palmar arch

The superficial palmar arch or artery (arcus superficialis volae, — Haller), is the continuation of the ulnar artery to the hand. Changing its course near the lower border of the annular ligament, this artery turns obliquely outwards across the palm of the hand towards the middle of the muscles of the thumb, where it terminates by inosculating with a branch of the radial artery. The branch of the radial artery which joins with the ulnar, and, as it may be said, completes the arch, varies in different cases ; most commonly it is a small one emerging from among the muscles of the thumb or the superficial volar. In its course across the hand, the artery describes a curve, having its convexity directed towards the fingers, and reaching downwards somewhat lower than a line on a level with the flexure of the first joint of the thumb.

The superficial palmar artery, at its commencement, rests on the annular ligament of the wrist, and slightly on the short muscles of the little finger ; then on the tendons of the superficial flexor of the fingers, and the divisions of the median and ulnar nerves, the latter of which accompanies the vessel for a time. It is covered towards the ulnar border of the hand by the palmaris brevis, and afterwards by the palmar fascia and the integument.

The branches given off by the superficial palmar arch, which are generally numerous, are as follows :

The deep or communicating branch (cubitalis mantis profunda, — Haller) arises from the ulnar artery at the commencement of the palmar arch ; a little beyond the pisiform bone, sinks deeply between the flexor brevis and the abductor of the little finger, and then inosculates with the palmar termination of the radial artery, thereby completing the deep palmar arch.

Small branches, some following a retrograde course to the annular ligament, are given off to the parts in the palm of the hand from the upper or concave side of the palmar arch.

The digital branches [digitales communes], usually four in number, proceed downwards from the convexity of the palmar arch to supply both sides of the three inner fingers, and the ulnar side of the fore-finger. The first digital branch inclines inwards to the ulnar border of the hand, and after giving minute offsets to the small muscles of the little finger, runs along the inner margin of its phalanges. The second runs along the fourth metacarpal space, and at the root of the fingers divides into two branches, which proceed along the contiguous borders of the ring-finger and little finger. The third is similarly disposed of to the ring-finger and middle finger, and the fourth to the latter and the index-finger. The radial side of the index-finger and the thumb are supplied from the radial artery.

The digital arteries, placed at first superficial to the tendons, then lie between them, accompanied by the digital nerves as far as the clefts of the fingers, where they are joined by the anterior interosseous arteries, branches of the deep arch. On the sides of the fingers, each artery lies beneath the corresponding nerve, and gives branches which supply the sheaths of the tendons, and the joints, some of them anastomosing across the front of the bone with similar branches from the opposite side. At about the middle of the last phalanx, the two branches for each finger converge and form an arch, from which proceed numerous small offsets to supply the matrix of the nail and all the structures at the tip of the finger.

The peculiarities observed in the branches of the superficial palmar arch, will be noticed after the description of the deep arteries of the hand.

From Quain's Anatomy.