The brachial artery enters the forearm from the arm by passing through the cubital fossa. At the apex of the cubital fossa, it divides into its two major branches, the radial and ulnar arteries.
The radial artery originates from the brachial artery at approximately the neck of the radius and passes along the lateral aspect of the forearm (Fig. 7.88). It is: just deep to the brachioradialis muscle in the proximal half of the forearm, related on its lateral side to the superficial branch of the radial nerve in the middle third of the forearm, and medial to the tendon of the brachioradialis muscle and covered only by deep fascia, superficial fascia, and skin in the distal forearm.
In the distal forearm, the radial artery lies immediately lateral to the large tendon of the flexor carpi radialis muscle and directly anterior to the pronator quadratus muscle and the distal end of the radius (Fig. 7.88). In the distal forearm, the radial artery can be located using the flexor carpi radialis muscle as a landmark. The radial pulse can be felt by gently palpating the radial artery against the underlying muscle and bone.
The radial artery leaves the forearm, passes around the lateral side of the wrist, and penetrates the posterolateral aspect of the hand between the bases of metacarpals I and II (Fig. 7.88). Branches of the radial artery in the hand often provide the major blood supply to the thumb and lateral side of the index finger.
Branches of the radial artery originating in the forearm include: a radial recurrent artery, which contributes to an anastomotic network around the elbow joint and to numerous vessels that supply muscles on the lateral side of the forearm (see Fig. 7.66B); a small palmar carpal branch, which contributes to an anastomotic network of vessels that supply the carpal bones and joints; a somewhat larger branch, the superficial palmar branch, which enters the hand by passing through, or superficial to, the thenar muscles at the base of the thumb (Fig. 7.88) and anastomoses with the superficial palmar arch formed by the ulnar artery.
The ulnar artery is larger than the radial artery and passes down the medial side of the forearm (Fig. 7.88). It leaves the cubital fossa by passing deep to the pronator teres muscle, and then passes through the forearm in the fascial plane between the flexor carpi ulnaris and flexor digitorum profundus muscles.
In the distal forearm, the ulnar artery often remains tucked under the anterolateral lip of the flexor carpi ulnaris tendon, and is therefore not easily palpable.
In distal regions of the forearm, the ulnar nerve is immediately medial to the ulnar artery.
The ulnar artery leaves the forearm, enters the hand by passing lateral to the pisiform bone and superficial to the flexor retinaculum of the wrist, and arches over the palm (Fig. 7.88). It is often the major blood supply to the medial three and one-half digits.
Branches of the ulnar artery that arise in the forearm include: the ulnar recurrent artery with anterior and posterior branches, which contribute to an anastomotic network of vessels around the elbow joint (see Fig. 7.66B); numerous muscular arteries, which supply surrounding muscles; the common interosseous artery, which divides into anterior and posterior interosseous arteries (Fig. 7.88); and two small carpal arteries (dorsal carpal branch and palmar carpal branch), which supply the wrist.
The posterior interosseous artery passes dorsally over the proximal margin of the interosseous membrane into the posterior compartment of the forearm.