Radial artery is one of the two arteries of the forearm (the other is ulnar artery). It lies to the lateral side along the radius bone according to which it is named. The radial artery is the smaller of the two terminal braches of the brachial artery.
Origin and termination of Radial artery:
The radial artery originates as the smaller terminal branch of the brachial artery in the elbow region at the level of head of the radius bone. It lies on the lateral side on the forearm and ends by taking part in the deep palmar arch of hand.
Course of Radial artery:
It runs inferolaterally under cover of brachioradialis muscle. Then it lies lateral to flexor carpi radialis tendon in distal forearm and finally it winds around lateral aspect of radius and crosses the floor of anatomical snuff box to pass between the two heads of first dorsal interosseous muscle and take part in forming the deep palmar arch of the hand.
Branches of Radial artery:
Branches of radial artery can be divided into three groups according to the region of upper limb where they arise;
In the forearm:
- Radial recurrent artery: It arises from the lateral side just below the origin of radial artery and passes upward to anastomoses with the radial collateral branch of Profunda brachii artery. It helps in the formation of anastomoses near the elbow joint.
- Palmar carpal branch: It arises near the lower border of pronator quadratus muscle. It runs across the fond of the wrist and ends by anastomosing with palmar carpal branch of ulnar artery.
- Superficial palmar branch: It arises from medial side of radial artery just when it is winding around the lateral side of the wrist. It ends by anastomosing with the terminal portion of ulnar artery, thus completing the superficial palmar arch of hand.
At the wrist:
- Dorsal carpal branch: It is a small vessel arising from the radial artery that anastomoses with corresponding branch coming from the ulnar artery to form the dorsal carpal arch of hand.
- First dorsal metacarpal artery: It arises just before the radial artery passes between the two heads of the first dorsal interosseous muscle. It divides into two branches to supply the adjacent sides of thumb and index finger.
In the hand:
- Princeps pollicis artery: It is also known as the principal artery of the thumb. It arises from the radial artery just at the point where it turns to the medial side of the hand. It supplies the lateral part of the thumb.
- Radialis indicis artery: It is the radial artery of index finger. It arises near the origin of princeps pollicis artery, and runs between the heads of first dorsal interosseous muscle to reach the lateral side of index finger. It supplies blood to the index finger.
- Deep palmar arch: It exists as an arterial network found in the palm, formed by terminal part of radial artery and deep palmar branch of ulnar artery.
Radial artery in the hand:
The radial artery leaves the lower end of the radius and slopes across the snuffbox over the trapezium and so passes into the hand between the two heads of the first dorsal interosseous muscle. Lying now between this muscle and adductor pollicis it gives off two large branches. The arteria radialis indicis passes distally between the two muscles to emerge on the radial side of the index finger, which it supplies. The princeps pollicis artery passes distally along the metacarpal bone of the thumb and divides into its two palmar digital branches at the metacarpal head. The main trunk of the radial artery now passes into the palm between the oblique and transverse heads of adductor pollicis to form the deep palmar arch.
The deep palmar arch is an arterial arcade formed by the terminal branch of the radial artery anastomosing with the deep branch of the ulnar artery. Unlike the superficial arch the deep arch is usually complete. The radial artery gains the palm by passing between the oblique and transverse heads of adductor pollicis, and runs across the palm at a level about 1 cm proximal to the superficial arch. The deep branch of the ulnar nerve lies within the concavity of the deep arch. From its convexity three palmar metacarpal arteries pass distally and in the region of the metacarpal heads they anastomose with the common palmar digital branches of the superficial arch. Branches perforate the interosseous spaces to anastomose with the dorsal metacarpal arteries. Accompanying veins drain most of the blood from the palm into the dorsal venous network. Branches from the anterior carpal arch also anastomose with the deep arch.
For a visual assessment of the contribution of the radial and ulnar arteries in the blood supply of the hand, make a clenched fist and occlude the radial and ulnar arteries. When the fist is released the skin of the palm is seen to be pale, but color should return rapidly on the release of either one of the arteries. If there is an obvious delay after releasing the ulnar artery compared with the radial, it suggests that the radial supply is dominant and that procedures that might damage the radial artery (such as cannulation) should be avoided.