The blood-supply of the upper limb is derived from the continuation of the subclavian artery, which at the lower border of the first rib changes its name and becomes the axillary artery.

Axillary Artery

From the lower border of the first rib to the lower border of the teres major.

The axillary artery passes through the axillary space, and lies on, successively, upper digitation of serratus magnus, subscapulars, latissimus dorsi, teres major, and is covered by pec-toralis major and minor.

The pectoralis minor muscle crosses the middle third of the artery and divides it into three parts.

The three cords of the brachial plexus lie respectively to the inner, outer, and posterior sides of the artery.

The axillary vein lies along the inner side of the artery.

Branches

From first and second parts :

Several thoracic branches to supply the neighbouring parts. From third part :

1. Subscapular, which arises opposite the lower border of the scapularis and supplies the adjacent muscles and inner wall of axillary space.

2. Anterior and Posterior Circumflex, which enclose the surgical neck of the humerus and supply the shoulder-joint and adjacent muscles (see Fig. 6).

The axillary artery is continued as the brachial artery, which passes down to supply the upper arm.

Brachial Artery

From the lower border'of teres major to the antecubital fossa, where, at the level of the neck of the radius, it terminates by dividing into the radial and ulnar arteries.

The brachial artery passes downwards and outwards, and lies on, successively, long head of triceps, insertion of coraco-brachialis, brachialis anticus, and is covered by the inner border of biceps.

In its upper half the median and ulnar nerves lie respectively on the external and internal sides of the artery, and at the middle the median nerve crosses over to the inner side of the artery, while the ulnar nerve passes to the back of the arm.

Branches

1. Superior Profunda, runs downwards and backwards with the musculo-spiral nerve to the back of the arm.

2. Inferior Profunda, runs downwards and backwards with the ulnar nerve to the back of the elbow-joint.

3. Anastomotic pierces the internal intermuscular septum and passes also to the back of the elbow-joint.

4. Small muscular branches are given off to the adjacent muscles.

Radial Artery

The radial artery is the smaller of the two terminal branches of the brachial arterv, but the more direct continuation of the parent trunk. It passes down the outer side of the forearm, and at the wrist winds round the trapezium to reach the back of the hand; it then comes back through the first interosseous space, and anastomoses with the deep branch of the ulnar artery to form the deep palmar arch.

It lies successively on insertion of biceps, supinator brevis, pronator radii teres, radial head of flexor sublimis digitorum, flexor longus pollicis, pronator quadratius, anterior ligament of wrist-joint.

It is covered by inner border of supinator longus (brachio-radialis) in its upper two-thirds. The lower third is subcutaneous.

The radial nerve is in relation to the artery in its middle third, and lies on its outer side.

Branches,-1. Superficial Volar, which arises just above the wrist, and, passing down over the ball of the thumb, anastomoses with the superficial branch of the ulnar artery to form the superficial palmar arch.

2. Anterior Carpal, given off at the wrist and anastomoses with a similar branch of the ulnar artery.

3. Posterior Carpal, a small branch which passes backwards and anastomoses with a similar branch from the ulnar artery to form the posterior carpal arch.

4. Muscular branches for the supply of the adjacent muscles.