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27. 2. 2013.

The arteries and pulses of the upper body

The main arterial stem of the upper limb passes through the root of the neck, the axilla and the arm before dividing into two in the forearm. It changes its name in each of the regions as it crosses particular bony or muscular landmarks. 

The subclavian artery

The right subclavian artery lies entirely within the root of the neck, having arisen from the brachiocephalic trunk. The left subclavian artery arises from the aortic arch in the superior mediastinum to enter the root of the neck. Both arteries pass laterally over the first rib towards the axilla, and end by becoming the axillary artery its lateral border. The subclavian artery is conveniently divided into three parts by scalenus anterior which crosses it anteriorly.
In the neck, the artery runs from the upper border of the sternoclavicular joint to the middle of the clavicle. The course is convex upwards. The artery can be compressed against the first rib by a downward and backward pressure applied behind the clavicle, lateral to the posterior border of sternocleidomastoid.
Branches from the subclavian artery supply structures within the neck, and the anterior chest wall, and give an important supply to the brain via the vertebral artery.

The axillary artery

The axillary artery is the continuation of the subclavian artery at the lateral border of the first rib and ends by becoming the brachial artery at the lower border of teres major, at the level of the lateral extremity of the posterior axillary fold. For descriptive purposes, it is divided into three parts by pectoralis minor. However, the length of each part will depend on the position of the arm. The cords of the brachial plexus are named according to their position with respect to the second part of the axillary artery.
The course of the artery is represented by a line drawn from the midpoint of the clavicle and passing immediately below the coracoid process to the medial lip of the intertubercular groove behind coracobrachialis. It thus describes a curve with the concavity facing downwards and medially.
The pulse of the axillary artery is readily palpated in the lateral wall of the axilla in the groove behind the coracobrachialis muscle. This is a useful pressure point to control distal bleeding, although paraesthesia may result from the inevitable pressure on the median, ulnar and radial nerves which are in close relation to the artery at this point.
Branches from the axillary artery supply the shoulder and pectoral regions, as well as the lateral chest wall. They anastomose with branches from the subclavian artery and the posterior intercostal arteries from the descending thoracic aorta. These anastomoses and their vessels may be enlarged in conditions where there is a narrowing of the aorta beyond the origin of the left subclavian artery(coarctation of the aorta), and serve as a collateral system bypassing the restriction.

The brachial artery

This is the continuation of the axillary artery beyond the lower border of teres major and ends in the cubital fossa opposite the neck of the radius. It lies successively on the long and medial heads of triceps, the coracobrachialis insertion and brachialis. Anteriorly it is covered by the medial border of the biceps, and is crossed from lateral to medial by the median nerve about halfway down the arm. In the cubital fossa it lies beneath the bicipital aponeurosis, which separates it from the median cubital vein, with the median nerve lying medial to the artery and with the biceps tendon lying lateral. The brachial artery divides into the radial and ulnar arteries.
High division of the brachial artery sometimes occurs proximal to the cubital fossa. Indeed, it may divide at any point between the axilla and the cubital fossa, in which case the two arteries descend side-by-side following the normal course of the brachial artery.
The brachial pulse may be felt along the whole course of the artery by compressing it against the humerus, directing lateral pressure proximally and dorsolateral pressure distally. It is best felt just medial to the bicipital aponeurosis at the level of the medial epicondyle of the humerus, and it is at this point that one listens for Korotkoff’s sounds when measuring blood pressure.
A major branch of the brachial artery is the profunda brachii, which runs with the radial nerve in the spiral groove between the lateral and medial heads of the triceps to pass into the posterior compartment of the arm. Branches from both the brachial artery and the profunda brachii supply the muscles of the arm and contribute to the anastomosis around the elbow joint.

The radial artery

The radial artery begins in the cubital fossa opposite the neck of the radius and ends by completing the deep palmar arch in the hand. It is usually thought of and described as having three parts. The first part is in the forearm, the second curves laterally around the wrist as far as the first interosseus space, and the third passes through the interosseus space into the palm.
If the arm is placed in a midpronated position and brachioradialis is tensed, then the course of the first part of the radial artery may be indicated by a slightly convex line beginning at the biceps tendon and running down the medial side of brachioradialis to a point just medial to the radial styloid process on the anterior aspect. As it curves around the wrist, the radial artery is within the “anatomical snuffbox” and lies on the radiocarpal ligament, the scaphoid and trapezium. It is crossed by the tendons of abductorpollicis longus and extensors pollicis brevis and longus from lateral to medial.
The third part of the artery passes between the two heads of the first dorsal interosseus and adductor pollicis before completing the deep palmar arch.
The radial pulses may be felt against the distal border of the radius lateral to flexor carpi radialis, and in the “anatomical snuffbox” against the scaphoid.
Branches from the first part of the artery are involved in the elbow anastomosis and supply the muscles on the radial side of the forearm. From the second part arise branches supplying the wrist and dorsum of the hand and thumb. Before completing the deep palmar arch, the third part of the artery gives off the princes pollicis and radialis indicis branches to the thumb and index fingers respectively.

The ulnar artery

The ulnar artery begins in the cubital fossa as a terminal branch of the brachial artery, and ends at the pisiform by dividing into deep and superficial palmar arteries. It may be represented by a line passing, medially convex, from the tendon of biceps to the pisiform bone and from there to the hook of the hamate. In its course, it lies on brachialis, flexor digitorum profundus and the flexor retinaculum, and is crossed anteriorly, from above downwards by: pronator teres, the median nerve, flexor carpi radialis, palmaris longus and flexor digitorum superficialis, being overlapped lower down by flexor carpi ulnaris. Just below the radial tuberosity, the common interosseus artery is given off, and this divides into anterior and posterior interosseus arteries which run down either side of the interosseus membrane, supplying the deep muscles of both flexor and extensor compartments. Branches from the proximal and distal ends of the artery are involved in the supply to the elbow and wrist joints respectively.

The superficial palmar arch

This is formed mainly by the ulnar artery, with a contribution from the superficial palmar branch of the radial artery. It lies deep to the palmar aponeurosis. The distal convexity of the arch lies level with the flexor surface of the extended thumb.
Four common palmar digital arteries arise from the superficial arch with the most medial running along the medial side of the little finger. The other three each divide into two proper digital arteries which supply adjacent sides of the little, ring, middle and index fingers.

The deep palmar arch

This is formed mainly by the radial artery with a contribution from the deep branch of the ulnar artery. It lies deep to the long flexor tendons and their synovial sheaths on the bases of the metacarpals and gives rise to the palmar metacarpal arteries. Its distal convexity is 2cm distal to the distal crease of the wrist.

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