Course
The main artery of the upper limb is named by region, and each segment begins where the previous one crosses a fixed landmark.
Subclavian artery
The right subclavian artery arises from the brachiocephalic trunk behind the right sternoclavicular joint; the left arises directly from the arch of the aorta. Each arches over the cervical pleura and passes behind scalenus anterior, which divides it into three parts: medial to, behind and lateral to the muscle. It becomes the axillary artery at the lateral border of the first rib.
Axillary artery
The axillary artery runs through the axilla, surrounded by the cords of the brachial plexus. Pectoralis minor crosses in front of it and divides it into three parts. It becomes the brachial artery at the lower border of teres major.
Brachial artery
The brachial artery runs down the medial side of the arm, in the groove beside biceps, and is superficial along its length. The median nerve crosses in front of it from lateral to medial in the middle of the arm. It passes under the bicipital aponeurosis into the cubital fossa and divides, usually at the level of the neck of the radius, into the radial and ulnar arteries.
Radial and ulnar arteries
The radial artery runs down the lateral forearm under brachioradialis, then lies superficially lateral to the tendon of flexor carpi radialis at the wrist. It winds backwards through the anatomical snuffbox, passes between the two heads of the first dorsal interosseous and then between the heads of adductor pollicis into the palm, and forms the deep palmar arch. The ulnar artery passes deep to pronator teres and flexor digitorum superficialis, runs under flexor carpi ulnaris with the ulnar nerve on its medial side, crosses the wrist superficial to the flexor retinaculum in Guyon's canal, and forms most of the superficial palmar arch.
Branches
The main branches are best learned segment by segment.
| Artery | Branches |
|---|---|
| Subclavian | Vertebral, internal thoracic, thyrocervical trunk (first part); costocervical trunk (second part); dorsal scapular (usually third part, but variable) |
| Axillary, first part | Superior thoracic |
| Axillary, second part | Thoracoacromial, lateral thoracic |
| Axillary, third part | Subscapular, anterior circumflex humeral, posterior circumflex humeral |
| Brachial | Profunda brachii (with radial nerve), superior and inferior ulnar collateral, nutrient artery to humerus, muscular branches |
| Radial | Radial recurrent, palmar carpal, superficial palmar branch, princeps pollicis, radialis indicis |
| Ulnar | Anterior and posterior ulnar recurrent, common interosseous (anterior and posterior interosseous), deep palmar branch |
The numbering rule for the axillary artery is simple: the first part has one branch, the second two and the third three.
Palmar arches and anastomoses
The two palmar arches join the radial and ulnar arteries in the hand, so either vessel can usually supply the whole hand alone.
- Superficial palmar arch: formed mainly by the ulnar artery, completed by the superficial palmar branch of the radial artery. It lies deep to the palmar aponeurosis, level with the distal border of the fully extended thumb, and gives the common palmar digital arteries.
- Deep palmar arch: formed mainly by the radial artery, completed by the deep branch of the ulnar artery. It lies about a finger's breadth proximal to the superficial arch, on the bases of the metacarpals, and gives the palmar metacarpal arteries.
Two anastomoses above the hand matter clinically. The scapular anastomosis links branches of the subclavian artery (suprascapular and dorsal scapular) with the subscapular branch of the axillary artery, so blood can bypass a block in the axillary artery between these points. Around the elbow, the collateral branches of the brachial and profunda brachii arteries join the recurrent branches of the radial, ulnar and interosseous arteries.
Clinical relevance
The upper limb arteries are used for pulses, blood pressure, sampling and access, and their anastomoses decide what can be ligated safely.
- Pulses: the brachial pulse is felt medial to the biceps tendon at the elbow; the radial pulse lateral to flexor carpi radialis at the wrist; the ulnar pulse lateral to flexor carpi ulnaris.
- Allen's test: checks that the ulnar artery can supply the hand through the palmar arches before radial artery cannulation, sampling or harvesting.
- Supracondylar fracture: the brachial artery can be kinked or torn, threatening the forearm with ischaemia and compartment syndrome.
- Ligation: the brachial artery can be clamped distal to profunda brachii with the elbow anastomosis keeping the forearm alive; proximal to it the risk is higher.
- Subclavian steal: stenosis of the proximal subclavian artery lets arm exercise draw blood backwards down the vertebral artery, causing dizziness.
- Thoracic outlet: a cervical rib or tight scalene triangle can compress the subclavian artery.