The axillary artery (Latin: arteria axillaris) is a major blood vessel that supplies oxygenated blood to the lateral aspect of the thorax, the axilla (armpit), as well as the upper limb.
The axillary artery lies deep to the pectoralis minor muscle. It is the direct continuation of the subclavian artery beneath the outer border of the first rib. The artery passes through the upper opening of the axillary cavity, between the clavicle and the first rib. It exits the axillary cavity through its inferior opening, becoming the brachial artery below the teres major muscle.
The artery may be divided into three parts based on its relation to the pectoralis minor muscle, which lies superficial to the artery:
- first part - the segment of the artery that is proximal (superior) to the pectoralis minor muscle;
- second part - the part posterior to the pectoralis minor;
- third part - the part distal (inferior) to the pectoralis minor.
On its course, the axillary artery gives off several branches arising from different parts of the artery:
- the first part gives rise to 1 branch:
- superior thoracic artery - a branch arising from the axillary artery at the region of the first and second intercostal spaces;
- the second part gives rise to 2 branches:
- thoracoacromial artery - a short trunk that wings around the upper border of the pectoralis minor medially, penetrates the clavipectoral fascia and divides into smaller branches (acromial branch, clavicular branch, deltoid branch, and pectoral branches);
- lateral thoracic artery - arises at the lateral border of the pectoralis minor, passes along the external surface of the serratus anterior below the pectoral fascia and supplies the serratus anterior, pectoralis major and minor, and the skin above these muscles; this artery also gives off mammary branches to supply the mammary gland;
- the third part gives rise to 3 branches:
- subscapular artery - the largest branch of the axillary artery, a short vessel, which gives off two branches at the level of the lateral border of the subscapularis muscle - the thoracodorsal artery (supplies the serratus anterior, subscapularis, and latissimus dorsi) and the circumflex scapular artery (forms an anastomosis with the suprascapular artery from the subclavian artery);
- anterior circumflex humeral artery - a small branch in front of the surgical neck of the humerus; extends behind the coracobrachialis and biceps brachii muscles, forms an anastomosis with the posterior circumflex humeral artery;
- posterior circumflex humeral artery - a large branch of the axillary artery that lies very close to the humerus, and supplies the shoulder joint, the deltoid, and forms an anastomosis with the anterior circumflex humeral artery.
At the lower border of the teres major muscle, the axillary artery continues as the brachial artery.
Relations to other structures
As mentioned, the axillary artery related to the pectoralis minor, as it travels deep to the muscle.
On its course, the axillary artery is accompanied by the axillary vein, which travels on the medial side of the artery.
Within the axillary cavity, the axillary artery is surrounded by the trunks of the brachial plexus.
The artery is enclosed within the axillary sheath, which is a fibrous layer covering the artery and three cords of the brachial plexus.