Axillary artery

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 1st rib. It exits the axillary cavity through its inferior opening, becoming the brachial artery below the teres major muscle.

Parts of axillary artery

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 axillary artery that is proximal (superior) to the pectoralis minor;
• Second part - the part of the artery posterior to the pectoralis minor;
• Third part - the part that is distal (inferior) to the pectoralis minor.

Branches of axillary artery

On its course, the axillary artery gives off several branches arising from different parts of the artery. The first part of the axillary artery gives rise to one branch - the superior thoracic artery. It originates from the axillary artery at the region of the first and second intercostal spaces, and supplies the pectoralis major and minor muscles, subclavius and serratus anterior muscles, as well as muscles of the first two intercostal spaces and skin covering them.

The second part gives rise to two branches: thoracocacromial artery and lateral thoracic artery. The thoracoacromial artery is a short trunk that wings around the upper border of the pectoralis minor medially. It penetrates the clavipectoral fascia and divides into smaller branches, such as the acromial branch, clavicular branch, deltoid branch, and pectoral branches.

The 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 of the axillary artery gives rise to three branches: subscapular artery, anterior circumflex humeral artery, and posterior circumflex humeral artery. The subscapular artery is 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 first branch is the thoracodorsal artery - it supplies the serratus anterior, subscapularis, and latissimus dorsi. The second branch of the subscapular artery is the circumflex scapular artery. This vessel forms an anastomosis with the suprascapular artery that arises from the subclavian artery.

The anterior circumflex humeral artery is a small branch arising from the third part of the axillary artery that passes in front of the surgical neck of the humerus. The artery extends behind the coracobrachialis and biceps brachii muscles, forms an anastomosis with the posterior circumflex humeral artery (another branch of the axillary artery).

The posterior circumflex humeral artery is a large branch of the axillary artery that lies very close to the humerus, and supplies the shoulder joint, the deltoid muscle, 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 artery is surrounded by the trunks of the brachial plexus. The axillary artery is enclosed within the axillary sheath, which is a fibrous layer covering the artery and three cords of the brachial plexus.