This large vessel begins at the lateral border of the first rib as the continuation of the subclavian artery. The axillary artery ends at the inferior border of the teres major muscle. Here it passes into the arm where it becomes the brachial artery. The axillary artery is divided into three parts by the pectoralis minor muscle as it passes posterior to this muscle.
First Part
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The First Part of the Axillary Artery – located between the lateral border of the first rib and the superior border of the pectoralis minor muscle. The first part of the artery is enclosed in the axillary sheath along with the axillary vein and the brachial plexus. The first part has one branch, the superior (supreme) thoracic artery, which helps supply the first and second intercostal spaces and the superior part of the serratus anterior muscle.
The Second Part of the Axillary Artery – lies deep to the pectoralis minor; has two branches: the thoracoacromial and lateral thoracic arteries. The thoracoacromial artery divides into four branches: acromial, deltoid, pectoral, and clavicular. The lateral thoracic artery supplies parts of the pectoral muscles and in the female is an important source blood to the lateral mammary gland. The lateral thoracic artery typically runs along the superficial surface of the serratus anterior muscle with the long thoracic nerve.
The Third Part of the Axillary Artery – has three branches: subscapular, anterior circumflex humeral, and posterior circumflex humeral arteries. The subscapular artery ends by bifurcating into the circumflex scapular and thoracodorsal arteries. The circumflex scapular artery passes around the lateral border of the scapula to supply muscles on the dorsum of the scapula. The thoracodorsal artery supplies the latissimus dorsi muscle. The anterior and posterior circumflex humeral arteries pass around the surgical neck of the humerus. The posterior circumflex humeral artery passes through the posterior wall of the axilla via the quadrangular space with the axillary nerve to supply the deltoid and teres minor muscles.
The Branches of Axillary Artery are named according to their distribution rather than by their point of origin. There are extensive arterial anastomoses around the scapula. The surgical importance of the collateral circulation becomes apparent during ligation of an injured axillary or subclavian artery. The axillary artery may be ligated between the thyrocervical trunk and the subscapular artery. In this case, the direction of blood flow in the subscapular artery is reversed and blood reaches the distal portion of the axillary artery first. Note that the subscapular artery receives blood via several anastomoses with the suprascapular artery, deep transverse cervical artery (dorsal scapular artery), and some intercostal arteries. Ligation of the axillary artery distal to the subscapular artery cuts off the blood supply to the arm.
