Axillary Artery

Origin

The axillary artery is a continuation of the subclavian artery once it reaches the lateral border of the first rib.

Course

As it runs distally, the axillary artery is divided into three portions according to its position relative to the pectoralis minor muscle. Its first, second, and third portions lie proximal, deep, and distal to the pectoralis minor muscle, respectively. Once it descends distal to the inferior edge of the teres major muscle, the axillary artery becomes the brachial artery.

Relations of the first part of the axillary artery:

- anterior: platysma, clavicle, and pectoralis major muscle;

- posterior: serratus anterior muscle and the medial cord of the brachial plexus;

- lateral: posterior cord of the brachial plexus;

- medial: axillary vein.

Relations of the second part of the axillary artery:

- anterior: pectoralis minor muscle;

- posterior: posterior cord of the brachial plexus;

- lateral: lateral cord of the brachial plexus;

- medial: medial cord of the brachial plexus and the axillary vein.

Relations of the third part of the axillary artery:

- anterior: pectoralis major muscle;

- posterior: latissimus dorsi and teres major muscles;

- lateral: coracobrachialis muscle;

- medial: axillary vein.

Branches

There is one branch from the first part (proximal to the pectoralis minor muscle) of the axillary artery, the superior thoracic artery. It arises inferior to the subclavius and extends to the thoracic wall to anastomose with the internal thoracic artery.

There are two branches from the second part (posterior to the pectoralis minor muscle) of the axillary artery. The thoracoacromial artery traverses the clavipectoral fascia and divides into pectoral, acromial, clavicular, and deltoid branches. The lateral thoracic artery courses along the lateral border of the pectoralis major distally to the fifth intercostal space

There are three branches from the third part (distal to the pectoralis minor muscle) of the axillary artery. The subscapular artery arises at the inferior edge of the subscapularis muscle and continues distally to the inferior angle of the scapula. The anterior circumflex humeral artery runs on the anterior aspect of the surgical neck of the humerus and anastomoses with its posterior counterpart. The posterior circumflex humeral artery runs posteriorly with the axillary nerve, through the quadrangular space to anastomose with the anterior circumflex humeral artery.

The axillary artery is highly variable and this classical arrangement of six individual branches is only found in 10% of individuals. In about 20% of individuals, the posterior circumflex humeral and the subscapular arteries originate from a common trunk. In a similar percentage, the anterior and the posterior circumflex humeral arteries originate from a common trunk. In 10–15% of individuals, the deep brachial artery originates from the axillary artery or from the posterior circumflex humeral artery (in 5% of individuals) as opposed to originating from the brachial artery (Tubbs, Shoja and Loukas, 2016).

Supplied Structures

The superior thoracic artery supplies the pectoralis muscles and the thoracic wall. The thoracoacromial artery supplies the pectoralis muscles, the cutaneous tissue of the clavipectoral region, and the clavicular part of the deltoid muscle.

The lateral thoracic artery supplies the serratus anterior, pectoralis, and subscapularis muscles, the axillary lymph nodes, and cutaneous tissue of the lateral thoracic wall. In females, it gives off the lateral mammary branches which contribute to the supply of the breast.

The subscapular artery contributes to the supply of the subscapularis and latissimus dorsi muscle and gives rise to the circumflex scapular and thoracodorsal arteries. The anterior and posterior circumflex humeral arteries supply the glenohumeral joint and the muscles surrounding the proximal humerus.

References

Tubbs, R. S., Shoja, M. M. and Loukas, M. (2016) Bergman's Comprehensive Encyclopedia of Human Anatomic Variation. Wiley.