Axillary artery is the continuation of the subclavian artery into the axilla. The artery is closely related to the cords of the brachial plexus and in fact the cords of the brachial plexus are named according to their relation with the second part of the axillary artery; the posterior cord of the brachial plexus lies posterior to the second part of the axillary artery, the medial cord lies medial and the lateral cord lies lateral to it.
Origin and termination of axillary artery:
The axillary artery begins at the lateral border of the first rib as a continuation of the subclavian artery into the axilla. It terminates at the lower border of the teres major muscle and then continues downward in the arm as the brachial artery.
Parts of the axillary artery:
The axillary artery is customarily divided into three parts;
1st part of axillary artery: It lies between the lateral border of the first rib and the medial border of the pectoralis minor muscle. It gives one branch named as the “highest thoracic artery”.
2nd part of the axillary artery: It lies under the pectoralis minor muscle. It gives two branches; the lateral thoracic artery and the thoracoacromial artery. The lateral thoracic artery continues downward along the lateral border of pectoralis minor. The thoracoacromial artery divides into 4 terminal branches namely acromial branch, clavicular branch, deltoid branch and pectoral branch.
3rd part of axillary artery: It lies between the lateral border of pectoralis minor and the lower border of the teres major muscle. It gives three branches; the subscapular artery, the anterior circumflex humeral artery and the posterior circumflex humeral artery.
Branches of the axillary artery:
In the lines below, I have provided the details of each branch of axillary artery.
Highest thoracic artery:
It passes between the pectoralis major and minor muscles to the side of the chest and supplies blood to the first and second intercostals spaces and to the superior portion of serratus anterior muscle. It ends by anastomosing with internal mammary and intercostals arteries.
Lateral thoracic artery:
It supplies blood to lateral structures of thorax and breast. Muscles supplied by this branch include the serratus anterior muscle, pectoralis major muscle and subscapularis muscle. It also supplies the axillary lymph nodes. It ends by anastomosing with internal thoracic artery and intercostals arteries. In females it gives an external mammary branch to supply the breast.
It gives 4 branches immediately after its origin from second part of axillary artery. The branches are;
- Pectoral Branch: It descends between the pectoralis major and minor, and supplies the mammary gland. It ends by anastomosing with intercostals branches of internal mammary artery.
- Acromial branch: It supplies the deltoid muscle and runs laterally over the coracoids process. It ends on acromion in an arterial network formed by branches from the suprascapular, thoracoacromial, and posterior humeral circumflex arteries.
- Clavicular branch: It supplies the sternoclavicular joint and the subclavius muscle.
- Deltoid branch: It supplies the pectoralis major and deltoid muscle.
Subscapular artery: It is the largest branch of axillary artery. It follows the subscapularis muscle to inferior angle of scapula where it anastomoses with lateral thoracic and intercostals arteries. It forms the arterial anastomoses around scapula.
Anterior circumflex humeral artery: It is considerably smaller than the posterior circumflex artery. It supplies the shoulder joint and the head of the humerus. It takes part in the formation of anastomoses around the shoulder joint.
Posterior circumflex humeral artery: It passes through the quadrangular space and winds around the neck of humerus. It supplies the deltoid muscle and shoulder joint. It takes part in the formation of anastomoses around shoulder joint.