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The axillary artery is a major artery of the upper limb that conveys oxygenated blood to the lateral aspect of the thorax, the axilla (armpit), and the upper limb. It is a continuation of the subclavian artery, which arises from the brachiocephalic trunk on the right and branches directly off the arch of the aorta on the left. The axillary artery is enclosed in the axillary sheath and is anatomically divided into three parts by the pectoralis minor muscle: medial to, behind, and lateral to the muscle. The first segment of the axillary artery gives off one branch, the second segment gives off two, and the third segment gives off three branches. The axillary artery terminates at the lower border of the teres major muscle, where it becomes the brachial artery, which supplies the distal upper limb.
| Characteristics | Values |
|---|---|
| Muscle that divides the axillary artery | Pectoralis minor muscle |
| Number of divisions | 3 |
| First division | Medial to the pectoralis minor muscle |
| First branch | Supreme thoracic artery |
| Second division | Behind the pectoralis minor muscle |
| Second branch | Thoracoacromial artery |
| Third division | Lateral to the pectoralis minor muscle |
| Third branch | Subscapular artery |
| Other branches | Lateral thoracic artery, medial humeral circumflex artery |
| Origin | Continuation of the subclavian artery |
| Termination | Brachial artery |
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What You'll Learn
The axillary artery is divided into three parts
The axillary artery is a large blood vessel that conveys oxygenated blood to the lateral aspect of the thorax, the axilla (armpit), and the upper limb. It is the continuation of the subclavian artery, which arises from the brachiocephalic trunk on the right and branches directly off the arch of the aorta on the left. The axillary artery is enclosed in the axillary sheath, a fibrous layer that also covers the three cords of the brachial plexus.
The axillary artery is anatomically divided into three parts by the pectoralis minor muscle, providing an intuitive way to conceptualize its course. The first part is located proximal to the pectoralis minor and has one branch: the superior thoracic artery, which supplies the pectoralis minor and major muscles. This segment lies on top of the serratus anterior muscle. The second part lies deep to the pectoralis minor and has two branches: the thoracoacromial trunk, which divides into the acromial, pectoral, clavicular, and deltoid arteries, and the lateral thoracic artery. The third part runs distally from the pectoralis minor and has three branches: the subscapular, medial, and lateral humeral circumflex arteries.
The axillary artery is bordered medially by the axillary vein, which lies alongside it along its entire course, and posteriorly by the cords of the brachial plexus. As the axillary artery moves distally, the cords of the brachial plexus surround it, eventually forming the named nerves of the arm at the level of the distal axillary and proximal brachial artery. The axillary artery itself gives off six branches before terminating at the lower border of the teres major muscle, where it becomes the brachial artery, the principal blood supply to the arm.
The axillary artery is an important landmark for understanding the position of other structures in the region, particularly the brachial plexus. It is also critical in trauma management, as traumatic disruptions can cause severe bleeding or ischemia in the upper limb. This artery is often exposed during surgical procedures, including bypass grafting, shoulder operations, and axillary lymph node dissections.
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The pectoralis minor muscle
The pectoralis minor is clinically important and serves as a surgical landmark due to the structures that lie below or deep to the muscle and its tendon. Running deep to the pectoralis minor muscle are the nerves and blood supply to the upper limb: the posterior, lateral, and medial cords of the brachial plexus. The axillary artery is enclosed in the axillary sheath, a continuation of the prevertebral fascia of the neck, and is anatomically divided into 3 parts by the pectoralis minor muscle.
The first part of the axillary artery is medial to the pectoralis minor muscle, the second part is directly posterior to the muscle, and the third part is lateral to the muscle. The first segment of the axillary artery gives one branch (supreme thoracic artery), the second segment gives two (thoracoacromial and lateral thoracic arteries), and the third segment gives three branches (subscapular, medial, and lateral humeral circumflex arteries).
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The axillary sheath
The axillary artery is the principal arterial supply of the upper limb, commencing as a continuation of the subclavian artery as it emerges from underneath the first rib. The axillary artery is enclosed in the axillary sheath, a continuation of the prevertebral fascia of the neck, and is anatomically divided into three parts by the pectoralis minor muscle. The first part is located proximal to the pectoralis minor and has one branch, the supreme thoracic artery. The second part lies behind the pectoralis minor and has two branches, the thoracoacromial and lateral thoracic arteries. The third part starts from the lateral border of the pectoralis muscle to the lateral border of the teres major muscle and gives off three branches: the subscapular artery, the lateral humeral circumflex artery, and the medial circumflex artery.
The axillary vein lies medial to the axillary artery and is separated from the artery by the medial pectoral nerve, the medial cord of the brachial plexus, and the ulnar nerve. It is also separated from the axillary sheath by a pad of fat. The close proximity of the vein to the artery can result in the occurrence of traumatic arteriovenous malformations.
Regional blockade of the brachial plexus within the axillary sheath may be performed at the interscalene, supraclavicular, infraclavicular, or axillary level. Axillary block provides excellent anaesthesia for the forearm and hand and has been used successfully for outpatient surgical procedures in the upper extremity in both adults and children.
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The subclavian artery
The axillary artery is enclosed in the axillary sheath and is anatomically divided into three parts by the pectoralis minor muscle. The axillary artery gives off six branches before terminating at the lower border of the teres major muscle, where it becomes the brachial artery. The axillary artery is critical in trauma management, as traumatic disruptions can cause severe bleeding or ischemia in the upper limb.
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The brachial artery
The axillary artery is enclosed in the axillary sheath and is anatomically divided into three parts by the pectoralis minor muscle. At the lower border of the teres major muscle, the axillary artery becomes the brachial artery.
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Frequently asked questions
The pectoralis minor muscle divides the axillary artery into three parts.
The first part is located proximal to the pectoralis minor and has one branch. The second part lies deep to the pectoralis minor and has two branches. The third part runs distally from the pectoralis minor and has three branches.
The superior (highest) thoracic artery is the first branch of the axillary artery.
The second part of the axillary artery gives rise to two vessels: the thoracoacromial (acromiothoracic) artery and the lateral thoracic artery.
The axillary artery is a large blood vessel that conveys oxygenated blood to the lateral aspect of the thorax, the axilla (armpit), and the upper limb.
