Axillary collateral circulation, venous drainage and lymph nodes
THE CONTEXT
The axilla contains arterial anastomoses, venous channels and lymph node groups with distinct drainage territories.
Arterial anastomoses
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Axillary artery branches anastomose with one another and with branches of the internal thoracic, intercostal, suprascapular, deep branch of transverse cervical and profunda brachii arteries.
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When the axillary artery is blocked, scapular anastomoses provide collateral circulation between the first part of the subclavian artery and the third part of the axillary artery. Communications with posterior intercostal arteries also exist.
Axillary vein
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The axillary vein continues from the basilic vein and is joined by the venae comitantes of the brachial artery a little above the lower border of teres major.
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It lies medial to the axillary artery and becomes the subclavian vein at the outer border of the first rib.
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It receives tributaries corresponding to five of the six branches of the axillary artery, as well as the cephalic vein. Veins accompanying thoracoacromial artery branches drain directly into the cephalic vein.
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The thoracoepigastric vein connects the lateral thoracic vein of the upper limb with the superficial epigastric vein of the lower limb, providing a route for blood to return to the heart when the inferior vena cava is blocked.
Axillary lymph node groups
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Axillary lymph nodes lie in the fibrofatty tissue of the axilla and are divided into five groups.
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Anterior or pectoral nodes lie along the lateral thoracic vessels at the lower border of pectoralis minor. They receive lymph from the upper half of the anterior trunk wall and the major part of the breast.
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Posterior or scapular nodes lie along the subscapular vessels on the posterior axillary fold. They receive lymph from the posterior wall of the upper half of the trunk and the axillary tail of the breast.
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Lateral nodes lie along the upper humerus, medial to the axillary vein, and receive lymph from the upper limb.