THE CONTEXT
The axilla contains vessels, nerves and five groups of lymph nodes embedded in fat and areolar tissue.
Main neurovascular arrangement
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The axillary artery and brachial plexus run from the apex to the base along the lateral wall, nearer the anterior wall than the posterior wall.
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The axillary nerve passes through the quadrangular space, while the radial nerve passes through the lower triangular space.
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The axillary artery continues from the subclavian artery and begins at the outer border of the first rib.
Vessel and nerve relations
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Thoracic branches of the axillary artery contact the pectoral muscles. The lateral thoracic vessels run along the lower border of pectoralis minor.
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The subscapular vessels run along the lower border of subscapularis. The subscapular and thoracodorsal nerves cross its anterior surface.
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The circumflex scapular vessels wind around the lateral border of the scapula.
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The axillary nerve and posterior circumflex humeral vessels pass backwards close to the surgical neck of the humerus.
Medial wall
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The medial wall is avascular apart from a few small branches of the superior thoracic artery.
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The long thoracic nerve descends on the surface of serratus anterior.
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The intercostobrachial nerve pierces the anterosuperior part of the medial wall and crosses the axillary space to reach the medial side of the arm.
Axillary lymph node groups
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There are 20–30 axillary lymph nodes arranged in five groups.
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The anterior group lies along the lower border of pectoralis minor on the lateral thoracic vessels.
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The posterior group lies along the lower margin of the posterior wall, along the subscapular vessels.
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The lateral group lies posteromedial to the axillary vein.
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The central group lies in the axillary fat.
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The apical group lies behind and above pectoralis minor, medial to the axillary vein.