What is the axilla and what is its main function?

The axilla, or armpit, is a pyramidal space between the upper arm and chest wall. Its primary function is to serve as a conduit for neurovascular structures traveling between the neck and upper limb, housing key components like the brachial plexus and axillary vessels.

What are the boundaries of the axilla?

The axilla has an apex, base, and four walls. The apex is bounded by the clavicle, scapula, and first rib. The base is formed by axillary fascia and bounded by anterior and posterior axillary folds. The walls are anterior (pectoral muscles), posterior (subscapularis, teres major, latissimus dorsi), medial (upper ribs with serratus anterior), and lateral (biceps tendon and coracobrachialis).

What structures are contained within the axilla?

The axilla contains several important structures, including the axillary artery and vein, brachial plexus cords, axillary lymph nodes, long thoracic and intercostobrachial nerves, axillary tail of the breast, and fibrofatty tissue for protection.

How is the axillary artery divided and what are its branches?

The axillary artery is divided into three parts by the pectoralis minor muscle. The first part, proximal to pectoralis minor, gives off the superior thoracic artery. The second part, posterior to pectoralis minor, gives off thoracoacromial and lateral thoracic arteries. The third part, distal to pectoralis minor, gives off subscapular and circumflex humeral arteries.

What are the groups of axillary lymph nodes and their clinical significance?

Axillary lymph nodes are grouped into anterior (pectoral), posterior (subscapular), lateral, central, and apical. They are clinically significant for breast cancer spread, with sentinel nodes often being the first affected, and are routinely palpated in exams. Axillary abscesses may also arise from infected nodes.

What is the clinical importance of the axillary vein?

The axillary vein is important clinically because axillary vein thrombosis can occur due to compression or excessive overhead arm activity, leading to venous obstruction and swelling. It runs medial to the axillary artery and ends as the subclavian vein.

Why is the axilla clinically significant in physical exams?

The axilla is clinically significant in physical exams because it houses axillary lymph nodes that are key for detecting breast cancer spread. It is also a site for assessing neurovascular structures and pathologies like abscesses, which may require surgical drainage.

Axilla Anatomy – Boundaries, Contents & Lymph Nodes

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