- Axilla (armpit): pyramidal space between the upper arm and the chest wall, bounded in front and behind by axillary folds.
- Acts as a funnel-shaped passage for neurovascular structures between the root of the neck and the upper limb; its lymph nodes drain the upper limb and the breast.
Boundaries
- Truncated four-sided pyramid with an apex, a base and four walls (anterior, posterior, medial, lateral); apex directed upward and medially toward the root of neck, base directed downward.
Boundaries of the axilla
Boundary
Apex (cervico-axillary canal)
- Formed by
- Clavicle in front, upper border of scapula behind, outer border of first rib medially
Base (floor)
- Formed by
- Axillary fascia; hollow bounded by anterior axillary fold (pectoralis major), posterior axillary fold (latissimus dorsi and teres major), chest wall medially
Anterior wall
- Formed by
- Pectoralis major, subclavius, pectoralis minor
Posterior wall
- Formed by
- Subscapularis above; latissimus dorsi and teres major below
Medial wall
- Formed by
- Upper four or five ribs and intercostal spaces, covered by serratus anterior
Lateral wall
- Formed by
- Tendon of biceps brachii (bicipital groove), coracobrachialis, short head of biceps brachii