Topic Overview

Boundaries of Axilla

Apex (Cervicoaxillary Canal)

• Bounded by:

  • Anteriorly → clavicle.

  • Posteriorly → upper border of scapula.

  • Medially → outer border of 1st rib.

• Provides passage between neck and axilla.

Base (Floor)

• Formed by:

  • Skin, superficial fascia, and axillary fascia.

• Extends between anterior and posterior axillary folds.

Anterior Wall

• Formed by:

  • Pectoralis major.

  • Pectoralis minor.

  • Clavipectoral fascia.

• Lower border of pectoralis major forms anterior axillary fold.

Posterior Wall

• Formed by:

  • Subscapularis (upper part).

  • Latissimus dorsi (lower part).

  • Teres major (lower part).

• Lower margin forms posterior axillary fold.

Medial Wall

• Formed by:

  • Upper 4–5 ribs with intercostal muscles.

  • Covered by serratus anterior.

Lateral Wall

• Formed by:

  • Intertubercular sulcus of humerus.

Contents of Axilla

1. Axillary Artery and Branches

• Continuation of subclavian artery.

• Divided into 3 parts by pectoralis minor:

  • 1st part → Superior thoracic artery.

  • 2nd part → Thoracoacromial artery, Lateral thoracic artery.

  • 3rd part → Subscapular artery, Anterior circumflex humeral artery, Posterior circumflex humeral artery.

2. Axillary Vein and Tributaries

• Lies anteromedial to axillary artery.

• Tributaries: cephalic vein, thoracoacromial vein, lateral thoracic vein, subscapular vein, circumflex humeral veins.

3. Brachial Plexus (Infraclavicular Part)

• Cords arranged around axillary artery:

  • Lateral cord → musculocutaneous nerve, part of median nerve, lateral pectoral nerve.

  • Medial cord → ulnar nerve, part of median nerve, medial cutaneous nerves of arm/forearm, medial pectoral nerve.

  • Posterior cord → axillary nerve, radial nerve, upper/lower subscapular nerves, thoracodorsal nerve.

4. Axillary Lymph Nodes

• 5 groups:

  • Pectoral (anterior).

  • Subscapular (posterior).

  • Humeral (lateral).

  • Central.

  • Apical.

• Major pathway for breast carcinoma spread.

5. Other Structures

• Long thoracic nerve (serratus anterior).

• Intercostobrachial nerve (sensory to axilla and upper arm).

• Axillary fat and areolar tissue (fills space, allows mobility).