Anatomy of the Axilla and Axillary Dissection [Simplified with Mnemonics]

The axilla, a pyramidal-shaped structure located between the chest wall and the upper arm, is filled with fatty tissues for cushioning.

The apex, also known as the cervicoaxillary canal, allows structures to pass from the neck to the upper limb. It is bordered by the clavicle, scapula (specifically the upper border), and the first rib (lateral border).

The anterior wall of the axilla is formed by two main muscles: the pectoralis major (superficial) and the pectoralis minor (deep), along with the subclavius and the clavipectoral fascia, which includes suspensory ligaments.

The medial wall consists of the upper four ribs, their corresponding intercostal spaces and muscles, and the serratus anterior muscle.

The posterior wall is composed of three muscles: the subscapularis, latissimus dorsi, and teres major. The latissimus dorsi and teres major originate from the intertubercular groove of the humerus.

The lateral wall includes the intertubercular groove of the humerus and the tendons of the long head of the biceps brachii, coracobrachialis, and short head of the biceps brachii.

The base of the axilla is formed by the axillary fascia and the skin. The concavity of the armpit is due to the suspensory ligament pulling up the axillary fascia.

The axilla contains three major components: the neurovascular bundle, fats, and lymph nodes. The neurovascular bundle includes the cords of the brachial plexus, intercostobrachial nerve, long thoracic nerve of Bell, axillary artery, and axillary vein. Fats include fibro-fatty tissue and the axillary tail of the breast (tail of Spence). The axilla also contains axillary lymph nodes.

Axillary dissection is a surgical procedure to remove axillary lymph nodes, often due to conditions like breast cancer. During this procedure, certain structures are at risk of damage, including the thoracodorsal nerve, intercostobrachial nerve, long thoracic nerve of Bell, and thoracodorsal artery.