Walls of the Axilla

Mnemonic

Four walls, remembered by what forms each:

• Anterior - Pectoralis major and minor
• Posterior - Subscapularis, teres major, latissimus dorsi. “A lady between two majors” places latissimus dorsi between teres major and pectoralis major at the humerus
• Medial - Serratus anterior over the ribs
• Lateral - the intertubercular groove of the humerus, the narrowest wall

The lateral wall is a groove rather than a muscle, which is why the axillary contents converge there to enter the arm.

Expansion

• Anterior wall - pectoralis major, pectoralis minor and subclavius
• Posterior wall - subscapularis, teres major and latissimus dorsi
• Medial wall - serratus anterior over the upper ribs
• Lateral wall - the intertubercular groove of the humerus

The apex opens into the neck through the cervicoaxillary canal, and the base is the skin of the armpit.