The Axilla

The anatomical snuff-box | Main Anatomy Index | The brachial plexus

The Axilla

• The axilla (armpit) is a roughly pyramidal-shaped space at the junction of the arm and thorax.
• It provides a passageway for the large, important nerves and vessels to reach the upper limb.
• The axilla has an apex, a base and four walls.

The Apex of the Axilla (p. 510)

• The apex is directed toward the root of the neck and is located at the medial side of the roof of the coracoid process of the scapula.

• It is formed by the convergence of the bones in its three major walls: the clavicle (anterior wall), the scapula (posterior wall) and the first rib (medial wall).
• The interval between these 3 bones is the entrance to the axilla through which all nerves and vessels pass to the upper limb.

The Base of the Axilla (p. 511)

• The base, facing inferiorly, is formed by the fascia and skin of the concave axilla.

The Anterior Wall of the Axilla (p. 511)

• The clavicle and pectoral muscles form the anterior wall.
• The lateral border of the pectoralis major forms the anterior axillary fold.
• Posterior to the pectoralis major, the pectoralis minor and subclavius muscles form the deep layer of the anterior wall.

The Posterior Wall of the Axilla (p. 511)

• This wall is formed chiefly by the scapula and the subscapularis muscle.
• Inferior to the subscapularis is the teres major muscle, which combines with the latissimus dorsi to form the posterior axillary fold.

• The tendon of the latissimus dorsi muscle wraps around the lateral part of the teres major and forms part of the posterior wall.

The Medial Wall of the Axilla (p. 511)

• The ribs and intercostal muscles form this wall.
• These are covered by the serratus anterior muscle. This muscle forms the majority of the medial wall.

The Lateral Wall of the Axilla (p. 511)

• This narrow wall is formed by the intertubercular groove in the humerus.

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Contents of the Axilla (p. 512)

• The axilla contains large nerves that are the branches of the brachial plexus.
• These nerves pass from the neck to the upper limb.
• The axilla also contains the axillary vessels (artery and branches, vein and tributaries, and lymph vessels).
• There are also several groups of axillary lymph nodes.

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