C) Axilla

The axilla is a space located between the medial arm and the chest wall.

Structure / Boundaries

The apex of the axilla is directed superomedially, and is formed by the medial aspect of the coracoid process, the lateral aspect of the first rib, the superior border of the scapula and the inferior aspect of the clavicle.
The posterior border of the axilla is formed by the subscapularis muscle, with teres major and latissimus dorsi forming the inferior part.
The anterior border of the axilla is formed by the deep margin of pectoralis major and minor. Above the pectoralis minor, the clavicopectoral fascia forms the boundary.
The narrow lateral border is formed by the intertubecular sulcus, between the attachments of latissimus dorsi and pectoralis major
The medial border is formed by the chest wall and the attachment of serratus anterior.
The base of the axilla is covered with skin and axillary fascia, forms a triangle between the chest wall and the inferior borders of pectoralis major and latissimus dorsi


At its apex, the axilla communicates with the root of the neck through the cervico-axillary canal. The base has no relations.
The axilla is related posteriorly with the subscapularis and scapula, and anteriorly with the pectoral muscles and clavicopectoral fascia.
Medially, the axilla is related to serratus anterior, the chest wall (ribs, intercostal muscles and vessels), and deep to those the lung.
Laterally, the intertubercular sulcus houses the short tendon of biceps brachii and coracobrachialis.


The axilla contains the axillary artery, axillary vein, and the subclavicular divisions of the brachial plexus. These all run within a neurovascular bundle from apex to the base along the lateral boundary, more anteriorly than posterior.
The anterior wall carries thoracic branches from the artery and vein. The subscapular vessels follow the posterior wall at the border of subscapularis. The long thoracic nerve descends above serratus anterior on the medial wall.
The axillary tail of the breast often extends from the chest wall into the axilla.
Numerous lymph nodes are located in the axilla, divided into pectoral, subscapular, lateral, central and apical groups.