Last revised by Joel Hng on 27 Feb 2024

The axilla (plural: axillae), colloquially known as the armpit, is a space located between the upper limb and thorax, which permits the passage of major neurovascular structures.

Gross anatomy

The axilla is pyramidal in shape with its apex opening superiorly towards the base of the neck between the subclavius muscle, first rib, superior border of the scapula and clavicle. The base/floor is composed of tough axillary fascia, which extends between the chest wall (at the level of the 4th rib), arm, and the posterior boundary.

The intercostobrachial nerve supplies the skin of the axilla.


The axilla has an abundance of fat, which surrounds the following structures to allows movement during scapulothoracic motion: 

A safe technique for insertion of intercostal catheters describes anatomical landmarks involving the axilla and a 'triangle of safety'.

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