Axillary fascia

The axillary fascia is a dense, fibrous sheet that forms the floor, or base, of the axilla (armpit). It is continuous with the deep fascia of the surrounding thorax, shoulder, and upper limb.

This fascia represents an inferolateral thickening of the pectoral fascia, which covers the pectoralis major muscle. From the pectoralis major anteriorly, the axillary fascia extends posteriorly to the latissimus dorsi muscle. At the lateral margin of the latissimus dorsi, the axillary fascia divides to envelop this muscle, extending medially to anchor into the vertebral column.

Furthermore, an upward extension of the axillary fascia passes deep to the pectoralis major, enveloping the pectoralis minor muscle, and then becomes continuous with the clavipectoral fascia. This intricate arrangement of the axillary fascia and its extensions collectively forms a comprehensive fascial envelope that supports and organizes the contents of the axilla.

A structure worth noting over here is the suspensory ligament of the axilla, which is an inferior (fibrous band-like) extension of the clavipectoral fascia that connects with the axillary fascia in the floor of the axilla. The traction exerted on the axillary fascia and the skin of the axillary floor, particularly during arm abduction, helps to maintain the characteristic concavity or hollow of the armpit.