axila

Axila, commonly referred to in English as the axilla or armpit, is a pyramidal-shaped region at the junction between the upper limb and the thorax. It serves as a passage and compression space for vessels, nerves, and lymphatics moving to and from the arm, shoulder, chest wall, and breast. The axilla forms a link between the neck and the upper limb and plays a key role in the vascular and neural supply of the upper extremity.

The boundaries of the axilla define its compact space. The apex is at the cervicothoracic inlet borders formed by the clavicle, first rib, and superior border of the scapula. The base is the skin and subcutaneous tissue of the axillary fold. Anteriorly are the pectoralis major and minor and the subclavius; posteriorly lie the subscapularis, teres major, and latissimus dorsi; medially is the upper depth of the thoracic wall with serratus anterior; laterally the intertubercular sulcus of the humerus serves as the boundary.

Contents typically include the axillary artery and vein with their branches and tributaries, the cords and branches of the brachial plexus, axillary lymph nodes (including sentinel nodes in some clinical contexts), fat, and lymphatic vessels. Several nerves pass through the axilla, such as the thoracodorsal, long thoracic, and various pectoral nerves, which supply the shoulder girdle and upper limb.

Clinical significance arises from the axilla’s role in vascular and nerve supply to the arm and its lymphatic drainage of the breast and upper limb. The region is a common site for breast cancer metastasis and is a focal point for procedures such as axillary lymph node dissection and sentinel node biopsy. Understanding its anatomy aids in managing injuries, surgeries, and regional anesthesia.