AXILLA

DEFINE AXILLA

The axilla is the name given to an area that lies underneath the glenohumeral joint, at the junction of the upper limb and the thorax.

This region is a passage by which structures such as vessels and nerves can enter and leave the up[image]per limb.

               Borders of Axilla

The overall 3D shape of the axilla looks slightly like a pyramid. The borders consist of four sides and a base with an opening at the apex.

• Apex –  Also known as the axillary inlet, this is formed by lateral border of the first rib, superior border of scapula, and the posterior border of the clavicle.

• Lateral wall – Formed by intertubecular groove of the humerus.

• Medial wall – Consists of the serratus anterior and the thoracic wall (ribs and intercostal muscles).

• Anterior wall – Contains the pectoralis major and the underlying pectoralis minor and the subclavius muscles.

• Posterior wall – Formed by the subscapularis, teres major and latissimus dorsi.

The size and shape of the axilla region varies with arm abduction. It decreases in size most markedly when the arm is fully abducted – at this point, the contents of the axilla are at most risk of injury

Passageways Exiting the Axilla

1)The main route of exit is immediately inferiorly and laterally, into the upper limb. The majority of contents of the axilla region leave by this method.

2) the quadrangular space.This is a gap in the posterior wall of the axilla, allowing access to the posterior arm and shoulder area. Structures passing through include the axillary nerve and posterior circumflex humeral artery (a branch of the axillary artery.

3)The last passageway is the clavipectoral triangle, which is an opening in the anterior wall of the axilla. It is bounded by the pectoralis major, deltoid, and clavicle. The cephalic vein enters the axilla via this triangle, while the medial and lateral pectoral nerves leave.