Overview
The axilla is a passageway between the upper arm and upper lateral thorax by which neurovascular and muscular structures can enter and leave the upper limb.
Boundaries
- Anterior wall
- Pectoralis major and pectoralis minor
- Clavipectoral fascia
- Subclavius muscle
- Posterior wall
- Latissimus dorsi
- Subscapularis
- Teres major
- Proximal part of long head of triceps
- Medial wall
- Ribs and intercostal spaces
- Upper part of serratus anterior
- Lateral wall
- Floor of bicipital (interbercular) groove of humerus
- Tendon of long head of biceps
- Tendon of latissimusdorsi
- Apex (axillary inlet)
- Posterior border of clavicle
- Superior border of scapula
- Lateral border of first rib
Lower limit of axilla is the level of the 4th rib.
Contents & Relations
- Axillary sheath, extension of prevertebral fascia
- Axillary artery – has three parts divided in relation to the pectoralis minor:
- First part: medial to pectoralis minor, gives superior thoracic artery
- Second part: posterior to pectoralis minor, gives lateral thoracic and thoracoacromial artery
- Third part: lateral to the pectoralis minor, gives subscapular, anterior and posterior circumflex humeral artery
- Only the medial and posterior parts pass through the axilla
- Axillary vein and tributaries
- Thoracoacromial vein
- Subscapular vein
- Anterior and posterior circumflex humeral vein
- Brachial vein
- Profundabrachii vein
- Inferior trunk, and all divisions of brachial plexus
- Long thoracic nerve
- Lymphatics
- Axillary lymph nodes (anterior, posterior, lateral, central and apical)
- Efferent lymph trunks
- Proximal short head of biceps brachii (muscle of the anterior compartment of the arm)
- Proximal coracobrachialis (muscle of the anterior compartment of the arm)
- Brachial plexus, divisions, cords, nerves
- Axillary process of mammary gland
Spaces
Quadrangular space
- Bound by: Teres major, subscapularis, surgical neck of humerus, long head of triceps
- Transmits: Axillary nerve, posterior circumflex humeral artery and vein
Triangular space
- Bound by: Teres major, subscapularis, long head of triceps
- Transmits: Circumflex scapular artery (branch of the subscapular artery, from the third part of the axillary artery) and vein