Axilla
The axilla (armpit) is a pyramid-shaped space between the upper arm and thoracic wall that serves as the main passageway for neurovascular structures entering the upper limb. It contains the brachial plexus, axillary artery and vein, and numerous lymph nodes critical in breast cancer staging.
Boundaries
superior
Apex (cervicoaxillary canal): formed by clavicle, 1st rib, scapula
inferior
Base: skin and fascia of armpit
anterior
Pectoralis major and minor muscles
posterior
Subscapularis, latissimus dorsi, teres major muscles
lateral
Intertubercular groove of humerus
medial
Serratus anterior covering the ribs
Contents
Brachial plexus
Vessels
Lymph nodes
Nerves
- • Brachial plexus cords and branches
- • Long thoracic nerve (on serratus anterior)
- • Thoracodorsal nerve (to latissimus)
- • Medial and lateral pectoral nerves
- • Intercostobrachial nerve
Vessels
- • Axillary artery
- • Axillary vein
- • Thoracoacromial artery
- • Lateral thoracic artery
- • Subscapular artery
- • Anterior and posterior circumflex humeral arteries
Muscles
- • Pectoralis major (anterior wall)
- • Pectoralis minor (anterior wall)
- • Subscapularis (posterior wall)
- • Latissimus dorsi (posterior wall)
- • Teres major (posterior wall)
- • Serratus anterior (medial wall)
Clinical Relevance
- •Breast cancer: Axillary lymph node involvement is critical for staging and prognosis; sentinel node biopsy or axillary dissection
- •Long thoracic nerve injury: Causes winged scapula due to serratus anterior paralysis
- •Axillary nerve injury: From shoulder dislocation or fracture, causes deltoid weakness and shoulder sensory loss
- •Erb-Duchenne palsy: Upper brachial plexus injury (C5-6) causing "waiter's tip" position
Study Tips
- ✓Axillary artery has 3 parts (divided by pectoralis minor): 1 branch, 2 branches, 3 branches
- ✓Cords are named by their position relative to the axillary artery
- ✓Long thoracic nerve (C5-7) runs on serratus anterior - vulnerable in surgery
- ✓5 groups of lymph nodes drain to the apical group, then to subclavian trunk
Axilla FAQs
Common questions about this region
The long thoracic nerve runs superficially on the serratus anterior muscle on the medial wall of the axilla. Its exposed position makes it vulnerable during mastectomy or axillary lymph node dissection.
The axillary artery is divided into 3 parts by pectoralis minor. Part 1 (medial) has 1 branch (superior thoracic). Part 2 (posterior) has 2 branches (thoracoacromial, lateral thoracic). Part 3 (lateral) has 3 branches (subscapular, anterior and posterior circumflex humeral).