The Axilla Overview

The Axilla Overview

• The axilla is a pyramid-shaped space located between the upper arm and the side of the chest.
• Serves as a crucial passage for nerves, blood, and lymph vessels from the neck to the upper limb.

Apex and Base

• Apex (cervico-axillary canal): The upper end of the axilla, bordered by:
  • Anterior: Clavicle
  • Posterior: Upper border of the scapula
  • Medial: Outer border of the first rib
• Base: Formed by:
  • Anterior: Pectoralis major muscle
  • Posterior: Latissimus dorsi and teres major muscles
  • Medial: Chest wall

Axillary Walls

• Anterior wall: Made up of pectoralis major, subclavius, and pectoralis minor muscles.
• Lateral wall: Composed of coracobrachialis and biceps muscles located in the bicipital groove of the humerus.
• Medial wall: Consists of upper ribs and intercostal spaces covered by the serratus anterior muscle.
• Posterior wall: Formed by subscapularis, latissimus dorsi, and teres major muscles.

Contents of the Axilla

• Axillary artery: Supplies blood to the upper limb.
• Axillary vein: Drains blood from the upper limb back to the heart.
• Lymph vessels and lymph nodes: Play a role in immune response.
• Brachial plexus: A network of nerves supplying the arm.

Axillary Artery

• Begins at the lateral border of the first rib, continuing from the subclavian artery.
• Terminates at the lower border of the teres major muscle, where it transitions into the brachial artery.
• Enclosed within the axillary sheath alongside the brachial plexus.

Axillary Artery Parts

• First part: Extends from the first rib to the upper border of the pectoralis minor.
  • Branches: Highest thoracic artery.
• Second part: Lies behind the pectoralis minor.
  • Branches:
    • Thoracoacromial artery
    • Lateral thoracic artery
• Third part: Extends from the lower border of the pectoralis minor to the teres major.
  • Branches:
    • Subscapular artery
    • Posterior circumflex humeral artery
    • Anterior circumflex humeral artery

Axillary Vein

• Formed at the lower border of the teres major by the union of the venae comitantes and the basilic vein.
• Runs medially to the axillary artery, becoming the subclavian vein at the first rib.

Brachial Plexus

• Composed of anterior rami from C5, C6, C7, C8, and T1 spinal nerves.
• Roots branch:
  • Dorsal scapular nerve (C5)
  • Long thoracic nerve (C5, C6, C7)
• Upper trunk branches:
  • Suprascapular nerve (C5, C6)
  • Nerve to subclavius (C5, C6)
• Cords branches:
  • Lateral cord: Lateral pectoral nerve, musculocutaneous nerve.
  • Posterior cord: Upper subscapular nerve, thoracodorsal nerve, lower subscapular nerve, axillary nerve, radial nerve.
  • Medial cord: Medial pectoral nerve, medial cutaneous nerves of the arm and forearm, ulnar nerve, medial root of the median nerve.

Axillary Lymph Nodes

• Comprises 20 to 30 nodes draining lymph from:
  • Lateral quadrants of the breast
  • Superficial lymph vessels
  • Thoracoabdominal walls above the umbilicus
  • Upper limb vessels
• Arranged in six groups:
  • Anterior (pectoral)
  • Posterior (subscapular)
  • Lateral
  • Central
  • Infraclavicular (deltopectoral)
  • Apical