Bronchial Arteries

The bronchial arteries are the primary systemic vessels responsible for supplying oxygenated blood to the conducting airways, supporting lung structures, and part of the esophagus. Unlike the pulmonary arteries, which carry deoxygenated blood for gas exchange, bronchial arteries nourish the bronchial walls, connective tissue, lymph nodes, and visceral pleura of the lungs. They arise directly from the thoracic aorta or indirectly via intercostal or subclavian branches.

Origin

There is variability in the number and origin of bronchial arteries, but the classic pattern includes:

• Two left bronchial arteries: Arise directly from the descending thoracic aorta
• One right bronchial artery: May arise from the third posterior intercostal artery or from a common trunk with the left superior bronchial artery

Despite this "2 left, 1 right" pattern being common, additional accessory arteries may also be present.

Course

Each bronchial artery follows the bronchial tree into the lung hilum and then runs along the posterior wall of the bronchi, descending with them and dividing as the bronchial tree branches. They give off numerous small vessels that supply the bronchial walls, peribronchial connective tissue, pulmonary lymph nodes, and visceral pleura.

The bronchial arteries enter the lung along the posterior surface of the main bronchi, accompanying the bronchial branches down to the terminal bronchioles.

Distribution and Supply

Structures supplied by the bronchial arteries include:

• Walls of the bronchi and bronchioles (up to respiratory bronchioles)
• Peribronchial connective tissue
• Visceral pleura (in part)
• Pulmonary arteries and veins (vasa vasorum)
• Thoracic esophagus (via esophageal branches)
• Bronchopulmonary lymph nodes

Anastomoses

Bronchial arteries form small anastomoses with pulmonary arteries and veins within the lung. These connections contribute to minor mixing of systemic and pulmonary blood and are important in collateral circulation during pulmonary artery obstruction.

Bronchial arteries may also anastomose with branches of the esophageal arteries and intercostal arteries in the mediastinum.

Venous Drainage

Venous return from the bronchial circulation occurs via bronchial veins, which are distinct from the pulmonary veins. These veins drain only a portion of the blood delivered by bronchial arteries; the rest returns via pulmonary veins, contributing to physiological right-to-left shunting.

• Right bronchial veins: Drain into the azygos vein
• Left bronchial veins: Drain into the accessory hemiazygos or left superior intercostal vein

Topographic Relations

• Anterior: Pulmonary arteries (as bronchial arteries lie posterior to bronchi)
• Posterior: Esophagus and vertebral bodies
• Lateral: Pulmonary hila

Histological Structure

Bronchial arteries have thick walls typical of systemic arteries:

• Tunica intima: Endothelium with subendothelial connective tissue
• Tunica media: Rich in smooth muscle and elastic fibers
• Tunica adventitia: Contains vasa vasorum and sympathetic nerve fibers

Clinical Relevance (Minimal)

• Hemoptysis: Massive hemoptysis in patients with chronic pulmonary diseases (e.g., bronchiectasis, tuberculosis) often originates from bronchial arteries due to their systemic pressure and hypertrophy.
• Bronchial artery embolization (BAE): A minimally invasive procedure used to control bleeding by selectively occluding hypertrophied or abnormal bronchial arteries using embolic agents.

Topographic Summary

• Number: Typically two on the left and one on the right
• Origin: Thoracic aorta or intercostal/subclavian branches
• Supplies: Bronchi, connective tissue, pleura, and esophagus
• Drains into: Azygos system and pulmonary veins (indirectly)