Bronchial veins

Anatomy and course

The bronchial veins are small veins draining the larger bronchi and other structures of the lung close to the hilum. There are usually two sets of veins for each of the lungs. Each set of bronchial veins is divided into deep and superficial bronchial veins.

• The deep bronchial veins receive blood from the intrapulmonary bronchiolar plexuses and therefore drain the larger intrapulmonary bronchi. They form a common trunk which drains into the main pulmonary vein or sometimes directly into the left atrium.
• The superficial bronchial veins consist of a subpleural venous network that commences towards the hilum of the lung. Along the way, they receive tributaries that drain the extrapulmonary bronchi. Upon entering the hilum of the lungs, they also drain the visceral pleura around the hilum and hilar lymph nodes. The superficial bronchial veins terminate by draining into the azygos vein on the right, and the accessory hemiazygos or left superior intercostal vein on the left. Just like the deep bronchial bronchial veins, they communicate with the pulmonary veins.

The communication between the bronchial and the pulmonary veins is important physiologically. The pulmonary veins are part of the pulmonary circulation, while the bronchial veins belong to the systemic circulation. The pulmonary circulation starts with the pulmonary arteries carrying deoxygenated blood to the lungs. These arteries are sequentially divided corresponding to the division of the tracheobronchial tree, ending as very fine capillaries in the walls of the alveoli, in which gas exchange occurs. At this point, the blood becomes 100 percent oxygenated and carried away from the alveoli by the pulmonary veins.

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On the other hand, being part of the systemic circulation, the bronchial veins carry blood that is oxygen poor. The mixing that occurs between the oxygenated blood from the pulmonary veins and the deoxygenated blood from the bronchial veins ensures that the blood within the pulmonary veins returns to the heart as only around 95 percent oxygenated, instead of 100 percent.

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