Lungs: blood supply, lymphatic drainage and nerve supply

Abstract

The pulmonary arteries, through their capillary plexus, are entirely concerned with alveolar gaseous exchange, while the nutrient supply of the lung parenchyma is provided by the bronchial arteries. The pulmonary vein tributaries derive partly from the capillaries of the bronchial and the pulmonary arteries. The bronchial veins drain the larger bronchi. The lymphatics of the lungs drain into the nodes lying at the bifurcations of the larger bronchi, then to the tracheobronchial nodes and then into the broncho-mediastinal lymph trunk on each side. These usually drain directly into the junction of the internal jugular and subclavian veins on each side, but may drain, on the right, into the right lymph trunk and, on the left, into the thoracic duct. If the subcarinal node is the site of secondary deposits it gives the typical bronchoscopic sign of widening of the carina. The principal function of the sympathetic (T2-4) supply to the lung is bronchodilatation, while the vagus fibres act as stretch receptors.