Pulmonary veins (anatomy)

The pulmonary veins are unique in so much as they are veins carrying largely oxygenated blood. They originate in the parenchyma of the lung where they drain both:

• the deep system of bronchial veins
• the alveoli as a direct continuation of the pulmonary capillaries

They converge to the septa between lobules, segments and then lobes, becoming ever larger vessels in sequence. During this course, they tend to run on the anterior surface of the associated bronchus. At the hila of the lungs the segmental veins form four main pulmonary veins which pass medially to converge on the left atrium:

• left superior pulmonary vein
• left inferior pulmonary vein
• right superior pulmonary vein
• right inferior pulmonary vein

In a quarter of the population, there is just one common pulmonary vein entering the left atrium. Rarely, there may be three pulmonary veins on the left.

The system of pulmonary veins must be contrasted with the bronchial veins.