The left pulmonary vein is a component of the human circulatory system, playing a role in blood movement. Its purpose is transporting blood back to the heart. This vessel is an important part of the body’s network of blood vessels that ensures proper blood flow.
Anatomy and Location
The left pulmonary vein originates from the left lung and drains into the left atrium of the heart. There are two main left pulmonary veins: the left superior pulmonary vein and the left inferior pulmonary vein. The left superior pulmonary vein collects oxygenated blood from the upper lobe and the lingula of the left lung. The left inferior pulmonary vein drains the lower lobe of the left lung.
As the left superior pulmonary vein exits the hilum, or root, of the left lung, it is positioned anterior to the left main bronchus and anteroinferior to the left pulmonary artery. It then travels medially, crossing anterior to the descending thoracic aorta before entering the posterosuperior aspect of the left atrium. The left inferior pulmonary vein, upon exiting the left lung hilum, passes medially and inferior to both the left pulmonary artery and the left main bronchus. It then merges with the pericardium to join the posterior border of the left atrium, situated inferior to the insertion point of the left superior pulmonary vein.
Role in the Circulatory System
The left pulmonary vein functions within the pulmonary circulation, the system of blood vessels moving blood between the heart and the lungs. This vein transports oxygenated blood from the left lung back to the heart. Unlike most veins in the body that carry deoxygenated blood, pulmonary veins are distinctive because they carry blood rich in oxygen.
After receiving oxygen in the lungs, blood flows into the left pulmonary vein. From there, it is directed into the left atrium, the upper left chamber of the heart. This oxygen-rich blood then moves from the left atrium into the left ventricle, which pumps it out to the rest of the body through the aorta. This cycle ensures oxygenated blood delivery throughout the body.
Common Anatomical Variations
While a standard configuration of two left pulmonary veins exists, anatomical variations are common and generally do not cause health problems. Approximately 38% of people have anatomical differences in their pulmonary vein structure, affecting the number of veins or their entry into the left atrium. One common variation involves the two left pulmonary veins merging into a single shared trunk before connecting with the left atrium. This “common left-sided trunk” means the blood drains through one opening instead of two, and this variation is observed in about 15% of individuals.
Other variations can include the presence of additional, or “accessory,” pulmonary veins, although these are more frequently observed on the right side of the heart. The entry points of the veins into the left atrium can also vary; for example, the ostia (openings) of the left pulmonary veins may be positioned more superiorly compared to the right pulmonary veins. Less common are conditions like partial anomalous pulmonary venous return (PAPVR), where one or more pulmonary veins connect to the right side of the heart or systemic veins instead of the left atrium. For instance, left upper lobe PAPVR, though rare, can involve the left superior pulmonary vein draining into the left brachiocephalic vein.