Pulmonary veins
Venae pulmonales
Definition
Pulmonary veins are blood vessels that carry oxygenated blood from the lungs to the left atrium of the heart. They are unique among veins in the body because they carry oxygen-rich blood rather than deoxygenated blood.
The pulmonary veins typically exist as four distinct branches:
But anatomic variations are common. In approximately 71% of individuals, the classic four-vein pattern is present, while about 19% have an additional middle right pulmonary vein. The veins drain into the posterior wall of the left atrium, with each vein surrounded by a myocardial sleeve that extends from the left atrium onto the adventitial surface of the pulmonary vein. This myocardial sleeve is clinically significant as it plays a critical role in the initiation and maintenance of atrial fibrillation.
Structurally, the pulmonary veins have a unique composition. The tunica media contains an outer layer of cardiac muscle cells and an intermediate smooth muscle cell layer lining the inner endothelium. This differs from typical veins and reflects their embryologic origin as an outgrowth of atrial cells that anastomose with the pulmonary venous plexus during development.
References
