Veins of the small (pulmonary) circulation.

Pulmonary veins. Venae pulmonales, pulmonary veins, carry arterial blood from the lungs to the left atrium. Starting from the capillaries of the lungs, they merge into larger veins, reaching the bronchi, segments and lobes, respectively, and in the gates of the lungs they form large trunks, two trunks from each lung (one is the top, the other is the bottom) to the left atrium and fall into its upper wall, each trunk flows into a separate hole: the right – at the right, left – at the left edge of the left atrium. The right pulmonary veins on the way to the left atrium cross transversely the back wall of the right atrium. The symmetry of the pulmonary veins (two on each side) is obtained because the trunks extending from the upper and middle lobes of the right lung merge into one trunk. The pulmonary veins are not completely separated from the veins of the pulmonary circulation, as they anastomose with the bronchial veins flowing into the v. azygos. Valves pulmonary veins do not have.