Why does the pulmonary vein not have valves?

The pulmonary veins do not have valves because the pressure exerted by the heart is strong enough to keep the blood flowing in one direction. read more

The pulmonary veins do not have valves because the pressure exerted by the heart is strong enough to keep the blood flowing in one direction. > There are four pulmonary veins, two from each lung. The left and right superior and inferior pulmonary veins carry oxygenated blood from the lungs back to the left atrium of the heart. read more

The pulmonary vein carries oxygenated blood from the lungs to the left side of the heart, from the pulmonary circulation. the heart contraction is enough to keep the blood flowing as the distance between the lungs and back to the heart is minimal compared to the systemic circulation. read more