Pulmonary vein three and five in the healthy population. The two left lobar veins may be united as a single pulmonary vein in about 25% of people; the two right veins may be united in about 3%. The pulmonary veins play an essential role in respiration, by receiving blood that has been oxygenated in the alveoli and returning it to the left atrium. As part of the pulmonary circulation they carry oxygenated blood back to the heart, as opposed to the veins of the systemic circulation which carry deoxygenated blood. A rare genetic defect of the pulmonary veins can cause them to
Caput medusae Determine the direction of flow in the veins below the umbilicus. After pushing down on the prominent vein, blood will: Caput medusae Caput medusae, also known as palm tree sign, is the appearance of distended and engorged superficial epigastric veins, which are seen radiating from the umbilicus across the abdomen. The name "caput medusae" (Latin for "head of Medusa") originates from the apparent similarity to Medusa's head, which had venomous snakes in place of hair. It is also a sign of portal hypertension. It is caused by dilation of the paraumbilical veins, which carry oxygenated blood from mother to fetus