Pulmonary vein pulmonary vein lies in front of and a little below the pulmonary artery; the inferior is situated at the lowest part of the lung hilum. Behind the pulmonary artery is the bronchus. The right main pulmonary veins (contains oxygenated blood) pass behind the right atrium and superior vena cava; the left in front of the descending thoracic aorta. Occasionally the three lobar veins on the right side remain separate, and not infrequently the two left lobar veins end by a common opening into the left atrium. Therefore, the number of pulmonary veins opening into the left atrium can vary between
Azygos vein and usually occurs simultaneously with situs inversus, asplenia, or polysplenism, persistent left superior vena cava (SVC), and congenital pulmonary venolobar syndrome. Azygos and hemiazygos continuation of the IVC is rare especially when it is not associated with congenital heart disease. The Greek root "zyg" refers to a pair. 'A-' means "not". Thus, "azygos" means "unpaired". The azygos vein is unpaired in that there is only one in the body, mostly on the right side. While there is the hemiazygos vein and its accessory on the left side of the body, they are considered tributaries of the azygos vein rather than