Azygos vein

(Ascends through the aortic opening in the diaphragm) (213-BDC-l) (128-Snell 7th)AZYGOS VEIN - The origin of the azygos vein is variable. It is often formed by the union of the right ascending lumbar vein and the right subcostal vein. It ascends through the aortic opening in the diaphragm on the right side of the aorta to the level of the fifth thoracic vertebra. Here it arches forward above the root of the right lung to empty into the posterior surface of the superior vena-cava.* In obstruction of the superior or inferior vena cava, the azygos veins provide an alternate pathway for the return of venous blood to the right atrium of the heart.