azygos

The azygos vein is a vein that drains the thoracic and abdominal walls, as well as the walls of the posterior thoracic and abdominal cavities. It is an important venous structure that provides an alternative route for blood flow when the superior vena cava is obstructed. The azygos vein originates in the abdomen and ascends through the thorax, eventually draining into the superior vena cava or the right atrium of the heart.