part of part of connected to connected to develops from develops from system anterior vena cava azygos vein azygos venous tree An unpaired vein which in humans arises from the right ascending lumbar vein or the vena cava, enters the thorax through the aortic orifice in the diaphragm, and terminates in the superior vena cava; unlike humans, mice have a single and left-sided azygos vein that develops from the paired embryonic cardinal venous system and drains most of the right and left thoracic walls into the left anterior vena cava[MP]. MESH:D001401 MA:0002085 galen:AzygosVein Wikipedia:Azygos_vein FMA:4838 GAID:528 NCIT:C53029 UBERON:0001594 EMAPA:18250 vein right supracardinal vein