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Etymology: Gk, hemi + a, without, + zygon, yoke
one of the tributaries of the azygous vein of the thorax. It starts in the left ascending lumbar vein, enters the thorax through the left crus of the diaphragm, ascends on the left side of the vertebral column as high as the ninth thoracic vertebra, and passes dorsal to the aorta to enter the azygous. The hemiazygous vein receives about four of the caudal intercostal veins, the left subcostal vein, and some of the esophageal and mediastinal veins.