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Retract the esophagus laterally and to the left to expose the azygos vein [cross-section] [cross-section ], which is a continuation of the right ascending lumbar vein. On the right side, the azygos vein receives venous blood from a number of posterior intercostal veins [probe] (from the fifth through the eleventh intercostal spaces) and the right superior intercostal vein [probe]. The azygos vein arches above the root of the right lung and enters the superior vena cava about the level of the fourth thoracic vertebra (Figure 21.5).

Links and References:
Grant's: 1.86, 1.87
Netter: 226
Rohen/Yokochi: 261