Azygos vein

Vena azygos

CardiovascularBlood vesselsWhole body

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What it is

Ascends on the right side of the thoracic vertebral bodies from the upper abdomen, then arches forward over the root of the right lung at T4 to enter the back of the superior vena cava.

Function

Drains the posterior intercostal veins and the chest wall, oesophagus and bronchi; it is a collateral route between the inferior and superior venae cavae.

Size

~1 cm diameter at its arch.

Clinical note

Its name is Greek for "unpaired"; if the IVC is blocked, the azygos system can carry lower-body blood back to the heart.