Formation

Union of left ascending lumbar and right sub costal veins

Components

• Azygous vein
• Hemiazygous veins
• Accessory hemiazygous veins.

Tributaries and territory of drainage

• The intercostal veins on the right drain into the azygous vein; while those on the left drain into the hemiazygous and accessory hemiazygous.
• Drains thoracic and abdominal walls
• Connects superior and inferior vena cava

Termination

• It joins the superior vena cava at the level of the sternal angle.