- Azygos system: azygos, hemiazygos and accessory hemiazygos veins, lying anterior to the thoracic vertebral column.
- Connect the superior vena cava (SVC) and inferior vena cava (IVC)
- Drain the thoracic wall and upper lumbar region
- "Azygos" means single, without a companion:
- Only the azygos vein is unpaired, on the right side
- Hemiazygos and accessory hemiazygos veins are its left-sided counterparts, mirroring its lower and upper parts respectively
azygos, hemiazygos and accessory hemiazygos veins Azygos, hemiazygos and accessory hemiazygos veins.