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Azygos vein: anatomy, location and function

The azygos vein is the main vein on the right of the thoracic spine, draining the chest wall and connecting the two venae cavae. It drains the posterior thoracic wall and mediastinal organs and offers a collateral route for blood between the IVC and SVC.

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Highlighted in the model: Azygos vein. Click any part to read about it, or switch off “Highlight topic” to see the whole body. 3D data: BodyParts3D, © The Database Center for Life Science, CC BY 4.0; meshes simplified and recoloured. The model is an adult male.

Azygos vein at a glance

What it is
The azygos vein is the main vein on the right of the thoracic spine, draining the chest wall and connecting the two venae cavae.
Location
It begins from the right ascending lumbar and right subcostal veins, passes through the diaphragm, ascends right of the vertebral bodies and arches over the root of the right lung at about T4 to drain into the superior vena cava. It receives the hemiazygos, accessory hemiazygos, right posterior intercostal, bronchial and esophageal veins.
Function
It drains the posterior thoracic wall and mediastinal organs and offers a collateral route for blood between the IVC and SVC.
Body system
Cardiovascular · single, midline structure
FMA ID
FMA4838 (Foundational Model of Anatomy)

Key facts

  • Azygos means unpaired.
  • Its arch is a landmark on chest imaging and at surgery, lying above the root of the right lung.

Clinical relevance

It enlarges when the IVC or SVC is obstructed.

Structures next to the azygos vein

The nearest named structures in the 3D model, measured from the centre of each part:

References

  1. Foundational Model of Anatomy: Azygos vein (FMA4838). EMBL-EBI Ontology Lookup Service.
  2. OpenStax. Anatomy and Physiology 2e, §20.1 Structure and Function of Blood Vessels. Rice University, 2022.
  3. Mitsuhashi N. et al. (2009). BodyParts3D: 3D structure database for anatomical concepts. Nucleic Acids Research 37, D782–D785. Data © The Database Center for Life Science, CC BY 4.0.

Explore the whole body in the interactive 3D human anatomy model, or browse the A–Z list of human structures.