Accessory hemiazygos vein

Definition

The accessory hemiazygos vein (vena azygos minor superior) is a vein on the left side of the vertebral column that generally drains the fifth through eighth intercostal spaces on the left side of the body[WP].

Also known as accessory hemi-azygos vein, superior hemi-azygos vein, vena azygos accessoria, vena hemiazygos accessoria — per UBERON

The Accessory hemiazygos vein is a part of the Cardiovascular.