Corpus: Posterior intercostal veins

The posterior intercostal veins are located in the posterior intercostal space, running above the corresponding posterior intercostal artery along the lower edge of each rib.

The intercostal vein of the 1st intercostal space, known as the supreme intercostal vein, drains into the vertebral vein or the brachiocephalic vein. The remaining posterior intercostal veins follow this drainage pattern:

• On the right side, they drain into the azygos vein. Veins from the 2nd and 3rd intercostal spaces drain through the superior intercostal vein, which mirrors the arrangement of the arteries.
• On the left side, the veins drain into the hemiazygos vein (for caudal spaces) or the hemiazygos accessoria vein (for cranial spaces).

The posterior intercostal veins are responsible for draining the posterior and lateral walls of the trunk, including both the external and internal vertebral venous plexuses.