Hemiazygos vein

A vein that plays a crucial role in draining blood from the thorax and abdomen.

The hemiazygos vein is a significant vein in the human body that contributes to the venous drainage of the thorax and abdomen. It primarily collects blood from the left side of the body's lower regions and directs it towards the superior vena cava, which ultimately returns blood to the heart.

Terminologia Anatomica

vena hemiazygos

System

Circulatory system

Function

The primary function of the hemiazygos vein is to transport deoxygenated blood from the left side of the torso to the heart. It collects blood from various sources, including the lower ribs, muscles, and skin on the left side. This vein connects with the azygos vein, forming a crucial pathway for venous return, particularly in circumstances where the superior vena cava is obstructed. The hemiazygos vein plays an essential role in maintaining proper blood circulation within the thoracic cavity, ensuring that blood flow remains adequate even when other vessels are compromised. Its ability to act as a collateral pathway during such instances highlights its importance in the venous system.

Location

The hemiazygos vein is located on the left side of the vertebral column, positioned posterior to the aorta and the thoracic organs. It typically begins in the lumbar region, ascending along the left side of the thoracic vertebrae. The vein passes through the diaphragm at the T9 vertebral level and ultimately drains into the azygos vein, which sits on the right side of the spine. This arrangement allows the hemiazygos vein to bridge the venous flow from the body's left side to the right side before returning to the heart. The hemiazygos vein runs adjacent to the thoracic duct, the major lymphatic vessel in the body, emphasizing the close anatomical and functional relationship between the venous and lymphatic systems.

Did You Know?

The hemiazygos vein frequently receives contributions from the left renal vein and several intercostal veins.
In some individuals, the hemiazygos vein can be absent or replaced by a more developed accessory hemiazygos vein.
The hemiazygos vein serves as a crucial bypass route for venous blood in cases of obstruction in other major veins.