Hemiazygous vein

Hemiazygous Vein

The hemiazygous vein is a significant vein located within the thoracic region of the human body. It plays a crucial role in the venous drainage system, particularly in the collection and return of deoxygenated blood from the lower half of the body back to the heart. This vein is part of the azygos system of veins, which is a network of veins that provides an alternate pathway for blood to return to the heart, bypassing the inferior vena cava when necessary.

Anatomy

The hemiazygous vein originates from the left ascending lumbar vein and runs superiorly on the left side of the vertebral column. At approximately the level of the ninth thoracic vertebra, it crosses over to the right side, typically behind the aorta, to join the azygos vein. The exact origin and course of the hemiazygous vein can vary significantly among individuals.

Throughout its course, the hemiazygous vein receives blood from various tributaries, including the lower posterior intercostal veins, which drain the lower thoracic wall, and the left subcostal vein. It may also receive blood from the left bronchial veins, thereby participating in the drainage of the lungs and bronchi.

Function

The primary function of the hemiazygous vein is to collect deoxygenated blood from the posterior walls of the thorax and abdomen and convey it to the azygos vein, which then drains into the superior vena cava. This pathway is particularly important in conditions where the inferior vena cava is blocked or narrowed, as it provides an alternative route for venous return to the heart.

Clinical Significance

The hemiazygous vein is of clinical significance due to its involvement in various medical conditions. Enlargement or dilation of the hemiazygous vein can be an indicator of increased pressure in the venous system, which may be due to obstruction of the inferior vena cava or heart failure. Additionally, during certain surgical procedures in the thoracic cavity, the hemiazygous vein may need to be navigated carefully to avoid complications.

See Also

• Azygos vein
• Superior vena cava
• Inferior vena cava
• Venous system