The brachiocephalic vein, also known as an innominate vein, is a vein that returns oxygen-depleted blood from the upper limbs, neck, and head to the heart through its continuation, the superior vena cava. It is formed at the level of the clavicle, precisely posterior to the sternal end of the clavicle, by the merging of inferior jugular veins (IJV) with the subclavian vein. The left brachiocephalic vein is usually longer than the right. These great vessels (left and right brachiocephalic veins) merge to form the superior vena cava behind the junction of the first costal cartilage with the manubrium sternum.
During embryogenesis, the left brachiocephalic vein is formed by an anastamosis formed between the left and right anterior cardinal veins following the degeneration of the caudal portion of the left anterior cardinal vein.
The brachiocephalic veins are located on the left and right side of the neck. The brachiocephalic vein on the left side of the neck is approximately 6 to 8 cm in length, while the brachiocephalic vein on the right is approximately 2 cm long. The two brachiocephalic veins merge together, with very small contribution from the azygous vein carrying deoxygenated blood from the rib cage, to form the superior vena cava. The blood that flows into the heart from the superior vena cava is controlled by the contractions of the heart. Hence the azygous vein also returns blood to the brachiocephalic vein. In addition, the brachiocephalic veins also receive drainage from the:
- Left and right internal thoracic veins, which drain into the inferior border of their corresponding vein
- Left and right inferior thyroid veins, which drain into the superior aspect of their corresponding veins near the confluence
- Left superior intercostal vein, which drains into the left brachiocephalic vein