It is a large-diameter (24 mm) short length vein that receives venous return from the upper half of the body, above the diaphragm.

[citation needed] The superior vena cava is formed by the left and right brachiocephalic veins, which receive blood from the upper limbs, head and neck, behind the lower border of the first right costal cartilage.

It passes vertically downwards behind the first intercostal space and receives the azygos vein just before it pierces the fibrous pericardium opposite the right second costal cartilage and its lower part is intrapericardial.

The superior vena cava is made up of three layers, starting with the innermost endothelial tunica intima.

Obstruction can lead to enlarged veins in the head and neck, and may also cause breathlessness, cough, chest pain, and difficulty swallowing.