What happens to the blood carried by vessels that drain directly into the inferior vena cava?

The question did not specify whether or not the heart of interest was a two, three, or four-chamber heart. Please note that the answer reflects the path that blood takes through a four-chamber heart that is composed of two atria and two ventricles.

Blood that is dumped into the inferior vena cava has been used by the body. Thus, the blood is deoxygenated and is returning to the heart. The path of the blood from the inferior vena cava in a four-chambered heart is sequenced below.  

• Oxygen-poor blood that has been used by the cells is delivered back to right atrium via the inferior or superior vena cava.


• The right atrium pumps this oxygen-depleted blood to the right ventricle.


• The right ventricle then pumps the blood to lungs, where oxygen is received.


• The oxygenated blood is brought back to the heart via the pulmonary veins.


• The pulmonary veins enter the left atrium.


• The left atrium receives this oxygen-rich blood from the pulmonary veins and pumps it to the left ventricle.


• The left ventricle then pumps the oxygenated blood to the body.

The oxygen is then used by the mitochondria of the vertebrate eukaryotic cells in the process that is known as cellular respiration. Cellular respiration occurs in the mitochondria of eukaryotic cells. During cellular respiration, oxygen gas and the sugar glucose are converted into water, carbon dioxide gas, and an energy source called adenosine triphosphate (ATP).

Once the blood has been delivered to the cells of the body and its oxygen has been used, the blood is again returned to the heart via the right atrium via either the superior or inferior vena cava. Thus, the cycle continues.