General

From the lungs back to the heart

The blood then absorbs oxygen again, becoming oxygenated. The capillaries merge into larger and larger blood vessels, which lead to the pulmonary vein.

The pulmonary vein brings the oxygen-rich blood back to the heart. The heart then pumps the blood on to the brain, intestines, liver, kidneys and the rest of the body.

Let’s first have a look at the brain.