BLOOD’S JOURNEY
Blood is constantly passing through the heart through four main openings: the pulmonary artery, pulmonary vein, aorta and vena cava. When the oxygen from blood has been used up, the deoxygenated blood travels into a chamber on the heart’s right side – the atrium. Blood from the upper body enters via a blood vessel called the superior vena cava, while blood returning from the lower body flows through the inferior vena cava. The heart then contracts, forcing blood out of the right atrium and into a lower chamber called the ventricle. As this ventricle contracts, blood is pumped through the pulmonary artery and to the lungs, where it will pick up oxygen and release carbon dioxide to be expelled from the body. After visiting the lungs, oxygen-rich blood is ready to be sent around the body. It returns to the heart into the left atrium, where the same contractions provide the energy to send it out through the aorta and around a network of arteries throughout the body.