The flow of blood through the heart
- De-oxygenated blood flows through the superior and inferior vena cava into the right atrium.
- The atrium walls contract, the atrioventricular valve opens and blood flows through the atrioventricular valve into the right ventricle, which relaxes at the same time.
- The ventricle muscles contract forcing blood out of the ventricle. The blood cannot run back into the atrium because the blood flow closes the atrioventricular valve. The pressure of the blood forces open the pulmonary valve and the blood passes into the pulmonary arteries.
- The blood flows along the pulmonary arteries into the lungs where the blood deposits nitrogen and takes up oxygen.
- From the pulmonary veins the oxygen-rich blood streams from the lungs into the left atrium.
- The atrium walls contract, the atrioventricular valve opens and blood flows out through the atrioventricular valve into the left ventricle which relaxes at the same time.
- The ventricle muscles contract and blood flows out of the ventricle. The blood cannot flow back into the atrium because the blood flow has the effect of closing the atrioventricular valve. The pressure from the blood opens the aortic valve and lets the blood flow into the aorta.
- Oxygenated blood now passes through the aorta into the rest of the body and is distributed via the arteries.
The Heart: The Flow of Blood
