Functioning of the Heart (Cambridge (CIE) O Level Biology): Revision Note

Functioning of the Heart

• Deoxygenated blood coming from the body flows into the right atrium via the vena cava

• Once the right atrium has filled with blood, the heart gives a little beat and the blood is pushed through the atrioventricular valve into the right ventricle

• The walls of the ventricle contract and the blood is pushed into the pulmonary artery through the semilunar valve, which prevents blood from flowing backwards into the heart

• The blood travels to the lungs and moves through the capillaries past the alveoli where gas exchange takes place

  • This is why there has to be low pressure on this side of the heart – blood is going directly to capillaries which would burst under higher pressure

• Oxygen-rich blood returns to the left atrium via the pulmonary vein

• It passes through the atrioventricular valve into the left ventricle

• The thicker muscle walls of the ventricle contract to push the blood forcefully into the aorta and all the way around the body

• The semilunar valve in the aorta prevents the blood from flowing back down into the heart