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

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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

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