Functioning of the Heart (Cambridge International IGCSE Biology)

Functioning of the heart: Extended

Spec point — 9.2.10 · Describe the functioning of the heart in terms of the contraction of muscles of the atria and ventricles and the action of the valves

Extended Tier Only

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

• Once the right atrium has filled with blood, it contracts, pushing the blood through the tricuspid (atrioventricular) valve into the right ventricle

• The walls of the ventricle contract, forcing the blood past the semilunar valve into the pulmonary artery; the valve then closes to prevent blood flowing backwards into the heart

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

  • The right side of the heart pumps blood at a lower pressure than the left, since it's going directly to capillaries in the lungs, which would burst under higher pressure

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

• Once the left atrium is full, it contracts, pushing blood through the bicuspid (atrioventricular) valve into the left ventricle

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

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