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The circulatory system

The heart

The heart pumps blood in two ways:

  • The right side pumps blood to the lungs
  • The left side pumps blood to the rest of the body

You need to be able to identify these parts, and where they are:

  • Atria (left and right)
  • Ventricles (left and right)
  • Semilunar, tricuspid and bicuspid valves
  • The four main blood vessels of the heart:
    • Vena cava
    • Pulmonary artery
    • Pulmonary vein
    • Aorta

The diagram and animation below shows the main parts of the heart, and how it is able to pump blood.

You also need to be able to state what some of these parts do:

  • Left and right atria receive blood from veins
  • Left and right ventricles pump blood into arteries
  • The valves stop the blood flowing backwards when the heart relaxes

Blood pressure

The left ventricle has a thicker muscle wall than the right ventricle. This is because the left ventricle has to pump blood all the way around the body, but the right ventricle only has to pump it to the lungs.

The blood in arteries is under higher pressure than blood in the veins. The high pressure in arteries lets blood flow into the capillaries, while the lower pressure in veins lets blood flow from the capillaries.

Read on if you're taking the higher paper.

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