The Heart

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  • Created by: rhiglynn
  • Created on: 05-03-16 21:46
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  • The Heart
    • The heart consists of two muscular pumps
      • The right side pumps deoxygenated blood to the lungs and the left side pumps oxygenated blood to the whole body
        • Right and left side are reversed on the diagrams.
    • The left ventricle of the heart is thicker- needs to contract blood to the whole body
      • The ventricles have thicker walls than the atria, because they need to pump blood a further distance
        • The AV valves stop backflow of blood to stop blood flowing backwards when the atria contract.
          • The SL valves link the ventricles to the pulmonary artery and aorta, and stop blood flowing back into the heart after the ventricles contract.
            • The cords attach the atrioventricular valves to the ventricles to stop them from being forced up to the atria when the ventricles contract
    • Valves only open one way- depends on the pressure.
      • If there's a pressure behind a valve it is forced open, but if the pressure is higher in front the valve is forced shut
        • Blood only flows in one direction round the heart.
    • THE CARDIAC CYCLE
      • 1. Ventricles relax, atria contract
        • The ventricles are relaxed. The atria contract, increasing pressure- pushes blood in to the ventricles- causes slight increase in pressure from the ventricles
        • 2. Ventricles contract, atria relax
          • The atria relax. The ventricles contract, increasing their pressure. Pressure is higher in the ventricles than the atria and the AV valves shut- SL valves open
          • 3. Ventricles relax, atria relax
            • The ventricles and the atria both relax. Higher pressure in the pulmonary artery and aorta closes the SL valves
              • Blood returns to the atria and they fill agaib due to the higher pressure in vena cava and pulmonary vein.
                • This starts to increase the pressure of the atria. As the ventricles continue to relax, their pressure falls below the pressure of the tria and so AV valves open
                  • Allows blood to passively flow into the ventricles from the atria. The atria contract and the process repeats.

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