The Heart

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  • The Heart
    • Two pumps
      • Right side pumps deoxygenated blood to lungs
      • Left side pumps oxygenated blood to whole body
    • Different parts
      • Left ventricle has thicker, more muscular walls- needs to contract powerfully  to pump blood to whole body
      • Ventricles have thicker walls than atria- have to push blood out of heart
      • Atrioventricular valves  stop backflow of blood into ventricles
      • Semi lunar valves link venricles to PA/ aorta- stop backflow into heart
      • Cords attach AV valves to ventricles to stop them from being forced up into atria
      • Valves only open one way- depends on pressure. Pressure behind valve= forced open. Pressure in front of valve= forced shut. Means blood only flows in one direction
    • Cardiac cycle
      • 1) Ventricles relax, atria contract- decreases vol of chambers, increases pressure. Pushes blood into ventricles. Increase in ventricular pressure/chamber volume as ventricles receive blood.
      • 2) Atria relax. Ventricles contract, decreases vol/increases pressure. Pressure higher in ventricles than atria- forces AV valves shut. Pressure in ventricles higher than in aorta/ PA- forces SL valves open, blood forced out into arteries
      • 3) Ventricles/atria relax. Atria fill with blood due to high pressure of VC/PV. Increases pressure of atria. Ventricles relax, pressure falls below pressure of atria, AV valves open. Blood flows passively into ventricles


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