Valves

• Atrioventricular valves open

  • This happens when the pressure in the atria is greater than the pressure in the ventricles.
  • The valve cusps are pushed open to allow blood to flow down a pressure gradient from the atria to the ventricles
• Atrioventricular valves close

  • makes a "lub" sound
  • This happens when the pressure in the ventricles is greater than the pressure in the atria
  • The valve cusps are pushed closed to prevent backflow of blood from the ventricles to the atria
• Tendons - chordae tendineae - ensure that the atrioventricular valves only open in one direction and prevent inversion of the valve during ventricle systole
• Semilunar valves open

  • This happens when the pressure is greater in the ventricle than in the aorta/pulmonary artery
  • The valve cusps are pushed open to allow blood to flow down a pressure gradient from ventricles to arteries
• Semilunar valves close

  • makes a "dub" sound
  • This happens when the pressure is greater in the aorta/pulmonary artery than in the ventricle.
  • The valve cusps are pushed closed to prevent backflow of blood from the aorta/pulmonary artery to the ventricle.
  • Pockets fill with blood, forcing the valves closed