General structure

The general structure of heart valves is dependent on the valve:

• tricuspid and mitral valves:
  • each leaflet is a flat sheet
  • the margin of each leaflet has serrations where the chordae tendineae attach
  • the chordae tendineae are attached to papillary muscles which contract during systole; the increased tension within the chordae and muscles acts to:
    • prevent eversion of the valve
    • limit ventricular distention as the left ventricular pressure rises
  • therefore, tricuspid and mitral valve competence depends on the active process of papillary muscle contraction
• during diastole, the valve leaflets merge at their free margins and overlap each other centrally
  
  
• aortic and pulmonary valves:
  • each leaflet is ballooned into a cup-shaped concavity when viewed from the aorta
  • during diastole, the column of blood superior to the vessel forces out the leaflets from above, filling their concavities and forcing the aortic valve leaflets together
  • therefore, closure of the aortic and pulmonary valves is a passive process
  • there is no attachment to chorae tendineae
  • a sinus - a dilation of the outflow vessel - exists superior to each valve leaflet:
    • vortices, circular currents of blood, develop within the sinus during systole
    • they prevent the individual leaflets from adhering to the wall of the outflow vessel, so rendering the valve incompetent
  • each leaflet has a fibrous nodule at its centre which is a thickening of its lamina fibrosa