Heart Valves

• Atrioventricular Valves


  the 2 AV valves, one located at each atrial-ventricular junction, prevent backflow into the atria when the ventricles contract
• AV Valve - Tricupsid Valve

  the right AV valve, tricupsid valve, has 3 flexible cusps

  = flaps of endocardium reinforced by connective tissue cores

  
• AV Valves - Mitral Valves

  the left AV valve, w 2 cusps = mitral valve = bicupsid valve
• AV Valves - Chordae Tendineae

  attached to each AV valve flap r tiny collagen cords = chordae tendineae

  = anchor the cusps to the papillary muscles protruding from the ventricular walls
• Opening of the AV Valves

  when the heart is completely relaxes, the AV flaps hang limply into the ventricular chambers below

  during this, blood flows into the atria + then thru the open AV valves into the ventricles
• Closing of the AV Valves

  when the ventricles contract, cmpressing the blood in their chambers, the intraventricular pressure rises, frocing the blood superiorly against the valve flaps

  as a result, the flap edges meet, closing the valve
• Closing of the AV Valves - Chordae Tendinae & Papillary Muscles

  the chordae tendinae + the papillary muscles act as tethers that anchor the valve flaps in their closed position

  if the cusps were not anchored, they would be blown upward into the atria

  the papillary muscles contact w the other ventricular musculature so that they take up the slack on the chordae tendineae as the full force of ventricular contraction hurls the blood against the AV valve flaps
• Semilunar Valves


  the aortic + pulmonary valves guard the bases of the large arteries issuing from the ventricles (aorta + pulmonary trunk, respectively) + prevent backflow into the associated ventricles

  each SL valve is fashioned from 3 cusps in a crescent shape
• Opening of SL Valves

  when the ventricles contract + intraventricular pressure rises above the pressure in the aorta + pulmonary trunk, the SL valves r forced open + thier cusps flaten against the arterial walls as blood rushes past them
• Closing of the SL Valves

  when the ventricles relax + the blood flows backward toward the heart, it fills the cusps + closes the valves