Blood flow

unidirectional – from atria to the ventricles and out the vessels • 4 heart valves enforce this unidirectional flow • The heart valves are paired – the atrioventricular and the semilunar valves • These valves open and close in response to pressure gradient

Fibrous flaps that form the bicuspid and tricuspid valves(AVvalves)

Free edges attach to chordae tendineae from papillary muscles of the ventricles

Prevents valve from opening backwards

Chordae Tendineae

o The chordae tendineae are tiny white collagen cords attached to each AV valve flap o They are attached to the Papillary Muscles

Papillary Muscles

Cone like muscle bundles attached to the chordae tendineae o Together, the chordae tendineae and the papillary muscles anchor the valve flaps in their

closed position

Atrioventricular(AV)Valves

Two AV valves

• Tricuspid Valve (right AV valve)

• Bicuspid Valve or Mitral Valve (left AV valve)  Located at the base of the atrio-ventricular junction  Prevents backflow (back into the atria) when the ventricles contract

• Open during ventricular diastole - allows blood to flow into the ventricles

• Closed during ventricular systole prevents backflow into atria  Blood pressure closes valve cusps during ventricular contraction