EVERYDAY SCIENCE

Detailed explanation-1: -At the onset of ventricular diastole, the mitral and tricuspid valves open, and their respective leaflets separate widely. Opening of these AV valves is normally silent. During ventricular filling, the leaflets of each AV valve begin to close; with the onset of atrial systole, the partially closed leaflets reopen.

Detailed explanation-2: -The first heart sound (S1) represents closure of the atrioventricular (mitral and tricuspid) valves as the ventricular pressures exceed atrial pressures at the beginning of systole (point a). S1 is normally a single sound because mitral and tricuspid valve closure occurs almost simultaneously.

Detailed explanation-3: -The mitral valve is located on the left side of the heart, between the left atrium and the left ventricle. This valve has two leaflets that allow blood to flow from the lungs to the heart. The tricuspid valve is located on the right side of the heart, between the right atrium and the right ventricle.

Detailed explanation-4: -During the thoracic compression of closed-chest cardiac massage the aortic valve opened, while the mitral and tricuspid valves closed. During the relaxation phase the mitral and tricuspid valves rapidly opened, the aortic valve closed.

Detailed explanation-5: -Hemodynamic data from right heart catheterization were available in 46 patients. Results: In all control subjects, the aortic valve closed before the pulmonary valve and the mitral valve closed before the tricuspid valve.