Relationship of the Heart Sounds to Heart Pumping
When listening to the heart with a stethoscope, one does not hear the opening of the valves because this is a relatively slow process that normally makes no noise. However, when the valves close, the vanes of the valves and the surrounding fluids vibrate under the influence of sudden pressure changes, giving off sound that travels in all directions through the chest.
When the ventricles contract, one first hears a sound caused by closure of the A-V valves. The vibration is low in pitch and relatively long-lasting and is known as the first heart sound. When the aortic and pulmonary valvesclose at the end of systole, one hears a rapid snap because these valves close rapidly, and the surroundings vibrate for a short period. This sound is called the second heart sound. The precise causes of the heartsounds, in rela-tion to listening to the sounds with the stethoscope.
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