Heart Valve Movement
Introduction to the Movement of the Heart Valves:
The four heart valves open and close in response to pressure changes that occur in the ventricles during each cardiac cycle.
When the ventricles relax, their pressures drop below those of the atria, pulmonary trunk artery, and aorta.
This allows the AV valves to open as their cusps passively drop downward. The pressure change additionally permits blood flow into the ventricles from the atria without restriction.
The semilunar valves close during this same period as blood flowing toward the ventricles collects in the pockets of the cusps. Closure of the semilunar valves prevents blood from re-entering the ventricles while they are relaxing.
- After filling with blood, the ventricles contract, and their rising pressure force blood up toward the atria and into the pulmonary trunk artery and aorta.
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Blood pushing up under the cusps causes atrioventricular valves to close. As a result, blood enter the atria from the pulmonary veins but not from the ventricles.
At the same time, rising pressure in the pulmonary trunk artery and aorta forces the semilunar valves to open and blood to flow into the systemic and pulmonary circulatory system.
When the ventricles begin to relax, pressure in the chambers drop again, and a new cardiac cycle begins.