Operation of the Heart Valves

Operation of the Heart Valves

Operation of the Heart Valves Let’s take a look at how the valves of the heart operate to direct a one-way flow of blood from the atria to the ventricles to the arteries. The AV valves are normally open. When a ventricle contracts, however, the pressure of the blood forces the cusps of an AV valve to meet and close. The force of the blood is often likened to a strong wind that can cause an umbrella to turn inside out. However, the papillary muscles contract, causing the chordae tendineae to tighten and pull on the valve and thus preventing it from reverting into an atrium.     A semilunar valve is normally closed-the contraction of a ventricle opens it. Then, when the ventricle relaxes, the blood in the artery pushes backward, closing the valve.     Like mechanical valves, the heart valves are sometimes leaky; they don’t close properly, and there is a backflow of blood. When a person has rheumatic fever, a bacterial infection that began in the throat has spread throughout the...
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