What are the heart valves?

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Heart Valves Image

While the myocardium or heart muscle is the workhorseof the heart, it is the heart valves that direct the flow ofblood. Without properly functioning heart valves, theheart would fail in a matter of hours. Blood circulatesthrough the human heart in only one direction. Theheart valves open and close with each beat of the heart.When the heart pushes blood out of the atria or ventri-cles, the valves open to allow the outflow of blood.When the valves close, the blood cannot flow backward.The valves are round and have thin pliable flaps, calledleaflets. The leaflets open and close in response to thechanging pressure of the blood on either side of them.

The human heart has four valves. There is one valve tocontrol the flow of blood for each chamber. Each heartvalve is slightly different in size and character from theothers and each has a different name.The names of the heart valves are:

● Mitral valve

● Aortic valve

● Tricuspid valve

● Pulmonic valve

The heart’s upper chambers are called  atria and thelower chambers are called  ventricles. Blood withoutoxygen returns from the body and flows into the rightatrium. From there, it is forced through the tricuspidvalve into the right ventricle beneath it. The right ven-tricle pumps the blood through the pulmonic valve andinto the lungs while simultaneously closing the tricus-pid valve. Therefore, the pulmonic valve opens to allowthe blood to flow into the lung and the tricuspid valvecloses to stop blood from flowing back into the rightatrium.

 

Heart Valve
Figure -a This figure shows the heart in late sysole. The atria are full but the ventricles are empty.
Heart Valves
Figure -b In early diastole, the mitral and tricus- pid valves open, allowing a large amount of blood to rush into the ventricles. This is the rapid filling phase of diastole.

 

Heart Valves
Figure -c In mid-diastole, the ventricles are full. Notice that the ventricular walls, however, are not distended in any way.
Heart Valve Health
Figure -d The atrial contraction allows an extra amount of blood to enter the ventricles, causing them to stretch and overfill. The slight stretch in the ventricular muscle caused by the atrial kick will maximize stroke volume and cardiac output.

 

Although the valves have different names on the leftside of the heart, they operate in the same way as theright-sided valves. Oxygen-rich blood returning fromthe lungs flows into the left atrium. When the atriumcontracts, this blood is forced through the mitral valveinto the left ventricle beneath it. When the left ventriclecontracts, the mitral valve closes, stopping the backflowof blood. At the same time, the aortic valve opens, al-lowing blood to flow into the rest of the body. Whenthe left ventricle has finished its contraction, the aorticvalve closes, stopping the backflow of blood, and themitral valve opens, allowing blood from the left atriumto fill the left ventricle.

At any given time in the cardiac cycle, two valves areopen, allowing blood to flow, and two valves are closed,stopping the backflow of blood. When your doctor lis-tens to your heart, he or she can usually hear the open-ing and closing of the valves.

Source: 100 Q&A About Congestive Heart Failure

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