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what are semilunar valves inn heart?

The semilunar valves (SV) are two valve structures that sit between the right ventricle and the pulmonary artery and between the left ventricle and the aorta. The flaps of the valves open and close to allow the unidirectional flow of blood out of the heart, while preventing backflow of blood. The valve between the left ventricle and aorta is called the aortic valve and the valve between the pulmonary artery and right ventricle is called the pulmonary valves.
The semilunar valves open to let blood pass out of the ventricles. The right ventricle pumps into the pulmonary artery, which leads to the lungs, and the left ventricle empties into the aorta, a main artery that distributes oxygen rich blood to the rest of the body.The semilunar valves are shaped like half moons and have three cusps, or flaps. Unlike the atrioventricular valves, they do not have tough cords of connective tissue called chordae tendineae to force the cusps open. Like valves in veins, both semilunar valves simply use pressure to determine when to open and close.


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