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exhaust valve - a valve through which burned gases from a cylinder escape into the exhaust manifold. exhaust system, exhaust - system consisting of the parts of an engine through which burned gases or steam are discharged. valve - control consisting of a mechanical device for controlling the flow of a fluid.
Blood passes through a valve before leaving each chamber of the heart. The valves prevent the backward flow of blood. Valves are actually flaps (leaflets) that act as one-way inlets for blood coming into a ventricle and one-way outlets for blood leaving a ventricle. Normal valves have 3 flaps (leaflets), except the mitral valve, which only has 2 flaps. The 4 heart valves include: