noun, plural: heart valves
(anatomy) Any of the valves of the heart that prevents the back flow of blood through its cusps or flaps of tissues
In humans, there are four main valves of the heart: (1) left atrioventricular valve, (2) right atrioventricular valve, (3) aortic valve, and (4) pulmonary valve. The left and right atrioventricular valves are also called mitral valve and tricuspid valve, respectively. These atrioventricular valves are made up of cusps of tissues between the atria and the ventricles. They allow the passage of blood into the ventricles but prevent the blood flow back to the atria during systole. Blood back flow is prevented when the atrioventricular valves close as determined by pressure gradients.
The aortic valve and the pulmonary valve make up the semilunar valve. The aortic valve is located at the base of the aorta whereas the pulmonary valve is at the pulmonary trunk. When closed, they prevent the flow of blood from the arteries back into the ventricles. The closure of the aortic valve and the pulmonary valve produces the second heart sound.