Mitral valve is also known as bicuspid valve or left atrioventricular valve. It is present between left atrium and left ventricle. It prevents the back flow of blood from left ventricle into left atrium during ventricular contraction. This valve has two flaps. When the pressure is high in atrium, it opens and the blood flows from the left atrium into left ventricle. When the pressure in ventricle is high, it closes and thus, prevents the backflow of blood. So, the correct answer is 'Left atrium and left ventricle'.

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