What prevents blood movement from left ventricle to left atrium

The Mitral valve which is also known as left atrioventricular prevents blood movement from left ventricle to left atrium.

Explanation:

Human heart is four chambered. Two of these are receiving chambers known as atria and the other two are distributing chamber known as Ventricles. Atria are superior chambers and ventricles are inferior chambers. The heart has four valves broadly grouped as Atrioventricular valves and Semi lunar valves. Atrioventricular valves allows flow of blood from atria to ventricle. These are tricuspid valve and bicuspid valve. Semi-lunar valves allow blood to pass out of the heart. These include the pulmonary and aortic valves. The pulmonary valve allows blood to flow from right ventricle to the heart while aortic valve allows blood to flow from left ventricle to the Aorta. The Tricuspid valve located between the right atrium and right ventricle allows blood to flow from right atrium to the right ventricle. The Bicuspid valve (Mitral valve) located between the left atrium and left ventricle allows the blood flow from left atria to left ventricle. Valves maintain the unidirectional flow of blood and thus prevent its back flow.