The valve that exists between the left atrium and left ventricle is called the bicuspid valve, it has two flaps and function by allowing the flow of blood in one direction only. After the oxygenated blood flow from the atrium to the ventricle the valve close to prevent back flow of blood.
The valve between the right atrium and the right ventricle is called the tricuspid valve, it has 3 flaps. It functions by allowing the pumping of blood from the right atrium to the right ventricle. Immediately the blood pass through the valve close to prevent back flow.