Which valve separates the left atrium and the left ventricle?

The valve that separates the left atrium from the left ventricle is known as the bicuspid valve, also commonly referred to as the mitral valve. This valve has two cusps, which are flaps that open and close to regulate blood flow. When the left atrium fills with oxygenated blood from the lungs, the bicuspid valve opens to allow that blood to flow into the left ventricle. Once the left ventricle is filled, the bicuspid valve closes to prevent the backflow of blood when the ventricle contracts to pump blood into the aorta and out to the rest of the body.

In contrast, the aortic valve is situated between the left ventricle and the aorta and is responsible for regulating blood flow out of the heart, not separating the atrium and ventricle. The tricuspid valve separates the right atrium and right ventricle, while the pulmonary valve is located between the right ventricle and the pulmonary arteries. Therefore, the bicuspid valve is the correct answer, as it specifically facilitates the flow between the left atrium and left ventricle.