The proper function of the cardiovascular system relies on blood following the correct pathway through the heart. Valves within the heart separate the organ's chambers and prevent blood from flowing in the wrong direction. What valve separates the left atrium and left ventricle?

The Mitral/Bicuspid Valve

Explanation:

The heart is composed of 4 chambers: left and right atria, and left and right ventricles. The "right heart" (right atrium and ventricle) receives deoxygenated blood from the systemic circulation through the Vena Cava, and impels this blood towards the lungs through the Pulmonary Arteries where it will be oxygenated. The "left heart" (left atrium and left ventricle) receives oxygenated blood from the pulmonary circulation through the Pulmonary veins and impels this blood towards the systemic circulation through the Aorta artery.

The systemic and pulmonary circuits work in series, and maintaining the unidirectional course of the blood flow is very important. This can be done by the presence of fibrous valves that are present between the atrium and the ventricles, and in between the ventricles and the Pulmonary/Aorta artery.

The location of these structures are as follows:

Systemic circulation ⇒ Right Atrium → [Tricuspid Valve] → Right Ventricle → [Pulmonary Valve] → Pulmonary Artery ⇒ Pulmonary circulation

Pulmonary circulation ⇒ Left Atrium → [Mitral/Bicuspid Valve] → Left Ventricle → [Aortic Valve] → Aorta ⇒ Systemic circulation