For example, the right and left atria are both full of blood, and that blood moves through the tricuspid and the mitral valve to get down into the ventricles.
The mitral valve only has two cusps or leaflets one in front, called the anterior leaflet (that's a little smaller), and one behind it, called the posterior leaflet.
From the lungs, freshly oxygenated blood flows back into the left atrium and passively passes through the mitral or bicuspid valve to fill the left ventricle.
Right after the S2 sound, the tricuspid and mitral valves open back up allowing blood to fill up the ventricles again and this period of time is called diastole.
Examples of conditions associated with common systolic murmurs include: mitral valve regurgitation, when the mitral valve does not close properly and blood surges back to the left atrium during systole.
Now that blood is freshly oxygenated from its trip to the lungs, it returns to the left atrium of the heart and passively flows through the bicuspid (or mitral valve).
That first heart sound, " lub" , is called S1, and the noise comes from the tricuspid and mitral valves snapping shut when the left and right ventricles contract, which happens at about the same time.
Oxygenated blood returns to the heart by way of pulmonary veins, which empty into the left atrium. Atrial contractions force blood from the left atrium through the mitral valve, also called bicuspid valve, into the left ventricle.