what keeps blood from flowing back into the chamber of the heart
By closing at this time, the mitral valve prevents the oxygenated blood in the left ventricle from flowing back to the lungs. The left ventricle is the pumping chamber of the left side of the heart and is the most muscular portion of the heart. When you hear some say their blood pressure is 120 over 80, it is the left ventricle that is generating these pressures.