ANATOMY

Detailed explanation-1: -The mitral and tricuspid valves, also known as the atrioventricular, or AV valves, open during ventricular diastole to permit filling. Late in the filling period the atria begin to contract (atrial systole) forcing a final crop of blood into the ventricles under pressure-see cycle diagram.

Detailed explanation-2: -The atrial systole is the last phase of a diastole during which the ventricular filling is completed. The atrioventricular valves are open; the semilunar valves are closed (fig. 6.1).

Detailed explanation-3: -During diastole, the build up of blood in the atria creates a pressure gradient that forces open the AV valves allowing for about 75% of this blood to pass into the ventricle causing a gradual increase in ventricular diastolic pressure (point A).

Detailed explanation-4: -The atrioventricular valves open from the atria and into the ventricle. They are forced open due to the increase in pressure during atrial systole. This allows blood to flow out of the atria and into the ventricles., which have a lower pressure during diastole to receive the blood coming from the atria.

Detailed explanation-5: -During systole, the two ventricles develop pressure and eject blood into the pulmonary artery and aorta. At this time the atrioventricular valves are closed and the semilunar valves are open. The semilunar valves are closed and the atrioventriular valves are open during diastole.