THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -During the early stages of ventricular diastole, both the atrioventricular and semilunar valves are closed. During this phase, there is no change in the amount of blood in the ventricle, but there is a precipitous fall in the intraventricular pressure. This is known as isovolumetric relaxation.

Detailed explanation-2: -As pressure drops within the ventricles, blood flows from the major veins into the relaxed atria and from there into the ventricles. Both chambers are in diastole, the atrioventricular valves are open, and the semilunar valves remain closed (see image below).

Detailed explanation-3: -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-4: -AV valves close at end of ventricular diastole; blood flow stops; ventricles begin to contract. ventricles contract (ventricular systole); blood flows from the heart-to the lungs and to rest of body during ventricular ejection.