MICROANATOMY

Detailed explanation-1: -In atrial systole, both the atria contract simultaneously, and the blood pass into the ventricles which are in a relaxed state. Bicuspid and tricuspid valves are open during both joint diastole and atrial systole. The opening of atrioventricular valves allows the blood to flow from the atria to the ventricles.

Detailed explanation-2: -In the systole phase, blood is forced to flow from the two atria into their respective ventricles as the atrial muscles contract due to the depolarization of the atria.

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). The atria contract to eject blood into the ventricles.

Detailed explanation-4: -So during atrial systole, the bicuspid and tricuspid valves are open, and the pulmonary/aortic semilunar valves are closed.