Zoology - Body Fluids and Circulation Question with Solution | TestHub

As the ventricular muscle relaxes, pressure on the blood within the ventricles drops even further. This causes closing of semilunar valves producing second heart sound called 'dub' and the phase is called ventricular diastole. Since at the same time atria is also under diastole state, it is called joint diastole stage. Eventually, it drops below the pressure in the atria. When this occurs, blood flows from the atria into the ventricles, pushing open the tricuspid and mitral valves.