Cardiac Cycle

Atrial Systole - 

Blood enters from the vena cava, the right atrial muscle contracts, and the right AV valve opens due to the PRESURE DIFFERENCE. 

Ventricular Systole -

Blood enters the right ventricle. The right ventricle muscle contracts, forcing the SEMI - LUNAR valves open in the pulmonary artery. Blood leaves through artery and enters the lungs

Diastole-

The atria and ventricles relax. Elastic recoil of…