During which phase does the Right Ventricle fill with blood?

The right ventricle fills with blood during diastole. This phase of the cardiac cycle is characterized by the relaxation of the heart muscle, allowing the chambers to expand and receive blood. During diastole, the tricuspid valve opens, and blood flows from the right atrium into the right ventricle, filling it with deoxygenated blood that will be pumped to the lungs for oxygenation during the subsequent contraction phase, which is systole.

In contrast to diastole, systole is when the heart muscle contracts to pump blood out of the chambers. Isovolumetric contraction occurs after the ventricles are filled and begin to contract, but before the valves open to eject blood, meaning no filling occurs during this phase. Isovolumetric relaxation follows the ejection of blood and is a brief period when the ventricles relax without changing volume, also indicating no filling occurs at this time. This clearly delineates diastole as the distinct phase when the right ventricle fills with blood, confirming the accuracy of the answer.