What happens tp the pressure in ther right atrium and ventricl when the valve is closed?

When the valve between the right atrium and right ventricle is closed, pressure in the right atrium increases as blood continues to flow into it from the vena cavae. Simultaneously, pressure in the right ventricle remains relatively low until the ventricle contracts during systole. This pressure differential helps facilitate the movement of blood through the heart and into the pulmonary artery when the valve opens again.