Final answer:
A raise in pressure in the ventricles leads to the closure of the mitral or tricuspid valves and the opening of the aortic or pulmonary valves for blood ejection from the heart.
Step-by-step explanation:
When the pressure in the ventricles increases, the mitral or tricuspid valves close, and the aortic or pulmonary valves open. This allows blood to be ejected from the heart. For example, during ventricular systole, contraction of the ventricular muscle raises the pressure in the ventricles, causing the aortic and pulmonary valves to open and blood to be pumped into the pulmonary trunk and aorta.