The majority of blood ejected from the left atrium to the left ventricle occurs during which phase?

The majority of blood ejected from the left atrium to the left ventricle occurs during the rapid filling phase of the cardiac cycle. During this phase, which is part of diastole, the mitral valve is open and blood flows passively from the left atrium into the left ventricle. This passive filling accounts for approximately 70-80% of the total ventricular volume before contraction.

The rapid filling phase is characterized by a significant flow of blood due to the gradient created by the pressure difference between the left atrium and the left ventricle as the ventricles are relaxing. This phase occurs early in diastole and is essential for effective ventricular filling.

In contrast, atrial contraction, while it does contribute to the overall filling of the ventricle, occurs later and is primarily responsible for the final portion of ventricular filling after most of the blood has already entered during the rapid filling phase. Isovolumetric contraction is a different part of the cycle where the ventricles begin to contract and there is no blood flow because all valves are closed. Diastasis, occurring after rapid filling, is a slower phase where the flow of blood slows as pressure equalizes, further contributing less to the volume already filled. These