During which phase of the cardiac cycle does the heart empty?

The heart empties during the systolic phase of the cardiac cycle. This phase is characterized by the contraction of the heart muscles, specifically the ventricles, which occur after electrical signals stimulate them to contract. As the ventricular pressure rises, it exceeds the pressure in the arteries, causing the valves to open and blood to be ejected into the aorta and pulmonary artery. This process is crucial for delivering oxygenated blood to the body and deoxygenated blood to the lungs for oxygenation. The systolic phase is essential for maintaining circulation and supplying organs and tissues with the necessary nutrients and oxygen.

In contrast, during the diastolic phase, the heart is filling with blood rather than emptying. The isometric phase refers to moments in the cardiac cycle when the ventricles contract, but there is no blood ejection. The electromechanical phase is not a standard term commonly used in describing the cardiac cycle phases and does not accurately represent the process of blood emptying from the heart. Understanding these distinctions helps clarify the dynamics of heart function and the importance of each phase within the cardiac cycle.