What occurs during systole in regards to semilunar and AV valves?

During systole, which is the phase of the cardiac cycle when the heart muscle contracts to pump blood out of the chambers, the semilunar valves open while the atrioventricular (AV) valves remain closed. This physiological process allows blood to flow from the ventricles into the arteries (the aorta and pulmonary artery) and prevents the backflow of blood into the ventricles from the arteries.

When the ventricles contract, the pressure within them rises, causing the semilunar valves to open. This opening facilitates the ejection of blood into the systemic and pulmonary circulation. At the same time, the higher pressure in the ventricles forces the AV valves to close, which helps to ensure that blood does not flow back into the atria during ventricular contraction. Understanding this mechanism is crucial for grasping how the heart functions during different phases of the cardiac cycle.