Ventricular pressure exceeding arterial pressure causes the aortic and pulmonary valves to open. These valves, known as the semilunar valves due to their half-moon shape, prevent backflow into the ventricles during ventricular diastole. This pressure differential is the critical factor governing their function within the cardiac cycle. For example, when the left ventricle contracts, the pressure within it rises above the pressure in the aorta, forcing the aortic valve open and allowing blood to flow into systemic circulation.
Proper functioning of these valves is essential for unidirectional blood flow through the heart and into the circulatory system. Malfunctions, such as stenosis (narrowing) or insufficiency (leakage), can significantly impact cardiac performance and overall health. Understanding the mechanics of valve opening and closing is crucial for diagnosing and treating these conditions. Historically, the study of these valves has been pivotal in advancing cardiovascular medicine and surgical techniques.
