Certified Rhythm Analysis Technician (CRAT) Practice Exam 2025 – All-in-One Study Guide for Exam Success!

The semilunar valves are specifically designed to prevent the backflow of blood from the aorta and the pulmonary arteries into the ventricles during diastole, the phase of the heartbeat when the heart muscles relax and the chambers fill with blood. The semilunar valves include the aortic valve, which separates the left ventricle from the aorta, and the pulmonary valve, which separates the right ventricle from the pulmonary artery.

During diastole, the pressure in the ventricles drops as they relax. This induces a higher pressure in the aorta and pulmonary arteries due to the ongoing pressure of blood that has just been ejected during systole. The semilunar valves have a unique structure that allows them to close tightly when the ventricular pressure decreases, effectively sealing off these pathways and ensuring that blood does not flow back into the ventricles. This function is crucial for maintaining efficient circulation and cardiac output.

Other valve types do not serve this specific function. The sinoatrial node is a pacemaker that initiates the heartbeat, the Eustachian valve is more relevant in fetal circulation and has minimal function in adults, and the atrioventricular valves (the tricuspid and mitral valves) connect the atria