During atrial diastole, which valves open to permit ventricular filling?

• A. Aortic and Pulmonic
• B. Tricuspid and Mitral
• C. Pulmonic and Tricuspid
• D. Aortic and Mitral

Answer: (B)

During atrial diastole, the ventricles fill primarily through the open atrioventricular valves—the tricuspid on the right and the mitral on the left. As the ventricles relax and their pressure falls below the atrial pressure, these valves open and blood flows passively from the atria into the ventricles, with atrial contraction providing a final push later in diastole. The semilunar valves—the aortic and pulmonic—are closed during this time to prevent backflow from the great arteries, and they only open during ventricular systole to eject blood. So, ventricular filling in atrial diastole is facilitated by the tricuspid and mitral valves.