Afterload is the pressure threshold that must be exceeded to open which valves?

Afterload is the pressure threshold that must be exceeded to open which valves?

• A. The mitral valve
• B. The aortic semilunar valve
• C. The pulmonary semilunar valve
• D. The aortic semilunar valve and the pulmonary semilunar valves

Answer: (D)

Afterload is the pressure the ventricle must overcome to eject blood. To do that, the ventricular pressure must exceed the pressure in the great arteries. Therefore, the valves that must open under afterload are the aortic semilunar valve and the pulmonary semilunar valve. The mitral valve, by contrast, is an AV valve that opens during filling when atrial pressure is higher than ventricular pressure, not during ejection against arterial pressure. If arterial pressures rise, afterload increases, making it harder to open the semilunar valves and reducing stroke volume.

Afterload is the pressure the ventricle must overcome to eject blood. To do that, the ventricular pressure must exceed the pressure in the great arteries. Therefore, the valves that must open under afterload are the aortic semilunar valve and the pulmonary semilunar valve. The mitral valve, by contrast, is an AV valve that opens during filling when atrial pressure is higher than ventricular pressure, not during ejection against arterial pressure. If arterial pressures rise, afterload increases, making it harder to open the semilunar valves and reducing stroke volume.