What happens to the SL valves during ventricular ejection?

What happens to the SL valves during ventricular ejection?

• A. SL valves remain closed.
• B. SL valves are pushed open due to higher ventricular pressure compared to arterial trunk pressure.
• C. SL valves open because arterial trunk pressure is higher.
• D. SL valves are pushed open by atrial pressure.

Answer: (B)

During ventricular ejection, the semilunar valves open because the ventricle’s pressure becomes higher than the pressure in the arterial trunk (aorta or pulmonary artery). That greater ventricular pressure pushes the valve cusps outward, allowing blood to flow into the arteries. Once ejection ends and ventricular pressure falls below arterial pressure, the valves close to prevent backflow. This contrasts with the other ideas: if the valves stayed closed, blood wouldn’t be ejected; opening due to higher arterial pressure would oppose ejection; and arterial or atrial pressure isn’t what opens the semilunar valves—atrium pressure mainly affects the atrioventricular valves.

During ventricular ejection, the semilunar valves open because the ventricle’s pressure becomes higher than the pressure in the arterial trunk (aorta or pulmonary artery). That greater ventricular pressure pushes the valve cusps outward, allowing blood to flow into the arteries. Once ejection ends and ventricular pressure falls below arterial pressure, the valves close to prevent backflow.

This contrasts with the other ideas: if the valves stayed closed, blood wouldn’t be ejected; opening due to higher arterial pressure would oppose ejection; and arterial or atrial pressure isn’t what opens the semilunar valves—atrium pressure mainly affects the atrioventricular valves.