What is the role of semi-lunar valves in the heart?

The semi-lunar valves play a crucial role in the heart by controlling the exit of blood from the ventricles into the arteries. Located at the base of the aorta and the pulmonary artery, these valves open to allow blood to flow out of the heart during ventricular contraction (systole) and then close during ventricular relaxation (diastole). This action prevents the backflow of blood once it has been pumped out, ensuring efficient circulation.

While the other options address different functions related to the heart's operation, they do not pertain to the specific role of the semi-lunar valves. For example, controlling blood flow into the atria is primarily managed by the atrioventricular valves, and facilitating oxygenation of blood occurs in the lungs, not directly through the function of the semi-lunar valves. The main function of the semi-lunar valves is critical for maintaining directional flow and preventing any backflow after the ventricles contract.