Final answer:
The semilunar valves, specifically the aortic and pulmonary valves, are responsible for preventing the backflow of blood from major blood vessels into the heart.
Step-by-step explanation:
The set of valves primarily responsible for preventing blood flow from major blood vessels back into the heart are the semilunar valves. These include the aortic and pulmonary valves. When the left ventricle contracts, the aortic semilunar valve opens allowing blood to be ejected into the aorta. As the ventricle relaxes, the valve closes to prevent backflow into the ventricle. Similarly, the pulmonary semilunar valve operates to control blood flow from the right ventricle into the pulmonary artery and then shuts to prevent backflow. The semilunar valves are primarily responsible for preventing the backflow of blood from the major blood vessels into the heart.
The heart is equipped with four main valves to ensure proper blood flow. Two of these, known as atrioventricular valves (tricuspid on the right, mitral/bicuspid on the left), regulate blood flow between the atria and ventricles. The other two valves are the semilunar valves: the aortic valve controls blood flow from the left ventricle into the aorta and the pulmonary valve regulates blood from the right ventricle into the pulmonary artery. Their function is crucial as they prevent blood from flowing back into the ventricles after it has been pumped out, which is essential for the maintenance of a one-way circulatory system. Incorrect functioning of these valves can lead to heart disease or complications requiring medical intervention.