ANATOMY

Detailed explanation-1: -When pressure within the ventricles drops below pressure in both the pulmonary trunk and aorta, blood flows back toward the heart, producing the dicrotic notch (small dip) seen in blood pressure tracings. The semilunar valves close to prevent backflow into the heart.

Detailed explanation-2: -As the ventricles contract, ventricular pressure exceeds arterial pressure, the semilunar valves open and blood is pumped into the major arteries. However, when the ventricles relax, arterial pressure exceeds ventricular pressure and the semilunar valves snap shut.

Detailed explanation-3: -The atrioventricular valves prevent backflow of blood into the atria during ventricular contraction (systole), and the aortic/pulmonic (semilunar) valves prevent backflow of blood into the ventricles during ventricular relaxation (diastole).

Detailed explanation-4: -The semilunar valves act to prevent backflow of blood from the arteries to the ventricles during ventricular diastole and help maintain pressure on the major arteries.