ANATOMY

Detailed explanation-1: -Answer and Explanation: The closing of atrioventricular (AV) valves takes place when the pressure in the ventricles rises more than the pressure inside the atria. The semilunar valves open to allow the blood to exit the ventricles during ventricular ejection.

Detailed explanation-2: -The ventricular contraction continues and blood is ejected from the left and the right ventricles to the aorta and the pulmonary artery, respectively. The atrioventricular valves are closed (fig. 2.1).

Detailed explanation-3: -As pressure in the ventricles rises above two major arteries, blood pushes open the two semilunar valves and moves into the pulmonary trunk and aorta in the ventricular ejection phase. Following ventricular repolarization, the ventricles begin to relax (ventricular diastole), and pressure within the ventricles drops.

Detailed explanation-4: -Ejection begins when the intraventricular pressures exceed the pressures within the aorta and pulmonary artery, which causes the aortic and pulmonic valves to open.

Detailed explanation-5: -The AV valves opening allowing blood to flow into the ventricles. semilunar valves close during this same period as blood flowing toward the ventricles collects in the pockets of the cusps. Closure of the semilunar valves prevents blood from re-entering the ventricles while they are relaxing.