ANATOMY

Detailed explanation-1: -During atrial systole, blood enters the ventricles through bicuspid and tricuspid valves. Pulmonary semilunar valves close to prevent the back flow of the blood into the ventricles. This closure produces a ‘Dubb’ sound which is the sound heard on placing a stethoscope onto the chest and listening.

Detailed explanation-2: -During systole, the two ventricles develop pressure and eject blood into the pulmonary artery and aorta. At this time the atrioventricular valves are closed and the semilunar valves are open. The semilunar valves are closed and the atrioventriular valves are open during diastole.

Detailed explanation-3: -The atrial systole is the last phase of a diastole during which the ventricular filling is completed. The atrioventricular valves are open; the semilunar valves are closed (fig. 6.1). The atria contract to eject blood into the ventricles.

Detailed explanation-4: -The mitral and tricuspid valves, also known as the atrioventricular, or AV valves, open during ventricular diastole to permit filling.

Detailed explanation-5: -When the ventricles relax, atrial pressure exceeds ventricular pressure, the AV valves are pushed open and Page 2 blood flows into the ventricles. However, when the ventricles contract, ventricular pressure exceeds atrial pressure causing the AV valves to snap shut.