AP BIOLOGY

Detailed explanation-1: -systole, period of contraction of the ventricles of the heart that occurs between the first and second heart sounds of the cardiac cycle (the sequence of events in a single heart beat). Systole causes the ejection of blood into the aorta and pulmonary trunk.

Detailed explanation-2: -Cardiac cycle events can be divided into diastole and systole. Diastole represents ventricular filling, and systole represents ventricular contraction/ejection. Systole and diastole occur in both the right and left heart, though with very different pressures (see hemodynamics below).

Detailed explanation-3: -During systole, the two ventricles develop pressure and eject blood into the pulmonary artery and aorta. At this time the AV valves are closed and the semilunar valves are open. The semilunar valves are closed and the AV valves are open during diastole.

Detailed explanation-4: -The oxygenated blood is brought back to the heart by the pulmonary veins which enter the left atrium. From the left atrium blood flows into the left ventricle. The left ventricle pumps the blood to the aorta which will distribute the oxygenated blood to all parts of the body.