Which best describe the isovolumetric contraction phase of the cardiac cycle? Which best describe the isovolumetric contraction phase of the cardiac cycle? The pressure from the atrial contractions opens the semilunar valves. As pressure builds up in the ventricles during systole, the AV valves open and allow blood to leave the heart. As ventricular systole starts, the AV valves are closed and the semilunar valves are closed. Because the ventricles are contracting and both valves are closed, pressure increases rapidly leading to ejection. As ventricular systole starts, the AV valves close, which immediately opens the semilunar valves.

The correct answer is: As ventricular systole start, the AV valves are closed and the semilunar valves are closed. Because the ventricles are contracting and both valves are closed, pressure increases rapidly leading to ejection.

Explanation:

The heart functions like a bomb that pumps blood to every part of the body, which is fundamental for the proper function of every organ.

The cardiac cycle has two main phases: the diastole and the systole. During the diastole, blood returns from the body through the vena cava and is deposited in the right atrium of the heart. When the pressure in the right atrium becomes bigger than the pressure in the right ventricle, the tricuspid valve opens and the blood flows to the left atrium.

During systole, the atria suffer a depolarization that makes the atria's muscle contract. Thanks to this, the blood goes through the atria to the ventricles.

During isovolumetric contraction, the ventricles contract but the pulmonary and aortic valves remain closed. When the ventricular muscle contracts, the semilunar valves open.