MICROANATOMY

Detailed explanation-1: -When the left ventricle contracts, the mitral valve closes and the aortic valve opens. This is so blood flows into the aorta and out to the rest of the body. While the left ventricle is relaxing, the right ventricle also relaxes. This causes the pulmonary valve to close and the tricuspid valve to open.

Detailed explanation-2: -The atria begin to contract (atrial systole), following depolarization of the atria, and pump blood into the ventricles. The ventricles begin to contract (ventricular systole), raising pressure within the ventricles.

Detailed explanation-3: -The cardiac cycle begins with atrial systole, the sequential activation and contraction of the 2 thin-walled upper chambers. Atrial systole is followed by the delayed contraction of the more powerful lower chambers, termed ventricular systole.

Detailed explanation-4: -Each contraction of the ventricles represents one heartbeat. The atria contract a fraction of a second before the ventricles so their blood empties into the ventricles before the ventricles contract.