Final answer:
Systole is the phase of the cardiac cycle where the heart's chambers contract, with ventricular systole pushing blood out of the heart into circulation.
Step-by-step explanation:
Systole is defined as the contraction phase of the cardiac cycle, during which the heart chambers contract and pump blood out of the heart. Specifically, during ventricular systole, the ventricles contract forcefully, pushing blood through the arteries to circulate throughout the body. In contrast, atrial systole involves the atria contracting to fill the relaxed ventricles with blood. This phase is essential for maintaining proper circulation and ensuring that oxygenated blood reaches all parts of the body.