Why do the ventricles contract upwards?

The ventricles contract upwards primarily due to the arrangement of cardiac muscle fibers, which are structured in a spiral pattern. This contraction begins at the apex of the heart and moves upwards toward the base, effectively pushing blood out of the ventricles and into the arteries. This upward contraction ensures efficient ejection of blood into the aorta and pulmonary artery, maximizing the heart's pumping efficiency. Additionally, this upward motion helps close the atrioventricular valves, preventing backflow into the atria during systole.