What vessels fill during systole?

During systole, the ventricles of the heart contract, which propels blood into the arteries. This phase primarily fills the aorta and pulmonary artery with oxygenated blood from the left ventricle and deoxygenated blood from the right ventricle, respectively. The atria, on the other hand, are filling with blood from the veins during this time, preparing for the next diastole phase.