Final answer:
The highest pressure against the artery walls, which occurs when the ventricles contract, is known as systolic pressure.
Step-by-step explanation:
Systolic pressure is the highest pressure against artery walls, created during the ventricular ejection phase when the ventricles contract and eject blood into the arteries. During this phase, also referred to as the ventricular ejection phase, the pressure in the ventricles rises above that in the pulmonary trunk and the aorta due to the contraction of ventricular muscles. The increased pressure results in the opening of the pulmonary and aortic semilunar valves, allowing blood to be pumped into the circulatory system. In this phase, the stroke volume, which is usually around 70-80 mL of blood, is ejected, leaving a residual volume called the end systolic volume (ESV) within the ventricles.