The upper number - systolic blood pressure, shows the pressure in the arteries at the time when the heart contracts and pushes blood into the arteries, it depends on the strength of the contraction of the heart, the resistance of the walls of blood vessels, and the number of contractions per unit of time.

Blood pressure is one of the most important parameters characterizing the work of the circulatory system. Blood pressure is determined by the volume of blood pumped per unit of time by the heart and the resistance of the vascular bed. Since the blood moves under the influence of the pressure gradient in the vessels created by the heart, the greatest pressure of the blood will be at the exit of the blood from the heart (in the left ventricle), a little less pressure will be in the arteries, even lower in the capillaries, and the lowest in the veins and at the entrance heart (in the right atrium).