Blood pressure in the systemic circulation is referred to as blood pressure (BP). Blood pressure is the pressure exerted on the blood vessel wall when blood flows in the blood vessels. It is the driving force that pushes blood to flow in the blood vessels. When the ventricles contract, blood flows from the ventricles into the arteries. At this time, the pressure of blood on the arteries is the highest, which is called systolic blood pressure (SBP). When the ventricles relax, the elasticity of the arteries shrinks, and the blood continues to flow forward slowly, but the blood pressure drops. The pressure at this time is called diastolic blood pressure (DBP).