Blood pressure is the force that blood exerts against the inner walls of blood vessels. Although this force occurs throughout the vascular system, the term blood pressure most commonly refers to pressure in arteries supplied by branches of the aorta. The oscillating pressure in these arteries produces a "pulse".
Arterial Blood Pressure
Arterial blood pressure rises and falls in a pattern corresponding to the phases of the cardiac cycle. That is, contracting ventricles (ventricular systole) squeeze blood out and into the pulmonary trunk and aorta, which sharply increases the pressures in these arteries. The maximum pressure during ventricular contraction is called the systolic pressure. When the ventricles relax (ventricular diastole), arterial pressure drops, and the lowest pressure that remains in the arteries before the next ventricular contraction is the diastolic pressure.
