Blood pressure is monitored using a sphygmomanometer (sphygmos, meaning “pulse,” and manometer, meaning a device for measuring pressure). Blood pressure is the pressure in the arterial system in the largest vessels near the heart as the heart pushes blood through vessels. It is measured in millimeters of mercury. The two numbers for blood pressure reflect two different pressures: systolic pressure and diastolic pressure. Systolic pressure (the upper number in a blood pressure reading) is the pressure of the blood against the arterial walls when the ventricles are contracting. Diastolic pressure (the lower number in a blood pressure reading) is the lowest point at which sounds can be heard as the blood flows through the smaller arteries. A blood pressure reading below 120/80 mm Hg is considered normal.