Systolic and Diastolic Blood Pressure: An Introduction
Blood pressure is the amount of force (pressure) that blood exerts on the walls of the blood vessels as it passes through them. Two pressures are measured for a
blood pressure reading:
- Systolic blood pressure is a measure of blood pressure while the heart is beating.
- Diastolic pressure is a measure of blood pressure while the heart is relaxed.
How Are Systolic and Diastolic Blood Pressures Measured?
When measuring systolic and diastolic blood pressures, your doctor will probably use a
sphygmomanometer. This familiar device with a long name contains a cuff, valve, gauge, and dial. The cuff is wrapped around your arm and then inflated slightly. The systolic and diastolic blood pressures are measured on a gauge attached to the cuff. The healthcare provider reads the numbers that appear on the gauge as air is released from the cuff.
The two numbers that measure your blood pressure are written like a fraction: one number on top and one on the bottom. For example, what many people consider
normal blood pressure is read as 120/80. The number on top is the systolic blood pressure. It measures the pressure inside your blood vessels at the moment your heart beats. The number on the bottom is your diastolic pressure, which measures the pressure in your blood vessels between heartbeats, when your heart is resting.
Why Are Systolic and Diastolic Blood Pressures Important?
As blood is pumped from your heart into your blood vessels, enough systolic blood pressure is created to send it to all other parts of your body.
As blood vessels travel away from the heart, they branch off and gradually get smaller -- just like a tree's branches. One branch may go to the brain while another may go to your kidneys. Systolic blood pressure keeps blood flowing through the branches so that your body's cells get the oxygen and nutrients they need and waste matter can be removed.
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