Blood pressure is the pressure of the blood in the arteries. This pressure enables the heart to pump blood around the body.

In the process known as circulation, the right side of the heart collects blood that has been used by the body, and pumps it into the lungs, to be re-oxygenated. The left side of the heart then pumps this oxygen-rich blood back through the body.

Arteries carry oxygenated blood to the body, and veins carry the used blood back to the heart. The arteries are strong and elastic. This enables them to handle the pressure of the blood being pumped through them.

How is blood pressure measured?

Blood pressure is recorded as two numbers, e.g. 120/70 (‘120 over 70').

Systolic pressure is the higher number. This is the pressure in the arteries as the heart squeezes blood out during a contraction.

Diastolic pressure is the lower number. This is the pressure in the arteries as the heart relaxes before the next beat.

What is normal blood pressure?

Normal blood pressure limits are between 100/60 and 130/80.

Acceptable blood pressure falls within a range, rather than being a specific pair of numbers. Blood pressure varies according to the body's needs and activities.

Read about hypertension (high blood pressure)

This information was first published in You and Your Heart - an education booklet for patients, families and friends. © 2006 Northern Sydney Central Coast Area Health Service