Introduction

The heart pumps blood around the body and the brain. In order for the blood to reach the muscles and organs, it is pumped away from the heart through the arteries. When blood has permeated the body's tissues it travels back, through the veins, to the right side of the heart. From there, it is pumped into the lungs, where carbon dioxide (CO2) is exchanged for fresh oxygen. The blood then returns to the left side of the heart to be pumped via the arteries to the tissues once again. The blood pressure depends on how forcefully the heart pumps the blood around the body and how narrowed or relaxed your arteries are.

Systolic and diastolic: Your heart can beat more than 100,000 times a day. Each time it beats, a surge of blood is pumped from your heart into your arteries. This increases the pressure in your arteries. In between heartbeats the pressure in your arteries decreases. That is why blood pressure is reported as two numbers, e.g. 120 over 80', which is written as '120/80'. The first, higher number (systolic) is the pressure of the blood against the artery walls when the heart contracts (e.g., 120). The second, lower number (diastolic) is the pressure against the artery walls when the heart relaxes between beats (e.g., 80).