Your heart pumps blood around your body through blood vessels. The blood vessels that carry oxygen around your body to all of your vital organs are called arteries. Blood pressure is the 'force' that keeps blood moving through your arteries. Arteries can widen or narrow, depending on the pressure of the blood flowing through them. Blood pressure is is recorded as two numbers, one over the other (eg, 120/80 mmHg, read as "120 over 80"). The first number shows the pressure when the heart pumps blood into the arteries (the 'systolic blood pressure' or SBP), and the second number is the pressure in the arteries when the heart relaxes (the 'diastolic blood pressure' or DBP). The higher the numbers, the harder your heart is working to move blood through your arteries.