What is Blood Pressure? Blood pressure refers to the force exerted by circulating blood on the walls of blood vessels and constitutes one of the principal vital signs. The pressure of the circulating blood decreases as blood moves through arteries, arterioles, capillaries, and veins; the term blood pressure generally refers to arterial pressure, i.e., the pressure in the larger arteries, arteries being the blood vessels which take blood away from the heart.
Blood pressure is always given as two numbers;
- Systolic Pressure (when the heart beats)
- Diastolic Pressure (when the heart relaxes)
When the measurements are written down, both are written one above, or before, the other with the systolic being the first number.