Blood pressure

Blood pressure - The pressure exerted by the flow of blood through the main arteries. The pressure at 2 different phases is measured. Systolic, the higher pressure, is created by the contraction of the heart.

Diastolic, the lower, is recorded during relaxation of the ventricles between heartbeats; it reflects the resistance of all the small arteries in the body and the load against which the heart must work.

The pressure wave that is transmitted along the arteries with each heartbeat is easily felt as the pulse. Blood pressure is measured using a sphygmomanometer and is expressed as millimetres of mercury (mmHg).

Blood pressure varies with age, between individuals, and at different times in the same individual but a healthy young adult usually has a blood pressure reading, at rest, of about 120/80 (that is 120 mmHg systolic and 80 mmHg diastolic). Abnormally high blood pressure is called hypertension; abnormally low pressure is termed hypotension.