WILL & DENI MCINTYRE / SCIENCE PHOTO LIBRARY WILL & DENI MCINTYRE / SCIENCE PHOTO LIBRARY
Blood pressure measurement. Woman doctor takes the blood pressure of a 33-year-old man. She uses an instrument called a sphygmomano- meter. It consists of an arm cuff (black) and a pressure gauge (on the wall). The cuff is inflated around the patient's upper arm until blood flow is stopped in a main artery. By slowly deflating the cuff, systolic pressure of the pumping heart is recorded; further cuff deflation gives diastolic pressure of the relaxed heart between pumps. Blood pressure is then expressed as a difference between these two measurements, in millimetres of mercury (mm Hg). Although blood pressure varies over the day, it is an important measure of bodily health.
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