blood pressure
Blood pressure is the push your blood makes against the walls of your arteries as your heart pumps it around the body. Think of a garden hose: the water inside presses outward on the rubber, and if you crank the tap higher, the walls feel the strain. Your arteries live with that push every second of your life.
It's read as two numbers — say, 120 over 80. The top, systolic, is the harder shove each time the heart beats; the bottom, diastolic, is the gentler pressure between beats, while the heart refills. A healthy adult sits around 120/80; doctors watch when it creeps up and stays there.
Here's the quiet danger: high blood pressure usually causes no symptoms at all. You can feel perfectly fine while years of extra strain slowly damage your heart, brain, kidneys, and eyes — which is why it earned the nickname "the silent killer." The only way to know is to measure it, and the good news is that catching it early makes it very treatable.
120/80 mmHg — read aloud as "120 over 80": systolic (heart beating) over diastolic (heart resting).
A typical healthy adult reading.
The numbers are measured in millimetres of mercury (mmHg) — a leftover from the old glass-tube instrument, the sphygmomanometer, whose column of mercury the blood pressure literally had to push up. The familiar inflatable arm cuff was introduced by the Italian physician Scipione Riva-Rocci in 1896.