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Unit 19: Biology Part 2 Page 55 of 137
You are considered healthy if your
systolic blood pressure is less than
120 mm Hg and your diastolic
blood pressure is less than 80 mm
Hg. Blood pressure can change for
many reasons, but if a person
always has high blood pressure,
they have hypertension. If
someone has hypertension, they
have a greater risk of getting other
Figure 34 – Although neither of cardiovascular diseases.
these sphygmomanometers use Hypertension can be treated by
actual mercury, they both improving diet, increasing exercise,
measure blood pressure in the or with medication.
unit millimeters of mercury
(mm Hg.) Coronary Heart Disease
Sphygmomanometers measure two One of the most common forms of
things – the highest pressure in the cardiovascular disease occurs when
artery, which is called systolic cell pieces, fatty substances,
pressure, and the lowest calcium, and connective tissue,
pressure, which is called diastolic which together are called plaque,
pressure. build up in the arteries and make it
harder for blood to flow. This is
Old-fashioned called atherosclerosis.
sphygmomanometers measured Atherosclerosis is very serious if it
pressure by making a column of blocks blood from getting to the
the liquid mercury rise a certain heart muscle. When this happens,
number of millimeters. Most it is known as coronary heart
modern sphygmomanometers don’t disease.
use mercury, but blood pressure is
still measured in millimeters of
mercury. Millimeters are
abbreviated mm and mercury is
abbreviated Hg, so millimeters of
mercury can be abbreviated mm
Hg.
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