II – For
a better understanding of blood pressure
Description
of the arteries and the blood pressure
2.1 - Working
of the blood circulation: the vessel and the heart
2.2 - Definition of
the blood pressure
Who
is concerned with high blood pressure?
2.3 - Epidemiological
data
2.4 - Influence of
sex
2.5 - Race
The risk is raised by the existence of other
diseases
2.6 - Cholesterol
2.7 - Diabetes
2.8 - Tobacco
2.9 - The age
2.1 -
Working of the blood circulation: the vessel and the heart
- The heart
It consists of 4 cavities,
two atria and two ventricles:
Blood is pumped to the limbs and other parts of the body by a large artery
called the aorta. Theoretically, blood pressure should be measured in this
artery.
At each beat or cardiac
contraction, called systole, the blood will be pumped by the aorta
with the energy transformed into pressure. The blood pressure measured
at this time is then called systolic and corresponds to the maximum.
As the heart is being filled
up with blood (called diastole), the valves of the aorta will closed
themselves so that the blood cannot re-enter the heart. The residual
pressure in the vessels is then called diastolic (corresponding to
the minimum).
Thus, a person who has
a blood pressure of 140/90 millimetres of Mercury (14/9) has in fact
a pressure in the artery (aorta) of 140 millimetres of Mercury when
the heart contracts and pumps the blood and 90 millimetres of Mercury
of residual blood pressure when the heart is not contracting.
- Arteries
The blood leaves the heart
by an artery of large diameter (approximately 3 centimetres), called
the aorta, and then passes to the smaller arteries. The blood pressure
increases in the small arteries.
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last modified on : 28 sep 2003 |
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