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The Heart

Structure and function

Mammals have a double circulation; a pulmonary circulation and a systemic circulation.

The pulmonary circulation takes blood on the relatively short journey to the lungs, where blood is
oxygenated. When blood passes through a system of capillaries it loses pressure, so it must return
to…

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Cardiac output is the volume of blood pumped by one ventricle of the heart in one minute.

Cardiac output = heart rate x stroke volume


Cardiac muscle is myogenic (contraction is initiated from within the muscle itself rather than by
nervous impulses from outside, as is the case with other…

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The biological basis of heart disease

Cardiovascular disease is the biggest single cause of death in the UK. The common underlying
cause of cardiovascular disease is the build up of an atheroma in the walls of arteries.

An atheroma begins as fatty streaks that are accumulations of white blood cells…

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Arteriosclerosis ­ loss of elasticity and hardening of the arteries making them more liable to
rupture.

Atherosclerosis ­ a build up of atheroma in the blood vessels.


Risk factors

Smoking:
Giving up smoking is the single most effective way of increasing life expectancy. There are two
main constituents of tobacco…

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High intake of saturated fats ­ increase in LDL levels and hence blood cholesterol
concentration.

By contrast dietary fibre and antioxidants reduce the risk of heart disease.

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