Heart muscle cells need their own blood supply to supply heart muscle cells with oxygen.

Arteries have elastic, muscular walls to protect against and maintain high blood pressure. Veins have valves and thinner walls because blood in them is at a much lower pressure.

Fatty deposits in the blood vessels supplying the heart muscle can produce a 'heart attack' when a poor oxygen supply damages part of the muscle.

Heart disease is usually caused by lifestyle factors and/or genetic factors, not microorganisms.

These lifestyle factors include poor diet, stress, cigarette smoking and excessive alcohol intake. They increase the risk of heart disease but do not always lead to it.

Heart disease is more common in the UK than in non-industrialised countries because many people have a high fat diet and exercise less.

Regular moderate exercise reduces the risk of developing heart disease.