DISORDERS OF THE CARDIOVASCULAR SYSTEM
The cardiovascular system comprises the heart, with its covering pericardium, and blood vessels, that is, arteries, arterioles, capillaries, venules and veins, which enclose and distribute blood to the tissues.
The heart is a muscular pump weighing about 500 g in an adult and is the strongest muscle in the body. It can contract for over a hundred years nonstop, beating about 100 000 times a day at a rate of about 70 beats min–1, to pump blood ) around the body. This supplies, for example, oxygen and nutrients to the tissues and removes their waste products. However, in such a complicated system many things can go wrong. In the developed countries, heart disease is responsible for about half of the annual deaths. Much of this is due to lifestyle, for example smoking, poor diets and excess weight. In developing countries rheumatic heart disease is more of a problem but this has decreased in the developed countries.