Cigarettes are plant leaves which have been dried & wrapped in special easy-burn paper. The leaves are ignited & allowed to smoulder. The smoke & vapors that are given off are inhaled into the {lungs} of the user. It is now known that smoking is a major health hazard both to the smoker & to those around them.
Cigarettes contain numerous harmful substances. The dangers of 3 of them are particularly important:
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NICOTINE: This is the substance that causes addiction to tobacco. It stimulates the body to produce {adrenalin} - this makes the {heart} beat faster & pushes up {blood pressure}.
TAR: This produces chronic irritation of the {respiratory system} & is thought to be a major cause of {lung} {cancer}.
CARBON MONOXIDE: A poisonous gas which cuts down the amount of {oxygen} the {blood} can carry to the {heart} & all other parts of the body.
Both nicotine & carbon monoxide may encourage {thrombosis}, or {blood} clotting. When you inhale cigarette smoke, the little hairs, {cilia}, in the air passages stop working. Mucus carrying waste substances, tar & nicotine slips back into your {lungs}. Eventually the cilia stop working even when you are not smoking.
