One of the main ways that smoking increases the risk of heart disease is by activating platelets, cells in blog that stick together and form blood clots. When you cut yourself, this is a good thing, because it stops bleeding. When platelets are activated inappropriately, they stick to the lining of arteries (the endothelium) and tear it up. When a blood clot floating around in your blood stream blocks an artery in your heart it causes a heart attack; when it blocks an artery in your brain is causes a stroke.
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