Plaque that accumulates on the inner walls of your arteries is made from various substances that circulate in your blood. These include calcium, fat, cholestrol, cellular waste, and fibrin, a material involved in blood clotting. In response to plaque buildup, cells in your artery walls multiply and secrete additional substances that can worsen the state of clogged arteries.
As plaque deposits grow, a condition called atheroclerosis results. This condition causes the arteries to narrow and harden.