Atherosclerosis

Atherosclerosis is what happens when a deposit called plaque builds up inside the wall of an artery, the tube blood runs through. Plaque isn't one single substance: inside it there are lipids, which is the word for fats, and pieces of cells as well. As it accumulates, the artery stops being the smooth channel it used to be and either narrows or changes shape, like an old pipe that no longer has the inside diameter it had the day it was installed.

There's a second event, separate from the first: the plaque can rupture. When that happens, a clot can form right there, a plug of thickened blood, and that plug can go one of two ways. It can stay where it is and block that artery, or it can break loose and travel with the blood to somewhere else in the body.