Updated:Nov 16,2017

Atherosclerosis and the role of cholesterol

Atherosclerosis is a big word for a big problem: fatty deposits that can clog arteries. These buildups are called plaque. They’re made of cholesterol, fatty substances, cellular waste products, calcium and fibrin (a clotting material in the blood). 

Watch an atherosclerosis animationSometimes deposits in arteries are compared to a plumbing problem. Think of sludge forming on the inside of pipes. That’s not a perfect comparison because buildups don’t just form on artery walls but inside them. Still, you get the idea.

As plaque builds up, an artery wall gets thicker. This narrows the opening, reducing blood flow and the supply of oxygen to cells.

The type of artery affected and where the plaque develops varies with each person. Plaque may partially or totally block blood flow through a large or medium-sized artery in the heart, brain, pelvis, legs, arms or kidneys. When this happens, various diseases may result. These include:

  • coronary heart disease (plaque in arteries in or leading to the heart),
  • angina (chest pain from reduced blood flow in arteries supplying the heart muscle),
  • carotid artery disease (plaque in neck arteries that supply blood to the brain),
  • peripheral artery disease (PAD; plaque in arteries of the extremities, especially the legs) and
  • chronic kidney disease.

Where plaque occurs, two things can happen. One is that a piece of plaque may break off and be carried by the bloodstream until it gets stuck. The other is that a blood clot (thrombus) may form on the plaque's surface.  If either of these things happen, the artery can be blocked and blood flow cut off.

If the blocked artery supplies the heart or brain, a heart attack or stroke occurs. If an artery supplying oxygen to the extremities (often the legs) is blocked, gangrene can result. Gangrene is tissue death.

How does atherosclerosis start and progress?
Atherosclerosis is a slow, progressive disease that may start in childhood. In some people, it progresses rapidly in their 30s. In others, it doesn't become dangerous until they reach their 50s or 60s. Some hardening of the arteries is normal as you age.

Exactly how atherosclerosis begins or what causes it isn't known, but some theories have been proposed. Many scientists believe plaque begins when an artery’s inner lining (called the endothelium) becomes damaged. Three possible causes of damage are:

Smoking has a big role in the growth of atherosclerosis in the coronary arteries, aorta and arteries in the legs. It makes fatty deposits more likely to form and to grow bigger and faster.

This content was last reviewed April 2017.

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