Atherosclerosis

Atherosclerosis is a disease process which leads to coronary heart disease and strokes. In atherosclerosis fatty deposits can either block an artery directly, or increase its chance of being blocked by a blood clot (thrombosis). 

The blood supply can be blocked completely. If this happens for too long, the affected cells are permanently damaged. In the arteries supplying the heart (coronary arteries) this results in a heart attack (myocardial infarction) and for the arteries that are supplying the brain, it can result in a stroke. 

1. The endothelium becomes damaged for some reason. The damage could have occured from high blood pressure, which puts an extra strain on the layer of cells, or it might result from some of the toxins from cigarette smoke in the blood stream.

2. After the endothelium is breached, there is an inflammatory response. White blood cells leave the blood vessel and move into the artery wall. These cells accumulate chemicals from the blood particulary cholestrol. A deposit builds up, called an atheroma. 

3. Calcium salts and fibrous tissue also build up at the site, resulting in a hard swelling called a plaque on the inner wall of the artery. The build-up of fibrous tissue means that the artery loses some if its elasticity; in other words it hardens. 

4. Plaque causes the artery to become narrower. This makes it more difficult for the heart to pump blood around the body and this can lead to a rise in blood pressure. Now there is a dangerous positive feedback building up. Plaques lead to raised blood pressure and raised blood pressure makes it more likely for other plaques to be formed.