Atherosclerosis is the hardening and narrowing of arteries caused by the build-up of fatty deposits in their walls. It develops over many years and is the main cause of most cardiovascular disease. It happens in arteries, not veins, because arterial blood is at high pressure.The process follows a sequence:1. Endothelial damage. The endothelium lining the artery is damaged, for example by high blood pressure or by toxins from smoking.2. Inflammatory response. The damage triggers an inflammatory response. White blood cells move into the artery wall.3. Atheroma formation. These white blood cells accumulate chemicals from the blood, particularly cholesterol (carried in low-density lipoproteins, LDLs). A fatty deposit called an atheroma builds up under the endothelium.4. Plaque formation. Calcium salts and fibrous tissue also build up at the site. This forms a hard, swollen area in the wall called a plaque. The artery wall becomes stiffer and loses its elasticity.5. Narrowing. The plaque bulges into the lumen, narrowing the artery. This makes it harder for blood to flow through.
Narrowed, less elastic arteries raise blood pressure. The raised pressure causes more damage to the endothelium elsewhere, so more atheromas form, which raises blood pressure further. This is positive feedback, and it explains why atherosclerosis tends to get worse over time.Atherosclerosis can lead to further problems, including blood clots, aneurysms, heart attacks and strokes.
Narrowed, less elastic arteries raise blood pressure. The raised pressure causes more damage to the endothelium elsewhere, so more atheromas form, which raises blood pressure further. This is positive feedback, and it explains why atherosclerosis tends to get worse over time.Atherosclerosis can lead to further problems, including blood clots, aneurysms, heart attacks and strokes.