Health Topics A-to-Z
What Is It? Atherosclerosis is a narrowing of the arteries that can significantly reduce the blood supply to vital organs such as the heart, brain and intestines. In atherosclerosis, the arteries are narrowed when fatty deposits called plaques build up inside. Plaques typically contain cholesterol from low-density lipoproteins (LDL), smooth-muscle cells and fibrous tissue, and sometimes calcium.