Atherosclerosis. Artwork illustrating a cross section through an artery narrowed by atherosclerosis. A raised yellow plaque is seen in the wall of the artery, this is made of lipids (yellow) and decaying muscle cells encasing crystals of calcium (white). At lower centre, red blood cells, yellow lipid particles, white blood cells (pink) and platelets (blue) are seen escaping. Plaques such as this are found most often in people who have a high concentration of cholesterol in their bloodstream. Narrowing of the arteries increases the risk of blood clots forming, and is associated with coronary heart disease and stroke.