Atherosclerosis. Light micrograph of a section through a human aortic aneurysm showing an atheroma plaque that has formed on the interior of the aortic wall. The aorta is the main artery that takes blood from the heart to the body. The fibrolipid atheroma plaque is composed of areas of lipid (fatty) and fibrous tissue. The process of atheroma formation is accompanied by a loss of supporting elastic tissue that results in the eventual dilation of the wall, and is the basis for the formation of an aneurysm (a balloon-like swelling) in the artery.