Light micrograph of a section through a human medium-sized artery, showing the partial obstruction of the interior (lumen) due to atheroma formation (atherosclerosis) on the wall (intima) of the artery. The consequent reduction in blood flow leads to ischemia of the tissue that the vessel supplies. Partial obstruction by atheroma formation is common in the coronary arteries of cigarette smokers, where it provokes the symptoms of angina pectoris, agripping pain in the chest that is experienced on exertion & disappears with rest. Magnification: x50 at 35mm size.