Blood Vessels

TS Artery endothelium lining muscle layer lumen connective tissue with elastic fibres connective tissue lumen

Vein Relatively large lumen Thin muscle layer

Capillaries Capillary networks in tissues

Capillaries Red blood cell Capillary endothelial cell Capillary wall is one cell thick Very small lumen

Atheroma Light micrograph of a cross section through an artery with mild atheroma. The artery wall is pink. The formation of a fatty plaque or atheroma (grey, centre) has greatly narrowed the size of the artery lumen (white, centre). This causes a considerable reduction in blood flow. When this occurs in the arteries leading to the heart symptoms of angina pectoris (gripping pains in the chest) are frequently experienced. In severe cases heart attacks or strokes may occur. Atherosclerosis is principally caused by high fat diets, cigarette smoking, obesity and inactivity

Atheroma & thrombus. Coloured light micrograph of a section through an artery almost completely blocked by atheroma and a thrombus. The large red mass in the centre is a thrombus, an abnormal blood clot. This is attached to a part of the arterial wall that has thickened with atheroma, a fatty deposit containing fibrous tissue, dead cells & cholesterol.

Heart bypass grafts. The coronary arteries are the small blood vessels seen running over the outer surface of the heart. They supply oxygenated blood to keep the heart muscle pumping, and a blockage can cause a fatal heart attack. The solution is to harvest arteries from elsewhere in the body and use them to bypass the blockage. Three grafts makes this a triple bypass operation, indicating an advanced state of heart disease.