The word ‘‘atheroma’’ is derived from the Greek stem ‘‘athere,’’ meaning porridge or gruel. When a plaque of atheroma is cut, one can see a gelatinous, thick, porridge¬like material that contains cholesterol and other fatty material. The plaque of atheroma involves the intima and the middle wall of the artery. Apart from a rich fat content, the plaque has a preponderance of smooth muscle cells that are derived from the media. These smooth muscle cells are believed to be very important in the formation and growth of the plaque. Substances such as cholesterol and products released from blood platelets stimulate the smooth muscle cells to proliferate, thus enlarging the plaque. The intima of the artery in contact with the blood is smooth. When atherosclerosis occurs, a plaque of athe¬roma juts into the lumen of the artery. The silky smooth lining of the arteries is damaged by the force of blood as it moves through arteries that are elastic and constantly moving in pulsation. With every pulse wave, the arterial wall yields and stretches; over many years some damage must occur. The damage is partially repaired by small blood particles (platelets), which clump together and plug the damaged surface. These platelet plugs form a temporary patch, just like the plug of coagulated blood that forms when you nick yourself and a very small clot forms. In the coronary arteries or aorta, small clots are commonly formed on the lining. Presumably, these clots are involved in the repair of injuries to the smooth lining of the arteries. These small blood clots are somehow welded into the lining as hard, thickened areas (fibrous plaques). The artery tries to strengthen its wall during this repair job.

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