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Coronary artery like any other artery is made up of 3 layers:-
1.tunica intima or inner layer
2.tunica media or middle layer3.tunica adventitia or outer layer
LDL cholesterol which is oxidised by free radicals tend to stick in between these damaged endothelial cells.Macrophages from the blood creep inside the tunica intima layer and engulf the oxidised LDL cholesterol.They form fatty streaks in the intima layer as early as infancy in the aorta.Smooth muscle cells from the tunica media proliferate and migrate to the site where macrophages with engulfed oxidised LDL are present.The oxidised LDL cholesterol,the macrophages,smooth muscle cells and fibrinogen form an elevated fatty deposit called plaque.These changes begin to appear in the coronary arteries during puberty.By the third decade most of the fibrous streaks are replaced by these fatty plaques which begin to protrude inside the lumen of the coronary artery.The lumen of the artery narrows.
The affected arteries will not be able to contract well and becomes rigid like a lead pipe.
When about 75% of the coronary artery lumen is occluded by these fatty plaques the second stage,namely angina pectoris sets in!
