Heart Attack Pathology: Photo Essay (cont.)
What happens to the coronary artery in atherosclerosis?
In coronary artery disease (coronary atherosclerosis), injury to the intima
of the artery leads to the formation of plaques, which are regions of thickening
on the inner lining of the artery. How then do the plaques form? In response to
the injury, the smooth muscle cells (SMCs) from the media and perhaps from the
adventitia move (migrate) into the intima. In the intima, these SMCs reproduce
themselves (divide) and make (synthesize) connective tissue. These processes of
migration, division, and synthesis, which collectively are referred to as
intimal proliferation (buildup), cause thickening of the intima. When cholesterol, other fats, and inflammatory cells, such as white blood cells,
enter the proliferating, thickened intima, the result is an atherosclerotic
plaque. Then, as these plaques grow, they accumulate scar (fibrous) tissue and
abundant calcium. (Calcium is the hard material in our teeth and bones.) Hence,
the plaques are often hard, which is why atherosclerosis is sometimes referred
to as "hardening of the arteries."
Who gets coronary artery plaques and what happens to the plaques?
Most adults in industrialized nations have some plaques (atherosclerosis) on the inner (lumenal)
surface of their coronary arteries. Autopsy studies of young soldiers who died
in World War II, the KOrean War, and the Vietnam War showed that even young adults in their 20s usually have
coronary arteries that exhibit localized (focal) thickening of the intima. This
thickening is the beginning of intimal proliferation and plaque formation. The
distribution, severity (amount of plaque), and rate of growth of the plaques in
the coronary arteries vary greatly from person to person. Figure 2 shows a
coronary artery with an uneven (asymmetric), stable atherosclerotic plaque. A
stable plaque may grow slowly, but has an intact inner (lumenal) surface with no
clot (thrombus) on this surface.
Figure 2: Coronary Artery with Stable Atherosclerotic Plaque
Cross-sectional Microscopic View
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