What Is Atherosclerosis

Atherosclerosis is the process that allows for the buildup of substances within the walls of arteries. This buildup or plaque consists mostly of lipid, protein, and calcium in conjunction with an excessive presence of macrophages and smooth muscle cells. The lipid is mostly cholesterol derived from LDLs while the protein is largely collagen.

As the atherosclerotic plaque grows in size, it causes the wall of that artery to protrude further and further into the blood vessel. This in turn decreases the area for blood to flow through (Figure 13.2). If the narrowing becomes severe enough, it becomes an occlusion and blood flow is reduced to a critical level. Furthermore, if a blood clot develops in this location or it circulates to and gets lodged in this narrowed area, it will dam up blood flow. This is often how heart attacks occur, making them seem so sudden—heart tissue "downstream" does not receive the oxygen that it needs to survive.

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