Atherosclerosis Primarily Affects the Inner Layer of Large and Medium-Sized Arteries

Atherosclerosis predominantly impacts the intima, or innermost layer, of large and medium-sized arteries. This condition begins when blood lipid levels rise, allowing lipids to penetrate the endothelial lining and accumulate beneath it. These lipids then attract inflammatory cells to the intima.

Formation of Foam Cells and Inflammatory Response

Once these inflammatory cells arrive, they engulf the lipids and transform into foam cells. Upon their death, foam cells release a cascade of inflammatory factors. These factors serve two key functions: they recruit more inflammatory cells to the intima and stimulate the smooth muscle cells in the arterial media to migrate and proliferate.

Migration and Fibrous Cap Development

The activated smooth muscle cells move from the media into the intima, where they multiply and secrete extracellular matrix proteins. This process contributes to the formation of a fibrous cap surrounding the developing atherosclerotic plaque.

Structure and Stability of Atherosclerotic Plaques

A typical atherosclerotic plaque consists of a peripheral fibrous layer and a central lipid-rich core. The stability of the plaque is largely determined by the size of the lipid core and the thickness of the fibrous cap.

If the lipid core is large and the fibrous cap is thin, the plaque is considered vulnerable and more likely to rupture, potentially leading to serious cardiovascular events. Conversely, when the lipid core is smaller and the fibrous cap is thick and robust, the plaque tends to be more stable and less prone to disruption.