Which vessel wall layer contributes to plaque lumen formation?

• A. Intima
• B. Media
• C. Adventitia
• D. Endothelium

Answer: (A)

The key idea is that atherosclerotic plaque forms in the innermost vessel wall layer, the intima. Lipids infiltrate through the endothelium into the intima and accumulate, with inflammatory cells and smooth muscle migrating from the media into this layer to build the fibrofatty plaque. As the intima thickens, it encroaches on the lumen, narrowing it. The endothelium lines the lumen and its dysfunction helps start the process, but the actual plaque sits in the intimal layer. The middle (media) and outer (adventitia) layers don’t form the plaque that reduces lumen size.