Atherosclerosis begins within which layer of the vessel wall?

• A. Adventitia
• B. Media
• C. Intima
• D. All of the above

Answer: (C)

Atherosclerosis begins in the intima, the innermost layer of the vessel wall. When endothelial function is impaired by risk factors like high cholesterol, hypertension, or smoking, the endothelium becomes more permeable to circulating lipids, especially LDL. LDL migrates into the intima and gets oxidized, which sparks an inflammatory response. Monocytes adhere to the endothelium, migrate into the intima, and become macrophages that uptake oxidized LDL, turning into foam cells. The accumulation of these foamy cells creates the fatty streak, the earliest lesion seen in this disease, and it sits in the intima. Over time, smooth muscle cells from the media can migrate into the intima and contribute to a more complex plaque, but the initial lesion originates in the intima. The adventitia, the outer layer, is not where the process starts.