An abdominal aortic aneurysm (AAA) occurs most commonly infrarenally and is associated with atherosclerosis. The key pathological mechanism causing vessel wall weakening is:

• A Inflammatory cell infiltration in adventitia and media with MMP-mediated elastin and collagen degradation ✓
• B Intimal fibrous plaque obstructing flow and causing pressure necrosis
• C Calcium deposition in the media replacing elastic lamellae
• D Smooth muscle cell proliferation reducing vessel compliance

Explanation

AAA pathogenesis involves inflammatory infiltration (macrophages, T cells) in the adventitia and media, which release matrix metalloproteinases (MMP-2, MMP-9) that degrade elastin and type I collagen. This leads to progressive medial thinning and loss of tensile strength. While atherosclerosis initiates the process by causing ischemia of the vasa vasorum and oxidative stress, the mechanical failure is due to MMP-mediated extracellular matrix destruction rather than obstructive plaque.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.