## Why option 1 is right The anchor fact is that sigmoid diverticulosis arises from increased intraluminal pressure (governed by Laplace's law: pressure is inversely proportional to radius) combined with anatomically weak points where the vasa recta penetrate the muscularis propria. The sigmoid colon's smaller diameter generates the highest pressure for the same wall tension, and over decades this pressure gradient forces the mucosa and submucosa through these vasa recta penetration sites, forming pseudodiverticula. This is the primary pathophysiological mechanism in Western diverticulosis (Sleisenger & Fordtran 11e Ch 124). ## Why each distractor is wrong - **Option 2**: The sigmoid colon does not have the thinnest wall; in fact, it has muscular hypertrophy. Mechanical trauma from stool is not the primary mechanism—increased intraluminal pressure is. - **Option 3**: The sigmoid colon's blood supply is adequate; ischemia is not the pathogenic driver. Vasa recta penetration sites are points of structural weakness, not ischemic weakness. - **Option 4**: All segments of the colon possess taeniae coli. The presence or absence of taeniae does not explain sigmoid predominance; the mechanism is pressure and anatomical weak points. **High-Yield:** Sigmoid diverticulosis = small diameter + high pressure (Laplace) + weak vasa recta penetration sites over decades. [cite: Sleisenger & Fordtran 11e Ch 124; AGA Clinical Practice Update on Diverticulitis 2021]
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