## Why option 1 is correct The spleen has an **end-arterial circulation** — the segmental arteries do not anastomose at the parenchymal level, meaning there is no collateral blood supply. When a segmental artery (or the splenic artery itself) is occluded by embolus or thrombus, the territory supplied by that artery undergoes ischemic necrosis. This creates a **wedge-shaped (pyramidal) infarct** with its **base at the splenic capsule** (where the artery enters) and its **apex pointing toward the hilum** (following the segmental vascular distribution). This is the pathognomonic gross appearance of splenic infarction and is directly explained by the end-arterial nature of splenic blood supply. [Robbins 10e Ch 4; Sabiston 21e Ch 56] ## Why each distractor is wrong - **Option 2**: The capsule is not more resistant to ischemia; rather, the wedge shape reflects the vascular territory of the occluded artery, not a pressure gradient. The base at the capsule is where the artery enters, not a site of relative resistance. - **Option 3**: Splenic infarction does not begin at the hilum and extend peripherally. The entire segmental territory becomes infarcted simultaneously when the supplying artery is occluded. The wedge shape reflects the arterial territory, not a centrifugal progression. - **Option 4**: The wedge shape is not an artifact of healing; it is the **primary gross morphology** of acute splenic infarction (visible at 24–48 hours) and directly reflects the segmental vascular territory of the occluded artery. It is a pathognomonic finding, not a secondary change. **High-Yield:** Wedge-shaped pale infarct with base at capsule and apex at hilum = end-arterial organ (spleen, kidney) with segmental arteries lacking parenchymal anastomoses. [cite: Robbins Pathologic Basis of Disease 10e Ch 4 (Infarction); Sabiston Textbook of Surgery 21e Ch 56]
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