## Why option 1 is correct The interlobar arteries (structure **B**) run between the renal pyramids in the renal columns and represent the first anatomical division to be END ARTERIES — meaning they have no anastomoses with adjacent vessels. The upper (apical) and anterosuperior segments of the kidney each receive blood from independent segmental arteries derived from the main renal artery. When a segmental artery is occluded (as from cardioembolic source in atrial fibrillation), the territory it supplies undergoes infarction without collateral compensation, producing the characteristic wedge-shaped infarct. This is the core anatomical principle: end-artery distribution + segment-specific vascular supply = segment-specific infarction risk. (Gray's Anatomy 42e Ch 73) ## Why each distractor is wrong - **Option 2**: Interlobar arteries do NOT anastomose with arcuate arteries; they are end arteries. While the upper pole does have limited collateral circulation, the primary reason for segmental infarction is the end-artery nature of the segmental supply, not poor collaterals alone. - **Option 3**: Segmental arteries supply NON-overlapping, distinct territories—this is precisely why segment-specific infarction is possible. Overlapping territories would provide collateral protection. - **Option 4**: Interlobar arteries do not communicate with contralateral renal circulation under any physiological condition. This is anatomically incorrect and confuses renal vascular anatomy with systemic collateral pathways. **High-Yield:** Renal segmental arteries are the FIRST end arteries in the renal vasculature → segment-specific infarction is possible; upper/anterosuperior segment infarcts are most common from cardioemboli in AF. [cite: Gray's Anatomy 42e Ch 73]
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