From which organ is the tissue sample taken in the image?

• A. Kidney
• B. Liver
• C. Heart
• D. Lung

Answer: (A)

Recognizing tissue origin on a histology image comes down to distinctive architecture and cell appearance. Kidney tissue in the cortex is characterized by renal corpuscles—rounded glomeruli surrounded by Bowman's capsule—mixed with tubular structures. The glomerulus, a compact tuft of capillaries enclosed by Bowman's capsule, is the hallmark of renal tissue. The tubules nearby show specific features: proximal tubules with a tall epithelium and a prominent brush border, giving a bright, granular cytoplasm; distal tubules with a smaller lumen and less prominent staining; and collecting ducts that are larger and pale-staining. This combination of renal corpuscles and specialized tubules is not seen in liver, heart, or lung, which exhibit different patterns—liver with hexagonal lobules and portal triads; heart with densely packed striated muscle fibers and intercalated discs; lung with alveolar air spaces and thin alveolar walls.