A 58-year-old man with a 30-pack-year smoking history undergoes elective coronary artery bypass surgery. During the procedure, the left anterior descending artery territory is subjected to 45 minutes of ischemia. Reperfusion is then established. On histological examination of the myocardium the following day, which ultrastructural finding is MOST characteristic of irreversible cell injury that occurred prior to reperfusion?
- A Disaggregation of polysomes from the endoplasmic reticulum
- B Flocculent densities within swollen mitochondria ✓
- C Nuclear chromatin clumping at the periphery of the nucleus
- D Cell membrane blebs containing intact organelles
Correct answer: B. Flocculent densities within swollen mitochondria
Explanation
Flocculent (amorphous) densities within swollen mitochondria are the hallmark ultrastructural finding of irreversible ischemic cell injury, representing denatured protein and lipid accumulation in the mitochondrial matrix. Polysome disaggregation, membrane blebbing, and peripheral chromatin clumping are all features of reversible injury that can resolve if the insult is removed in time.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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