Pathology MCQs: Cell Injury, Cell Death, and Adaptations

**60 Challenging Questions with Detailed Explanations** ## SECTION 1: MECHANISMS OF CELL INJURY **1.** A 52-year-old patient undergoes partial hepatectomy. Despite adequate blood supply, some hepatocytes near the resection margin show reversible injury. Which finding would BEST distinguish this from early irreversible injury? a) Presence of cellular swelling and ER dilationb) Detachment of ribosomes from rough endoplasmic reticulumc) Preservation of mitochondrial membrane potentiald) Accumulation of myelin figures in the cytoplasm **Answer: c) Preservation of mitochondrial membrane potential** **Explanation:** The ability to maintain mitochondrial membrane potential and prevent opening of the mitochondrial permeability transition pore is the key distinction between reversible and irreversible injury. Options a, b, and d can all occur in reversible injury. Once the mitochondrial permeability transition pore opens permanently, the injury becomes irreversible. **2.** During reperfusion of ischemic myocardium, IgM antibodies are deposited in the tissue. This contributes to injury primarily by: a) Direct cytotoxic effects on myocytesb) Activating the complement system locallyc) Blocking membrane ion channelsd) Enhancing free radical production by neutrophils **Answer: b) Activating the complement system locally** **Explanation:** IgM deposition in ischemic tissues leads to complement activation upon reperfusion, contributing to inflammation and tissue injury. While neutrophils do produce free radicals (option d), the specific role of IgM antibodies is complement activation. This is a subtle mechanism of reperfusion injury often overlooked. **3.** A patient with carbon tetrachloride (CCl4) poisoning develops severe hepatotoxicity. The tissue MOST affected is the liver primarily because: a) Hepatocytes have the highest concentration of mitochondriab) The liver concentrates and metabolizes CCl4 via cytochrome P-450c) Hepatic blood flow is slower, allowing more exposure timed) Liver cells lack antioxidant defense mechanisms **Answer: b) The liver concentrates and metabolizes CCl4 via cytochrome P-450** **Explanation:** CCl4 requires metabolic conversion by cytochrome P-450 to the toxic free radical •CCl3. The liver is most affected because it's the primary site of this metabolic conversion, not because of blood flow, mitochondrial content, or lack of antioxidants. This illustrates the principle that organs metabolizing toxins are most vulnerable to indirect chemical injury. **4.** In a hypothermic patient (core temperature 92°F) following traumatic brain injury, which mechanism PRIMARILY accounts for the neuroprotective effect? a) Increased production of heat shock proteinsb) Enhanced activity of membrane ion pumpsc) Decreased metabolic demands and free radical formationd) Improved cerebral blood flow and oxygen delivery **Answer: c) Decreased metabolic demands and free radical formation** **Explanation:** Induced hypothermia reduces metabolic demands of stressed cells, decreases cell swelling, suppresses free radical formation, and inhibits inflammatory responses. It does NOT improve blood flow or enhance ion pump activity—rather, it reduces the need for these energy-dependent processes. Heat shock proteins are produced in response to heat, not cold. **5.** A researcher observes that cells in culture survive longer under hypoxic conditions compared to ischemic conditions, despite similar oxygen levels. This difference is BEST explained by: a) Hypoxia allows continued removal of toxic metabolitesb) Ischemia causes more severe mitochondrial swellingc) Blood flow maintains extracellular pH in hypoxiad) Ischemia prevents delivery of glucose for glycolysis **Answer: d) Ischemia prevents delivery of glucose for glycolysis** **Explanation:** While hypoxia reduces oxygen, blood flow continues, allowing delivery of glucose for anaerobic glycolysis. In ischemia, blood flow stops, so substrate delivery for glycolysis also ceases and metabolites accumulate. Options a and c are partially correct but d is the PRIMARY reason—without glucose, even anaerobic ATP production fails. **6.** Which statement about the mitochondrial permeability transition pore is MOST accurate? a) Its opening is an early reversible event in cell injuryb) It forms channels primarily in the inner mitochondrial membranec) Opening results in loss of membrane potential and ATP depletiond) It is composed primarily of BAX and BAK proteins **Answer: c) Opening results in loss of membrane potential and ATP depletion** **Explanation:** Opening of the mitochondrial permeability transition pore is a high-conductance channel in the mitochondrial membrane that causes loss of membrane potential, failure of oxidative phosphorylation, and ATP depletion—marking irreversible injury. BAX and BAK form different channels specifically for apoptosis. The pore opening is NOT reversible once it occurs persistently. **7.** A patien