Test your knowledge with Year 3 Pathology MCQs on cell injury, cell death, and cellular adaptations. Master key concepts for your exams.
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 patient with severe burns shows elevated serum levels of cardiac troponin despite no chest pain. This finding indicates: a) Subclinical myocardial infarctionb) Loss of plasma membrane integrity in cardiac myocytesc) Increased synthesis of troponin due to stressd) False positive due to hemolysis Answer: b) Loss of plasma membrane integrity in cardiac myocytes Explanation: Troponins are intracellular proteins released into circulation when plasma membrane integrity is lost during necrosis. Their detection indicates membrane damage and cell death, not increased synthesis. While burns can cause cardiac stress, elevated troponin specifically reflects membrane rupture and protein leakage—a hallmark of necrosis. 8. Acetaminophen overdose causes hepatotoxicity. Administration of N-acetylcysteine is protective primarily because it: a) Inhibits cytochrome P-450 enzymesb) Directly neutralizes the toxic metabolitec) Replenishes glutathione storesd) Blocks apoptosis pathways in hepatocytes Answer: c) Replenishes glutathione stores Explanation: N-acetylcysteine replenishes glutathione (GSH), which is depleted when detoxifying the toxic metabolite of acetaminophen (NAPQI). It doesn't inhibit P-450 or directly neutralize the metabolite. This question tests understanding of the role of glutathione in free radical scavenging and detoxification. 9. In a patient with prolonged ischemia followed by reperfusion, which event occurs LAST in the sequence of injury? a) Calcium influx into mitochondriab) Generation of reactive oxygen speciesc) Loss of selective membrane permeabilityd) Karyolysis with complete nuclear dissolution Answer: d) Karyolysis with complete nuclear dissolution Explanation: Karyolysis (nuclear dissolution) is a late morphologic manifestation of necrosis taking 1-2 days. Calcium influx, ROS generation, and loss of membrane selectivity occur much earlier in the injury sequence. This tests understanding of the temporal progression from biochemical changes to visible morphology. 10. Which mechanism of membrane damage is MOST characteristic of severe ATP depletion? a) Lipid peroxidation by hydroxyl radicalsb) Failure of phospholipid synthesisc) Increased phospholipase activityd) Direct complement-mediated lysis Answer: b) Failure of phospholipid synthesis Explanation: Severe ATP depletion directly impairs energy-dependent biosynthetic pathways, including phospholipid synthesis, affecting all cellular membranes. While calcium-mediated phospholipase activation (c) occurs, decreased synthesis (b) is the MOST direct consequence of ATP loss. ROS generation requires some residual metabolism. SECTION 2: NECROSIS & APOPTOSIS 11. A pathologist examines tissue from a myocardial infarct that occurred 18 hours ago. The expected microscopic finding would be: a) Complete loss of tissue architecture with liquefactionb) Preserved cellular outlines with loss of nucleic) Granulomatous inflammation with caseous necrosisd) Apoptotic bodies surrounded by macrophages Answer: b) Preserved cellular outlines with loss of nuclei Explanation: Coagulative necrosis (typical of myocardial infarction) preserves tissue arc