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Questions and Answers
Which of the following is a cause of cell injury?
What characterizes reversible cell injury?
What can lead to depletion of ATP in cells?
What is the earliest manifestation of all forms of cell injury?
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Which mechanism is NOT associated with cell injury?
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What is the most significant target of injurious stimuli in cells?
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Which of the following cellular changes occurs during reversible injury?
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What occurs due to irreversible cell injury?
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Which organ is most likely affected by fatty change due to active lipid metabolism?
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What staining characteristic indicates loss of RNA in injured cells?
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Which agent is a cause of cell injury related to nutrition?
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What is one of the consequences of mitochondrial membrane damage?
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What is a common feature observed in early ischemic injury?
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What triggers apoptosis in the process of mitochondrial permeability transition?
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What happens to intracellular calcium levels during mitochondrial permeability transition?
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Which of the following is a byproduct of mitochondrial respiration and can cause oxidative stress?
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Which of the following antioxidants is effective in scavenging free radicals?
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What indicates the presence of oxidative stress in cells?
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What is the ultimate consequence of increased permeability of cellular membranes?
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What response is triggered by the accumulation of misfolded proteins in the endoplasmic reticulum?
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Which enzyme is NOT a free radical scavenger?
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Study Notes
Etiology of Cell Injury
- Hypoxia and Ischemia
- Physical Agents
- Chemical Agents and Drugs
- Microbial Agents
- Immunologic Agents
- Nutritional Derangements
- Aging
- Psychogenic Diseases
- Iatrogenic Factors
- Idiopathic Diseases
- Genetic Causes
Mechanisms and Morphology of Cell Injury
- Irreversible cell injury occurs when the cell is unable to recover from damage
- The relationship between normal, adapted, reversibly injured, and dead myocardial cells demonstrates the progressive nature of cell injury
Reversible Cell Injury
- Characterized by functional and structural alterations in early stages or mild forms of injury
- Reversible if the damaging stimulus is removed
General Mechanisms of Cell Injury
- ATP Depletion: Failure of energy-dependent functions leading to reversible injury and eventually necrosis
- Mitochondrial Membrane Damage: Results in permeability transition, loss of membrane potential, and leakage of cytochrome C, triggering apoptosis
- Influx of Calcium Ions: Leads to activation of enzymes like ATPases, phospholipases, proteases, and endonucleases, causing membrane damage and increased mitochondrial permeability
- Reactive Oxygen Species (ROS): Highly reactive chemicals capable of damaging lipids, proteins, and nucleic acids, causing oxidative stress
The Most Important Targets of Injurious Stimuli
- Mitochondria
- Cell Membranes
- Protein Synthesis
- Cytoskeleton
- Genetic Apparatus
Depletion of ATP
- ATP is crucial for essential cellular functions like membrane transport, protein synthesis, and lipogenesis
- Depletion of ATP: Triggers failure of energy-dependent functions, leading to reversible injury and ultimately necrosis
- Associated with hypoxic and chemical (toxic) injury
Mitochondrial Membrane Damage
- Result of increased intracellular calcium, oxidative stress, and breakdown of phospholipids
- Formation of MPT (Mitochondrial Permeability Transition): Loss of membrane potential and leakage of cytochrome C, ultimately triggering apoptosis
Influx of Calcium Ions
- Normal intracellular calcium levels are low (<0.1 mmol) compared to extracellular calcium (1.3 mmol)
- Increased cytosolic calcium: Activates various enzymes, leading to membrane damage
Oxygen Free Radicals
- Unstable byproducts of mitochondrial respiration
- Capable of damaging lipids, proteins, and nucleic acids
Removal of Free Radicals
- Spontaneous decay
- Antioxidant mechanisms: Vitamins E, A, C, and glutathione, storage proteins like transferrin, ferritin
- Free radical scavengers: Enzymes such as catalase, superoxide dismutase (SOD), and glutathione peroxidase
Membrane Damage
- Affects plasma membrane, lysosomal membranes, and mitochondrial membranes
- Often culminates in necrosis
Protein Misfolding
- Accumulation of unfolded or misfolded proteins in the ER leads to the unfolded protein response
- Triggers apoptosis
Reversible Cell Injury: Morphology
- Generalized swelling of the cell and its organelles (hydropic change or vacuolar degeneration): Earliest manifestation of cell injury
- Blebbing of the plasma membrane
- Detachment of ribosomes from the ER
- Clumping of nuclear chromatin
- Fatty Change: Occurs in organs involved in lipid metabolism (e.g., liver)
Morphologic Changes in Cell Injury
- The cytoplasm of injured cells appears red (eosinophilic) due to loss of RNA, which binds the blue hematoxylin dye.
- The eosinophilia becomes more pronounced with progression toward necrosis.
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Description
This quiz covers the various causes and mechanisms of cell injury, focusing on topics like hypoxia, ischemia, and the roles of different agents in cell damage. Explore the differences between reversible and irreversible cell injury, and gain insights into the morphology changes associated with these processes.
