Cell Injury Etiology and Mechanisms

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Questions and Answers

Which of the following is a cause of cell injury?

Excessive exercise

High nutrient levels

Normal aging process

Decreased oxygen levels (correct)

What characterizes reversible cell injury?

Correctable upon removal of stimulus (correct)

Permanent cellular changes

Structural alterations are irreversible

Immediate cell death

What can lead to depletion of ATP in cells?

Hypoxic conditions (correct)

Normal mitochondrial function

Decreased anaerobic glycolysis

Increased protein synthesis

What is the earliest manifestation of all forms of cell injury?

Generalized swelling of the cell and its organelles Signup and view all the answers

Which mechanism is NOT associated with cell injury?

Increased blood flow Signup and view all the answers

What is the most significant target of injurious stimuli in cells?

Cell membranes Signup and view all the answers

Which of the following cellular changes occurs during reversible injury?

Increased eosinophilia of the cytoplasm Signup and view all the answers

What occurs due to irreversible cell injury?

Cell death Signup and view all the answers

Which organ is most likely affected by fatty change due to active lipid metabolism?

Liver Signup and view all the answers

What staining characteristic indicates loss of RNA in injured cells?

Eosinophilia of the cytoplasm Signup and view all the answers

Which agent is a cause of cell injury related to nutrition?

Excessive fat intake Signup and view all the answers

What is one of the consequences of mitochondrial membrane damage?

Loss of calcium homeostasis Signup and view all the answers

What is a common feature observed in early ischemic injury?

Surface blebs Signup and view all the answers

What triggers apoptosis in the process of mitochondrial permeability transition?

Leakage of cytochrome C Signup and view all the answers

What happens to intracellular calcium levels during mitochondrial permeability transition?

Increases due to influx of Ca++ ions Signup and view all the answers

Which of the following is a byproduct of mitochondrial respiration and can cause oxidative stress?

Oxygen Free Radicals Signup and view all the answers

Which of the following antioxidants is effective in scavenging free radicals?

Vitamin C Signup and view all the answers

What indicates the presence of oxidative stress in cells?

Imbalance between radical generating and scavenging systems Signup and view all the answers

What is the ultimate consequence of increased permeability of cellular membranes?

Necrosis Signup and view all the answers

What response is triggered by the accumulation of misfolded proteins in the endoplasmic reticulum?

Unfolded protein response Signup and view all the answers

Which enzyme is NOT a free radical scavenger?

ATP synthase Signup and view all the answers

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.