Cellular Dysfunction

Page 1: Introduction to Cellular Dysfunction

Page 2: Overview of Cellular Dysfunctions

  • Cellular dysfunctions can be categorized into:

    • Normal Cell: Functions optimally.

    • Adapted Cell: Adapts to stress.

    • Reversible Injury: Mild, temporary cell injury that can progress or resolve.

    • Irreversible Injury: Leads to cell death.

Page 3: Adaptation Mechanisms

  • Understanding adaptation in cells is crucial for recognizing injury responses.

Page 4: Types of Cellular Adaptation

  • Atrophy: Reduction in cell size and subsequently organ size.

  • Hypertrophy: Increase in cell size and organ size due to increased demand or stimulation.

  • Hyperplasia: Increase in the number of cells due to enhanced division.

  • Metaplasia: Replacement of one mature cell type with another.

  • Dysplasia: Atypical hyperplasia characterized by abnormal changes in cell size, shape, and organization.

Page 5: Atrophy

  • Definition: Decrease in cell size leading to a reduction in organ size.

  • Causes:

    • Reduced workload or use.

    • Decreased blood supply.

    • Nutritional deficiencies.

    • Absence of nervous stimulation.

Page 6: Hypertrophy

  • Definition: Increase in cell size leading to larger organs.

    • Physiologic Hypertrophy: e.g., muscle cell enlargement from weightlifting.

    • Pathologic Hypertrophy: e.g., enlarged heart cells from hypertension.

  • Mechanism: Increased protein synthesis, not fluid.

Page 7: Metaplasia and Dysplasia

  • Metaplasia: Reversible replacement of one mature cell type with another.

  • Dysplasia: Result of chronic or severe injury, featuring abnormal cell growth.

Page 8: Hyperplasia

  • Definition: Increase in the number of cells due to increased division.

    • Types:

      • Compensatory Hyperplasia: Not observed in heart, nerve, muscle, and eye lens cells.

      • Hormonal Hyperplasia: Increase in cell numbers due to hormonal stimulation.

      • Pathologic Hyperplasia: Abnormal multiplication of normal cells.

Page 9: Dysplasia

  • Definition: Characterized by changes in size, shape, and organization of mature cells.

    • Mild Dysplasia: Presence of abnormal cells but not invading.

Page 10: Definitions of Cellular Adaptation Types

  • Atrophy: Decreased cell size.

  • Hypertrophy: Increased cell size.

  • Hyperplasia: Increased cell number.

  • Metaplasia: Conversion of one cell type to another.

  • Dysplasia: Disorderly growth of cells.

Page 11: Introduction to Cellular Injury

  • Explore the etiology and implications of cellular injury.

Page 12: Causes of Cellular Injury

  • Most common cause: Hypoxia/Ischemia.

    • Examples include Myocardial Infarction (MI) and Cerebrovascular Accident (CVA).

    • Risk of reperfusion injury (oxidative stress) associated with these conditions.

Page 13: Mechanisms of Ischemia-Induced Injury

  • Obstruction of blood flow leads to:

    • Severe vacuolization of mitochondria.

    • Altered ATP production and sodium pump function.

    • Results in cellular swelling and reduced protein synthesis.

Page 14: Oxidative Stress

  • Causes include:

    • Free Radical Formation: From normal respiration, radiation, inflammation, drug exposure, or reperfusion injury.

Page 15: Reperfusion Injury

  • Definition: Injury following restoration of blood flow after ischemia.

    • Results in necrosis and generation of damaging radicals (O2, H2O2, OH).

Page 16: Additional Causes of Cellular Injury

  • Chemical Exposures: Tylenol, heavy metals (lead, mercury), carbon monoxide, ethanol.

  • Infectious Agents: Exotoxins and endotoxins from bacteria.

Page 17: Other Mechanisms of Injury

  • Electrical Injury: Disrupts neural and cardiac impulses.

  • Hyperthermia: Causes thermal damage.

  • Immunologic or Inflammatory Injury: Results from immune responses.

  • Physical Trauma: External injuries.

  • Genetic Disorders: Inherited cellular dysfunctions.

Page 18: Reversible Cell Injury Manifestations

  • Initial signs include:

    • Cellular infiltrations (accumulated substances such as water and energy stores).

Page 19: Infiltrations (Accumulations)

  • Common infiltrates: Water, energy stores (lipids, carbohydrates), calcium.

Page 20: Hydropic Swelling Manifestation

  • Mechanism involves malfunctioning Na+/K+ pump leading to increased intracellular sodium and water, causing cell swelling.

  • Early manifest of all types of cellular injury.

Page 21: Hydropic Degeneration

  • Develops from hypoxic conditions leading to:

    • Distended endoplasmic reticulum and extensive vacuolation due to osmotic pressure increase.

Page 22: Energy Stores and Supply

  • Imbalance in lipid and carbohydrate production/utilization compresses cellular components, affecting organs such as liver, blood vessels, kidneys, or heart.

Page 23: Calcium Imbalance

  • Altered levels lead to calcification, which affects membrane permeability.

  • Importance of maintaining serum calcium levels for cardiac and bone health.

Page 24: Systemic Manifestations of Injury

  • Symptoms include:

    • Fatigue, malaise, altered appetite, fever (often from inflammatory response), and tachycardia.

Page 25: Irreversible Cell Injury Manifestations

  • Discussion of necrosis types following irreversible injury.

Page 26: Types of Cellular Necrosis

  • Coagulative: Due to hypoxia, causing protein denaturation.

  • Liquefactive: ischemic injury damaging neurons and glial cells.

  • Caseous: Characteristic of Mycobacterium tuberculosis in lung tissue.

Page 27 to 29: Necrosis Types Descriptions

  • Specific descriptions of coagulative, liquefactive, and caseous necrosis types, citing relevant sources.

Page 30: Gangrenous Necrosis

  • Definition: Cellular death in a large tissue area due to hypoxic injury.

  • Types:

    • Dry, Wet, and Gaseous (Clostridium infection).

Page 31: Gangrene Overview

  • Details of gangrene as a significant form of tissue necrosis due to various factors.

Page 32: Apoptosis

  • Definition: Programmed cell death triggered by lack of survival signals.

    • Involves intrinsic and extrinsic cellular pathways.

Page 33: Characteristics of Apoptosis

  • Non-inflammatory process initiated via signal pathways.

  • Considered a scheduled death mechanism.

Page 34: Comparison of Apoptosis vs. Necrosis

  • Apoptosis: Involves single cells with nuclear fragmentation and macrophage cleanup.

  • Necrosis: Involves groups of cells with cell swelling and rupturing.


Reversible vs. Irreversible Cellular Injuries

Reversible Injury:

  • Definition: Mild, temporary cell injury that can progress or resolve.

  • Characteristics:

    • Cells can recover fully if the stressor is removed.

    • Initial signs include cellular infiltrations, such as an accumulation of water and energy stores.

    • Commonly associated with hydropic swelling due to malfunctioning Na+/K+ pump.

Irreversible Injury:

  • Definition: Cellular injury that leads to cell death.

  • Characteristics:

    • Results in necrosis, which can manifest in different forms (e.g., coagulative, liquefactive, caseous).

    • Associated with severe hypoxia, ischemia, and other damaging factors that cannot be reversed.

    • Death of the cell is evident, often leading to extensive tissue damage.


Cells are susceptible to various types of injuries, including but not limited to:

  1. Hypoxia/Ischemia: Lack of adequate oxygen supply, leading to cellular injury and potential necrosis.

  2. Chemical Exposures: Harmful substances such as Tylenol, heavy metals (like lead and mercury), carbon monoxide, and ethanol can induce cellular injury.

  3. Infectious Agents: Bacterial exotoxins and endotoxins can cause direct injury to cells.

  4. Electrical Injury: Disruption of neural and cardiac impulses due to electrical currents.

  5. Hyperthermia: Excessive heat leading to thermal damage to cells.

  6. Immunologic or Inflammatory Injury: Damage resulting from immune responses, including inflammation.

  7. Physical Trauma: Direct injury from external sources.

  8. Genetic Disorders: Inherited defects that lead to cellular dysfunction.



Manifestations of Reversible InjuryInitial signs of reversible injury include several types of cellular infiltrations, particularly:

  1. Water Infiltration: This occurs due to malfunctioning Na+/K+ pumps, leading to increased intracellular sodium and water, which causes cell swelling.

  2. Energy Stores/Supply Infiltration: This involves the accumulation of lipids, carbohydrates, proteins, and glycogen within the cells. Imbalances in lipid and carbohydrate production/utilization can compress cellular components, affecting organs such as the liver, blood vessels, kidneys, or heart.

  3. Calcium Infiltration: Altered calcium levels can lead to calcification, impacting membrane permeability. Maintaining serum calcium levels is crucial for cardiac and bone health.



Manifestations of NecrosisNecrosis is a form of irreversible cell injury that leads to cell death. The main types of necrosis include:

  1. Coagulative Necrosis:

    • Description: Characterized by protein denaturation due to hypoxia, causing the affected tissues to retain their architecture but appear pale and firm. Commonly seen in myocardial infarction.

    • Cause: Commonly caused by ischemia, leading to oxygen deprivation in tissues.

  2. Liquefactive Necrosis:

    • Description: Involves the transformation of the tissue into a liquid viscous mass due to the enzymatic digestion of dead cells. It often results in the formation of abscesses.

    • Cause: Typically occurs in brain tissue following ischemic injury, where the tissue becomes soft and liquefied.

  3. Gangrenous Necrosis:

    • Description: Refers to the death of tissue in a large area, generally due to severe hypoxic injury. It can be classified into three types:

      • Dry Gangrene: Characterized by the dry and shriveled appearance of affected tissues, often due to reduced blood supply (ischemia).

      • Wet Gangrene: Involves moist and swollen tissues, typically resulting from bacterial infection and associated with liquefaction necrosis.

      • Gaseous Gangrene: Caused by Clostridium infections that produce gas within tissues, leading to swelling and systemic problems.

These manifestations highlight the variations in presentation and causes of necrosis, each with distinct pathological implications for affected tissues.