Pathophysiology: Cell Injury Mechanisms

Pathophysiology: Cell Injury Mechanisms

• Definition of Cell Injury

  • Disruption of normal cellular structure or function.
  • Can be reversible (mild injury) or irreversible (severe injury leading to cell death).

• Types of Cell Injury

  • Reversible Injury
    • Cellular adaptations: hypertrophy, hyperplasia, atrophy, metaplasia.
    • Characterized by cellular swelling and fatty change.
  • Irreversible Injury
    • Leads to cell death: necrosis or apoptosis.

• Mechanisms of Cell Injury

  1. Hypoxia

     • Insufficient oxygen supply.
     • Causes ATP depletion, leading to metabolic failure.

  2. Ischemia

     • Reduced blood flow.
     • Results in hypoxia and accumulation of metabolic waste.

  3. Chemical Injury

     • Direct damage from toxins (e.g., heavy metals, drugs).
     • Indirect damage via reactive oxygen species (ROS) and oxidative stress.

  4. Infectious Agents

     • Bacteria, viruses, fungi, and parasites can damage cells.
     • Mechanisms include toxin production and immune response activation.

  5. Immune Reactions

     • Autoimmune diseases can lead to cell damage.
     • Inflammatory responses can cause collateral damage to healthy tissues.

  6. Genetic Factors

     • Mutations can lead to metabolic dysfunctions.
     • Congenital abnormalities may predispose cells to injury.

  7. Physical Agents

     • Mechanical trauma, radiation, temperature extremes.
     • Can directly damage cellular structures.

• Cell Death Types

  • Necrosis

    • Uncontrolled cell death due to injury.
    • Often results in inflammation.
    • Types: coagulative, liquefactive, caseous, fat, and gangrenous necrosis.

  • Apoptosis

    • Programmed cell death, a controlled process.
    • Does not elicit an inflammatory response.
    • Important for normal development and homeostasis.

• Consequences of Cell Injury

  • Tissue damage and dysfunction.
  • Potential for regeneration or scarring.
  • May lead to chronic diseases or organ failure.

• Key Concepts

  • Early detection of cell injury is crucial for intervention.
  • Understanding mechanisms aids in developing therapeutic strategies.
  • Cellular response varies based on type and severity of injury.

Definition and Types of Cell Injury

• Cell injury disrupts normal structure or function, which can be reversible (mild injury) or irreversible (severe leading to cell death).
• Reversible injury includes cellular adaptations: hypertrophy (increase in cell size), hyperplasia (increase in cell number), atrophy (decrease in size), and metaplasia (change in cell type).
• Irreversible injury results in cell death, categorized as either necrosis or apoptosis.

Mechanisms of Cell Injury

• Hypoxia: Insufficient oxygen supply that depletes ATP, leading to metabolic failure.
• Ischemia: Reduced blood flow causes hypoxia and the accumulation of metabolic waste products.
• Chemical Injury: Direct damage from toxins like heavy metals or drugs, and indirect damage from reactive oxygen species (ROS) causing oxidative stress.
• Infectious Agents: Bacteria, viruses, fungi, and parasites damage cells through toxin production or triggering an immune response.
• Immune Reactions: Autoimmune diseases may lead to cell damage due to inflammatory responses that can harm healthy tissues.
• Genetic Factors: Mutations can cause metabolic dysfunctions; congenital abnormalities can increase susceptibility to injury.
• Physical Agents: Mechanical trauma, radiation, and extreme temperatures lead to direct damage of cellular structures.

Types of Cell Death

• Necrosis: Uncontrolled cell death often accompanied by inflammation; types include:
  • Coagulative
  • Liquefactive
  • Caseous
  • Fat
  • Gangrenous necrosis
• Apoptosis: Programmed and controlled cell death without inflammation; vital for normal development and maintaining homeostasis.

Consequences of Cell Injury

• Leads to tissue damage and dysfunction, with the potential for regeneration or formation of scar tissue.
• Can result in chronic diseases or organ failure if cell injury is severe or prolonged.

Key Concepts

• Early detection of cell injury is crucial for effective intervention.
• Understanding injury mechanisms informs the development of therapeutic strategies.
• Cellular response to injury varies based on type and severity, influencing outcomes.