SW

Patho cht 2 study

Introduction to Cellular Injury and Adaptation

  • Cell Injury: Damage to cells and their environment (extracellular matrix) leads to tissue/organ injury.

  • Homeostasis: Cells can adapt to physiological demands or stress to maintain a steady state.

  • Adaptation: Reversible structural or functional response to normal or adverse conditions.

    • Example: Uterus enlarges during pregnancy.

Types of Cellular Responses

  • Adaptation to Stress: Increases size (hypertrophy) or number (hyperplasia) of cells.

  • Cellular Injury Classification:

    • Reversible Injury: Sublethal.

    • Irreversible Injury: Lethal.

    • Types of injury:

      • Chemical

      • Hypoxic (lack of oxygen)

      • Free radical

      • Unintentional/intentional

      • Immunologic/inflammatory.

Mechanisms of Cellular Injury

  • Cellular injury disrupts structures/deprives oxygen and nutrients.

  • Pathologic Calcification: Involves calcium accumulation due to cellular death.

  • Cellular Death: Confirmed by nuclear changes; two main types:

    • Necrosis: Uncontrolled death due to injury.

    • Apoptosis: Programmed cell death.

  • Autophagy: Nutrient deprivation can trigger survival strategies leading to cell death.

Cellular Aging

  • Aging leads to structural and functional changes, reducing recovery capacity from injury.

  • Distinguishing between physiologic and pathologic changes with aging is challenging.

Cellular Adaptation Mechanisms

Types of Adaptation

  • Atrophy: Decrease in cell size.

    • Can be physiologic (e.g., thymus gland in childhood) or pathologic (e.g., disuse atrophy from immobilization).

    • Affects skeletal muscle, heart, brain, etc.

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

    • Types:

      • Physiologic: E.g., muscle growth from exercise.

      • Pathologic: E.g., heart enlargement due to hypertension.

  • Hyperplasia: Increase in cell number from increased cell division, can be compensatory or hormonal.

    • Example: Liver regeneration post-surgery.

Dysplasia and Metaplasia

  • Dysplasia: Abnormal growth not a true adaptation, characterized by disorganized cell architecture.

    • Not cancer, but reversible if stimulating factors are removed.

  • Metaplasia: Reversible replacement of one cell type by another, often seen in response to chronic irritation.

    • Example: Replacement of ciliated cells in smokers by squamous cells.

Conclusion

  • Understanding cellular adaptations, injuries, and death processes is crucial for disease comprehension and management.