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.