Lecture I
Cards (8)
- Cell injury is reversible up to a point, but if the injurious stimulus is persistent or severe, the cell suffers irreversible injury and ultimately undergoes cell death
- Causes of cell injury include:
- Oxygen Deprivation: reduction of aerobic oxidative respiration
- Physical Agents: mechanical trauma, extremes of temperature (burns and deep cold), sudden changes in atmospheric pressure, radiation, and electric shock
- Chemical Agents and Drugs
- Infectious Agents
- Immunologic Reactions
- Genetic Abnormalities
- Nutritional Imbalances
- Progression of Cell Injury and Death:
- Reversible Cell Injury:
- Early stage: characterized by reversible cellular swelling (e.g., hydropic degeneration)
- Late stage: characterized by irreversible membrane damage and cell death
- Adaptations of Cellular Growth and Differentiation:
- Changes experienced by cells in response to physiological or pathological stimuli
- Persistent stress can lead to cell injury
- Hypertrophy:
- Increase in the size of cells that increases the size of the affected organ
- Mechanisms of Hypertrophy:
- Result of increased cellular protein production
- Activation of signaling pathways and production of growth factors
- Hyperplasia:
- Increase in the number of cells in an organ or tissue in response to a stimulus
- Mechanisms of Hyperplasia:
- Result of growth factor-driven proliferation of mature cells and, in some cases, increased output of new cells from tissue stem cells
- Atrophy:
- Reduction in the size of an organ or tissue due to a decrease in cell size and number
- Mechanisms of Atrophy:
- Results from decreased protein synthesis and increased protein degradation in cells
- Metaplasia:
- Reversible change in which one differentiated cell type is replaced by another cell type
- Metaplasia does not result from a change in the phenotype of an already differentiated cell type; it results from either the reprogramming of local tissue stem cells or colonization by differentiated cell populations from adjacent sites