Cellular Adaptation and Injury Quiz

Cellular Adaptation

• Cellular adaptation describes how cells respond to various stimuli, maintaining homeostasis or altering their structure and function.
• Adaptation can be reversible, if the stimulus ceases, or irreversible, leading to cell death.

Causes of Cell Injury

• Cell injury can be caused by a variety of factors grouped as hereditary or acquired.
• Hypoxia (oxygen deprivation) is a common cause.
• Physical agents like trauma, burns, radiation, and extreme temperatures.
• Chemicals, including high concentrations of specific substances, alcohol, and smoke.
• Infectious agents, such as bacteria and viruses.
• Immunological reactions, for example, eczema or systemic lupus erythematosus (SLE).
• Genetic mutations.

Morphogenesis of Cell and Intercellular Matrix Injury

• Infiltration: Excessive accumulation of metabolites in cells and the surrounding matrix.
• Decomposition (phanerosis): Breakdown of cellular and extracellular membranes.
• Perverted synthesis: Production of abnormal substances incompatible with normal cellular/tissue function.
• Transformation of initial metabolites to atypical end products.

Cell Injury

• Cells encounter physiologic or pathologic stimuli adapting to preserve viability and function.
• Reversible cell injury is when cells can revert to their normal state after the stimulus ceases, including processes like hyperplasia, hypertrophy, atrophy, and metaplasia.
• Irreversible injury means the cell can't recover, resulting in cell death (necrosis or apoptosis).
• The outcome of cell injury depends on the type, severity, and duration of the injury, and the specific cell type.

Irreversible Cell Injury

• Severe or persistent stimuli result in irreversible cell injury.
• Ultimate cell death can occur through necrosis, apoptosis, pyroptosis, or autophagy.
• Necrosis is a pathological process associated with inflammation.
• Apoptosis is a programmed cell death regulated by specific biochemical processes.
• Necrosis vs. Apoptosis: Necrosis is unorganized/chaotic and inflammatory, whereas apoptosis is ordered/regulated and doesn’t evoke inflammation. Necrosis causes cells and their contents to spill out into the tissue.

Necrosis

• Necrosis is a form of cell death characterized by the breakdown of cellular components.
• It leads to the disruption of cell membranes and the release of cellular contents causing inflammation.
• Necrosis is a pathological process and associated with various types including coagulative, liquefactive, caseous, and fat necrosis.

Apoptosis

• Apoptosis is a programmed cell death process crucial for development and homeostasis.
• It involves cytoplasmic blebbing, formation of apoptotic bodies, resulting in phagocytosis.
• It's a regulated process and does not cause inflammation.
• Apoptosis might indicate DNA damage and apoptosis failure may lead to cancerous phenotypes.

Cell Adaptation Processes

• Hyperplasia is an increase in the number of cells.
  • Physiological: Occurs during normal development or in response to specific physiological stimuli (hormonal hyperplasia, compensatory hyperplasia)
  • Pathological: Occurs due to aberrant signals (hormonal hyperplasia, viral infections)
• Hypertrophy is an increase in the size of cells.
  • Physiological: Skeletal muscle hypertrophy due to exercise
  • Pathologic: Cardiac hypertrophy due to hypertension
• Atrophy: Reduction in cell size.
  • Physiological: Normal aging
  • Pathological: Loss of trophic hormones, diminished blood supply, nerve injury, or disuse
• Metaplasia: Replacing one cell type with another as an adaptive strategy.
  • Pathological (often): Replacement of respiratory columnar cells to squamous cells when exposed to irritants