Cell Swelling (Morphological Features of Cell Injury)
Early sign of reversible cell injury due to the influx of water and ions (mainly sodium).
Causes:
Malfunction of energy-dependent ion pumps caused by hypoxia, toxins, or other disruptions to energy production.
Microscopy:
Enlarged, pale, and turgid cells.
Outcome:
Reversible if the stressor is removed; may progress to irreversible injury and cell death if persistent.
Intracellular Accumulation
Abnormal build-up of substances within the cell, which can be endogenous (proteins, lipids, carbohydrates) or exogenous (infectious agents, minerals, pigments).
Examples:
I. Fatty Change: Lipid accumulation.
II. Hyaline Change: Protein accumulation.
III. Hemosiderin Deposition: Iron accumulation.
Outcome:
Can cause cellular dysfunction, injury, or death depending on the nature and severity of the accumulation.
Calcification
Types:
A. Dystrophic Calcification: Localized deposition in injured or dead tissues, such as necrotic areas, heart valves, or atherosclerotic plaques. Not related to calcium metabolism disturbances.
B. Metastatic Calcification: Occurs in normal tissues due to hypercalcemia or calcium metabolism disturbances, affecting organs like kidneys, lungs, blood vessels, and stomach.
Outcome:
Impairs organ function and may lead to further tissue injury or inflammation.
Enzyme Leakage
Release of intracellular enzymes into the extracellular space or circulation due to cell membrane damage.
Causes:
Mechanical trauma, toxins, ischemia.
Clinical Relevance:
Measurement of specific enzymes in the blood (e.g., creatine kinase for myocardial infarction, alanine aminotransferase for liver injury) helps diagnose and monitor tissue damage.
Outcome:
Indicator of cell injury or death, reflecting loss of membrane integrity.
Cell Death
Forms:
A. Apoptosis:
Programmed cell death involving caspase activation.
Features: Cell shrinkage, chromatin condensation, nuclear fragmentation, formation of apoptotic bodies, and phagocytosis by neighboring or immune cells.
Outcome: Typically, does not induce an inflammatory response
B. Necrosis:
Unregulated cell death due to severe injury or membrane damage.
Features: Cell swelling, membrane rupture, leakage of cellular contents, and inflammation in surrounding tissues.
Subtypes: Coagulative necrosis and others with distinct morphological features.
Outcome:
Final consequence of irreversible cell injury.