4. Learning objectives
• General mechanisms of cell injury
• Causes of cell injury
• Pathogenesis of cell injury
• Free radical induced cell injury
• Examples of reversible cell injury
5. Cell Injury – General Mechanisms
• Four very interrelated cell systems are
particularly vulnerable to injury:
– Membranes (cellular and organellar)
– Aerobic respiration
– Protein synthesis (enzymes, structural
proteins, etc)
– Genetic apparatus (e.g., DNA, RNA)
7. • Hypoxia
– Reduced blood flow [ischemia]
– Inadequate oxygenation of the blood due to
cardiorespiratory failure
– Decreased oxygen carrying capacity of the
blood as in anemia and CO poisoning
– Severe blood loss
9. Pathogenesis
• Basic principles
• Nature of injury, duration and severity
• Type , state and adaptability of the injured cell
• Biochemical mechanisms acting on several
essential cellular components.
14. • These are the chemical species that have
single unpaired electron in their outer
orbit.
• Highly reactive, unstable chemicals
• Associated with cell injury
– Chemicals/drugs, reperfusion injury,
inflammation, irradiation, oxygen toxicity,
carcinogenesis
18. Antioxidants
• Endogenous or exogenous substances
which inactivate free radicals
– Vitamins A, C , E
– Sulphydryl containing compounds
• Cysteine and glutathione
– Serum proteins
• Ceruloplasmin and transferrin
19. Hydroxyl free radical
( the most reactive)
Lipid
peroxidation
Protein
oxidation
DNA
damage
Cytoskeletal
damage
Cell death
Mechanism of injury
23. Hydropic change
• Accumulation of water in the cytoplasm
• Cloudy swelling, vacuolar degeneration
• Appears when cells are incapable of
maintaining ionic and fluid homeostasis
• It is the first manifestation of almost all
forms of cell injury
• Reversible cell injury
• Due to impaired regulation of sodium &
potassium on cell membrane.
24.
25.
26. Hydropic swelling. A needle biopsy of the liver of a patient with toxic hepatic
injury shows severe hydropic swelling in the centrilobular zone. The affected
hepatocytes exhibit central nuclei and cytoplasm distended (ballooned) by excess
fluid.