Cell injury occurs when cells encounter stresses that disrupt their internal or external environment. The type and severity of injury depends on factors like the cell/tissue type, extent of injury, and type of injuring agent. Injuries can be caused by genetic defects, hypoxia/ischemia, physical/chemical/microbial agents, nutritional issues, and aging. Initial responses include ATP depletion, mitochondrial damage, calcium influx, and free radical accumulation. Reversible injury may be repaired upon stress removal, but irreversible injury leads to cell death through DNA breakdown and autolysis.

1. Dr. Tulika Chaudhary

3.  Cell injury is defined as a variety of stresses a cell
encounters as a result of changes in its internal &
external environment.
 The cellular response to strees may vary & depends
upon following:
 The type of cell and tissue involved
 Extent and type of cell injury
and type of cell injury

4.  Genetic causes:-
• Developmental defect: errors in morphogenesis
• Cytogenetic defects: chromosomal abnormalities
• Single gene defects

5.  Hypoxia and ischemia
 Physical agents
 Chemical agents
 Microbial agents
 Immunological agents
 Nutritional derangements
 Ageing
 Psycogenic factors
 Idiopathic disease

6.  Hypoxia result from reduced blood supply
(Ischemia)
 Loss of oxygen carrying capacity of the blood
(anemia or CO poisoning)

7.  Trauma
 Heat
 Cold
 Radiation
 Electric shock

8.  Chemical poisons; cynide,arsenic
 Strong acids and alkali
 Environmental pollutants
 Insecticides and pesticides

9.  Injuries by microbes include infections caused
by: bacteria,viruses,fungi,protozoa,metazoa and other
parasites.

10.  Nutritional deficiency disease:
 Marasmus,Anaemia
 Nuritional excess problems:
 Obesity,hypertension,heart disease

11.  Depletion of ATP
 Mitochondrial damage
 Influx of intracellular calcium and loss of calcium
homeostatis
 Accumulation of oxygen-derived free radical
 Defects in membrane permeability

12.  ATP depletion and decreased ATP synthesis and are
associated with both hypoxic & chemical injury.
 ATP required for many synthetic and degradative
processes within the cell.

13.  Reversible cell injury
 Irreversible cell injury

15.  If the ischaemia or hypoxia is of short duration, the
effect are reversible on rapid restoration of circulation.
 Changes in reversible cell injury are:
• Decreased cellular ATP
• Reduced intracellular PH
• Damage to plasma membrane sodium pump
• Swelling of mitochondria and endoplasmic reticulum
• Cellular swelling and vacuole formation

17.  Cell death is a state of irreversible cell injury
 The changes are produced by enzymatic digestion of
dead cellular elements, denaturation of protein and
autolysis.
 In nucleus non specific breakdown of DNA, these may
lead to:
 Pyknosis(shrinkage)
 Karyolysis(fading)
 Karyorrhexis(fragmentation)