Reversible cell injury - B. Pharma 2nd Semester Pathophysiology notes pdf

Reversible cell injury


Reversible cell injury




At the end of this lecture, student will be able to

         Explain the sequence of changes occurring during reversible cell injury

         Explain the morphology of cell injury

         Describe the pathogenesis of cell injury due to hypoxia and ischemia

Reversible cell injury

Pathogenesis of reversible cell injury due to hypoxia and ischemia

       If hypoxia and ischemia is for short duration, the effects are reversible

Sequence of changes occurring during reversible cell injury

  • ↓ cellular ATP
  • ↓ intracellular pH
  • Damage to plasma membrane Na+ pump
  • ↓ protein synthesis
  • Functional consequences
  • Ultra structural changes

Decreased cellular ATP

       ATP required for – Membrane transport

                                     - Protein synthesis

                                     - Lipid synthesis

                                     - Phospholipids metabolism

       Source of ATP – Aerobic and anaerobic respiration

       Hypoxia and ischemia limits the supply of oxygen to cells, decreases ATP production

Decreased intracellular pH

       Low oxygen supply

       Aerobic respiration by mitochondria fails

       ATP generation by anaerobic glycolytic pathway

       Depletion of glycogen

       Accumulation of lactic acid

       Low pH of cell

       Acidosis and clumping of chromatin

Damage to plasma membrane sodium pump

       Na+ /K+ ATP ase -  operates at plasma membrane

       Allows active transport of Na+  out of a cell

       Diffusion of K+ into cell after depolarization

       Low ATP affects Na+ pump functioning

       Outward diffusion of K+ ions

       Intracellular accumulation of Na+    

       Increased intracellular  water -  swelling of affected cell

Decreased protein synthesis

       Continuation of hypoxia

       Detachment of ribosome from granular ER

       Polysomes degraded to monosomes

       Decreased protein synthesis

Functional consequences

       Myocardial contractility ceases in 60 sec of coronary occlusion

       Reversed if circulation restored 

Ultra structural changes

       Normal structure of ER is affected

       Membrane bound polyribosome detach from rough ER

       Swelling of mitochondria

       Myelin figures appear in cytoplasm

       Loss of microvilli

       Reduced synthesis of ribosomal RNA in nucleolus

Morphology of reversible cell injury

Reversible cell injury causes cell degeneration

Cellular swelling

       Due to influx of Na+ ions & H2O , escape of K+ 

       Common causes  - Bacterial toxins

                                     - Chemicals

                                     - Poisons

                                     - Burns

       Most affected organs – Kidney, Liver and Heart

       More vacoules appear

       ER dilates, ribosomes detach

       Mitochondrial swelling

Fatty changes

       Steatosis - Accumulation of fat within parenchymal cells

       Occurs common in liver

       In non – fatty tissues – heart skeletal muscles and kidney

Other changes

       Cytoskeletal changes

       Lysosomal changes

       Hypertrophy of smooth ER

       Intracellular accumulation of protein and glycogen

       Mitochondrial changes


       Hypoxia and ischemia causes cell injury

       If hypoxia and ischemia is for short duration, cell injury can be reversed

       Reversible cell injury brings about decreased cellular ATP, intracellular pH, damage to plasma membrane, decreased protein synthesis and ultra-structural changes

       Reversible cell injury causes cell degeneration

Post a Comment