Ultrastructural finding of irreversible injury
Ans. is 'b' i.e. Amorphous densities in mitochondria Reversible injuryIrreversible injuryGeneralized swelling of the cell and its organelleBlebbing of the plasma membraneDetachment of ribosome from the endoplasmic reticulumClumping of nuclear chromatingIncreased swelling of the cellSwelling and disruption of lysosomesPresence of large amorphous densities in the swollen mitochondriaProfound nuclear changes which include:Pyknosis (nuclear condensation)Karyorrhexis (nuclear fragmentation)Karyolysis (dissolution of nucleus)The earliest changes associated with various forms of cell injury are:decreased generation of A.T.P.loss of cell membrane permeabilitydefect in protein synthesiscytoskeletal damageDNA damageWithin limits the cell can compensate for these derangements and if injurious stimulus is removed, it will return to normality.Persistent or excessive injury, however causes cells to pass the threshold and cause irreversible injury.But the "point of no return" at which irreversible damage has occurred is still largely undetermined thus we have no precise cut off points to establish irreversibility.Actually, there is probably no single final common pathway by which cells die. It is therefore difficult to define the stage beyond which the cell is doomed for destruction.However, two phenomenon consistently characterize irreversibilityFirst is the inability to reverse mitochondrial dysfunction.The second is the development of profound disturbances in membrane function.Membrane damage leads to massive leak of intracellular enzymes and massive influx of calcium.Injury to lysosomal membranes results in leakage of hydrolysis in the cytoplasm, which degrade cytoplasmic and nuclear components.Massive influx of calcium and release of calcium from intracellular stores result in activation of enzymes that can catabolize membranes, proteins, ATP and nucleic acid and cause irreversible damage to the cells.
Ribosomal detachment from endoplasmic reticulum
Amorphous densities in mitochondria
Formation of phagolysosomes
Cell swelling
Mechanisms of Cell Injury