reversible cell injury

Two patterns of reversible cell injury can be recognized under the light microscope: cellular swelling and cellular fatty change.

Cellular swelling

Cellular swelling appears whenever cells are incapable of maintaining ionic and fluid homeostasis and is the result of loss of function of plasma membrane energy-dependent ion pumps. Fatty change occurs in hypoxic injury and various forms of toxic or metabolic injury.

It is manifested by the appearance of small or large lipid vacuoles in the cytoplasm and occurs in hypoxic and various forms of toxic injury. It is principally encountered in cells involved in and dependent on fat metabolism, such as the hepatocyte and myocardial cell.

Cellular swelling is the first manifestation of almost all forms of injury to cells. It is a difficult morphologic change to appreciate with the light microscope; it may be more apparent at the level of the whole organ. When it affects many cells in an organ, it causes some pallor, increased turgor, and increase in weight of the organ. On microscopic examination, small clear vacuoles may be seen within the cytoplasm; these represent distended and pinched-off segments of the endoplasmic reticulum. This pattern of nonlethal injury is sometimes called hydropic change or vacuolar degeneration. Swelling of cells is reversible.

The ultrastructural changes of reversible cell injury include:

- plasma membrane alterations

  • plasma membrane blebbing
  • plasma membrane blunting
  • distortion of microvilli
  • creation of myelin figures
  • loosening of intercellular attachments

- mitochondrial changes

  • mitochondrial swelling (swollen mitochondria)
  • mitochondrial rarefaction
  • small phospholipid-rich amorphous densities

- dilation of the endoplasmic reticulum

  • detachment
  • disaggregation of polysomes

- nuclear alterations

  • disaggregation of granular and fibrillar elements

See also

- cellular injury

References

- Robbins

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