Cellular injury happens when the cell is unable to maintain homeostasis in the face of injurious stimuli or stress, which was caused by lack of oxygen, toxic chemicals, infectious agents, genetic factors or physical and mechanical trauma from many causes.
The three factors that determine the level of cellular injury are the severity of the injury from the insult, the duration of the said insult and lastly, the nutritional status of the injured cell. Moreover, injury can be reversible, meaning the injured cells may recover or irreversible type of injury, which the cell will die.