Adaptation and Injury of Cells and Tissues

Cells and tissues can react and adjust due to different forms of stimuli, either functional or metabolism-related in vitro and in vivo. The cells, tissues, and organs are capable of adapting when experiencing an excessive or insufficient physiological load, or when a mild and persistent pathological stimulus is present. Damage to cells, tissues, and organs will result in modifications to their morphology, function, and metabolism if the stimulation exceeds their capacity for tolerance and adaptation. Most of the mild damage to cells is reversible, but an irreversible injury to the cell can occur in severe cases. Morphologically, normal cells, adaptive cells, reversible damaged cells, and irreversibly damaged cells are ongoing processes. Under certain conditions, they can transform each other, and their boundaries are sometimes unclear. A specific stimulus can induce adaptation, reversible injury, or irreversible injury. However, which one it induces depends on a number of factors, including the type and degree of stimulation as well as the cells’ susceptibility, differentiation, blood supply, nutrition, and previous state. Adaptation and damage change are fundamental pathological changes in the development of most diseases.