Apoptosis

apoptosis, also called programmed cell death, in biology, a mechanism that allows cells to self-destruct when stimulated by the appropriate trigger. Apoptosis can be triggered by mild cellular injury and by various factors internal or external to the cell; the damaged cells are then disposed of in an orderly fashion. As a morphologically distinct form of programmed cell death, apoptosis is different from the other major process of cell death known as necrosis. Apoptosis involves condensation of the nucleus and cytoplasm, followed by cellular partitioning into well-defined fragments for disposal. In multicellular organisms, cell number normally results from the rate of cell production minus the rate of apoptosis.