ABSTRACT
Programmed cell death in animals usually, but not exclusively, occurs by apoptosis. Although apoptosis is only one form of programmed cell death, it is by far the most common and best understood, and, confusingly, biologists often use the terms programmed cell death and apoptosis interchangeably. Cells dying by apoptosis undergo characteristic morphological changes. Apoptosis occurs at a staggeringly high rate in the adult human bone marrow, where most blood cells are produced. Animal cells can recognize damage in their various organelles and, if the damage is great enough, they can kill themselves by undergoing apoptosis. Animal cells can recognize damage in their various organelles and, if the damage is great enough, they can kill themselves by undergoing apoptosis. Cells undergoing apoptosis not only have a characteristic morphology but also display characteristic biochemical changes, which can be used to identify apop- totic cells.
