The death of a cell characterized by the breakdown of cell structures
Cell death pertains to the events leading to the death of a cell either when they have completed a fixed number of division cycles (around 60, the Hayflick limit) or at some earlier stage when programmed to do so, as in digit separation in vertebrate limb morphogenesis. Whether this is due to an accumulation of errors or a programmed limit is unclear, some transformed cells have undoubtedly escaped the limit.
Cell death has two major kinds: (1) programmed cell death and (2) necrosis. Programmed cell death is a kind of cell death that is regulated by an innate physiological system. The cell undergoes a natural process of death after completing a number of cell divisions. The cell ceases to carry out its functions and dies to be replaced by new ones. The programmed type of cell death is further categorized into type I cell death or apoptosis and type II cell death or autophagy. In contrast, necrosis is the death of the cell due to factors such as disease, injury, or the death of the organism.