Cell death is the event of a
biological cell ceasing to carry out its functions. This may be the result of the natural process of old cells dying and being replaced by new ones, or may result from such factors as
disease, localized
injury, or the death of the organism of which the cells are part. Kinds of cell death include:
Programmed cell death (or PCD) is cell death mediated by an intracellular program. PCD is carried out in a regulated
process, which usually confers advantage during an organism's
life-cycle. For example, the differentiation of fingers and toes in a developing human embryo occurs because cells between the fingers
apoptose; the result is that the digits are separate. PCD serves fundamental functions during both plant and
metazoa (multicellular animals) tissue development.