Apoptosis

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Apoptosis (pronounced /ˌæpəˈtoʊsɪs/ or /ˌæpəpˈtoʊsɪs/)[1][2] is the process of programmed cell death (PCD) that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes include blebbing, loss of cell membrane asymmetry and attachment, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation. (See also Apoptosis DNA fragmentation.) Apoptosis differs from necrosis, in which the cellular debris can damage the organism.

In contrast to necrosis, which is a form of traumatic cell death that results from acute cellular injury, apoptosis, in general, confers advantages 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. Between 50 and 70 billion cells die each day due to apoptosis in the average human adult.[medical citation needed] For an average child between the ages of 8 and 14, approximately 20 billion to 30 billion cells die a day.[medical citation needed]

Research in and around apoptosis has increased substantially since the early 1990s. In addition to its importance as a biological phenomenon, defective apoptotic processes have been implicated in an extensive variety of diseases. Excessive apoptosis causes atrophy, such as in ischemic damage, whereas an insufficient amount results in uncontrolled cell proliferation, such as cancer.

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