Apoptosis is a form of programmed cell death that occurs in multicellular organisms and in some eukaryotic, single-celled microorganisms such as yeast. Biochemical events lead to characteristic cell changes (morphology) and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, DNA fragmentation, and mRNA decay. The average adult human loses 50 to 70 billion cells each day due to apoptosis. For the average human child between 8 and 14 years old, each day the approximate loss is 20 to 30 billion cells.
An etoposide-treated DU145 prostate cancer cell exploding into a cascade of apoptotic bodies. The sub images were extracted from a 61-hour time-lapse microscopy video, created using quantitative phase-contrast microscopy. The optical thickness is color-coded. With increasing thickness, color changes from gray to yellow, red, purple and finally black. See the video at The Cell: An Image Library
John Sulston won the Nobel Prize in Medicine in 2002, for his pioneering research on apoptosis.
A section of mouse liver showing several apoptotic cells, indicated by arrows
A section of mouse liver stained to show cells undergoing apoptosis (orange)
Programmed cell death is the death of a cell as a result of events inside of a cell, such as apoptosis or autophagy. PCD is carried out in a biological process, which usually confers advantage during an organism's lifecycle. 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 animal tissue development.
Dying cells in the proliferate zone
Cell death in the peripheral vs central nervous system
A conserved apoptotic pathway in nematodes, mammals and fruitflies