Cell Death

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Cell death can be either uncontrolled (necrosis) or controlled and naturally occurring (apoptosis)

While necrosis is detrimental and causes inflammation, apoptosis is a very important and necessary cellular process


Necrosis

  • Necrosis is the premature death of a cell, caused by disruption to the cell by injury, toxins or nutritional deprivation
  • The cell loses functional control and there is destabilisation of the plasma and organelle membranes
  • This leads to swelling of the cell and organelles due to increased osmotic pressure, and the cell eventually bursts
  • The uncontrolled release of cell contents causes inflammation, potentially damaging surrounding tissue


Apoptosis

  • Apoptosis is programmed cell death (i.e. cell suicide) and is regulated by molecular signals which inhibit or promote this process
  • Mitochondrial proteins play an important role in initiating apoptotic processes
  • Catabolic reactions are triggered which digest cytoplasmic components, including the cytoskeleton
  • The plasma membrane undergoes irregular bulging, or blebbing, and cell contents are repackaged for safe removal
  • The cell shrinks and fragments into apoptotic bodies which are subsequently engulfed by adjoining cells


Apoptosis versus Necrosis


Apoptotic Processes

Examples of processes that involve apoptosis include:

  • The development of fingers and toes in the foetus (as a result of the controlled loss of tissue between them)
  • The loss of endometrial tissue during menstruation occurs via the loss of cells forming part of the uterine lining
  • The removal of excess plasma cells after a successful immune response occurs due to apoptosis
  • Certain infected or cancerous cells may be destroyed via apoptosis