Cell Death and Damage

• Cell Death and Damage

  Cells divide and they die
• Necrosis


  Most common cause of cell death. Occurs after stresses such as restriction of blood supply, trauma, chemical injury. Cell death by accident.
• Apoptosis


  Programmed cell death. Designed to eliminate unwanted or superfluous host cells through activation of a co-ordinated, internally programmed series of events effected by a dedicated set of gene products.
• Necrosis


  Caused by injury, infection, cancer, infarction, inflammation etc.
• Necrosis


  • Cell swelling, disorganisation of organelles and cell lysis (cell bursts open and contents spill out). The debris that escapes due to cell lysis causes inflammation.
• External factors causing necrosis

  • Mechanical trauma
  • Electric shock
  • Damage to blood vessels
  • Extremely high or low temperature
• Internal factors causing necrosis

  • Toxins
  • Immune system (natural killer cells, peritoneal macrophages)
  • Ischemia/hypoxia (shortage of oxygen)
• Examples of apoptosis

  • Degeneration of tissue between digits
  • Tadpoles lose their tails during metamorphosis
  • Humans lose a tail during embryogenesis
  • Elimination of autoreactive T cells in the thymus
  • Death of neurons that don't successfully connect to target cells
  • Elimination of lymphocytes following an immune response
  • Sloughing of the endometrium at the start of menstruation
  • Induction by cytotoxic killer cells of virus-infected cells to commit "suicide"
  • Recognition of virus-infected cells by cytotoxic T-lymphocytes
• Pharmacists need to know about apoptosis as many cancer drugs cause cells to die by apoptosis