28-10-2010, 05:09 PM
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Apoptosis and necrosis
Cell death
• Cells die by one of two mechanisms – necrosis or
apoptosis
• Two physiologically different processes
– Necrosis – death by injury
– Apoptosis – death by suicide
• Apoptosis and necrosis have different characteristics
Necrosis
• Death by accident
• Associated with nonphysiological circumstances that
disrupt cellular homeostasis (eg., ischemia, hypoxia and
poisoning)
• Necrosis is caused by membrane dissolution (osmotic lysis,
shear stress, pore-forming proteins, loss of ATP)
• Necrosis is bad because cellular material (including
degradative enzymes) is released into surrounding tissue
• Affects contiguous groups of cell
• Necrosis usually causes inflammatory reaction