Cell Death: Apoptosis and Necrosis PDF

Cell Death Bio 4311| Lauri Keogh| AC Cell death – APOPTOSIS Apoptosis naturally occurs to eliminate worn‐out cells, Apoptosis is controlled or cells that have been (programmed), or...

Cell Death Bio 4311| Lauri Keogh| AC Cell death – APOPTOSIS Apoptosis naturally occurs to eliminate worn‐out cells, Apoptosis is controlled or cells that have been (programmed), or produced in excess, that normal cell death develop improperly or have damage to their DNA  Apoptosis Apoptosis is involved in normal physiologic cell deletion and can be involved in abnormal pathologic loss of cells, some examples: during embryonic development of the heart, separation of webbed fingers and toes (physiologic) removal of white blood cells after an inflammatory response (physiologic) the removal of self‐reacting lymphocytes during the development of the immune system (physiologic) Loss of liver cells when infected with hepatitis C (pathologic) During the process of apoptosis, enzymes are activated to degrade cellular DNA and proteins; the plasma membrane is altered (leaky) which leads to phagocytosis of the dying cell Cell death – Necrosis is a pathologic form (dying of Necrosis UN-NATRUAL causes) of cell death resulting from cell injury er … characterized by: cell swelling, rupture urd of the cell membrane and inflammation el l m C there is an unregulated enzymatic digestion of cell components there are different types of necrosis – coagulative, liquefactive, caseous, fat, gangrenous  NECROSIS Coagulative Necrosis most common form of necrosis normally results from hypoxia of tissues/cells proteins coagulate (stick together) forming a solid mass Occurs primarily in: kidneys, heart, & adrenal glands Cell death Liquefactive Necrosis commonly results from ischemia (death from prolonged interruption of blood flow) to neurons and glial cells (support cells to the CNS) in the brain cells are digested by their own hydrolases (enzymes), become soft and liquefy can also occur due to bacterial infection whereby neutrophils release hydrolases to kill bacteria and create an area of pus (we will later call this purulent exudate)  Cell death Caseous Necrosis commonly occurs in the lungs during a primary tuberculosis infection combination of coagulative and liquefactive necrosis dead cells disintegrate, but the debris is not completely digested which leaves the tissue with a cheese‐like appearance (nom nom) necrotic tissue is walled off from rest of tissue Cell death Fat Necrosis Describes death of fat cells. Although it can occur anywhere, it usually occurs in breast tissue, the pancreas and other abdominal organs, often following trauma/injury. It is usually both benign and painless. cellular breakdown is due to powerful lipases (enzymes that breakdown fat) free fatty acids combine with calcium, magnesium and necrotic tissue appears opaque and chalky white lumps  Cell death Gangrenous Necrosis large mass of tissue undergoes necrosis due to severe hypoxic injury because of arteriosclerosis or blockage of major arteries hypoxia followed by bacterial invasion leads to this type of necrosis Includes WET, DRY, GAS gangrene  Gangrene Dry Gangrene is a form of coagulative necrosis area becomes dry and shrinks Dry gangrene from covid skin wrinkles and color changes to dark brown or Dry gangrene, a complication from type II, Diabetes black usually occurs in the extremities  Gangrene Wet gangrene form of liquefactive necrosis area becomes cold, swollen skin is moist can occur on extremities or internal organs foul odor is present due to bacterial invasion release of bacterial toxins into bloodstream could be life‐ threatening (sepsis)  Gangrene GAS gangrene due to the infection of tissue by specific anaerobic bacteria (the ones that don’t need oxygen) (Clostridium). These bacteria are commonly found in soil and so can occur during a compound fracture where dirt/debris are embedded in the wound; gas bubbles are formed in tissue; potentially fatal Compare apoptosis and necrosis  What is the difference between apoptosis and cell necrosis? In apoptosis, does the cell shrink or swell? Which type of necrosis is most common? In fat necrosis, what happens to the fat cells? Which type of necrosis resembles a delicious hors d’oeuvre? What type of gangrene is associated with anaerobes? Why does wet gangrene smell so bad? What type of gangrene is best associated with frostbite? Study questions Test your knowledge