Cell Injury Flashcards
How is a steady cell state maintained?
- Preservation of genetic integrity
- Normal enzyme content
- Intact membranes and transmembrane proteins
- Adequate supply of substrates and oxygen
Define hyperplasia/hypertrophy, metaplasia and atrophy, give examples of these
Hyperplasia/hypertrophy- increased cellular activity- heart
Atrophy- decreased cellular activity- adrenal glands
Metaplasia- Changed cell morphology- uterus/vagina, Barrett’s oesophagus
What are types of physical trauma?
Mechanical- Disruption of cell structures, thrombosis leading to ischaemia
Extreme temperatures- Fever, ice crystals and heat denature
Name some chemical agents that cause damage to the body
Alcohol Tobacco Drugs Poison Environmental Occupational
Describe infectious organisms
- Produce bacterial endotoxin or exotoxin (C.Diff)
- Collateral damage by inflammation
- Hijacking of cell machinery by viruses (cell lysis)
Describe Irradiation and its mechanism
- Ionising (x-rays, UV light)
- Generates free radicals and direct damage to macromolecules
- Different organs have different sensitivity- high=bone marrow, gonads and intestines low=uterus, pancreas and adrenal
- Induce inflammatory response several hours after exposure
What might be affected by cell injury?
- Mitochondrial function
- Membrane integrity and function
- Protein synthesis
- Cytoskeleton
- Genetic apparatus
Describe the mechanism of action for reversible ischaemic injury
- Cellular swelling/oedema caused by hypoxia/toxins/fever
- Decreased oxidative phosphorylation so reduced ATP levels
- Activity of ATP plasma membrane Sodium pump reduced so influx of Na and Ca= isosmotic gain of water and cellular swelling
- Anaerobic glycolysis inc to generate ATP from glycogen, dec glycogen stores = accumulation of lactic acid = dec intracellular pH
- Dec pH and ATP= ribosomes detach from rough ER and reduction in protein synthesis
What is Sublethal cell injury?
Cell swelling (cloudy) and fatty change - usually alcohol & liver
How does free radical toxicity cause injury?
- Chain reaction with molecules in membrane to produce more radicals
- Damages proteins & nucleic acids leading to apoptosis
- Detoxification by Superoxide dismutase & antioxidants (Vit A,C,E)
- Bacterial killing by neutrophils& macrophages depends on formation of superoxide
How can membrane defects occur by cell injury?
-Compromised by bacterial toxins, viral proteins, cytolytic lymphocytes
-Loss of membrane barriers lead to breakdown in metabolite gradients
-Inc Ca2+ leads to activation of enzymes:
ATPase, Phospholipase(causes membrane damage), Protease(breakdown membrane & cytoskeletal proteins), Endonuclease(DNA fragmentation)
What is necrosis? What types of necrosis are there?
- Passive multiple cell death due to injury causing an inflammatory reaction
- plasma membrane disrupted and enlarged cell size
- Coagulative, Caseous, Gangrene, Fibrinoid(fat), Colliquative
Describe Coagulative necrosis
- Denaturation of intracytoplasmic proteins
- Dead tissue = firm and slightly swollen
- Retention of microscopic architecture
- Most common & typical of ischaemic injury (NOT brain)
- Cellular proteins may leak into blood
- Protein levels can be checked in a blood test of a suspected MI
Describe Colliquative necrosis
- Brain due to no collagen structure
- Liquefaction and then cyst formation
Describe Caseous necrosis
- Characteristic of Tuberculosis
- Cheese like
- Cellular detail destroyed surrounded by granulomatous inflammation
- Dead tissues lack structure
