Cell Injury Flashcards
What is hypoxia?
oxygen deprivation
Which cells are most quickly affected by hypoxia?
Neurones
Name 4 types of hypoxia
- Hypoxaemic hypoxia
- Anaemic hypoxia
- Ischaemic hypoxia
- Histiocytic hypoxia
What is hypoxaemic hypoxia and what might be the cause
The arterial content of O2 is low
Due to decreased pO2 at high altitude or decreased absorption due to lung disease
What is anaemic hypoxia and what might be the cause
Decreased ability of Hb to carry O2
Due to anaemia or cardon monoxide poisoning
What is ischaemic hypoxia and what might be the cause
An interruption interruption in blood supply
Due to blockage of vessel/heart failure
What is histiocytic hypoxia and what might be the cause
Inability of the cells to use O2 due to disabled oxidative phosphorylation
Due to cyanide poisoning
Name 7 mechanisms of cellular injury
- Hypoxia
- Physical agent
- Chemical agents and drugs
- Microorganisms
- Immune mechanisms
- Dietary insufficiency
- Genetic abnormalities
Describe the process of reversible hypoxic injury
- Decrease in oxidative phosphorylation –> decrease in the production ATP
- Lipid deposition due to detachment of ribosomes and therefore decreased protein synthesis and therefore lipid deposition
- Clumping of nuclear chromatin due to increase in glycolysis –> decrease pH, decrease in glycogen
- Oncosis due to decrease in Na+ pump therefore cellular influx of Ca2+, Na+, H2O and efflux of K+ –> cellular swelling, blebbing, ER swelling
What two things occur in irreversible hypoxic injury
-Influx of Ca2+ into the cytoplasm –> also release from stores in mitochondria and ER
-Activation of enzymes e.g. ATPases, phospholipases, proteases, endonucleases
Lysosomal membranes also become damaged and leak their enzymes into the cytoplasm
What is ischaemia reperfusion injury?
The damage caused by blood flow returning to an ischaemic area which isn’t yet necrotic
Damage caused by:
- increased production of free radicals
- increased no. of neutrophils –> inflammation and tissue injury
- delivery of complement proteins and activation of complement
What are free radicals? Give the 3 main free radicals
Reactive oxygen species
OH. O-2 H2O2
What use do we use free radicals for?
Oxidative bursts by leukocytes
What are two reactions that produce free radicals
- Fenton reaction uses Fe2+
- Haber-Weiss reaction
What anti-oxidants do we have?
- Enzymes e.g. catalases, peroxidases
- Scavengers which neutralise free radicals e.g. glutathione, vitamins A,C and E
- Storage proteins - sequester transition metals in ECM (transferrin)
When are heat shock proteins produced?
In response to stress there production is increased
What is the function of heat shock proteins?
Recognised incorrectly folded proteins and repair them by ensuring they are folded correctly and if not then destroying them
What do you see under a light microscope when cellular injury occurs?
- decreased pink staining due to accumulation of H2O
- followed by increased pink staining due to detachment and loss of ribosomes from ER accumulation of denatured proteins
- Nuclear changes
- Abnormal intracellular accumulations
Describe the pattern of nuclear changes that occur with cell injury
Chromatin clumped (reversible)
Pyknosis (shrinkage)
Karryohexis (fragmentation)
Karrolysis (dissolution)
What is oncosis?
Cell death with swelling
The spectrum of changes that occur in injured cells prior to death
What is necrosis?
In living organisms the morphological changes that occur after a cell has been dead some time (4-24 hours)
What is apoptosis?
Cell death with shrinkage induced by regulated intracellular program where cell activates enzymes that degrade its own nuclear DNA and proteins
Uses energy
What is coagulative necrosis and when is it seen?
Denaturation of proteins predominates
‘Ghost outline remains’
White
Solid consistency of tissue
What is liquefactive necrosis and when is it seen
Enzymatic degradation of tissues
Seen in massive neutrophil infiltration due to release of proteases –> seen in bacterial infection
Pus can be present
Occurs in fragile tissues such as brain
