Cell Injury & Cell Death Flashcards
How do myocytes in the heart adapt to an increased load?
Hypertrophy
They get larger allowing them to pump more blood around the body to allow cells to receive the same amount of oxygen
What happens to myocytes in the cells if there is a second injury to the heart?
It leads to cell injury
If this is not treated, it leads to irreversible cell death
What is meant by hypertrophy and atrophy?
hypertrophy - increase in size of cells
atrophy - shrinkage of cells
What is necrosis?
severe cell swelling and rupture
What is apoptosis?
internally controlled cell death
What is oncosis?
the series of cellular reactions following injury that precede cell death
What are the major 7 causes of cell injury?
- hypoxia
- physical agents
- chemical agents
- immunological reactions
- infectious agents
- genetic derangements
- nutritional imbalances
How does trauma cause cellular injury?
through mechanical disruption of tissue
How does carbon monoxide inhalation cause cellular injury?
it prevents oxygen transport around the body as carbon monoxide has a higher affinity for haemoglobin
How does contact with strong acid cause cellular injury?
It coagulates tissue protein
How does paracetamol overdose cause cellular injury?
metabolites bind to liver cell protein and lipoproteins
How do bacterial infections cause cellular injury?
they release toxins and enzymes that cause cellular injury
How does ionising radiation cause cellular injury?
it damages the DNA
What are the 5 general biochemical mechanisms behind cellular injury?
- ATP depletions
- oxygen and oxygen derived free radicals can damage tissues
- loss of intercellular calcium hemostasis
- defects in membrane permeability
- irreversible mitochondrial damage
What are the 2 types of cell injury?
- reversible
2. irreversible
What 3 features characterise reversible cell injury?
- decreased generation of ATP
- loss of cell membrane integrity
- defects in protein synthesis and DNA damage
What further 3 features lead to irreversible cell injury?
- severe mitochondrial changes
- extensive damage to plasma membrane
- swelling of lysosomes
How does cellular swelling occur in reversible cell injury?
- depletion of ATP leads to decreased activity of the Na/K pump
- this leads to more Na being in the cell
- Water moves into the cell by osmosis
- this leads to cellular swelling
In irreversible cellular injury, what happens when there is membrane damage to the mitochondria?
- this leads to cytochrome c leakage
- this activates caspaces
- this triggers apoptosis
In irreversible cellular injury, what happens when there is damage to the cell membrane?
- this allows calcium to enter the cell
- calcium activates proteases and enzymes, leading to enzymatic degradation of the cell
- increased calcium also activates caspaces, which trigger apoptosis
In irreversible cellular injury, what happens when there is damage to the lysosome membrane?
- this leads to leakage of lysosomal enzymes into the cytosol
- this leads to enzymatic degradation of the cell
How many cells are affected in apoptosis?
It can involve just a single cell
What happens if there is increased apoptosis?
it results in excessive cell loss e.g. atrophy
What are the stages of apoptosis?
- chromatin condenses and the membrane blebs
- this is followed by cellular fragmentation as apoptotic bodies form
- there is phagocytosis of apoptotic cells and fragments
What is the inflammatory response like in apoptosis and necrosis?
necrosis involves an inflammatory response
apoptosis has NO inflammatory response
What happens to cellular contents in necrosis?
they leak into the surroundings and can damage adjacent cells
What is the difference in the size of the areas affected by apoptosis and necrosis?
apoptosis can affect just a single cell
necrosis affects large areas of tissue
What are the 6 types of necrosis?
- coagulative
- liquefactive
- gangrenous
- caseous
- fat necrosis
- fibrinoid necrosis
What is the commonest form of necrosis?
coagulative necrosis
What happens to cells in coagulative necrosis?
the architecture of the cell is preserved
there is loss of proteins and enzymes
there is no proteolysis
What is coagulative necrosis?
Coagulative necrosis is a type of accidental cell death typically caused by ischaemia or infarction
What is liquefactive necrosis?
a type of necrosis which results in a transformation of the tissue into a liquid viscous mass
What is gangrenous necrosis?
death of tissue due to lack of blood flow
it appears black
What are the 3 types of gangrene?
wet, dry or gas
What is caseous necrosis and what does it look like?
it is structureless dead tissue
it is amorphous pink material with necrotic debris in the centre
What usually causes fat necrosis?
enzymes or trauma
In what 2 conditions is fibrinoid necrosis seen?
- malignant hypertension
2. autoimmune diseases
