P: week 1 Flashcards
what are the 2 types of cell death?
necrosis
apoptosis
how do cells respond to stress?
they adapt, if they cannot adapt they become injured
injury = reversible or irreversible
describe reversible cell injury?
application of stimulus or stress, that once removed can return to normal state
what actually happens in reversible cell injury?
cellular swelling due to -> reduced oxidative phosphorylation -> leading to ATP depletion -> ATP pump stops working, causing Na to flow in, osmosis, water follows salt => Cell Swells! also the accumulation of fat
what happens to cell after reversible injury? **
- > swelling of endoplasmic reticulum and mitochondria
- > membrane “blebs”, picture bubbling on memebrane
- > clumping of chromatin
example of liver cell injury?
hepatocytes - fat accumulation
eg.
stress/applied stimulus = alcohol
if the alcohol were to stop, the cells could recover
what happens in irreversible cell death? **
- severe mitochondrial damage
- irreversible membrane defects
- lysosomal digestion
what happens to the cell AFTER irreversible injury?
first 3 things that happen are the same as reversible injury..THEN
- lysosomal rupture
- myolin figures breakdown products of organelles
=> leading to fragmentation of cell membrane and nucleus
is the accumulation of fat reversible or irreversible injury?
reversible!
think fatty liver disease due to alcoholism
is the severe damage to mitochondrion reversible or irreversible injury?
irreversible
is cell swelling reversible or irreversible injury?
reversible
is chromatin clumping reversible or irreversible injury?
reversible
define necrosis?
unregulated enzymatic digestion of cell components, loss of cell membrane integrity with uncontrolled release of the products of cell death into the intracellular space, and initiation of the inflammatory response
define apoptosis:
controlled autodigestion of cell components due to activation of endogenous enzymes
how does ATP depletion cause swelling?
sodium and water move into cell and potassium moves out of cell
- osmotic pressure increases
- more water moves in(follows salt Na)
what are the principle mechanisms of cell injury?
- decrease ATP, mitochondrial damage
- entry of Ca2+
- increased oxidative stress(free radicals)
- membrane damage - defects in membrane permeability
- protein misfolding DNA damage
what are free radicals?
have an unpaired electron in outer orbit
- molecules that react with free radicals themselves turn into free radicals = chain reaction
what does injury mechanism influx of calcium cause?
activation of ATPases, Endonucleases and Proteases
what does injury mechanism damage to mitochondria cause?
release of cytochrome C into the cytoplasm
what does injury mechanism oxidative stress cause?
lipid peroxidation
what does injury mechanism damage to DNA and proteins cause?
activation of apoptosis after failure of DNA repair
what does injury mechanism ATP depletion cause?
failure of Sodium potassium pump and cell swelling
what does injury mechanism defects in membrane permeability cause?
leakage of lysosomal enzymes into cytoplasm
major causes of ATP depletion as a principle mechanism of cell injury
- reduced supply of oxygen and nutrients
- mitochondrial damage
- toxins
major causes of damage to mitochondia as a principle mechanism of cell injury
- increased cytosolic calcium
- reactive oxygen species
- oxygen deprivation
major causes of influx of calcium as a principle mechanism of cell injury
- increased influx across plasma membrane
- ischaemia and certain toxins
- release of calcium from the intracellular stores
define hypertrophy:
existing muscles cells get bigger
=> increase in functional capacity
define hyperplasia:
increase in number of cells
eg. calluses, unusual hardening of skinn
why does the difference of hyperplasia and hypertrophy exist?
cell characteristics…not all cells can divide
- Labile cells can divide easily
- Stable cells can undergo hyperplasia and regenerate
- Permanent cells cannot undergo hyperplasia but can undergo hypertrophy
what can cause atrophy?
- reduced functional demand
- inadequate O2
- insufficient nutrients
- persistent cell injury
- endocrine insufficiency
define metaplasia:
when one fully differentiated cell type is replaced by another fully differentiated cell type
..why? replacement of stressed cells with cells better equipped to suit the adverse environment
does not result in a change in phenotype of a cell, but is the result of reprogramming of stem cells that exists in normal tissues
example of metaplasia?
ciliated columnar epithelial in trachea/bronchi
=> to stratified squamous epithelial
“smokers lungs”
metaplasia is not always a harmless adaptive process:
normal > metaplasia > dysplasia > neoplasia
potentially reversible up to dysplasia
