how cells respond to injury Flashcards
What is hypertrophy?
increase in cell size
What is hyperplasia?
increase in cell number
What is metaplasia?
change of a tissue into another in response to a change in environment
What are the ways a tissue can grow?
- multiplicative
- auxetic
- accretionary
What is multiplicative growth of tissue?
increase in cell number by mitotic division
What is auxetic growth of tissue?
increase in cell size
What is accretionary growth of tissue?
increase in extracellular tissue
What are the ways cells can respond to stress?
- adapt
- suffer reversible injury
- suffer irreversible injury
- die
What are the 4 options cells have to adapt?
- hypertrophy
- hyperplasia
- atrophy
- metaplasia
What is atrophy?
reduction in cell size and/or number
What is starvation?
atrophy of an entire organism
How is growth calculated?
increase in cell number - decrease
What adaptive response is available to permanent cells?
only hypertrophy
What are the 3 types of cells when it comes to proliferation?
- labile cells
- stable cells
- permanent cells
Describe the proliferation, cell turnover and lifespan of labile cells
- continuous proliferation
- high cell turnover
- short lifespan
Describe the proliferation, cell turnover and lifespan of stable cells
- good regeneration ability
- low cell turnover
- longer lifespan
Describe the proliferation, cell turnover and lifespan of permanent cells
- little/no regeneration
- very low/no cell turnover
- long lifespan
Give examples of labile cells
- epithelial cells
- white blood cells
Give examples of stable cells
hepatocytes (liver cells)
Give examples of permanent cells
- neurons
- cardiac/skeletal muscle
- red blood cells
What is an example of physiological hypertrophy?
hypertrophy of skeletal muscle through training
What is an example of pathological hypertrophy?
cardiac hypertrophy owing to hypertension/valvular disease
What are the two types of physiological hyperplasia?
- hormonal
- compensatory
What is hormonal physiological hyperplasia?
hyperplasia that increase the functional capacity
What is compensatory hyperplasia?
hyperplasia when tissue is lost
What is pathological hyperplasia often due to?
usually excess hormonal stimulation of cells
How is pathological hyperplasia distinct from neoplasia?
because if the stress influence goes away, the cells go back to normal
In what tissues is metaplasia commonly seen?
- usually in epithelium
- possible in mesenchymal tissues
Explain the mechanism behind metaplasia?
stem cell differentiate along a different pathway owing to a change in the local microenvironment
Describe smoking’s involvement in metaplasia
bronchial ciliated epithelium to stratified squamous epithelium
Describe the sort of cycle that happens with reversible cell injury?
- changes in ion conc means changes in osmosis
- swelling of cell means changes in organelles and cytoskeleton
- increasing eosinophilia and redness
At what point does reversible cell injury become irreversible cell injury
when lysosome ruptures and autodigestion starts
What are the 3 nuclear changes that can happen because of irreversible cell injury
- karyolysis
- karyorrhexis
- pyknosis
What is karyolysis?
breakdown of nucleus because of enzymes released by lysosome
What is karyorrhexis?
rupture of nuclear membrane
What is pyknosis?
process of nuclear shrinkage
What is the mechanism of necrosis?
- mitochondrial damage
- influx of calcium
- accumulation of oxygen radicals
- increased membrane permeability
- DNA and protein damage
- drop in pH (lactic acid)
What are the 3 macroscopic patterns of necrosis
- coagulative
- liquefactive/colliquative
- caseous necrosis
Describe coagulative necrosis
shape preserved for some time
Describe liquefactive/colliquative necrosis
shape quickly lost
Describe caseous necrosis
cheese-like appearance
What are the two pathways for apoptosis?
- death receptor mediated
- mitochondrial mediated
What is the final mechanism for apoptosis no matter the pathway?
activation of intracellular caspase 3 to degrade DNA and cell proteins
What is the estimated human cell turnover?
a million a second
