12 Cellular injury and repair Flashcards
What is necrosis?
Chaotic cell death
What is apoptosis?
Programmed cell death
What stimuli is apoptosis caused by?
Killer T cell signalling (immune response to cancer or viral infection)
Tissue shedding and turnover
Genetics
What stimuli is necrosis caused by?
Physical agents (shocks, trauma, radiation)
Ischemia / oxygen stress (limitation of ATP)
Infectious toxins
When does necrosis happen?
When ATP is lacking
What does apoptosis need to occur?
ATP
what happens to cell membranes in apoptosis?
intact
what happens to cell membranes in necrosis?
They burst
What happens after cell death - apoptosis
Phagocytes remove cell debris
What happens after cell death - necrosis
explosion releases lysosomes damaging neighbouring cells - leading to further cell death.
What is cell swelling caused by?
- damage to membranes
- loss of ATP production
- inflammatory signals
The Sodium-Potassium (Na+K+) pump helps to maintain fluid balance in cells (cytoplasmic volume homeostasis).
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It actively transports 3Na+ out of the cytoplasm (into the surrounding tissue fluid) and 2K+ into the cytoplasm (from the surrounding tissue fluid).
A lack of ATP production leads to disruption of the Na+:K+ pump and therefore a loss of ion and water homeostasis.
Cell accumulate Na+ ions which decreases the water potential of the cytoplasm.
This leads to water entering the cells by osmosis (down the water potential gradient).
As a result, cells start to swell.
What happens as a result of cell swelling?
- Damage to membranes
- Loss of ATP production
- Decreased water potential
- Water moves into cell via osmosis
LEADS TO CYTOPLASMIC SWELLING
Why are cell adaptations created?
As responses to stimuli and are driven by alterations to gene expression
Hyperplasia
exercise, inc calorie intake, cell membrane damage
cell numbers increase - more mitosis
Hypertrophy
exercise, increased calorie intake
cell size increases - more interphase
Atrophy
Response to starvation, loss of blood supply, lack of use, disease.
Cell size decrease leads to autophagy - cell eats itself
Atrophy
Response to starvation, loss of blood supply, lack of use, disease.
Cell size decrease leads to autophagy - cell eats itself
Metaplasia
An early phase of malignant carcinogenesis (needs treatment)
Metaplasia = transformation of one differentiated cell type into another in response to a normal maturation process or abnormal stimulus.
