Injuries to cells Flashcards
What can stress of the cell lead to?
-cell adaptation and if cell cant adapt cell injury
Cell injury is reversible, what happens if it is irreversible?
cell death, by either :
- necrosis
- apoptosis
Cell adaptation has four main types what are these?
- Hyperplasia
- Hypertrophy
- metaplasia
- atrophy
What happens with hyperplasia?
increase in number of cell
normally results in large organ
Give a pathological and physiological example of hyperplasia.
- Pathological = endometrial hyperplasia if hormone stimulus continues (gets to much cells than normal, can progress on to cancer)
- Physiological = menstrual cycle
What is hypertrophy?
increase in cell size
What is a physiological example of hypertrophy?
- body builders when their muscles get bigger
What is a pathological example of hypertrophy?
- heart in hypertension (when high blood pressure causes heart to work harder, thickening of left ventricular wall)
What is atrophy?
shrinkage of the cell due to loss of cell substance
Why may cause atrophy ?
- decreased workload
- general ageing process
- reduced blood supply
- inadequate nutrition
- loss of hormonal stimulation
What happens in metaplasia?
- when one adult cell type is replaced by another adult cell type
What is an example of metaplasia ?
chronic gastro-oesophageal reflux or Barretts oesophagus
In barrett’s oesophagus what happens?
squamous epithelium changes to columnar epithelium due to acid reflux leaking in to lower end of the oesophagus ad causing damage
Is metaplasia reversible?
yes
What are the 3 most common causes of cell injury?
- Hypoxia ( low oxygen supply)
- Ischaemia (loss of blood supply leading to low oxygen and nutrients)
- Chemical exposure ( eg. smoking, alcohol, paracetamol)
What are the other causes of cell injury?
- infection
- radiation
- immunologic reactions
- ageing
What are the findings of reversible cell injury (when looking under a microscope)?
- cellular swelling
- fatty change
Cell death occurs via two main pathways, what are these?
necrosis and apoptosis
Which cell death pathway causes local inflammation?
necrosis
How does apoptosis and necrosis cause cell death?
necrosis - damage to cell membrane allows enzymes to digest the cell
Apoptosis - programmed cell death. irreparable damage to cells DNA or deprived of growth factors
Is necrosis pathological or physiological?
it is always pathological
Is apoptosis pathological or physiological?
both
In apoptosis how are dead cells rapidly removed?
phagocytosis
When is physiological apoptosis needed?
- to get rid of cells which have served their purpose
- to get rid of potentially harmful self-reactive lymphocytes
Give an example of physiological apoptosis when it is supposed to occur.
- embryogenesis
- Involution of hormone dependent tissues upon hormone deprivation ( uterus in postmenopausal women )
When might pathological apoptosis occur?
- DNA damage ( radiation)
- certain infections ( hepatitis )
- cell death induced by cytotoxic T cells
What does apoptosis result from ?
enzymes called caspases
What are the types of necrosis?
- coagulative
- liquefactive
- caseous
- fat
These describe what the necrosis looks like after it has died
What is an example of where coagulative necrosis may occur?
Heart attack
What does caseous necrosis look like ?
cheese
What is the most common type of necrosis?
coagulative
Coagulative necrosis most commonly occurs after…
- infection
- loss of blood supply
What is caseous necrosis normally?
TB
-Can be fungus but normally air on the side of caution and presume its TB
What is liquefactive necrosis common with ?
common with brain injuries or brain infarctions or strokes
What is fat necrosis ?
is death of fat tissue
Which necrosis do you often get a hole in the brain ?
liquefactive necrosis
Why does fat necrosis occurs
occurs due to activation of lipases
What is a common example of fat necrosis ?
breast damage
can be secondary to trauma
normally relatively benign process
What are the mechanisms of cell injury?
- depletion of ATP
- mitochondrial damage
- influx of calcium
- oxidative stress
- damage to the cell membrane
- DNA damage
What are the effects of depletion of ATP?
- ATP dependent sodium pumps ( electrolyte imbalance)
- Increase intracellular lactic acid
- failure of calcium pump (electrolyte imbalance)
- damage to protein structures
What are the effects of mitochondrial damage?
- failure of production of energy
- failure of free radical production
What are the effects of influx of calcium?
- increased intracellular calcium
- this leads to activation of enzymes
- may trigger apoptosis
Influx of calcium most commonly happens after what?
ischaemic injury (lack of blood supply after poisons
Oxidative stress may happen after?
paracetamol overdose
What happens after defects in membrane permeability?
- results in necrosis
- various sites of damage this results in proteins and electrolytes being in the wrong place
When may damage to DNA and proteins happen?
- After radiation injury or oxidative stress
What can damage to DNA lead to ?
can result in apoptosis
what happens in intracellular accumulation normally due to alcohol misuse?
fat in hepatocytes (fatty liver)
If you get intracellular accumulation of cholesterol in smooth muscle cells what does this lead to ?
atherosclerosis
What is neoplasia ?
means new growth ( a tumour of some sort)
