Cell injury Flashcards
What is meant by cell injury?
reversible
cells adapt to changes in environment
return to normal once stimulus removed
irreversible
permanent
cell death as consequence
What does whether an injury is reversible or irreversible depend on?
on type, duration, severity of injury and on the susceptibility/ adaptivity of the cell
What are some causes of cell injury?
hypoxia- decreased oxygen supply
physical agents (radiation)
chemicals/drugs
infections( bacterial toxins, viruses)
immunological agents
nutritional imbalance
genetic defects
Describe hypoxia- what is it? Causes?
Deficiency of oxygen, disrupts oxidative respiratory processes in cell- decreased ATP, cells can still release energy via anaerobic mechanisms
causes anaemia, respiratory failure
describe Ischaemia
reduction in blood supply to tissue
caused by blockage of aterial supply of venous drainage
more rapid/severe damage than hypoxia
What are some physical agents that can cause cell injury?
mechanical trauma – affects structure, cell membranes
extremes of temperature – affect proteins, chemical reactions
ionising radiation – DNA damage
electric shock - burn
What does chemical/ drug damage do to a cell?
disruption of cell membranes and proteins
simple chemicals (glucose), in excess cause osmotic disturbance
poisons (cyanide blocks oxidative phosphorylation), environmental (insecticides)
occupational hazards (asbestos) causes inflammation
alcohol, smoking and recreational drug
what is an example of nutritional imbalance?
too little- scurvy, rickets
too much- hypervitaminosis A/D
what is an example of nutritional imbalance?
too little- scurvy, rickets
too much- hypervitaminosis A/D
What is an example of genetic defects affecting cell injury?
sickle cell anemia, cancer
What happens to cells during reversible injury?
disruption to
aerobic respiration/ATP synthesis (mitochondrial damage)
plasma membrane integrity
enzyme and structural protein synthesis
DNA maintenance
What in regards to morphology happens to the cell in reversible cell injury?
cloudy swelling
fatty change
Describe cloudy swelling during cell injury
cells are incapable of maintaining ionic and fluid homeostasis
failure of energy dependent ion pumps in cell membrane loss of ATP/ energy, no build up of intracellular metabolites
describe a “fatty change” during reversible cell injury
accumulation of lipid vacuoles in cytoplasm due to fatty acid metabolism released especially in liver
occurs with toxic and hypoxic injury- alcohol abuse, diabetes
What is necrosis?
cell death- usually due to pathology and is IRREVERSIBLE
cell membrane is disrupted leading to leakage of cell contents- inflammatory response around tissue
Describe the microscopical changes of necrosis?
pyknosis = nucleus shrinks; darker staining
karyorrhexis = nucleus fragments (K)
karyolysis = the blue staining DNA in nucleus is digested by endonucleases and the blue staining fades away (K)
end result is loss of the blue staining nucleus – a useful sign that a cell is necrotic
What are the different types of necrosis?
1- coagulative necrosis-
2- liquefactive necrosis-digestion of dead tissues, tissues in liquid viscous state
3- caseous necrosis- usually seen in tuberculous infection
4/5- gangrenous and fat necrosis- bacteria and areas of fat destruction
fibrinoid necrosis
describe fibrinoid necrosis
special type seen in immune reactions in blood vessels
What are effects of necrosis?
functional depends on organ/ tissue
inflammation
release of cell contents activates inflammation
replaced by scar- undergoes repair
if remains are not removed then calcium salts may be depositeded in necrotic tissue
What is apoptosis?
genetically programmed cell death
orderly elimination of unwanted cells
can occur in pathological situautions
Requires energy
does NOT cause inflammatory
What are pathological triggers of apoptosis?
hypoxia/ ischemia
viral infection
DNA damage
caspases ACTIVATED ENZYMES that trigger apoptosis
What are physiological roles of apoptosis?
deletion of cell populations during embrogenisis
hormone chnage depentent involution- uterus, breast, ovary
deletion of inflammatory cells after an inflammatory response
deletion of self reactive lymphocytes in the thymus
What is the morphology of the cell during apoptosis?
cell shrinkage
chromatin condensation – packaging up of nucleus
cell membrane remains intact, with formation of cytoplasmic blebs
break off to form apoptotic bodies
phagocytosed, but no widespread inflammation
everything is contained in cell membrane
compare necrosis with apoptosis
cell size- N- enlarged A- reduced
nuclues- N-pyknosis-karyorhexis-karyolysis A-fragmentation into nucleosome size fragments
plasma membrane N-disrupted A-intact may be released
Cellular contents N- leak out A- intact
inflammation- N- Frequent A-No
Pathogenic role N-invariably pathogenic A- often physiolgic- eliminated unwanted cells
