Cell Injury Flashcards
Is cell injury reversible
initially it is reversible;
then becomes irreversible.
if injury is severe from onset, cell undergoes apoptosis
2 ways cell death occurs
apoptosis
necrosis
causes of cell injury (8)
- oxygen deprivation
- nutritional imbalances
- infectious agents
- immune response
- genetic defects
- chemical agents
- physical agents
- AGING
hypoxia
deficiency of oxygen
ischaemia
inadequate blood flow to tissues . leads to hypoxia.
ischaemia - causes
- narrowing of blood vessel
- blockage of bv
- decresed blood pressure
effects of ischaemia
oxygen deficiency
glucose deficiency
nutrient deficiency
causes of hypoxia (4)
- lung disease
- ischaemia
- low O2 concn (high altitudes)
- reduced oxygen carrying capacity of blood (anaemia/ CO poisoning)
when are gross morphological changes visible in a cell
long after cell has died
sequence of events in cell death?
- decreasing cell function
- cell death ensues
- ultrastructural changes
- light microscopic changes
- gross morphological changes
morphological changes of reversibly injured cell detectable by light microscope
- swelling
- vacuolar degeneration OR hydropic change (accumulation of water intracellularly)
- fatty change
morphological changes of reversibly injured cell detectable by electron microscope (ultrastructurally)
- nuclear: clumping of CHROMATIN
- dilation of ER
- swelling of mitochondria & appearance of phospholipid-rich densities & calcification
- PM blebbing;
- loosening of intercellular attachments
- distortion of microvilli/blunting
define the fatty change in reversible injury
abnormal build up of triglycerides within parenchymal cells
causes for fatty change
- alcohol / toxins
- protein malnutrition
- diabetes
- obesity.
- hypoxia
cells affected by fatty change
those dependent on fat metabolism: -myocardial cells -hepatocytes skeletal muscle kidney and others
what’s different about necrotic, H&E stained cells
they have increased eosinophilia (redness) due to loss of RNA and less proteins (denatured proteins)
what can ultimately happen to necrotic cells
become calcified (dystrophic calcification)
ultrastructural changes in cell necrosis
- discontinuities in membrane of organelles and plasma membrane
- dilation of mitochondria
- disruption of lysosomes
- nuclear dissolution
- intracytoplasmic myelin figures
nuclear changes in necrotic cells
dissolution of basophilic chromatin (KARYOLYSIS)
PYKNOSIS - nuclear shrinkage +increased basophilia
KARYorrHEXIS - fragmentation pyknotic nucleus
why all these nuclear changes
due to breakdown of DNA and chromatin
types of tissue necrosis (patterns) (6)
- fibrinoid necrosis
- fat necrosis
- coagulative necrosis
- liquefactive necrosis
- gangrenous necrosis
- caseous necrosis
coagulative necrosis facts
basic tissue architecture preserved;
but firm texture
infarction
term can be used to describe necrosis of all organs/tissues EXCEPT brain
liquefactive necrosis
digestion of dead cells = transformation into liquid viscous mass
typical of bacterial infections (pus) = abscesses
gangrenous necrosis
caused by acute ischaemia
may/not have infection present too
coagulative&often superimposed liquefactive necrosis
caseous necrosis
cheese-like, friable white appearance. encountered mainly w TB
with which necrosis pattern is granuloma often seen
caseous necrosis
granuloma?
gathering of cell debris and fragmented cells bordered by inflammatory cells
fat necrosis
saponification of fat - whitish/chalky material produced.
examples of fat necrosis
breast - following trauma
acute pancreatitis
fibrinoid necrosis
deposition of fibrin in the walls of blood vessels
how to detect tissue necrosis
detect biochemical markers (enzymes and other proteins) in blood and urine
biochemical markers of tissue necrosis?
substances released from necrotic cells
Apoptosis
programmed cell death
activation of internal self-destruction programme
is apoptosis only pathological?
it’s necessary for normal function also
when apoptosis
injury beyond repair
morphology of apoptosis
- cell membrane stays intact
- fragmentation into apoptotic bodies
fate of apoptotic bodies
phagocytosed by macrophages and neighbouring cells
pro of apoptosis
minimal disruption to neighbouring cells
compare cell size in APOPTOSIS v NECROSIS
A - reduced (shrinkage)
N - swelling
compare nucleus
A - fragmentation
N - Pyknosis –> karyorrhexis –> Karyolysis (?)
compare PM
A - intact
N- disrupted
compare Adjacent inflammation
A - no
N - frequent
compare Physiologic or pathologic
A - can be either
N - always PATHOLOGIC
