Irreversible cellular injury and cellular death Flashcards
Autolysis
post-mortem self-digestion of tissues and cells due to hydrolytic enzymes normally present in those tissues
Putrefaction
bacterial post-mortem breakdown of tissues
Postmortem changes include
autolysis and putrefaction
why does the appearance of necrotic cells vary?
due to the tissue involved, the cause of cell death and the duration of time
oncosis
oncotic necrosis
cells die due to acute swelling
pyknosis
chromatin clumps together
nucleus looks extra dark
karyolysis
breakdown of nucleus (no visible nucleus)
absence of nucleus
later stage of karyolysis
karyohexis
early stage of nucleus breakdown
cytoplasm of necrotic cells
becomes pink due to the loss of basophilic nucleus and degradation of cytoplasmic proteins
necrotic cells in lumen and surfaces
become free and lose adherence to their neighbours
first stage of all necrosis
coagulation necrosis
cell outlines in coagulation necrosis?
are preserved
cytoplasm in coagulation necrosis?
eosinophilic and homogenous (cell proteins coagulate)
why proteolysis is delayed in coagulation necrosis?
because as well as structural proteins, also enzymes are denatured
nuclei in coagulation necrosis?
pyknotic, karyorrhectic, karyolytic or absent
how does coagulation necrosis look like
whitish-yellow lesion with red rim due to acute inflammation
where is coagulation necrosis seen?
usually in liver, kidney and muscle, but can be anywhere except in brain
what causes coagulation necrosis
hypoxia
ischemia
sometimes bacterial exotoxins or chemical toxins
caseation necrosis
dead cells get converted in granular friable mass
how does caseation necrosis look alike?
like cottage cheese
of what is the caseation necrosis focus composed of?
nuclear, cytoplasmic debris, mainly dead leukocytes
which is more recent, coagulation or caseous necrosis?
coagulation is more recent, caseous necrosis tells about chronic problem
what tissues are affected by caseation necrosis?
any except brain. usually found in lungs
what happens to cell walls in caseous necrosis?
they are disrupted and cell architecture is altered. sometimes cells are mineralised
dystrophic calcification
mineralisation that happens in caseation necrosis
what is thought to be the cause of dystrophic calcification?
delayed decradation of bacterial cell wall
common cause of dystrophic calcification?
tuberculosis and pseudotuberculosis
liquefactive necrosis
cells turn into liquid after hypoxic death
what tissues are affected by liquefactive necrosis?
CNS
what happens to neuron cell bodies before liquefactive necrosis?
they show signs of coagulation necrosis
why hypoxic death causes liquefactive necrosis in CNS
CNS cells have high amount of cell membrane which is rapidly dissoluted enzymatically in hypoxia
what happens before gangrenous necrosis?
coagulation necrosis
gangrenous necrosis types?
moist, dry and gas gangrene
moist gangrene necrosis
liqufactive extra-degradation of already necrotic area by saprophytic bacteria
what causes moist gangrene necrosis?
infarction of extremity or intestine
- for example too tight bandage that cuts the blood
supply
aspirated irritant agents in lungs
where do the saprophytic bacteria come to the already necrotic tissue?
from environment
- soil
- air
- skin
- contamination
what is the gross appearance of moist gangrene necrosis?
tissues are:
- soft
- moist
- reddish-brown to black
gas and putrid (mätä) odor might be present
what happens to moist gangrene tissues if not death?
tissue gets separated and drops of
dry gangrene necrosis
coagulation necrosis is followed by mummification
where does dry gangrene necrosis usually happen?
in extremities (tail, ears, udders)
what causes dry gangrene necrosis?
frostbite or ingested toxins
why does mummification happen in dry gangrene necrosis?
after necrosis, the tissues get depleted of water
is there bacteria present in dry gangrene necrosis?
no, dry tissues are not suitable for proliferation
how does dry gangrene necrosis look in gross appearance?
- shriveled (ruttuinen)
- dry
- brown to black
gas gangrene necrosis
anaerobic bacteria (clostridium) proliferate in already necrotic tissues and produces gas
what causes gas gangrene necrosis?
deep wounds allow the penetration of clostridia which get anaerobic medium from necrotic tissue
how gas gangrene looks in gross appearance?
dark red to black with gas bubbles
bloody exudate sometimes present
how gas gangrene necrosis looks microscopically?
coagulation necrosis of a muscle with gas bubble and serohaemorrgaic exudate
fat necrosis types
enzymatic/pancreatic fat necrosis
traumatic fat necrosis
cattle abdominal fat necrosis
enzymatic fat necrosis
breakage of fat near pancreas due to leaked pancreatic lipases
how does enzymatic fat necrosis look alike?
chalky to gritty white/pale fat near pancreas
often saponified
traumatic fat necrosis
adipose tissue is crushed
often after giving birth/trauma in the subcutaneous tissue/recumbency in cattle
cattle abdominal fat necrosis
large masses of necrotic fat in cattle abdomen (retroperitoneally, in the omentum, mesentery) due to an unknown cause
how does saponified fat look microscopically?
necrotic adipocytes look basophilic if saponification present
