Irreversible cell injury
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What are the morphological changes seen in reversible cell injury?
Cell swelling, fatty change, plasma membrane blebbling, loss of microvilli, mitochondrial swelling, dilation of ER, eosinophilia
What are the morphological changes seen in necrosis?
Eosinophilia, nuclear shrinkage, fragmentation, dissolution
What are the morphological changes seen in apoptosis?
Nuclear chromatin condensation, formation of apoptotic bodies (nuclear and cytoplasmic fragments)
What are the different types of necrosis? (5)
What can be seen morphologically in coagulative necrosis?
- Preservation of basic cell outlines
- Cytoplasm homogeneous and eosinophilic
- Nucleus pyknotic, karryorectic, karrylolytic or absent
What are the common causes of coagulative necrosis?
- Hypoxic cell injury (local loss of blood supply due to ishcaemia and then infarction - necrosis due to ischaemia)
- Bacterial or chemical toxins
What is a common nephrotoxin in a) cattle b) cats c) dogs and d) horses
- a) oak, acorn (tannins)
- b) easter lillies, ethylene glycol
- c) raisins/grapes
- d) red maple
What common disease in dogs shows coagulative necrosis?
Canine parvovirus enteritis (canine parvovirus)
What does caseous necrosis look like on gross inspection?
- "Cottage cheese" appearance
- Dystophic calcification often seen centrally
What does caseous necrosis look like on microscopic appearance?
- Collection of fragmented/lysed cells with an amorphous granular appearance
- Tissue architecture obliterated, no cell outlines visible
What are common examples of diseases that cause caseous necrosis?
- Corynebacterium in sheep
Where does liquefactive necrosis occur?
In the CNS, commonly the brain
What would liquefactive necrosis look like on microscopic appearance?
- There would be areas of pallor where there was fluid (odema) in life
- May see 'gitter cells' clearing up necrotic debris
What happens during liquefactive necrosis?
There is little or no fibrous connective tissue in the CNS. Once tissue becomes necrotic there is no fibrous (scar) tissue to replace the tissue lost. The resulting cavity is filled with fluid an debris of neuronal membrane lipid. The debris will be cleared up by macrophages.
What are the three types of gangrene?
What is gangrene?
Loss of vascular supply followed by bacterial invasion and putrefaction
What are the gross findings in moist gangrene?
- Soft, moist, reddish-brown/black
- +/- gas bubbles, putrid smell
What are the histological findings in moist gangrene?
- Coagulative necrosis and proliferating bacteria
- Liquefaction +/- gas bubbles
What is dry gangrene?
Coagulative necrosis secondary to infarction with mummification (water depletion)
Where does dry gangrene normally take place?
On the extremities i.e. lower portion of the limbs, tail, ears, udder
What is gas gangrene?
Anaerobic bacteria proliferating and producing toxins in necrotic tissue
What is the gross appearance of wet gangrene?
Tissues are dark red to black with gas bubbles and a fluid exudate that may contain blood
What are the different causes of fat necrosis?
- Enzymatic - destruction of fat adjacent to pancreas by activated pancreas lipase's.
- Traumatic - crushed fat e.g. pelvic fat during dystocia or sternal fat of recumbent animals
- Abdominal fat necrosis of cattle - necrotic fat in mesentery, momentum and retroperitoneum
What happens to tissues after necrosis?
- There is an inflammatory response within viable tissues - band of white blood cells and hyperaemia (increased blood supply to the area)
- Digestion and liquefaction of necrotic tissue - phagocytosis by macrophages and diffusion by vessels
- Regeneration of normal tissue or fibrous scarring
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