Lecture 6 - Lethal Cell injury Flashcards Preview

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Flashcards in Lecture 6 - Lethal Cell injury Deck (11)

What could happen to cell membranes and cell staining in irreversible cell injury?

-Irregular contours
-Eosinophillia as a result of released protein into the cell


Define necrosis

The spectrum of morphological changes following cell death or tissue death. Always a pathological process


When do you see microscopic changes in cells undergoing necrosis, and what is the sequence of nuclear changes you will see?

-4-12 hours

-Nucleus will go from normal, to Pyknosis as a result of shrinkage, darkening and condensation (black dot). From there, to Karyorrhexis, which is breakdown of the nucleus. This is followed by Karyolysis, where the nucleus is gone
-Throughout this process, the cell will become more and more eosinophilic


What are some other microscopic changes you will see in necrotic tissue?

Cytoplasmic vacuolation
Cell membrane blebbing/rupture


Describe coagulative necrosis

-Most common type
-Usually follows ischaemia, which causes an infarct (localised necrotic area). Tissue is softer than normal, and either more pale (pale infarct) or haemorrhagic (red). Over time, a haemorrhagic border will develop around a pale infarct.
-The cellular architecture is preserved, and cell outline remains for days/weeks. --There is a delayed breakdown of cells, and an inflammatory response.
-Histologically you might see pink cytoplasms still in the shape of cells, missing nuclei.


Describe colliquative necrosis

-The necrotic cell releases powerful hydrolytic enzymes, as well as inflammatory exudate - particularly neutrophils. This leads to liquefaction of the entire cells. Later on, there is an inflammatory reaction and liquid material is removed by macrophages, leaving a cystic space, often with a fibrous peripheral border.
-Cellular architecture almost completely disintegrates
-Occurs in two main settings: the brain, or an abscess cavity in the lung


Describe Caseous necrosis

-Almost exclusively in TB patients
-Has a white, cheesy appearance
Microscopically is an amorphous, granular debris, lacking in cell detail and outline. H&E sections will show eosinophilia.
-Usually have granulomatous adjacent inflammatory reactions i.e. giant cells and macrophages everywhere
-Histological sections will show the absence of cell outlines and tissue destruction


What is the difference between wet, gas and dry gangrene?

-Wet gangrene is necrosis with superadded putrefaction, usually due to gram negative bacteria
-Gas gangrene is usually due to gram-positive bacteria found in soil, like Clostridium species. It causes crepitant swelling
-Dry gangrene is essentially mummification - tissue is dry and black. Often a result of coagulative necrosis


What does fat necrosis look like from a macroscopic perspective?

Chalky deposits, as a result of released fatty acids reacting with calcium


What are the outcomes of necrosis dependent on?

The tissue involved: susceptibility to injurious stimuli and ability to regenerate, extent of necrosis, and time elapsed.
Subsequent fibrosis is often seen


What is autolysis?

Self-digestion of tissue, ot technically necrosis

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