Necrosis Flashcards
Necrosis histologically
Eosinophilia attribute - = loss of cytoplasmic RNA + cytoplasmic proteins
When enzymes have digested the cytoplasmic organelles, the cytoplasm becomes vacuolated and appears moth-eaten.
The pale necrosis
left is necrosis, which is usually a mass of cells
right is apoptosis where it is individual discrete cells undergoing it at once
Describe Histology nuclear changes
The three types
1) pyknosis: nuclear condensation with shrinkage and intense basophilia;
2) karyorrhexis: nuclear fragmentation;
3) karyolysis: nuclear dissolution or loss
The 4 types of necrosis
Coagulative
Liquefactive
Caseous
Gangrenous
Coagulate necrosis
- how it occurs
- what it looks like and why it looks like that
- where is it most common
Loss of architecture of dead tissues preserved for at least some days > removal by leukocytes
Denaturation of stuctural and and also the enzymes and so it blocks the proteolysis of the dead cells
Therefore, eosinophilic, anucleate cells may persist for days or weeks
Ultimately, the necrotic cells are removed by phagocytosis of the cellular debris by infiltrating leukocytes and by digestion of the dead cells by the action of the lysosomal enzymes of the leukocytes.
Most common in liver, kidney, myocardium or skeletal muscle
Looks like —> pale tan to pale grey, often demarcated from the normal colour of adjacent viable tissue, and solid/firm.
Liquefactive necrosis
how it occurs
what looks like it and why it does
where is most susceptible
Digestion of dead cells > abcess transformation of the tissue into a liquid viscous mass (due to presence of dead leukocytes and is called pus)
Seen in bacterial infection
Doesn’t need to be a bacterial infection
Eg brain with infarct —> lack of fibrous interstititum will cause liquefactive necrosis
Caseous necrosis
how it occurs
what looks like it and why it does
where is most susceptible
Tissue replaced by crumbled, granular or laminated yellowish exudate
Complete loss of tissue architecture
most often in foci of tuberculous infection
In comparison to coagulative necrosis, caseous necrosis is an older lesion with complete loss or cellular or tissue architecture. On microscopic examination, the necrotic area appears as a structure less collection of fragmented or lysed cells and amorphous granular debris.
Gangrenous necrosis
how it occurs
what looks like it and why it does
where is most susceptible
Dry gangrene - term used in the clinical practice
Common in the distal aspect of extremities
Wet gangrene - if the dependant necrotic tissue is infected by certain bacteria
- red-black and wet
examples are aspiration pneumonia in the lung or staphylococcal infection of the mammary gland in ruminants
distal aspect of extremities (limbs, tail, pinnae) or dependent portions of organs, such as the mammary glands or lung lobes.
