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==Introduction==
==Introduction==
* '''Necrosis''' means the death of cells within the living body.
* '''Necrosis''' means the death of cells within the living body.
===Loss of Blood Supply===
===Loss of Blood Supply===
* Necrosis due to interuption of blood supply to a portion of tissue is known as '''ischaemic necrosis''', or [[Ischaemia and Infarction - Pathology#Infarction|'''infarction''']].
* Necrosis due to interuption of blood supply to a portion of tissue is known as '''ischaemic necrosis''', or [[Infarction|'''infarction''']].
* The effects of [[Ischaemia and Infarction - Pathology#Ischaemia|ischaemia]] on a tissue vary according to:
* The effects of [[Ischaemia|ischaemia]] on a tissue vary according to:
** The tissue affected.
** The tissue affected.
*** Some tissues are more susceptible than others.
*** Some tissues are more susceptible than others.
* Tissue [[Ischaemia and Infarction - Pathology#Ischaemia|ischamia]] can be brought about in three ways:
* Tissue [[Ischaemia|ischamia]] can be brought about in three ways:
** Compression of the blood vessel.
** Compression of the blood vessel.
** Narrowing of the lumen.
** Narrowing of the lumen.
====Blocking of the Lumen====
====Blocking of the Lumen====
* Important causes are [[Thrombosis - Pathology#Introduction|thrombi]] and [[Thrombosis - Pathology#Embolism|emboli]].
* Important causes are [[Thrombosis#Introduction|thrombi]] and [[Embolism|emboli]].
* Renal vessels are commonly affected.
* Renal vessels are commonly affected.
** Also contains the remnants of the necrotic tissue cells.
** Also contains the remnants of the necrotic tissue cells.
* Although in favourable cases the [[Neutrophils|neutrophils]] may eventually kill the organisms, in most cases the organisms persist, producing more pus.
* Although in favourable cases the [[Neutrophils|neutrophils]] may eventually kill the organisms, in most cases the organisms persist, producing more pus.
** Produces an expanding sphere of pus known as an [[Acute Inflammation - Pathology#Purulent|'''abscess''']].
** Produces an expanding sphere of pus known as an [[Purulent Inflammation|'''abscess''']].
*** If the abscess is near to the skin and pressure becomes sufficient after build up, it will burst.
*** If the abscess is near to the skin and pressure becomes sufficient after build up, it will burst.
**** Pus is discharged, hopefully along with the organisms responsible.
**** Pus is discharged, hopefully along with the organisms responsible.
** E.g. tuberculosis in the ox, pig and sheep.
** E.g. tuberculosis in the ox, pig and sheep.
** Necrotic tissue is not derived from the organ in which it occurs.
** Necrotic tissue is not derived from the organ in which it occurs.
*** Formed from [[Macrophages - WikiBlood|Macrophages]] sent into the tissue in large numbers to engulf the causative organism.
*** Formed from [[Macrophages|Macrophages]] sent into the tissue in large numbers to engulf the causative organism.
** The organism has defences against the enzymes of the [[Macrophages - WikiBlood|Macrophages]].
** The organism has defences against the enzymes of the [[Macrophages|Macrophages]].
*** Is able to grow and multiply within these macrophages and eventually causes their death.
*** Is able to grow and multiply within these macrophages and eventually causes their death.
** In some granulomas, the macrophages will combine together and form giant cells.
** In some granulomas, the macrophages will combine together and form giant cells.
* The zone of inflammation between the dead putrefying tissue and living tissue is indistinct.
* The zone of inflammation between the dead putrefying tissue and living tissue is indistinct.
=====Gas Gangrene=====
=====[[Gas Gangrene]]=====
====Dry Gangrene====
====Dry Gangrene====
*** Commonly seen following a septicaemic condition when an embolus blocks the blood supply.
*** Commonly seen following a septicaemic condition when an embolus blocks the blood supply.
**** When seen in calves, the possibility of [[Salmonellosis|salmonellosis]] must be kept in mind.
**** When seen in calves, the possibility of [[Salmonellosis|salmonellosis]] must be kept in mind.
*** Other causes are frostbite and [[Skin Environmental - Pathology#Ergot poisoning|ergot poisoning]].
*** Other causes are frostbite and [[Ergot Poisoning|ergot poisoning]].
==Calcification==
==Calcification==
* The colour is usually chalk-white.
* The colour is usually chalk-white.
** There may be a yellowish-green tinge if the inciting cause is a parasite.
** There may be a yellowish-green tinge if the inciting cause is a parasite.
*** Due to attraction of a large number of [[Eosinophils - WikiBlood|eosinophils]].
*** Due to attraction of a large number of [[Eosinophils|eosinophils]].
===Histological Appearance===
===Histological Appearance===
** The cell breaks up into fragments that are engulfed by neighbouring cells or local macrophages.
** The cell breaks up into fragments that are engulfed by neighbouring cells or local macrophages.
*** Their remnants can be seen in the neighbouring cells’ cytoplasm.
*** Their remnants can be seen in the neighbouring cells’ cytoplasm.
[[Category:General Pathology]]