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Acute Inflammation - Introduction (view source)
Revision as of 11:09, 4 August 2010
, 11:09, 4 August 2010Created page with "==Introduction== * Acute inflammation is characterised sudden onset and may last for a few hours to a few days. * Vascular, humoral and cellular alterations cause the 5 cardinal..."
==Introduction==
* Acute inflammation is characterised sudden onset and may last for a few hours to a few days.
* Vascular, humoral and cellular alterations cause the 5 cardinal signs as a result of exposure of tissues to various causes.
* Acute inflammation can:
*# Be fatal
*# Resolve by regeneration in association with the host defence mechanisms.
*#* May be assisted by therapeutic measures.
*# Undergo repair by fibrosis.
*# Become chronic.
*#* First goes through a subacute phase.
*#* Is dependent upon the persistence of the agent and the amount of damage caused.
==Sequence of Events==
* The following sequence of events is provoked by the presence of the irritant.
# '''Momentary vasoconstriction'''
#* Following contact with the irritant, there is momentary vasoconstriction of the blood vessels in the affected area.
#* This is reversed within minutes.
# '''Dilation of the blood vessels'''
#* Initially, dilation of the capillaries is caused by the release of chemical mediators.
#* Arterioles then dilate under the influence of a local axon reflex.
#* This gives rise to an initial acceleration of the blood flow to the area.
#** This later gives way to a slowing of blood flow, caused by alterations in vascular endothelial permeability and the filling of previously closed capillaries.
# '''[[Exudation of fluid]]'''
#* Follwing the slowing of blood flow and altered capillary permeability, a protein-rich fluid is exudated.
# '''Margination of leukocytes'''
#* Circulating white blood cells are attracted to the altered endothelial surfaces.
# '''Emigration of leukocytes'''
#* [[Leukocytes|Leukocytes]] migrate through the altered endothelium to reach the injured area.
#* This is an active process - [http://www.cellsalive.com/chemotx.htm| chemotaxis].
#** The cells are attracted to the endothelium by release of proteins, and further into the tissues by factors released from cells in the damaged area.
#** The emigrated leukocytes and components of the fluid exudate are also chemotactic.
#** More cells and fluid are attracted to the area.
# '''Emigration of red blood cells'''
#* [[Erythrocytes|Erythrocytes]] migrate through the gaps in the altered endothelium to the damaged tissue.
# '''Induction of an increase in temperature'''
#* This may occur either locally or systemically.
#* A systemic rise in temperature is known as pyrexia.
#** Occurs in generalise acute inflammation.
#** Pyrogens act on the temperature control centres in the hypothalamus, and are released from:
#*** [[Neutrophils|Neutrophils]], [[Eosinophils|eosinophils]] and [[Macrophages|macrophages]]
#**** Particulary [[Neutrophils|neutrophils]] when they begin to phagocytose.
#*** The cellular coat of gram-negative organisms.
#*** Necrosis of damaged tissue cells.
#*** Antigen-antibody complexes.
#*** Tumours.
#**** Particularly those which have metastasised
#**** It may be difficult to separate this from the pyrexia caused by the central necrosis in such tumours.
==Cells==
* The classical cells of acute inflammation are [[Neutrophils|neutrophils]], [[Eosinophils|eosinophils]], [[Macrophages|macrophages]], [[Mast Cells|mast cells]] and [[Basophils|basophils]].
** [[Macrophages|Macrophages]] are a common feature of acute and chronic inflammation.
[[Category:Acute Inflammation|A]]
* Acute inflammation is characterised sudden onset and may last for a few hours to a few days.
* Vascular, humoral and cellular alterations cause the 5 cardinal signs as a result of exposure of tissues to various causes.
* Acute inflammation can:
*# Be fatal
*# Resolve by regeneration in association with the host defence mechanisms.
*#* May be assisted by therapeutic measures.
*# Undergo repair by fibrosis.
*# Become chronic.
*#* First goes through a subacute phase.
*#* Is dependent upon the persistence of the agent and the amount of damage caused.
==Sequence of Events==
* The following sequence of events is provoked by the presence of the irritant.
# '''Momentary vasoconstriction'''
#* Following contact with the irritant, there is momentary vasoconstriction of the blood vessels in the affected area.
#* This is reversed within minutes.
# '''Dilation of the blood vessels'''
#* Initially, dilation of the capillaries is caused by the release of chemical mediators.
#* Arterioles then dilate under the influence of a local axon reflex.
#* This gives rise to an initial acceleration of the blood flow to the area.
#** This later gives way to a slowing of blood flow, caused by alterations in vascular endothelial permeability and the filling of previously closed capillaries.
# '''[[Exudation of fluid]]'''
#* Follwing the slowing of blood flow and altered capillary permeability, a protein-rich fluid is exudated.
# '''Margination of leukocytes'''
#* Circulating white blood cells are attracted to the altered endothelial surfaces.
# '''Emigration of leukocytes'''
#* [[Leukocytes|Leukocytes]] migrate through the altered endothelium to reach the injured area.
#* This is an active process - [http://www.cellsalive.com/chemotx.htm| chemotaxis].
#** The cells are attracted to the endothelium by release of proteins, and further into the tissues by factors released from cells in the damaged area.
#** The emigrated leukocytes and components of the fluid exudate are also chemotactic.
#** More cells and fluid are attracted to the area.
# '''Emigration of red blood cells'''
#* [[Erythrocytes|Erythrocytes]] migrate through the gaps in the altered endothelium to the damaged tissue.
# '''Induction of an increase in temperature'''
#* This may occur either locally or systemically.
#* A systemic rise in temperature is known as pyrexia.
#** Occurs in generalise acute inflammation.
#** Pyrogens act on the temperature control centres in the hypothalamus, and are released from:
#*** [[Neutrophils|Neutrophils]], [[Eosinophils|eosinophils]] and [[Macrophages|macrophages]]
#**** Particulary [[Neutrophils|neutrophils]] when they begin to phagocytose.
#*** The cellular coat of gram-negative organisms.
#*** Necrosis of damaged tissue cells.
#*** Antigen-antibody complexes.
#*** Tumours.
#**** Particularly those which have metastasised
#**** It may be difficult to separate this from the pyrexia caused by the central necrosis in such tumours.
==Cells==
* The classical cells of acute inflammation are [[Neutrophils|neutrophils]], [[Eosinophils|eosinophils]], [[Macrophages|macrophages]], [[Mast Cells|mast cells]] and [[Basophils|basophils]].
** [[Macrophages|Macrophages]] are a common feature of acute and chronic inflammation.
[[Category:Acute Inflammation|A]]