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Category:Acute Inflammation (view source)
Revision as of 11:05, 4 August 2010
, 11:05, 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.
==Fluids==
===Serous===
* Serous fluids are formed due to mild vascular injury in an organ or in vessels underlying a
surface.
* The fluid is clear to cloudy fluid.
** Little protein is present.
* Examples:[[Image:hand burn injury.jpg|right|thumb|150px|<small><center>'''Burn injury'''. (Courtesy of T. Scase)</center></small>]]
** Vesicles of the skin.
** Many inflammations in joints.
===Catarrhal===
* Catarrhal inflammation is a mild form of inflammation.
* Occurs on mucous membranes where there are many mucus cells.
* The consistency of catarrhal exudate varies from water to gelatinous.
* Colour varies from cloudy to pinkish.
* This form of exudation is essentially a shedding of epithelium containing many mucus cells, neutrophils, some RBCs, and flecks of fibrin.
* Common in mild forms of rhinitis, tracheitis, bronchitis, gastritis and enteritis.
===Fibrinous===
* Fibrinous exudation occurs in more severe endothelial injury.
** Injury results in the escape of fibrinogen, which is converted to fibrin.
* The fibrin formed appears as a yellowish coagulation on the surface of or within a tissue.
** Common in the lungs and on serous surfaces.
* In hollow organs the fluid may coagulate to form casts of the lumen.
* Fibrin will peel off from the underlying tissue without causing damage to it.
===Diptheritic===
* Diphtheritic exudate a more severe form of fibrinous exudate in which there is considerable necrosis of the underlying tissues.
* Diptheritic exudate is firmly adherent to the underlying tissue.
** Attempts at removal cause tearing of this tissue>
* Commonly seen with internal surface fungal infections.
** E.g. in the nose of the dog and the guttural pouch of the horse.
** Fungal toxins penetrate the underlying tissue causing coagulation necrosis.
===Haemorrhagic===
* This is a severe acute to peracute inflammation in which haemorrhage is the main component.
* Seen in the lymph nodes, lungs and intestine in severe inflammation.
===Purulent===
* In purulent inflammation, pus is the predominant feature.
** Pus is an admixture of dead and dying neutrophils with necrotic cells and a pyogenic agent.
*** Proteolytic enzymes released by the dying neutrophils lyse tissue cells to produce a fluid.
* Colour varies depending upon the agent.
** May be white, yellow, green or brown.
* An abscess is a circumscribed sphere of pus surrounded by a pyogenic membrane.
** The pyogenic membrane is composed of capillaries bringing neutrophils into the sphere.
** This rapidly becomes enveloped by a fibrous tissue capsule.
*** A local connective tissue response attempting to wall off the purulent irritant from nearby normal tissue.
===Functions of Exudate===
# Dilutes the toxic agent, reducing its effect upon the tissue cells.
# The protein components may contain antibodies which attack or coat (opsonise) the irritant.
#* This makes the irritant more digestible to neutrophils and macrophages.
# Exudates may contain fibrin.
#* This is very sticky - immobilises the irritant.
#* Provides a framework over which the leukocytes crawl to reach the irritant.
#* Fibrin is also chemotactic to neutrophils, bringing more of these cells into the injured area.
# Exudate on a suface will wash away the irritant.
#* E.g the skin and alimentary track.
# Brings the irritant to the lymph nodes, via the lymphatics, for further processing or antigen presentation.
#* Preferably within white blood cells such as macrophages and neutrophils.
#* Local lymph nodes may also be inflamed following inflammation of a tissue which drains into them.
===Sequelae to Exudation===
* Catarrhal and serous exudationresolve when the irritant is overcome.
** Alternatively, they may progress to a more serious reaction.
* Fibrinous exudates may also resolve if the fibrin is digested by macrophages.
** In the pleural and peritoneal cavities, the fibrin may become rganised into fibrous tissue, producing adhesions between the visceral surface.
* Diphtheritic inflammation will only repair by scar formation.
* If haemorrhagic lesions are widespread, they most commonly associated with acute deaths.
** For example in acute viral, bacterial or toxic diseases.
* If the exudation is strictly localised, for example in brusing, then repair may occur.
* The resolution of abscesses depends upon their location.
** If the abscess is near to a surface it will rupture onto it.
** This is beneficial in the skin where it discharges to the exterior, hopefully getting rid of the pyogenic organism.
** If the abscess is in deeper tissues, there is extensive fibrous capsule formation.
*** The fluid becomes inspissated due to withdrawal of water content.
*** Macrophages digest the necrotic remains.
*** Fibrous tissue organises the interior.
*** The very end result is a fibrous scar.
==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:Inflammation]]
* 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.
==Fluids==
===Serous===
* Serous fluids are formed due to mild vascular injury in an organ or in vessels underlying a
surface.
* The fluid is clear to cloudy fluid.
** Little protein is present.
* Examples:[[Image:hand burn injury.jpg|right|thumb|150px|<small><center>'''Burn injury'''. (Courtesy of T. Scase)</center></small>]]
** Vesicles of the skin.
** Many inflammations in joints.
===Catarrhal===
* Catarrhal inflammation is a mild form of inflammation.
* Occurs on mucous membranes where there are many mucus cells.
* The consistency of catarrhal exudate varies from water to gelatinous.
* Colour varies from cloudy to pinkish.
* This form of exudation is essentially a shedding of epithelium containing many mucus cells, neutrophils, some RBCs, and flecks of fibrin.
* Common in mild forms of rhinitis, tracheitis, bronchitis, gastritis and enteritis.
===Fibrinous===
* Fibrinous exudation occurs in more severe endothelial injury.
** Injury results in the escape of fibrinogen, which is converted to fibrin.
* The fibrin formed appears as a yellowish coagulation on the surface of or within a tissue.
** Common in the lungs and on serous surfaces.
* In hollow organs the fluid may coagulate to form casts of the lumen.
* Fibrin will peel off from the underlying tissue without causing damage to it.
===Diptheritic===
* Diphtheritic exudate a more severe form of fibrinous exudate in which there is considerable necrosis of the underlying tissues.
* Diptheritic exudate is firmly adherent to the underlying tissue.
** Attempts at removal cause tearing of this tissue>
* Commonly seen with internal surface fungal infections.
** E.g. in the nose of the dog and the guttural pouch of the horse.
** Fungal toxins penetrate the underlying tissue causing coagulation necrosis.
===Haemorrhagic===
* This is a severe acute to peracute inflammation in which haemorrhage is the main component.
* Seen in the lymph nodes, lungs and intestine in severe inflammation.
===Purulent===
* In purulent inflammation, pus is the predominant feature.
** Pus is an admixture of dead and dying neutrophils with necrotic cells and a pyogenic agent.
*** Proteolytic enzymes released by the dying neutrophils lyse tissue cells to produce a fluid.
* Colour varies depending upon the agent.
** May be white, yellow, green or brown.
* An abscess is a circumscribed sphere of pus surrounded by a pyogenic membrane.
** The pyogenic membrane is composed of capillaries bringing neutrophils into the sphere.
** This rapidly becomes enveloped by a fibrous tissue capsule.
*** A local connective tissue response attempting to wall off the purulent irritant from nearby normal tissue.
===Functions of Exudate===
# Dilutes the toxic agent, reducing its effect upon the tissue cells.
# The protein components may contain antibodies which attack or coat (opsonise) the irritant.
#* This makes the irritant more digestible to neutrophils and macrophages.
# Exudates may contain fibrin.
#* This is very sticky - immobilises the irritant.
#* Provides a framework over which the leukocytes crawl to reach the irritant.
#* Fibrin is also chemotactic to neutrophils, bringing more of these cells into the injured area.
# Exudate on a suface will wash away the irritant.
#* E.g the skin and alimentary track.
# Brings the irritant to the lymph nodes, via the lymphatics, for further processing or antigen presentation.
#* Preferably within white blood cells such as macrophages and neutrophils.
#* Local lymph nodes may also be inflamed following inflammation of a tissue which drains into them.
===Sequelae to Exudation===
* Catarrhal and serous exudationresolve when the irritant is overcome.
** Alternatively, they may progress to a more serious reaction.
* Fibrinous exudates may also resolve if the fibrin is digested by macrophages.
** In the pleural and peritoneal cavities, the fibrin may become rganised into fibrous tissue, producing adhesions between the visceral surface.
* Diphtheritic inflammation will only repair by scar formation.
* If haemorrhagic lesions are widespread, they most commonly associated with acute deaths.
** For example in acute viral, bacterial or toxic diseases.
* If the exudation is strictly localised, for example in brusing, then repair may occur.
* The resolution of abscesses depends upon their location.
** If the abscess is near to a surface it will rupture onto it.
** This is beneficial in the skin where it discharges to the exterior, hopefully getting rid of the pyogenic organism.
** If the abscess is in deeper tissues, there is extensive fibrous capsule formation.
*** The fluid becomes inspissated due to withdrawal of water content.
*** Macrophages digest the necrotic remains.
*** Fibrous tissue organises the interior.
*** The very end result is a fibrous scar.
==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:Inflammation]]