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==Introduction==
==Introduction==
When stimulated by antigen presentation, the respective areas undergo an increase in size by hyperplasia. The lymphocytes produced, later leave the lymph node to seek out the source of the antigen in the damaged portion. Bacteria surviving the initial local inflammatory reaction also travel to the lymph node, either in macrophages or as a bacteraemia/septicaemia.
When stimulated by antigen presentation, the respective areas undergo an increase in size by hyperplasia. The lymphocytes produced, later leave the lymph node to seek out the source of the antigen in the damaged portion. Bacteria surviving the initial local inflammatory reaction also travel to the lymph node, either in macrophages or as a bacteraemia/septicaemia.
In the lymph node, many bacteria are trapped, degraded and killed, or exposed to antibody produced by plasma cells in the medullary area. The bacteria therefore set up an acute inflammatory response in the lymph node. If they are pyogenic, baceria can produce abscessation in the lymph node, e. g. Strangles.
In the lymph node, many bacteria are trapped, degraded and killed, or exposed to antibody produced by plasma cells in the medullary area. The bacteria therefore set up an acute inflammatory response in the lymph node. If they are pyogenic, bacteria can produce abscessation in the lymph node, e. g. Strangles.
'''[[Strangles]]'''
An upper respiratory tract pathogen in the horse. Abscesses in the cervical lymph nodes burst to the exterior and abscesses in the retropharyngeal node burst into the pharynx . Infection is usually localised to the head and neck, but can spread to cause abscessation elsewhere in the body.
An upper respiratory tract pathogen in the horse. Abscesses in the cervical lymph nodes burst to the exterior and abscesses in the retropharyngeal node burst into the pharynx . Infection is usually localised to the head and neck, but can spread to cause abscessation elsewhere in the body.
==Bacteraemia==
Bacteria may continue through the lymph nodes and circulate in the blood. These are then generally cleared from the blood by other organs containing phagocytes, e.g. the [[Liver - Anatomy & Physiology|liver]], [[Spleen - Anatomy & Physiology|spleen]] and lungs. There are, however, species differences in the ability to remove bacteria. In most species, the majority of clearance is carried out by the [[Liver - Anatomy & Physiology|liver]] and spleen, however, in the pig, the lung removes 60-80% of such bacteria.
Septicaemia is a condition where there are highly pathogenic bacteria circulating and rapidly multiplying in the blood. This is accompanied by severe signs of clinical illness, due to the liberation of bacterial toxins. These signs can include; high fever, rapid respiration, shock and can even result in the death of the animal.
==Septicaemia==
Septicaemia is a condition where there are highly pathogenic bacteria circulating and rapidly multiplying in the blood. This is accompanied by severe signs of clinical illness, due to the liberation of bacterial toxins. These signs can include: high fever, rapid respiration, shock and can even result in the death of the animal.
'''Gross appearance'''
'''Gross appearance'''
The lymph nodes, [[Liver - Anatomy & Physiology|liver]] and spleen are very hyperaemic and swollen.
The lymph nodes, [[Liver - Anatomy & Physiology|liver]] and spleen are very hyperaemic and swollen.
'''Histological appearance'''
'''Histological appearance'''
The capillaries in tissues taken immediately after death show bacteria in their lumens.
The capillaries in tissues taken immediately after death show bacteria in their lumens.
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{{Jim Bee 2007}}
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[[Category:Lymph Nodes|B]]
[[Category:Lymph Nodes|B]]
[[Category:To Do - AimeeHicks]]
[[Category:A&P Done]]