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| − | ==Role of the Lymph Node in Inflammation== | + | ==Role of the [[Lymph Node in Inflammation]]== |
| | ''Back to [[Inflammation - Pathology]] | | ''Back to [[Inflammation - Pathology]] |
| − | * Antigenic material is transported in phagocytes via the tissue lymphatics to the local lymph node.
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| − | * In the subcapsular sinusoids of the lymph node, antigens are exposed to the reticular cell macrophages.
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| − | ** These macrophages form a meshwork around the subcapsular, cortical and medullary sinusoids.
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| − | ** These reticular cells present the antigen to the appropriate lymphocyte population.
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| − | *** To B-cells in the follicular centres
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| − | *** To T-cells in the parafollicular areas.
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| − | * When stimulated by antigen presentation, the respective areas undergo an increase in size by hperplasia.
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| − | ** The lymphocytes produced later leave the lymph node to seek out the source of the antigen in the damaged portion.
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| − | * Bacteria surviving the initial local inflammatory reaction also travel to the lymph node.
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| − | ** Travel either in macrophages or as a bacteraemia/septicaemia.
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| − | ** In the lymph node, many bacteria are trapped, degraded and killed, or exposed to antibody produced by plasma cells in the medullary area.
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| − | ** Bacteria set up an acute inflammatory response in the lymph node.
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| − | *** If they are pyogenic, baceria can produce abscessation in the lymph node.
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| − | **** E. g. Strangles.
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| − | ***** An upper respiratory tract pathogen in the horse.
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| − | ***** Abscesses in the cervical lymph nodes burst to the exterior.
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| − | ***** Abscesses in the retropharyngeal node burst into the pharynx
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| − | ***** Infection is usually localised to the head and neck, but can spread to cause abscessation elsewhere in the body.
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| − | ===Bacteraemia===
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| − | * Bacteria may continue through the lymph nodes and circulate in the blood.
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| − | * These are generally cleared from the blood by other organs containing phagocytes.
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| − | ** E.g. the [[Liver - Anatomy & Physiology|liver]], [[Spleen - Anatomy & Physiology|spleen]] and lungs.
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| − | * There are species differences in the ability to remove bacteria.
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| − | ** In most species, the majority of clearance is carried out by the [[Liver - Anatomy & Physiology|liver]] and spleen.
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| − | ** However, in the pig, the lung removes 60-80% of such bacteria.
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| − | ===Septicaemia===
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| − | * Septicaemia is a condition where there are highly pathogenic bacteria circulating and rapidly multiplying in the blood.
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| − | ** Accompanied by severe signs of clinical illness due to the liberation of bacterial toxins.
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| − | *** High fever
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| − | *** Rapid respiration
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| − | *** Shock
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| − | ** Can result in the death of the animal.
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| − | ====Gross Appearance====
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| − | * The lymph nodes, [[Liver - Anatomy & Physiology|liver]] and spleen are very hyperaemic and swollen.
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| − | ====Histological Appearance====
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| − | * Capillaries in tissues taken immediately after death show bacteria in their lumens.
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| | ==Diseases Involving Reactive Nodes== | | ==Diseases Involving Reactive Nodes== |