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| − | ==Anatomy & Physiology== | + | {{frontpage |
| − | [[Lymph Nodes - Anatomy & Physiology|See here]]
| + | |pagetitle =Lymph Nodes |
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| − | ==Lymph node responses in disease (The Total Node Response)== | + | |pagebody = |
| − | ===reactive nodes===
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| − | *immunological response to antigens
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| − | *hyperplasia
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| − | *cell proliferation in cortex
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| − | :- germinal centre activity
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| − | :- multiplication of cells in thymus-dependent area (paracortex)
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| − | *accumulation of newly-formed plasma cells in medullary cords
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| − | *macroscopically
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| − | :- bulging white cortex which may almost obliterate the medulla
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| − | ===lymphadenitis=== | + | |contenttitle = Content |
| − | *true inflammation
| + | |contentbody =<big><b> |
| − | *swollen due to
| + | <categorytree mode=pages>Lymph Nodes</categorytree> |
| − | :- congestion
| + | </b></big> |
| − | :- oedema
| + | |logo = Anat logo.png |
| − | :- leukocyte (neutrophil) accumulation
| + | }} |
| − | *pyogenic organisms
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| − | :- abscessation can develop
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| − | :- there will be pus and necrosis in the node itself
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| − | *lymphangitis: inflammation of lymphatics
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| | | | |
| − | ==Role of the Lymph Node in Inflammation==
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| − | ''Back to [[Inflammation - Pathology]]
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| − | * 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.
| + | [[Category:Secondary Lymphoid Tissue|A]] |
| − | * 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==
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| − | ===Parasitic Diseases===
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| − | ====bovine parasitic bronchitis====
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| − | ====ostertagiasis====
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| − | ====fascioliasis====
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| − | ===Bacterial Diseases===
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| − | ====clostridial====
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| − | | |
| − | ==Diseases Involving Both Reactive Nodes and Lymphadenitis==
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| − | ===[[Tuberculosis - Cattle]]===
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| − | | |
| − | ===viz. brucellosis and Johne's disease===
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| − | * chronicity is caused by persistence of intacellular bacteria in lymph node macrophages
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| − | * Type IV hypersensitivity, but does not result in visible necrosis as in TB
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| − | | |
| − | ===Johne's disease===
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| − | ===Actinobacillosis===
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| − | ===Actinomycosis===
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| − | ===Equine strangles===
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| − | * acute inflammation
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| − | * produce pyogenic or necrotic foci in the drainage nodes
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| − | * involves submaxillary nodes
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| − | | |
| − | ===Streptococcal adenitis or head gland disease===
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| − | * dogs
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| − | * acute inflammation as in above
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| − | | |
| − | ==Diseases Parasitising the Lymphocytes==
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| − | *organism grows in the lymphocytes and ruptures them
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| − | *if large infecting dose
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| − | :- may be rapidly fatal since animal may no tb e able to mount an immunological attack | |
| − | *if smaller infecting dose
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| − | :- loss of mature lymphocytes causes a dramatic stimulation of the remaining lymphocyte precursors
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| − | :- node hyperplasia follows
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| − | :- competition between lymphocytolysis by the organism and lymphocyte production by the nodes
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| − | :- clinically
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| − | ::- may be swelling of the node at one stage and reduction in size at another
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| − | | |
| − | ===canine distemper===
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| − | *virus
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| − | ===swine fever===
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| − | *virus
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| − | ===bovine east coast fever===
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| − | *protozoan
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| − | ===[[Leishmania|Leishmaniasis in the dog]]===
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| − | ==Other Lymphadenopathy==
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| − | ===Lymph node pigmentation===
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| − | *Lungs
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| − | :- anthracosis
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| − | ::- carbon derived from soot finds its way to the local nodes in macrophages
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| − | *Skin
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| − | :- dermatopathic lymphadenopathy or melanic reticulosis
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| − | ::- in pigmented animals, especially black dogs
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| − | ::- chronic inflammatory skin conditions lead to melanin deposition in hyperplastic nodules
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| − | :- also occurs in nodes draining skin melanomas where the pigment may be the result of skin ulceration or secondary tumour deposit
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| − | ::- these two should not be confused since the prognosis is very different following surgery
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| − | ===Emphysema===
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| − | *interstitial emphysema
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| − | :- common in cases of dyspnoea
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| − | :- more commonly affects bovine lung
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| − | ::- due to well developed pulmonary lobulation and hence much loose interstitial lung tissue
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| − | *collection of gas bubbles in bronchial and mediastinal lymph nodes
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| − | :- gas travels to these nodes after gaining entry to the many lymphatic vessels present in the interstitial tissue
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| − | ===Neoplasia===
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| − | * Primary tumours
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| − | ** Lymphosarcoma (lymphoma)
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| − | :- of lymphoid cells with lymph node enlargement
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| − | :- smooth, pale hemogenous but may have areas of necrosis
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| − | :- may cause [[Parathyroid Glands - Pathology#Pseudo-Hyperparathyroidism|pseudo-hyperparathyroidism]]
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| − | * Secondary tumours
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| − | :- nodes often involved in the spread of tumours by extension or metastasis
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| − | :- usually carcinomas
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| − | ==Haemal Lymph Nodes==
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| − | *ruminants only
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| − | *small; dark red/brown
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| − | *develop during foetal life
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| − | :- lymph node primordia which lose their lymph vessles
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| − | :- receive all cells and antigen from the BLOOD
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| − | *functional significance unclear
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| − | *probably respond to blood-borne antigen
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