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| | + | {{frontpage |
| | + | |pagetitle =Chronic Inflammation |
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| − | ==Types== | + | |contenttitle = Content |
| − | ===Granulomatous Inflammation=== | + | |contentbody =<big><b> |
| | + | <categorytree mode=pages>Chronic Inflammation</categorytree> |
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| − | * Granulomatous inflammation is usually caused by organisms of low virulence but great persistence, or by implanted foreign bodies.
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| − | * Classically appears as a '''granuloma'''.
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| − | ** NOT a tumour, despite the suffix "-oma".
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| − | ** A circumscribed sphere of chronic inflammatory cells enveloped by poorly organised attempts at encapsulation by local connective tissue.
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| − | * The differences between a granuloma and an abscess must be appreciated.
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| − | ** The fibrous envelope is never as well developed as that of an abscess.
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| − | ** The inner contents are never as completely fluid as in an abscess.
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| − | ====Structure of a Granuloma====
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| − | =====Central core=====
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| − | * The central core which contains the agent.
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| − | * The agent may be visible with H&E staining in section, e.g.
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| − | ** ''[[Actinobacillus lignieresii]]''
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| − | *** The cause of "Wooden tongue" in cattle.
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| − | *** Appears as a granule, with a central core of the bacterial colony surrounded by radiating eosinophilic "clubs".
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| − | **** Clubs are considered to be formed from degenerating collagen and antigen-antibody complexes.
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| − | ** ''[[Actinomyces bovis]]''
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| − | *** The cause of "Lumpy Jaw" in cattle.
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| − | *** Forms granules containing bacteria and "clubs".
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| − | ** Fungal hyphae
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| − | ** Parasitic larvae
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| − | ** Foreign bodies
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| − | * The agent might not be visible without being selectively stained.
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| − | ** E.g. [[:Category:Mycobacterium species|''Mycobacterium tuberculosis'']] and ''[[Brucella abortus]]''.
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| − | *** Stain using an acid-fast stain (Ziehl-Neelsen), or a modification.
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| − | *** These organisms are intracellular in the macrophages.
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| − | =====Chronic Inflammatory Cells=====
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| − | * Outside the core is a substantial number of chronic inflammatory cells.
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| − | ** Mainly macrophages.
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| − | *** Often appear as epithelioid cells.
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| − | ** Lymphocytes
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| − | ** Plasma cells.
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| − | * Neutrophils and necrotic remnants of cells can be quite prominent in the granulomas of [[:Category:Actinobacillus species|''Actinobacillus'']] and [[:Category:Actinomyces|''Actinomyces'']] species.
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| − | * Eosinophils are prominent in parasitic granulomas.
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| − | * A scattered and variable number of Giant cells are often seen, but not always in every granuloma.
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| − | =====Outer Envelope=====
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| − | * The final layer is an outer envelope of incomplete fibrous tissue.
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| − | * Giant cells can also be seen in this area.
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| − | ====Gross Appearance of Granulomas====
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| − | * The cut surface of granulomas varies considerably;
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| − | ** Tuberculous granulomas tend to have solid whitish cores which are often calcified.
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| − | *** Grate on the knife when cut through.
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| − | ** Parasitic granulomas are often greenish in colour due to the substantial numbers of eosinophils.
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| − | *** Older ones are also often calcified.
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| − | ** [[:Category:Actinobacillus species|''Actinobacillus'']] and [[:Category:Actinomyces|''Actinomyces'']] species often have liquefied cores due to the necrosis and [[Neutrophils|neutrophils]].
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| − | *** I.e. they are purulent.
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| − | *** May discharge to the surface along sinus tracts.
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| − | *** The central core of bacteria and ‘clubs’ may appear as yellowish granules in this pus.
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| − | **** Often called "sulphur granules".
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| − | ===Granulation Tissue===
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| − | [[Image:granultion tissue histology.jpg|thumb|right|150px|Granulation tissue (Courtesty of BioMed Archive)]]
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| − | * Is completlely different to granulomatous inflammation, despite the similarity in name!
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| − | * Occurs on the surface of the skin where large areas of the epithelium have been lost.
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| − | * Makes up the lining of sinus tracts discharging from deeper lesions.
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| − | * Takes its name from the gross appearance of the small vessels which appear at the surface.
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| − | ** Look like red granules.
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| − | ** These vessels supply inflammatory cells, mainly [[Neutrophils|neutrophils]], to the infected surface.
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| − | * The most frequent example in domestic animals is the formation of excessive granulation tissue on the legs of horses with poorly healing wounds.
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| − | ** "Proud flesh"
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| − | * Ulcers and open wounds may heal by granulation.
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| − | ===Lymphocytic Inflammation===
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| − | * Lymphocytic inflammation is a diffuse chronic ongoing inflammation.
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| − | * Seen in:
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| − | *# Diseases of the central nervous system.
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| − | *#* Lymphocytes appear microscopically as several layers of cells around blood vessels in the perivascular space.
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| − | *#* They indicate that there is damage to the nervous tissue further in.
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| − | *#** Should alert to the possibility of viral infection, which is a common cause of central nervous system disease.
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| − | *#*** E.g. louping ill.
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| − | *# The gut.
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| − | *#* An excessive number of lymphocytes diffusely infiltrating the lamina propria, often in conjunction with plasma cells, indicate an ongoing non-specific chronic enteritis.
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| − | *# The respiratory tract.
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| − | *#* Peribronchial and peribronchiolar cuffing may occur to the point of actual lymphoid follicle formation in these areas.
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| − | *#** Follicles are sometimes large enough to cause partial occlusion of the airways.
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| − | *#* A feature of some chronic lung diseases.
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| − | *#** Ee.g. [[:Category:Mycoplasmas|Mycoplasmosis]] in swine and calves.
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| | [[Category:Inflammation]] | | [[Category:Inflammation]] |