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Category:Chronic Inflammation (view source)
Revision as of 11:25, 4 August 2010
, 11:25, 4 August 2010Created page with " ==Types== ===Granulomatous Inflammation=== * Granulomatous inflammation is usually caused by organisms of low virulence but great persistence, or by implanted foreign bodies...."
==Types==
===Granulomatous Inflammation===
* Granulomatous inflammation is usually caused by organisms of low virulence but great persistence, or by implanted foreign bodies.
* Classically appears as a '''granuloma'''.
** NOT a tumour, despite the suffix "-oma".
** A circumscribed sphere of chronic inflammatory cells enveloped by poorly organised attempts at encapsulation by local connective tissue.
* The differences between a granuloma and an abscess must be appreciated.
** The fibrous envelope is never as well developed as that of an abscess.
** The inner contents are never as completely fluid as in an abscess.
====Structure of a Granuloma====
=====Central core=====
* The central core which contains the agent.
* The agent may be visible with H&E staining in section, e.g.
** ''[[Actinobacillus lignieresii]]''
*** The cause of "Wooden tongue" in cattle.
*** Appears as a granule, with a central core of the bacterial colony surrounded by radiating eosinophilic "clubs".
**** Clubs are considered to be formed from degenerating collagen and antigen-antibody complexes.
** ''[[Actinomyces bovis]]''
*** The cause of "Lumpy Jaw" in cattle.
*** Forms granules containing bacteria and "clubs".
** Fungal hyphae
** Parasitic larvae
** Foreign bodies
* The agent might not be visible without being selectively stained.
** E.g. [[:Category:Mycobacterium species|''Mycobacterium tuberculosis'']] and ''[[Brucella abortus]]''.
*** Stain using an acid-fast stain (Ziehl-Neelsen), or a modification.
*** These organisms are intracellular in the macrophages.
=====Chronic Inflammatory Cells=====
* Outside the core is a substantial number of chronic inflammatory cells.
** Mainly macrophages.
*** Often appear as epithelioid cells.
** Lymphocytes
** Plasma cells.
* Neutrophils and necrotic remnants of cells can be quite prominent in the granulomas of [[:Category:Actinobacillus species|''Actinobacillus'']] and [[:Category:Actinomyces|''Actinomyces'']] species.
* Eosinophils are prominent in parasitic granulomas.
* A scattered and variable number of Giant cells are often seen, but not always in every granuloma.
=====Outer Envelope=====
* The final layer is an outer envelope of incomplete fibrous tissue.
* Giant cells can also be seen in this area.
====Gross Appearance of Granulomas====
* The cut surface of granulomas varies considerably;
** Tuberculous granulomas tend to have solid whitish cores which are often calcified.
*** Grate on the knife when cut through.
** Parasitic granulomas are often greenish in colour due to the substantial numbers of eosinophils.
*** Older ones are also often calcified.
** [[:Category:Actinobacillus species|''Actinobacillus'']] and [[:Category:Actinomyces|''Actinomyces'']] species often have liquefied cores due to the necrosis and [[Neutrophils|neutrophils]].
*** I.e. they are purulent.
*** May discharge to the surface along sinus tracts.
*** The central core of bacteria and ‘clubs’ may appear as yellowish granules in this pus.
**** Often called "sulphur granules".
===Granulation Tissue===
[[Image:granultion tissue histology.jpg|thumb|right|150px|Granulation tissue (Courtesty of BioMed Archive)]]
* Is completlely different to granulomatous inflammation, despite the similarity in name!
* Occurs on the surface of the skin where large areas of the epithelium have been lost.
* Makes up the lining of sinus tracts discharging from deeper lesions.
* Takes its name from the gross appearance of the small vessels which appear at the surface.
** Look like red granules.
** These vessels supply inflammatory cells, mainly [[Neutrophils|neutrophils]], to the infected surface.
* The most frequent example in domestic animals is the formation of excessive granulation tissue on the legs of horses with poorly healing wounds.
** "Proud flesh"
* Ulcers and open wounds may heal by granulation.
===Lymphocytic Inflammation===
* Lymphocytic inflammation is a diffuse chronic ongoing inflammation.
* Seen in:
*# Diseases of the central nervous system.
*#* Lymphocytes appear microscopically as several layers of cells around blood vessels in the perivascular space.
*#* They indicate that there is damage to the nervous tissue further in.
*#** Should alert to the possibility of viral infection, which is a common cause of central nervous system disease.
*#*** E.g. louping ill.
*# The gut.
*#* An excessive number of lymphocytes diffusely infiltrating the lamina propria, often in conjunction with plasma cells, indicate an ongoing non-specific chronic enteritis.
*# The respiratory tract.
*#* Peribronchial and peribronchiolar cuffing may occur to the point of actual lymphoid follicle formation in these areas.
*#** Follicles are sometimes large enough to cause partial occlusion of the airways.
*#* A feature of some chronic lung diseases.
*#** Ee.g. [[:Category:Mycoplasmas|Mycoplasmosis]] in swine and calves.
[[Category:Inflammation]]