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| − | ==Introduction==
| + | #REDIRECT[[:Category:Degenerations and Infiltrations]] |
| − | * Degenerations and infiltrations are the morphological manifestation of an altered metabolism within the cell.
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| − | ** A particular kind of change within a cell or tissue may suggest that a specific type of alteration has occurred.
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| − | * Degenerations and infiltrations are types of structural changes.
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| − | ** These are best considered at a cellular level.
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| − | ** These structural changes are deviations from the cell's normal structure and function.
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| − | *** Parameters are outside the normal physiological range for the cell.
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| − | * '''Degeneration'''
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| − | ** The tissue cell shows some change in itself.
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| − | * '''Infiltration'''
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| − | ** Something accumulates in the cell or tissue.
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| − | ==[[Cellular Swelling]]==
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| − | ==[[Hydropic Degeneration]]==
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| − | ==[[Cellular Fatty Change]]==
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| − | ==Mucoid Degeneration==
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| − | * Mucoid degeneration is also known as mucinous or myomatous degeneration.
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| − | * Mucoid degeneration involves changes in epithelial tissue or the extracellular matrix/ ground substance.
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| − | * An extracellular phenomenon of some specific cells.
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| − | ** Tend to show a bluish tinge in H&E stained sections.
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| − | ===Epithelium===
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| − | * The specific cells involved in mucoid degeneration in the eptihelium are:
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| − | ** The goblet cells of wet mucous membranes.
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| − | ** The mucous glands themselves.
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| − | * This is not really a degeneration, but an increased production of mucin.
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| − | ** It is a beneficial reaction; the product
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| − | *** Is important as a lubricant.
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| − | *** Soothes inflamed surfaces.
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| − | *** Traps and dilutes harmful agents.
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| − | *** Carries specific antibodies against infectious agents.
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| − | *** Provides a means for removal of infectious agents.
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| − | ===Connective tissue===
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| − | * Here, the mucin forms part of the ground substance between the fibroblasts that produce it.
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| − | * A disturbance in the metabolism of the fibroblasts under some circumstances,means the ground substance takes on a bluish hue in H&E sections.
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| − | * Mucoid degeneration in the heart valves of middle-aged and older dogs is a common example.
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| − | ** Causes '''endocardiosis'''.
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| − | *** A condition specific to the dog.
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| − | ===Endocardiosis===
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| − | * Tends to affects middle-aged and older dogs.
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| − | * Primarily occurs in the mitral valve.
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| − | * Results in slowly developing heart failure
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| − | * The valves become swollen and misshapen
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| − | ** The heart cannot pump blood effectively to the circulation from the left ventricle.
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| − | *** Blood passes back into the left atrium, compromising the filling from the pulmonary vein.
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| − | **** Leads to back pressure on the pulmonary capillaries.
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| − | ***** [[Oedema|Oedema]] forms in the lungs, and can be heard as moist sounds on auscultation.
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| − | ***** Reduces the oxygenation of blood leading to exercise intolerance.
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| − | *** Failure of the left side eventually compromises the function of the right side.
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| − | **** There is pooling of blood in the venous system i.e. in the [[Liver - Anatomy & Physiology|liver]].
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| − | [[Category:Degenerations and Infiltrations]]
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| − | ==Hyaline Degeneration==
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| − | * The term "hyaline degeneration" is applied to several types of degeneration or infiltration.
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| − | ** "Hyaline" is a descriptive term meaning "glassy".
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| − | *** Used in pathology when structureless material appears in section, and stains red with eosin
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| − | **** Describes a variety of conditions in which structureless materials are present.
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| − | * Is applied to both extra- and intra-cellular degenerations/ infiltrations. ** '''Extracellular'''
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| − | *** Protein hyaline casts in the renal tubules.
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| − | **** From excessive protein passing through glomerulus.
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| − | **** When fresh urine is examined under the microscope, casts may be seen as elongated glassy tubes.
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| − | *** Hyaline membranes
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| − | **** Proteinaceous effusions into pulmonary alveoli
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| − | **** Prevent gaseous exchange. ** '''Intracellular'''
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| − | *** Hyaline degeneration of skeletal muscle.
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| − | **** In vitamin E/ selenium deficiency.
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| − | * There are two forms of hyaline degeneration that deserve their own mention.
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| − | ** Fibrinoid degeneration.
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| − | ** Amyloid infiltration.
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| − | ===Fibrinoid Degeneration===
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| − | * Fibrinoid degeneration features a material which is fibrin-like.
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| − | * Is essentially a focal death of cells in the walls of small blood vessels (usually arterioles).
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| − | ** Parts of the vessel wall become replaced by a granular material.
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| − | *** Pinkish-red (i.e. eosin-staining).
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| − | *** Has some of the appearance and staining properties of fibrin.
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| − | *** Consists partly of degenerated muscle and elastic fibres, and partly of an increased amount of protein ground substance around the degenerated fibres.
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| − | *** Looks like a red smudge in the vessel wall when viewed histologically.
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| − | * The presence of the fibrin-like material may suggest
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| − | ** A local hypersensitivity reaction
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| − | ** Hypertension
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| − | ===Amyloidosis===
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| − | * Also known as amyloid infiltration
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| − | * Deposition of a proteinaceous hyaline substance in extracellular sites.
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| − | ** Sites of deposition vary with species.
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| − | * The kidney is a common site of deposition.
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| − | ** Amyloid is deposited under the capillary endothelium and progressively increases in volume.
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| − | * There are various categories of amyloid.
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| − | ** Is essentially an abnormal protein produced in the body
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| − | ** In most cases, it is produced in response to sustained antigenic stimulation caused by a chronic suppurative process.
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| − | *** E.g. a foot abscess, mastitis.
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| − | * Amyloid is a relatively inert substance.
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| − | ** When it accumulates, it is not easily removed.
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| − | [[Category:Degenerations and Infiltrations]]
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| − | ==Glycogen Infiltration==
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| − | * Glycogen is normally present in substantial amounts in the [[Liver - Anatomy & Physiology|liver]] and muscle.
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| − | ** Is a readily utilisable source of energy.
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| − | * Moderate glycogen infiltration in the [[Liver - Anatomy & Physiology|liver]]:
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| − | ** Grossly - doesn't have much effect.
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| − | ** Histologically - shows up as foamy cytoplasmic vacuoles, similar to that of fat.
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| − | * Some conditions may result in an increase in glycogen deposits.
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| − | ** [[DM|'''Diabetes mellitus''']]
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| − | *** Gives an increase in hepatic glycogen stores.
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| − | *** May be overshadowed by the increased fat in the hepatocytes, and therefore difficult to see.
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| − | **** Renal tubular deposits are more easily observed.
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| − | ** '''Excessive glucocorticoids'''
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| − | *** Could be due to:
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| − | **** Hyperadrenocortism
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| − | **** Animals being maintained on glucocorticoid therapy over a long period of time.
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| − | ***** Has more dramatic effect.
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| − | *** Huge amounts of glycogen infiltration.
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| − | **** [[Liver - Anatomy & Physiology|Liver]] appears larger and paler.
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| − | **** Vacuoles may be so extensive that the rest of the cytoplasm appear as pink strands passing from the nucleus to the plasma membrane.
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| − | ***** A "feathery appearance" or "web-like effect".
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| − | ** '''Glycogen storage diseases'''
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| − | *** Due to an inherited deficiency of an enzyme required for the breakdown of glycogen to glucose.
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| − | **** Cells continuously accumulate glycogen.
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| − | *** Seen in all tissues of the body but exerts its major effect in the CNS.
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| − | * Selective staining must be employed to distinguish glycogen vacuoles from fatty vacuoles in the [[Liver - Anatomy & Physiology|liver]].
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| − | ** Alcohol fixation is preferred.
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| − | ** Best's Carmine is the commonly used stain.
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| − | *** Stains the intracellular glycogen red.
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| − | [[Category:Degenerations and Infiltrations]]
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| − | ==Cellular Inclusions==
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| − | ===[[Viruses|Viruses]]===
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| − | * Either in the nucleus or cytoplasm.
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| − | ===Storage Products===
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| − | * Due to '''hereditary storage diseases''' in which there is a missing or defective cellular enzyme. There are many types known in domestic animals.
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| − | ** Break down/ build up of intracellular substances is halted.
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| − | *** The intermediate substance accumulates in the lysosomes.
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| − | ** Affects all tissues
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| − | *** The central nervous system is particularly vulnerable.
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| − | * Due to '''age'''
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| − | ** Lysosomes will accumulate non-degradable products
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| − | *** E.g. lipofuscin - the 'ageing' or 'wear and tear pigment'.
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| − | **** Commonly seen in middle-aged cats in the hepatocytes nearest the centrilobular veins.
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| − | ===Intracellular Bacteria===
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| − | * For example, [[:Category:Mycobacterium species|''Mycobacterium tuberculosis'']] in macrophages.
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| − | ===Protein Accumulation===
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| − | * In the renal tubular epithelium.
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| − | * Occurs when there is leakage of protein out through a damaged glomerulus.
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| − | [[Category:Degenerations and Infiltrations]]
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