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| − | {{review}}
| + | #REDIRECT[[:Category:Degenerations and Infiltrations]] |
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| − | {{toplink
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| − | |linkpage =General Pathology
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| − | |linktext =General Pathology
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| − | |maplink = General Pathology (Content Map)
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| − | |pagetype =Pathology
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| − | }}
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| − | <br>
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| − | ==Introduction==
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| − | * 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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| − | * Cellular swelling is
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| − | ** The earliest detectable degenerative change.
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| − | ** The mildest form of cellular degeneration.
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| − | ** The first stage in injury to a cell.
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| − | ** Caused by a variety of insults, e.g.
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| − | *** Lack of oxygen (anoxia) to a tissue.
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| − | *** Toxic influences.
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| − | * Is due to the impairment of the integrity of the cell membrane.
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| − | * Cellular swelling is characterised by a moderate swelling of the individual cells.
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| − | ** Due to an influx of water into the cell.
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| − | ===Gross Appearance===
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| − | * Organs diffusely affected with cloudy swelling grossly appear pale.
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| − | ** This may be partly due to the swollen cells impeding the tissue's blood supply.
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| − | * Without cutting into an organ, it may be difficult to appreciate a gross enlargement of it.
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| − | ** Each individual cell is increased in size, meaning the entire volume of the organ is also increased.
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| − | ** E.g. on cutting the [[Liver - Anatomy & Physiology|liver]] or kidney capsule, the underlying swollen parenchyma bulges outwards, making the cut ends of the capsule retract.
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| − | * The degree of gross swelling is not great.
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| − | ** Could be easily confused with early post-mortem changes in the organ.
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| − | | |
| − | ===Histological Appearance===
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| − | * Individual cells appear somewhat swollen.
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| − | * The cytoplasm appears more red in colour in hematoxylin and eosin (H&E) stained sections.
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| − | * The nucleus of the cell remains normal.
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| − | * Cellular swelling is best histologically appreciated in the [[Liver - Anatomy & Physiology|liver]] and kidney in damage caused by circulating toxins that are not powerful enough to actually kill the cells.
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| − | ===Significance of Cellular Swelling===
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| − | * Cellular swelling is an important stage in degeneration.
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| − | ** Not commonly observed on its own without more serious changes
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| − | *** Not easy to identify at post-mortem unless the examination is performed very soon after the animal's death.
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| − | **** Early post-mortem (autolytic) change in dead tissue looks rather similar.
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| − | *** Cellular swelling is also reversible.
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| − | **** When the toxin is no longer exerting its effect, the tissue returns to normal.
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| − | *** Cellular swelling may be a transient stage in the more serious forms of degenerations which follow.
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| − | ==Hydropic Degeneration==
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| − | * Hydropic degeneration often indicates severe cellular damage due to viruses.
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| − | ** Is a more severe or advanced form of cellular swelling.
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| − | * There are two types of hydropic degeneration, in which:
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| − | *# The cells may swell up like a balloon prior to their destruction.
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| − | *#* '''Ballooning Degeneration'''
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| − | *# There is a discrete bleb (vacuole) of fluid within the cytoplasm.
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| − | *#* '''Vacuolar Degeneration'''
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| − | ===Ballooning Degeneration===
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| − | * May occur in a variety of conditions.
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| − | ** Is particularly seen in viral conditions of epithelial tissue.
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| − | * [[Foot and Mouth Disease|Foot and Mouth Disease]] is the best example.
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| − | ** Foot and Mouth virus attacks the stratum spinosum of the epithelium of the [[Oral Cavity - Tongue - Anatomy & Physiology|tongue]] and feet.
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| − | ** Affected cells balloon up with water containing the replicating virus, swelling until they burst.
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| − | *** The fluid contained in the cells then forms microvesicles (blisters) in the stratum spinosum.
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| − | **** Blisters may later burst, shedding vast quantities of the virus.
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| − | ** On bursting, the edges of the erosions look ragged.
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| − | *** Within weeks, the germinal epithelium at the base of the erosion regenerates the epithelium, leaving no trace of a scar.
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| − | | |
| − | ===Vacuolar Degeneration===
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| − | * In vacuolar degeneration, excess water is transferred to the endoplasmic reticulum (ER).
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| − | * The ER swells and eventually fragments.
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| − | ** A fluid vacuole remains in the cytoplasm.
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| − | * Commonly occurs in cells that are very metabolically active and have well developed pumping mechanisms.
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| − | ** E.g. as the hepatocyte, renal tubular epithelium and pancreatic acinar cell.
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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 - Pathology|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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| − | ==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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| − | ==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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| − | ==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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