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| − | ==Degeneration==
| + | #redirect[[:Category:Muscles - Degenerative Pathology]] |
| − | [[Image:Degenerate muscle fibres.jpg|right|thumb|100px|<small><center>Degenerate muscle fibres (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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| − | *Different types of degeneration
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| − | *May, or may not, be reversible
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| − | *Cloudy swelling, hydropic, vacuolar, granular and fatty change
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| − | *Occur following many different types of insult and are usually '''segmental'''
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| − | *If regeneration does not occur after formation of small vacuoles, [[Muscles Degenerative - Pathology#Necrosis|necrosis]] follows
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| − | **Vacuolation -> floccular degeneration -> granular degeneration -> [[Hyaline Degeneration|hyaline]] and [[Zenker Degeneration - Pathology|Zenker’s degeneration]]
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| − | *[[Hydropic Degeneration#Vacuolar Degeneration|'''Vacuolar degeneration''']]:
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| − | **Due to swelling of organelles or due to glycogen or fat accumulation
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| − | **May be caused by hypokalaemia, hyperkalaemia or necrosis
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| − | *Histologically:
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| − | **Swollen
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| − | **Hypereosinophilic
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| − | **Lost cross striations
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| − | ===[[Muscle Calcification]]===
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| − | ===[[Muscle Ossification]]===
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| − | ===[[Muscle Pigmentation]]===
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| − | ==[[Muscle Necrosis]]==
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| − | ==[[Muscle Atrophy]]==
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| − | ==[[Toxic Myopathy]]==
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| − | ==[[Endocrine Myopathy]]==
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| − | ==Nutritional myopathy==
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| − | [[Image:White muscle disease.jpg|right|thumb|100px|<small><center>White muscle disease (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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| − | [[Image:White muscle disease histo.jpg|right|thumb|100px|<small><center>White muscle disease (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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| − | ===[[White Muscle Disease - Pathology|White muscle disease]]===
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| − | *Very important economic disease of sheep, cattle and pig
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| − | *Caused by:
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| − | **Deficiency of selenium, vitamin E or both
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| − | **Exacerbated by rapid growth, unaccustomed exercise or other dietary factor
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| − | *Pathogenesis:
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| − | **Oxygen free radicals (OFR) can damage cell membranes
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| − | **Vitamin E usually mops up OFRs
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| − | **Selenium as part of glutathione peroxidase neutralises effects of OFRs
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| − | **If Vit E or Se are deficient -> the balance shifts to membrane damage, calcium entry and mitochondrial damage -> cell swells and dies -> segmental muscle [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
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| − | *Grossly:
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| − | **Lesions are bilaterally symmetrical in hard working muscles (vary with species)
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| − | **Early lesions are pale areas and streaks
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| − | ***Difficult to see especially in pale muscles
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| − | **Later becoming calcified necrotic areas
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| − | ***More obvious
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| − | **Pigs also have lesions in their [[Hyaline Degeneration|heart]] and [[Liver Fibrosis#Hepatosis dietica|liver]]
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| − | *Histologically:
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| − | **[[Muscles Degenerative - Pathology#Necrosis|Segmental necrosis]] +/- [[Muscles Degenerative - Pathology#Calcification|calcification]] and [[Muscle Regeneration|regeneration]]
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| − | **Multifocal and multiphasic lesions
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| − | [[Category:Muscles - Degenerative Pathology]]
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| − | ==Exertional myopathies==
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| − | *Caused by intensive and exhaustive activity of major muscle masses
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| − | *Glycogen used up -> local heat and lactic acid -> muscle degeneration
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| − | *Other forms include '''capture myopathy''', racing greyhounds, sheep chased by dogs
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| − | ===Equine rhabdomyolysis===
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| − | *'''Azoturia''' (Monday morning disease)
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| − | **Acute
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| − | **Due to exercise following a prolonged period of rest
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| − | **Clincal signs:
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| − | ***Unable to move
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| − | ***Sweating
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| − | ***Tremors
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| − | ***Swollen and hard lumbar, gluteal and femoral muscles
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| − | **Myoglobin leaks from muscle cells -> leaks into urine -> urine is dark red/brown (myoglobinuria) -> damages renal tubules
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| − | **Grossly:
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| − | ***Salmon pink muscles -> dark, moist, swollen +/- pale streaks
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| − | **Histologically:
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| − | ***Segmental myofibre [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
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| − | ****Multifocal and monophasic, but may be multiphasic if repeated bouts
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| − | ***Both, type IIA and IIB fibres affected; type IIB preferentially affected in acute disease
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| − | ***Minor inflammatory reaction and calcification
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| − | *'''Tying-up'''
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| − | **Similar to azoturia but much milder
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| − | **Grossly - normal muscle
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| − | **Histologically - same as azoturia
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| − | [[Category:Muscles - Degenerative Pathology]]
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| − | ===[[Porcine Stress Syndrome]]===
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| − | ==Neuromuscular junction diseases==
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| − | ===Aquired myasthenia gravis===
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| − | *See [[Myasthenia Gravis|congenital MG]]
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| − | ===Botulism===
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| − | *Caused by:
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| − | **Ingestion of ''[[Clostridium botulinum]]'' toxin which inhibits acetyl choline release
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| − | *Diagnosis by demonstration of toxin in faeces, ingested material or serum
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| − | [[Category:Muscles - Degenerative Pathology]]
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| − | ==Circulatory disturbances==
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| − | ===Congestion===
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| − | *Localised or generalised stasis -> dark red muscle
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| − | *E.g. in ruminal tympany ([[Bloat|bloat]]) - congestion of muscles cranial to thoracic inlet
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| − | *May resemble haemorhage grossly
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| − | [[Category:Muscles - Degenerative Pathology]]
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| − | ===Ischaemia===
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| − | *Firstly [[Muscles Degenerative - Pathology#Necrosis|segmental necrosis]]
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| − | *-> death of satellite cells
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| − | **Causes [[Muscle Regeneration|regeneration]] but myoblast precursors have to be recruited from viable fibres
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| − | *-> death of all cells
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| − | *Mostly healed by fibrosis and scar formation
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| − | *May attempt regeneration by [[Muscle Regeneration|budding]]
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| − | Main causes:
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| − | *'''Vascular occlusion'''
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| − | **Infarction from embolism is rare due to collateral circulation
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| − | **Extension of infarcts depends on size of vessels occluded
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| − | ***Small capillaries -> segmental [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
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| − | ***Large arteries -> whole muscle areas, including sattelite cells, are killed
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| − | **Healed by fibrosis
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| − | **May be due to:
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| − | ***Blockage of iliac arteries by aortic-iliac thrombosis in horses
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| − | ***Blockage of aortic bifurcation in cats
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| − | ***[[Dirofilaria immitis|''Dirofilaria immitis'']] arteritis in dogs
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| − | ***Vasculitis due to [[Reoviridae#Bluetongue Virus|bluetongue virus]] in sheep
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| − | ***[[Haemorrhage#Purpura haemorrhagica|'''Equine purpura haemorrhagica''']]
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| − | ****Non-contagious, sporadic
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| − | ****Grossly:
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| − | *****Subcutaneous oedema
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| − | *****Scattered haemorrhagic foci throughout skin and muscles
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| − | *****Vasculitis -> infarcts of muscles
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| − | ****May cause myoglobinuria if extensive
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| − | ****Possibly immune mediated
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| − | ****In horses post [[:Category:Streptococcus species|streptococal]] infection, especially [[Respiratory Bacterial Infections - Pathology#Strangles|strangles]]
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| − | *'''External pressure'''
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| − | **During prolonged recumbency, e.g. anaesthesia, inability to rise, or due to too tightly fitting bandages or casts
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| − | **Post anaesthesia myopathy especially in horses
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| − | ***Dorsal recumbancy -> gluteals and longissimus ischaemia
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| − | ***Lateral recumbancy -> triceps brachii, pectoralis, deltoideus and brachiocephalicus ischaemia
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| − | **Caused by pressure on muscle > perfusion pressure of capillaries
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| − | **Downer cows - vetral recumbency -> ischaemia of pectoral muscles and muscles of limbs tucked under the animal
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| − | **Pregnant ewes with twins or triplets -> internal abdominal oblique muscle ischaemic necrosis -> potential rupture
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| − | *'''Muscle swelling''' where it cannot expand
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| − | **E.g. supracoracoid muscle infarction in some breeds of turkeys after flapping their wings
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| − | ***Surrounded by inelastic fascial sheath and bone
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| − | [[Category:Muscles - Degenerative Pathology]]
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| − | ==Trauma==
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| − | *Due to:
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| − | **Direct transection of myofibres
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| − | **Compression of myofibres
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| − | **Secondary from haemorrhage (bruising)
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| − | ***May increase muscle pressure -> [[Muscles Degenerative - Pathology#Ischaemia|ischaemia]] -> [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
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| − | **Partial rupture - ''e.g.'' of diaphragm in road traffic accident
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| − | **Complete rupture - ''e.g.'' quadriceps of racing greyhounds
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| − | **Myorrhexis (tearing) - ''e.g.'' slippery floor causing 'splits' in cattle -> adductor muscle tear
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| − | *Healing is by [[Muscle Regeneration|regeneration]]
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| − | *Fibrosis (scarring) will compromise function
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| − | *During [[Bones Fractures - Pathology|fractures]], fragments may cause further trauma if moved
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| − | [[Category:Muscles - Degenerative Pathology]]
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| − | [[Category:Musculoskeletal System - Pathology]]
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