|
|
(10 intermediate revisions by the same user not shown) |
Line 1: |
Line 1: |
− | ==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>]]
| |
− | | |
− | *Different types of degeneration
| |
− | *May, or may not, be reversible
| |
− | *Cloudy swelling, hydropic, vacuolar, granular and fatty change
| |
− | *Occur following many different types of insult and are usually '''segmental'''
| |
− | *If regeneration does not occur after formation of small vacuoles, [[Muscles Degenerative - Pathology#Necrosis|necrosis]] follows
| |
− | **Vacuolation -> floccular degeneration -> granular degeneration -> [[Hyaline Degeneration|hyaline]] and [[Zenker Degeneration - Pathology|Zenker’s degeneration]]
| |
− | *[[Hydropic Degeneration#Vacuolar Degeneration|'''Vacuolar degeneration''']]:
| |
− | **Due to swelling of organelles or due to glycogen or fat accumulation
| |
− | **May be caused by hypokalaemia, hyperkalaemia or necrosis
| |
− | *Histologically:
| |
− | **Swollen
| |
− | **Hypereosinophilic
| |
− | **Lost cross striations
| |
− | | |
− | | |
− | ===[[Muscle Calcification]]===
| |
− | | |
− | | |
− | | |
− | | |
− | | |
− | ===[[Muscle Ossification]]===
| |
− | | |
− | | |
− | ===[[Muscle Pigmentation]]===
| |
− | | |
− | | |
− | | |
− | ==[[Muscle Necrosis]]==
| |
− | | |
− | | |
− | | |
− | ==[[Muscle Atrophy]]==
| |
− | | |
− | | |
− | ==[[Toxic Myopathy]]==
| |
− | | |
− | | |
− | | |
− | ==Endocrine myopathy==
| |
− | | |
− | *[[Hyperadrenocorticism|Hyperadrenocorticism]]
| |
− | **Muscle weakness is a clinical sign
| |
− | **-> [[Muscles Degenerative - Pathology#Atrophy|muscle atrophy]]
| |
− | ***Type II myofibre atrophy is non-specific
| |
− | ***Type IIB myofibre atrophy is preferential in hyperadrenocorticism
| |
− | *[[Hypothyroidism|Hypothyroidism]] can cause muscle atrophy
| |
− | | |
− | | |
− | [[Category:Muscles - Degenerative Pathology]]
| |
− | | |
− | | |
− | ==Nutritional myopathy==
| |
− | [[Image:White muscle disease.jpg|right|thumb|100px|<small><center>White muscle disease (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
| |
− | [[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>]]
| |
− | ===[[White Muscle Disease - Pathology|White muscle disease]]===
| |
− | *Very important economic disease of sheep, cattle and pig
| |
− | *Caused by:
| |
− | **Deficiency of selenium, vitamin E or both
| |
− | **Exacerbated by rapid growth, unaccustomed exercise or other dietary factor
| |
− | *Pathogenesis:
| |
− | **Oxygen free radicals (OFR) can damage cell membranes
| |
− | **Vitamin E usually mops up OFRs
| |
− | **Selenium as part of glutathione peroxidase neutralises effects of OFRs
| |
− | **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]]
| |
− | *Grossly:
| |
− | **Lesions are bilaterally symmetrical in hard working muscles (vary with species)
| |
− | **Early lesions are pale areas and streaks
| |
− | ***Difficult to see especially in pale muscles
| |
− | **Later becoming calcified necrotic areas
| |
− | ***More obvious
| |
− | **Pigs also have lesions in their [[Hyaline Degeneration|heart]] and [[Liver Fibrosis#Hepatosis dietica|liver]]
| |
− | *Histologically:
| |
− | **[[Muscles Degenerative - Pathology#Necrosis|Segmental necrosis]] +/- [[Muscles Degenerative - Pathology#Calcification|calcification]] and [[Muscle Regeneration|regeneration]]
| |
− | **Multifocal and multiphasic lesions
| |
− | | |
− | | |
− | [[Category:Muscles - Degenerative Pathology]]
| |
− | | |
− | | |
− | ==Exertional myopathies==
| |
− | | |
− | *Caused by intensive and exhaustive activity of major muscle masses
| |
− | *Glycogen used up -> local heat and lactic acid -> muscle degeneration
| |
− | *Other forms include '''capture myopathy''', racing greyhounds, sheep chased by dogs
| |
− | | |
− | | |
− | ===Equine rhabdomyolysis===
| |
− | | |
− | *'''Azoturia''' (Monday morning disease)
| |
− | **Acute
| |
− | **Due to exercise following a prolonged period of rest
| |
− | **Clincal signs:
| |
− | ***Unable to move
| |
− | ***Sweating
| |
− | ***Tremors
| |
− | ***Swollen and hard lumbar, gluteal and femoral muscles
| |
− | **Myoglobin leaks from muscle cells -> leaks into urine -> urine is dark red/brown (myoglobinuria) -> damages renal tubules
| |
− | **Grossly:
| |
− | ***Salmon pink muscles -> dark, moist, swollen +/- pale streaks
| |
− | **Histologically:
| |
− | ***Segmental myofibre [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
| |
− | ****Multifocal and monophasic, but may be multiphasic if repeated bouts
| |
− | ***Both, type IIA and IIB fibres affected; type IIB preferentially affected in acute disease
| |
− | ***Minor inflammatory reaction and calcification
| |
− | | |
− | *'''Tying-up'''
| |
− | **Similar to azoturia but much milder
| |
− | **Grossly - normal muscle
| |
− | **Histologically - same as azoturia
| |
− | | |
− | [[Category:Muscles - Degenerative Pathology]]
| |
− | | |
− | | |
− | ===[[Porcine Stress Syndrome]]===
| |
− | | |
− | | |
− | ==Neuromuscular junction diseases==
| |
− | | |
− | ===Aquired myasthenia gravis===
| |
− | | |
− | *See [[Myasthenia Gravis|congenital MG]]
| |
− | | |
− | | |
− | ===Botulism===
| |
− | | |
− | *Caused by:
| |
− | **Ingestion of ''[[Clostridium botulinum]]'' toxin which inhibits acetyl choline release
| |
− | *Diagnosis by demonstration of toxin in faeces, ingested material or serum
| |
− | | |
− | | |
− | [[Category:Muscles - Degenerative Pathology]]
| |
− | | |
− | ==Circulatory disturbances==
| |
− | | |
− | ===Congestion===
| |
− | | |
− | *Localised or generalised stasis -> dark red muscle
| |
− | *E.g. in ruminal tympany ([[Bloat|bloat]]) - congestion of muscles cranial to thoracic inlet
| |
− | *May resemble haemorhage grossly
| |
− | | |
− | [[Category:Muscles - Degenerative Pathology]]
| |
− | ===Ischaemia===
| |
− | | |
− | *Firstly [[Muscles Degenerative - Pathology#Necrosis|segmental necrosis]]
| |
− | *-> death of satellite cells
| |
− | **Causes [[Muscle Regeneration|regeneration]] but myoblast precursors have to be recruited from viable fibres
| |
− | *-> death of all cells
| |
− | *Mostly healed by fibrosis and scar formation
| |
− | *May attempt regeneration by [[Muscle Regeneration|budding]]
| |
− | Main causes:
| |
− | *'''Vascular occlusion'''
| |
− | **Infarction from embolism is rare due to collateral circulation
| |
− | **Extension of infarcts depends on size of vessels occluded
| |
− | ***Small capillaries -> segmental [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
| |
− | ***Large arteries -> whole muscle areas, including sattelite cells, are killed
| |
− | **Healed by fibrosis
| |
− | **May be due to:
| |
− | ***Blockage of iliac arteries by aortic-iliac thrombosis in horses
| |
− | ***Blockage of aortic bifurcation in cats
| |
− | ***[[Dirofilaria immitis|''Dirofilaria immitis'']] arteritis in dogs
| |
− | ***Vasculitis due to [[Reoviridae#Bluetongue Virus|bluetongue virus]] in sheep
| |
− | ***[[Haemorrhage#Purpura haemorrhagica|'''Equine purpura haemorrhagica''']]
| |
− | ****Non-contagious, sporadic
| |
− | ****Grossly:
| |
− | *****Subcutaneous oedema
| |
− | *****Scattered haemorrhagic foci throughout skin and muscles
| |
− | *****Vasculitis -> infarcts of muscles
| |
− | ****May cause myoglobinuria if extensive
| |
− | ****Possibly immune mediated
| |
− | ****In horses post [[:Category:Streptococcus species|streptococal]] infection, especially [[Respiratory Bacterial Infections - Pathology#Strangles|strangles]]
| |
− | *'''External pressure'''
| |
− | **During prolonged recumbency, e.g. anaesthesia, inability to rise, or due to too tightly fitting bandages or casts
| |
− | **Post anaesthesia myopathy especially in horses
| |
− | ***Dorsal recumbancy -> gluteals and longissimus ischaemia
| |
− | ***Lateral recumbancy -> triceps brachii, pectoralis, deltoideus and brachiocephalicus ischaemia
| |
− | **Caused by pressure on muscle > perfusion pressure of capillaries
| |
− | **Downer cows - vetral recumbency -> ischaemia of pectoral muscles and muscles of limbs tucked under the animal
| |
− | **Pregnant ewes with twins or triplets -> internal abdominal oblique muscle ischaemic necrosis -> potential rupture
| |
− | *'''Muscle swelling''' where it cannot expand
| |
− | **E.g. supracoracoid muscle infarction in some breeds of turkeys after flapping their wings
| |
− | ***Surrounded by inelastic fascial sheath and bone
| |
− | | |
− | | |
− | [[Category:Muscles - Degenerative Pathology]]
| |
− | | |
− | | |
− | ==Trauma==
| |
− | | |
− | *Due to:
| |
− | **Direct transection of myofibres
| |
− | **Compression of myofibres
| |
− | **Secondary from haemorrhage (bruising)
| |
− | ***May increase muscle pressure -> [[Muscles Degenerative - Pathology#Ischaemia|ischaemia]] -> [[Muscles Degenerative - Pathology#Necrosis|necrosis]]
| |
− | **Partial rupture - ''e.g.'' of diaphragm in road traffic accident
| |
− | **Complete rupture - ''e.g.'' quadriceps of racing greyhounds
| |
− | **Myorrhexis (tearing) - ''e.g.'' slippery floor causing 'splits' in cattle -> adductor muscle tear
| |
− | *Healing is by [[Muscle Regeneration|regeneration]]
| |
− | *Fibrosis (scarring) will compromise function
| |
− | *During [[Bones Fractures - Pathology|fractures]], fragments may cause further trauma if moved
| |
− | | |
− | [[Category:Muscles - Degenerative Pathology]]
| |
− | | |
− | | |
− | [[Category:Musculoskeletal System - Pathology]]
| |