Musculoskeletal Pathology - muscle Flashcards
what determines muscle colour
Myoglobin and haemoglobin determines muscle colour
Histological examination of muscle
- how do we sample? what does this depend on?
◼ Sampling depends on suspected disease.
◼ Multifocal lesions - take multiple biopsies
◼ General lesions – one biopsy
◼ Select the appropriate muscle
> take samples with the grain and against the grain
Jake the 5yo Golden Retriever
◼ Pain and reluctance to open mouth
◼ Temporal muscle atrophy (macroscopic/clinical)
> what are our differentials?
Atrophic diseases
◼ Bilateral neuropathy (neuropathic)
◼ Temporomandibular joint disease (disuse)
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Degeneration/death diseases
◼ Exertional myopathy (metabolic)
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Inflammatory diseases
◼ Masticatory myositis (immune)
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◼ Other!
myositis - distibution, chronicity? testing?
Myositis can be focal and occur over a long period of time
- can biopsy or use serological test
muscle atrophy confirmation test, what it looks like
biopsy - Myofibres small, fibrous tissue relatively increased.
Muscle Diseases (diagnoses) - broad categories
- Atrophic
- Degenerative
- Myositis
Muscle Disease: Muscle atrophy types
◼ Neuropathic (neurogenic, denervation)
◼ Disuse
◼ Malnutrition
◼ Cachexia
◼ Senility (sarcopenia)
how long it takes for muscle atrophy in cases of inactivity or nerve loss
It takes several weeks or longer for muscle to atrophy in inactivity or nerve loss
Muscle Disease: Atrophy; histology
◼ Histology (regardless of cause):
1. Myofibre smaller
2. Evenually loss of myofibre
3. Fat replacement
4. ‘fibrosis’
Muscle Diseases: Degenerative myopathy;
myodegeneration and death
> what do we see in the myofibre?
Myofibre
◼ Swelling
◼ Hypereosinophilia
◼ Loss of striation
◼ Coagulation
◼ Fragmentation
◼ Tension bands
◼ Mineralization
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coagulation of protein > swelling > loss of striations
> weak fibers separate upon conratcion: fragmentation
> we now have some viable parts and some coagulated parts > the working parts will form ‘tension bands’ as they contract
- muscle fiber contaction depends on Ca, so there is a lot of it in muscle > dead muscle will mineralize > the white part of ‘white muscle disease’
Muscle Disease: Degenerative myopathy;
‘Regeneration’ - is it possible? how?
◼ Sarcolemmal tube and satellite cells
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◼ Satellite cells divide – become myoblasts
◼ Myoblasts proliferate until they contact
◼ Form myotube
◼ Enlarge and differentiate – central nuclei
◼ Nuclei peripheralize and reposition
Muscle Diseases: Degenerative myopathy;
causes broad categories
◼ Trauma
◼ Ischemia
◼ Exertion
◼ Nutritional
◼ Toxic
degenerative myopathy - types of trauma that can cause
◼ Crush
◼ Tear
◼ Lacerate
◼ Injection
◼ Penetrating injury
degenerative myopathy - types of ischemia that can cause
Ischemia of:
◼ Myofibre
◼ Satellite cell
◼ Fibrocyte
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◼ Vascular obstruction
> Saddle thrombus
◼ Swelling
> Compartment
◼ Recumbancy
> Downer
> Anesthesia
what is compartment syndrome?
Compartment syndrome is a condition in which increased pressure within one of the body’s anatomical compartments results in insufficient blood supply to tissue within that space.
degenerative myopathy - how can exertion cause?
◼ Hypoxia
◼ Lactic acidosis
◼ +- nutritional
> reduced vitamin E / selenium + some event that increases activity = white muscle disease
degenerative myopathy - how can nutritional factors cause?
◼ Hypovitaminosis E
◼ Selenium deficiency
- oxidative injury
toxins that can cause degenerative myopathy
◼ Monensin
◼ Salinomycin
◼ Growth promotants
◼ Doxycycline overdose in calves
◼ Seasonal pasture myopathy (Box Elder/Maple associated in horses; hypoglycin A)
Muscle Disease: Myositis; infectious causes
Bacteria
◼ Direct injection from penetrating injury
> Clostridium and Paeniclostridium – multiple types
> T. pyogenes
> Actinobacillus ligneresi – wooden tongue
◼ Blackleg - Clostridium chauvei
> Spores ingested,
> Within macrophages in tissue
> Anaerobic condition
> Bacterial exotoxins
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Parasites
◼ Protozoa – Sarcosystosis
◼ Cestodes – Cysticercosis (ovis, bovis)
Muscle Disease: Myositis; idiopathic causes
Immune mediated myositis of dogs
◼ Masticatory muscle myositis (MMM)
> Masseter and temporal muscles
> Autoantibody to mMyBP-C (aka myosin 2M)
◼ Idiopathic polymyositis
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Eosinophilic myositis of cattle
◼ Sarcocystosis
◼ Immune mediated
