Muscle path Flashcards
Explain the structure of muscle
- Myofibres (muscle cells) - Long, multinucleate giant cells. Contractile proteins: Myofibrils made of actin and myosin
- Satellite cells (reserve cells or resting myoblasts)
- Endomysium: CT surrounding myofiber
- Perimysium: CT surrounding groups of myofibres
- Epimysium: CT surrounds whole muscle and is continue with fascia
- Huge blood supply
- Skeletal muscles insert via tendons (usually onto bones)
- Different types of myofibres: 1, 2a, 2b, Fast, slow, Rate of fatigue
- Skeletal muscle requires innervation
What are satellite cells?
reserve cells or resting myoblasts - when we see skeletal muscle degeneration its usually the resting myoblasts
What is the perimysium?
CT surrounding groups of myofibres
What is the endomysium?
CT surrounding myofibres
What is the epimysium
CT surrounds whole muscle and is continue with fascia
What aer the common causes of muscle atrophy?
Catabolism or disuse
Common cause of hypertropy
Increased use
What are the two adaptive changes to muscle cell injury?
Atrophy and hypertrophy
What do you expect to see in muscular necrosis?
- Segmental cell death
- Hyaline degeneration
- granular degeneration
What microscopic changes are considered to be reversible cell injury?
- Swelling
- vacuolation
- fatty change
If sarcolemma (cell membrane) is intact, what kind of regeneration would you expect to see?
o If sarcolemma (cell membrane) remains intact, regeneration of myofiber will occur through satellite cell proliferation
If sarcolemma (cell membrane) is NOT intact, what kind of regeneration would you expect to see?
o If not, fibrosis predominates: Cell injury → necrosis → mononuclear cell infiltrate → phagocytosis → repair (regeneration or fibrosis)
What musclar post mortem changes would you expect to see?
- Rigor mortis
- Colour changes - haemolysis, pallor (anaemia, exsanguination), dark colour (cachexia, congestion)
How do you detect muscle pathology?
- Physical examiation
- Serum biochem - (CK and AST)
- Biopsy (can be difficult)
- Functional studies
- Ultrastructural studies - not common
What is assoicatde with pallor?
Necrosis
Degeneration
Anaemia
Youth
What is associated with pale streaking?
Myofibre necrosis
Mineralisation
Fibrosis
What is associated with dark red mottling?
Congestion
Haemorrhage
Haemorrhagic necrosis
Inflammation
Myoglobin imbibition
What is associated with green discolouration?
Eosinophilic infiltration
Putrefaction (bacteria)
What is associated with tan discolouration?
lipofuscin
What are exertional myopathies?
- Probably involve metabolic derangements associated with lowered pH
- Affected muscles may be oedematous, haemorrhagic or pale
- May lead to myoglobinuric nephropathy
- important in kangaroos and horses
- Includes capture myopathy, equine rhabodomyolysis
What is porcine stress syndrome?
- Excessive muscle contraction
- Occurs in several strains: Landrace, Duroc, Yorkshire, Hampshir
- Genetic defect results in abnormal activity of ryanodine receptor
- Hypercontraction/hyperthermia triggered by stress, halothane, switch to anaerobic glycolysis
- Lesions: May be subtle on shoulders, back, thighs
- Histology: Hypercontraction, coagulative necrosis (PSE pork)
What are nutritional and toxic muscle diseases classified as?
Degeneration
What is meant my myositis?
Myositis is muscle inflammation
What can cause myositis?
- Bacterial (wooden tongue in cattle, botryomycosis in pigs, TB, streptococcal associated myopathies in horses)
- Clostridial (gas gangrene and malignant oedema in all species, blackleg
- Viral (Porcine enceohalomyelitis, FMD, akabane, bluetongue [reovirus])
- Parasitic (cysticercus, toxoplasma, neospora caninum, Sarcocystis, Trypanosoma, Babesia, Hepatozoon spp)
What are some examples of immune mediated muscle diseases?
- Masticatory myositis
- polymyositis
Give some examples of toxic muscle diseases
- From plants: gossypol and cassia occidentalis. Cause multifocal monophasic segmental necrosis
- From feed additives: ionophores
What are some nutritional causes of muscle disease?
- Deficient soils
- hyperkalaemia (cats) and hypocalaemia - muscle weakness
What are some endocrine causes of muscular disease?
Hypothyroidism
hyperadrenocorticism
