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RUSVM Pathology I > Skeletal Muscle > Flashcards

Skeletal Muscle Flashcards

1
Q

Necropsy of a lamb, show s pale, swollen, and dry skeletal muscles. They have a history of weakness and stiff gait.

What pathological process could account for this appearance?

A

Degeneration/necrosis

Circulatory disorder

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2
Q

Necropsy of a lamb, show s pale, swollen, and dry skeletal muscles. They have a history of weakness and stiff gait.

What is your gross morphological diagnosis ?

A

Skeletal muscle degeneration and necrosis
Rhabdomyolysis
Myonecrosis
Zenker’s necrosis

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3
Q

What is the histopathological appearance of muscles when they die?

A

Vacuolation of sarcoplasm
Condensation of sarcoplasm-> hyper-eosinophilic and lose striations
Nuclear pyknosis
Calcification (dystrophic)

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4
Q

What is the histopathological appearance of muscles when they regenerate?

A

Internalization of nuclei

Macrophage infiltrate

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5
Q

What are the causes of polyphasic lesions in muscle?

A

Nutritional deficiency -vitamin E/Se
Ongoing toxicities
Genetic defects in myoctye structural/metabolic elements

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6
Q

What is the pathogenesis of vitamin E/Se deficiency leading to muscular degeneration ?

A

Glutatione peroxidase/reductase requires vit E/Se for function -> lack of ability to scavenge free radicals -> oxidative damage (lipoperoxidation of cell membrane)-> myocyte injury

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7
Q

Sudden onset of a wobbly gait, colic, and decreased exercise tolerance, recumbency, and death in horse. Histopathology shows monophasic skeletal muscle.

What is the most likely cause?

A

Monophasic lesions -single insult

Trauma (focal)
Exertion/capture
Toxin

This case is toxin- ionoophores

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8
Q

What is an ionophore coccidiostat that results in a Ca overload of myocytes in horses?

A

Monensin

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9
Q

What causes white muscle disease? Where do you see these lesions

A

Vitamin E/Se deficiency

Lesions in most active muscles (eg heart)

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10
Q

_______________ is when ionic events of contraction produce an adverse environment

A

Exertional rhabdomyolysis

Under extreme stress or have underlying metabolic conditions

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11
Q

__________ is excess nitrogen in the urine

A

Azoturia

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12
Q

What is capture myopathy?

A

Exertion, stress during capture

Anaerobic glycolysis -> hyperthermia and metabolic acidosis

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13
Q

What leads to abnormal kidney in capture myopathy

A

Damage muscle -> free myoglobin filtered in glomerulus -> renal failure

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14
Q

What is the pathogenesis of porcine stress syndrome?

A

Inherited defect in skeletal muscle ryanodine receptor -> excessive Ca release and contraction when stimulated -> heat production and myocyte necrosis

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15
Q

Muscles are dark red, swollen, softened/friable, and have palpable crepitus.

What pathological process could account for this appearance?

A

Circulatory disorder

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16
Q

Muscles are dark red, swollen, softened/friable, and have palpable crepitus.

Histopathology shows acute necrotic and hemorrhagic myositis and a gram positive bacilli?

What is your Dx?

A

Black leg - clostridium chauvoei

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17
Q

What is the pathogenesis of black leg?

A

Ingest spore-> muscle via blood -> tissue hypoxia/acidosis (anaerobic bacteria) -> bacterial proliferation -> production of exotoxins -> myonecrosis and systemic endothelial damage -> death from septicemic shock/bacterial toxemia

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18
Q

What are outbreaks of clostridium chauvoei associated with?

A

Parturition
Holding- IM meds, marking, shearing
Trauma during confinement
Soil disturbance

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19
Q

What are the causes of inciting myositis?

A

Necrotic/hemorrhage - C. Chauvoei / C. Septicemia

Superlative - pyogenic bacteria

Lymphocytic - immune mediated

Eosinophilic -Protozoa/parasite/immune mediated

Granulomatous

20
Q

What intralesional protozoa are present in the muscle of small animals?

A

Toxoplasma

Neospora

21
Q

Sarcocystis spp infection will cause __________ myositis in cows or horse

A

Eosinophilic (protozoa)

22
Q

What is your MDx for muscle that has discrete areas of muscle pallor bordered by reddened zones ?

A

Muscle infarct

23
Q

What is the pathogenesis of muscle infarct due to increased pressure?

A

Increase pressure -> poor perfusion -> ischemia -> infarct

24
Q

What is compartment syndrome?

A

Rapid muscle growth -> period of increased circulation (exertional) -> muscle swelling confined by facia -> impeded blood supply -> ischemia -> infarct

25
Q

Since birth, animal cannot stand. Histology of muscle shows small myofibers.

What pathological process could account for this appearance?

A

Disorder of growth

26
Q

What is the MDx for small myofibers?

A

Myocyte hypoplasia

27
Q

What is the Dx for a dog that is unable to stand since birth, has a flattened chest. Histology shows myocyte hypoplasia.

A

Splay leg or swimmer syndrome

28
Q

What might the etiology for “splay leg” be?

A

Unknown

Genetic
Primary spinal/ neuromuscular disease
Infection
Overfeeding

29
Q

T/F: myocyte proliferation is callled myoctye hyperplasia.

A

All lies!!

Muscles do not proliferated, they are terminally differentiated.. myocyte hyperplasia is not a thing

30
Q

How do myocytes regenerate?

A

Satellite cells proliferate, internalized in the muscle cells -> form myoblast -> mature to myocyte

31
Q

What are causes of myoctye hypertrophy?

A

Excercise conditioning

Compensatory
-decreased number/size of functional myocytes–> increase workload on the remaining cells

32
Q

What is the one and only thing you will cause myocyte hyperplasia?

A

Double muscling

Inactivation of regulatory gene myostatin (involved in myobalst cell progression to muscle fiber)

33
Q

What often develops in long-standing atrophy?

A

Fibrosis and fatty infiltration (steatosis)

34
Q

What is mastacatory myositis? What pathological process leads to this

A

Muscle atrophy of the muscles of mastication

Chronic eosinophilic myositis (immune-mediated)

35
Q

Eosinophilic myositis of the extraocular muscles is called

A

Extraocular poly myositis

-> exophthalamus

36
Q

Damage to the L recurrent laryngeal nerve will lead to what?

A

Paralysis and atrophy of the L cricroarytenoideus dorsalis muscle

37
Q

What type of cells do neoplasms with striated muscle differentiation derive from?

A

Multipotential stem cells

38
Q

What do you call a neoplasm of striated muscle?

A

Rhabdomyoma

Sarcoma

39
Q

Golden retriever dog…
Exercise intolerant
Progressive generalized muscle weakness, atrophy
Joint contracture and angular deformities
Excessive drooling, problems eating

Histopathology shows…
Polyphasic myocyte degeneration and necrosis, chronic with hypertrophy, atrophy, and fibrosis

What could this be??

A

Polyphasic lesions

  • nutritional deficiency
  • ongoing toxicity
  • genetic

Muscular dystrophy -> x-linked inherited myopathy reported in cat and dogs, especially in G retrievers
Defects in dystrophin gene - cytoskeletal protein

40
Q

What three pigments and tissue deposits are observed in skeletal muscle

A

Lipofuscin
Dystrophic calcification
Exogenous pigments

41
Q

Ducks with flaccid paralysis of the neck and limbs?
Histopathology shows no lesions in the muscles or nervous system.

What is this?

A

Botulism.

Inhibits transmission at neuromuscular junction, does not produce lesions. Diagnosis by rule out.

42
Q

What is the pathogenesis of botulism?

A

Decaying organic matter-> ingest extotoxin -> inhibits ACh release from nerve terminals at neuromuscular junction -> progressive generalized paralysis with death by cardiorespiratory failure

43
Q

What are disorders of the neuromuscular junctions

A

Botulism
Myasthenia gravis
Tick paralysis

44
Q

Cervical ventrofliexion see in cats is due to what?

A

Hypokalemia (electrolyte derangement)

-secondary to chronic renal failure

45
Q

What electrolyte derangement in cattle results in severe muscular clinical signs

A

Hypocalcemia

RUSVM Pathology I (17 decks)

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