Skeletal Muscle Flashcards
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?
Degeneration/necrosis
Circulatory disorder
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 ?
Skeletal muscle degeneration and necrosis
Rhabdomyolysis
Myonecrosis
Zenker’s necrosis
What is the histopathological appearance of muscles when they die?
Vacuolation of sarcoplasm
Condensation of sarcoplasm-> hyper-eosinophilic and lose striations
Nuclear pyknosis
Calcification (dystrophic)
What is the histopathological appearance of muscles when they regenerate?
Internalization of nuclei
Macrophage infiltrate
What are the causes of polyphasic lesions in muscle?
Nutritional deficiency -vitamin E/Se
Ongoing toxicities
Genetic defects in myoctye structural/metabolic elements
What is the pathogenesis of vitamin E/Se deficiency leading to muscular degeneration ?
Glutatione peroxidase/reductase requires vit E/Se for function -> lack of ability to scavenge free radicals -> oxidative damage (lipoperoxidation of cell membrane)-> myocyte injury
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?
Monophasic lesions -single insult
Trauma (focal)
Exertion/capture
Toxin
This case is toxin- ionoophores
What is an ionophore coccidiostat that results in a Ca overload of myocytes in horses?
Monensin
What causes white muscle disease? Where do you see these lesions
Vitamin E/Se deficiency
Lesions in most active muscles (eg heart)
_______________ is when ionic events of contraction produce an adverse environment
Exertional rhabdomyolysis
Under extreme stress or have underlying metabolic conditions
__________ is excess nitrogen in the urine
Azoturia
What is capture myopathy?
Exertion, stress during capture
Anaerobic glycolysis -> hyperthermia and metabolic acidosis
What leads to abnormal kidney in capture myopathy
Damage muscle -> free myoglobin filtered in glomerulus -> renal failure
What is the pathogenesis of porcine stress syndrome?
Inherited defect in skeletal muscle ryanodine receptor -> excessive Ca release and contraction when stimulated -> heat production and myocyte necrosis
Muscles are dark red, swollen, softened/friable, and have palpable crepitus.
What pathological process could account for this appearance?
Circulatory disorder
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?
Black leg - clostridium chauvoei
What is the pathogenesis of black leg?
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
What are outbreaks of clostridium chauvoei associated with?
Parturition
Holding- IM meds, marking, shearing
Trauma during confinement
Soil disturbance
What are the causes of inciting myositis?
Necrotic/hemorrhage - C. Chauvoei / C. Septicemia
Superlative - pyogenic bacteria
Lymphocytic - immune mediated
Eosinophilic -Protozoa/parasite/immune mediated
Granulomatous
What intralesional protozoa are present in the muscle of small animals?
Toxoplasma
Neospora
Sarcocystis spp infection will cause __________ myositis in cows or horse
Eosinophilic (protozoa)
What is your MDx for muscle that has discrete areas of muscle pallor bordered by reddened zones ?
Muscle infarct
What is the pathogenesis of muscle infarct due to increased pressure?
Increase pressure -> poor perfusion -> ischemia -> infarct
What is compartment syndrome?
Rapid muscle growth -> period of increased circulation (exertional) -> muscle swelling confined by facia -> impeded blood supply -> ischemia -> infarct
Since birth, animal cannot stand. Histology of muscle shows small myofibers.
What pathological process could account for this appearance?
Disorder of growth
What is the MDx for small myofibers?
Myocyte hypoplasia
What is the Dx for a dog that is unable to stand since birth, has a flattened chest. Histology shows myocyte hypoplasia.
Splay leg or swimmer syndrome
What might the etiology for “splay leg” be?
Unknown
Genetic
Primary spinal/ neuromuscular disease
Infection
Overfeeding
T/F: myocyte proliferation is callled myoctye hyperplasia.
All lies!!
Muscles do not proliferated, they are terminally differentiated.. myocyte hyperplasia is not a thing
How do myocytes regenerate?
Satellite cells proliferate, internalized in the muscle cells -> form myoblast -> mature to myocyte
What are causes of myoctye hypertrophy?
Excercise conditioning
Compensatory
-decreased number/size of functional myocytes–> increase workload on the remaining cells
What is the one and only thing you will cause myocyte hyperplasia?
Double muscling
Inactivation of regulatory gene myostatin (involved in myobalst cell progression to muscle fiber)
What often develops in long-standing atrophy?
Fibrosis and fatty infiltration (steatosis)
What is mastacatory myositis? What pathological process leads to this
Muscle atrophy of the muscles of mastication
Chronic eosinophilic myositis (immune-mediated)
Eosinophilic myositis of the extraocular muscles is called
Extraocular poly myositis
-> exophthalamus
Damage to the L recurrent laryngeal nerve will lead to what?
Paralysis and atrophy of the L cricroarytenoideus dorsalis muscle
What type of cells do neoplasms with striated muscle differentiation derive from?
Multipotential stem cells
What do you call a neoplasm of striated muscle?
Rhabdomyoma
Sarcoma
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??
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
What three pigments and tissue deposits are observed in skeletal muscle
Lipofuscin
Dystrophic calcification
Exogenous pigments
Ducks with flaccid paralysis of the neck and limbs?
Histopathology shows no lesions in the muscles or nervous system.
What is this?
Botulism.
Inhibits transmission at neuromuscular junction, does not produce lesions. Diagnosis by rule out.
What is the pathogenesis of botulism?
Decaying organic matter-> ingest extotoxin -> inhibits ACh release from nerve terminals at neuromuscular junction -> progressive generalized paralysis with death by cardiorespiratory failure
What are disorders of the neuromuscular junctions
Botulism
Myasthenia gravis
Tick paralysis
Cervical ventrofliexion see in cats is due to what?
Hypokalemia (electrolyte derangement)
-secondary to chronic renal failure
What electrolyte derangement in cattle results in severe muscular clinical signs
Hypocalcemia
