MSK 4 Flashcards
what is the cell type that is key to muscle regeneration?
satellite cells, they are able to divide, fuse, and can form mature myofibers
if there is muscle damage, what are 3 general clinical findings you might see?
- increased creatinine kinase (CK)
- increased AST
- myoglobinuria
what are 3 causes of pale muscles?
- necrosis
- mineral
- replacement by fat or collagen
what are two species that can cause parasitic muscle cysts?
- trichinella spiralis
- sarcocystis sp
name 4 reasons why a muscle would appear dark red
- hemorrhage
- necrosis
- inflammation
- myoglobin
name two reasons why a muscle might have a green appearance
- autolysis/putrefaction
- eosinophilic inflammation
what do you see nd how does this help you figure out what it is?
green discoloration due to eosinophils (bovine eosinophilic myositis)
define the following:
- myopathy
- myositis
- myonecrosis
- cachexia
- polymyositis
- muscle disease
- muscle inflammation
- muscle necrosis
- generalized muscle atrophy caused by disease or malnutrition
- inflammation of multiple muscles
how does muscle necrosis appear acutely and chronically?
acutely: red
chronic: white chalkly due to progression of mineralization caused by increased intracellular calcium
regernation of muscle requires what two things? what happes if you don’t have these two things?
- an in tact basal lamina
- viable satellite cells
if either of these are damaged, you’ll get healing by fibrosis
define muscle atrophy
decreased muscle volume, usually reversible if cause is corrected
list 3 physiological causes of muscle atrophy
- disuse (asymmetrical and localized)
- cachexia (symmetrical and generalized)
- senility (symmetrical and generalized)
how does cancer cause cachexia?
catabolic cytokines like tissue necrosis factor
name 3 endocrine causes of muscle atrophy
- hypothyroidism (dogs_
- hypercortisolism (dogs)
- pituitary dysfunction/tumors (horses)
why does denervation cause muscle atrophy?
muscle fibers require growth factors from nerves for maintenance and loss of nerve supply leads to rapid atrophy
this is the skull of a dog. what is happening here?
muscle atrophy due to denervation (tumor/disease in trigeminal nerve)
laryngeal hemiplasia is an example of _____. explain the pathogenesis
denervation atrophy
left recurrent laryngeal nerve is longer and prone to nerve degernation–>denervation of the left circoarytenoideus muscle–>laryngeal paralysis–>loud breathing and possibly aspiration penumonia
what is this?
laryngeal hemiplasia due to denervation (can see atrophy of left circoaretynoideus muscle)
in degenerative muscle diseases, is there inflammation?
yes, but inflammation is not the cause of the damage. damage is done first, then inflammatory reaction starts to heal the damage done
since muscles have lots of blood supply, how does infarction happen and give one example
infarction requires occlusion of large blood vessels or severe intramuscular vascular damage to occur
example is feline aortic thromboembolism where blood supply to the hind legs is blocked and causes paralysis
in regards to cell types in the muscles, which are most susceptible to oxygen and which are not? what does this mean for healing?
myofibers most susceptible to hypoxia, then satellite cells, then fibroblasts. this means that regernative ability depends on the time in the hypoxic state. If the hypoxia is prolonged, the satellite cells will be damaged and all that’s left is the fibroblasts so healing will occur via fibrosis/scar tissue
explain what compartmental syndrome is and provide an example
there is muscle damage of some sort leading to inflammation and swelling which increases intramuscular pressure (because the overlying fascia cannot expand), and this leads to ischemic necrosis
ex: recumbency in LA: ischemic necrosis of muscles under pressure when “down” for too long
prolonged recumbency in large animals causes what 3 things?
- pressure on the muscle arterial supply
- compartmental syndrome (inflammation and pressure in muscles)
- reperfusion injury
what is white muscle disease? what are the gross lesions?
nutritional deficinecy in Vitamin E/Selenium, which are antioxidants, so without them there are increased free radicals in the skeletal and cardiac muscles
gross lesions: muscles are pale pink to white (degeneration and mineralization), lesions ofen obvious in muscles with high workload like the tongue, heart, limbs, etc
horses are susceptible to ionophore toxicity. what does it do to them (pathogenesis) and what will it look like? give an example of an ionophore
toxic levels of inophores disrupt ion equilibrium leading to calcium overload–>this leads to skeletal and cardiac muscle necrosis which leads to death
it will cause the muscles to be quite pale from the necrosis, may look like streaks. BUT if acute enough there will be no lesions, just death quickly!
ex: monensin
give an example of one toxic plant that can cause a toxic myopathy
gossypol in cottonseed
explain a brief pathogenesis of capture myopathy
the capture and restraint of wildlife leads to struggling and lots of stress for the animal. this leads to massive myonecrosis and death
what is exertional rhabdomyolysis?
describe the clinical signs, gross findings, and predisposing factors for the disease
- essentially it is skeletal muscle lysis, mainly in horses (sometimes dogs)
- clinical signs: stiff gait, swelling, sweating
- grossly: red swollen muscles and myoglobinuria
- predisposing: selenium/vit E def, EPSSM
name some examples of traumatic myopathies
lacerations, surgical incisions, tearing, etc
what is myositis?
inflammation of the muscle, and this inflammation is then the cause of muscle damage
describe a general pathogenesis of bacterial myositis and give examples of common eitologies for this disease in different species
usually a result of an inoculation wound–>introduction of bacteria to the area–>suppurative inflammation and necrosis–>abscess formation and extension along fascial planes when severe
strep zooepidemicus in horses
trueperella pyogenes in cattle and sheep
corynebacterium psuedotuberculosis in sheep and goats
this is an example of what
bacterial myositis
this is an example of
bacterial myositis (can see the yellow/green fibrinopurulent material in muscle and along fascial planes)
how do clostridial species cause myositis? what are some gross lesions of clostridial myositis?
they produce toxins that cause hemorrhagic muscle necrosis that can often progress to fatal tomexia/septicemia
gross: localized affected muscles are hemorrhagic, swollen, edematous, with suppurative inflammation and gas pockets
breifly explain the clostridial myositis general pathogenesis
muscle damage leads to anaerobic conditions, which allows spores to germinate and the bacteria can produce toxins. These toxins damage blood vessels and muscles leading to hemorrhage and necrosis, leading to myositis and even more anaerobic tissue for bacterial proliferation (vicous positive feedback cycle)
this cow was found acutely dead. what is your differential?
blackleg/clostridial myositis
explain the specific pathogenesis of clostridial myositis in cattle via clostridium chauvoei
the cow ingests the spores–>spores cross the intestinal mucosa–>hematogenous spread to the muscles–>muscle trauma leads to anaerobic conditions allowing bacteria to proliferate–>bacteria produce toxins and cause vascular damage–>hemorrhage, necrosis, and edema–>myositis
grossly how does a cow look with clostridial myositis caused by clostridium chauvoei?
skeletal muscles will be hemorrhagic, edematous, and there will be crepitus, and myonecrosis
how do horses get clostridial myositis, what is the cause, and what is the unique namefor this disease in horses?
name: malignant edema or gas gangrene
cause: clostridium septicum
usually a penetrating wound is how it starts–>creates localized muscle damage and introduction of spores–> these spores germinate in anaerobic conditions–>bacteria proliferate and produce toxins–>vascular injury–>hemorrhage, necrosis, edema–>myositis
what are they doing to this horse? what are they trying to treat?
this horse likely has clostridial myositis, and the small incisions allow oxygen into the site of infection to try and eliminate proliferation of anaerobic bacteria
what two bacteria species are associated with pyogranulomatous and fibrosing glossitis?
actinobacillus lignerisii (wooden tongue), actinomyces bovis (lumpy jaw, less common)
what is this an example of?
pyogranulomatous glossitis caused by actinobacillus lignerisii (wooden togue), very severe case
this is a tongue cross section. what do you see and what is your differential?
there is multifocal areas od pyogranulomatous inflammation surrounded by fibrous connective tissue, likely a bacterial myositis/glossitis caused by actinobacillus lignerisii
viral myositis is rare, but one virus that can cause it is:
blue tongue virus in sheep causing systemic vasculitis leading to muscle infarcts
in regards to parasitic myositis, is there associated disease/clinical signs? what are some species that are associated with parasitic myositis?
muscle infection occurs in intermediate hosts usually
neosporum caninum in calves and dogs
cysticercus in cattle, sheep, goats, pigs
sarcocystis in large animals and wildlife
what is an example of an immune mediated myositis in horses?
following a strep equi infection, antibody complexes deposit in blood vessels causing an immune mediated vasculitis which can lead to muscle hemorrhage and infarction affecting multiple muscles
if you have a horse with muscle hemorrhage and infarction, what are two potential diagnoses and how would you tell them apart?
- immune mediated myositis after strep equi infection (multiple muscles affected, no gas)
- clostridial myositis (more localized, gas)
what kinds of animals are prone to double muscling?
belgium blues and whipets/greyhound dogs
genetic defect in myostatin gene, increased # of myofibers
are diseases of the neuromuscular junction associated with denervation atrophy?
NO! growth promotants are still able to get to the muscle so there is do denervation atrophy in these diseases
botulism is caused by:
is causes disease by:
animals get this disease by:
who gets it the worst?
- clostridium botulinum
- blocks release of Ach from nerve synapse resulting in severe flaccid paraylsis, the respiratory muscles become paralysed, death
- ingestion of preformed toxin like in rodent carcasses that get into feed
- horses are the most sensitive
there are two forms of myasthenia gravis. describe them and the differences between the two
- the first is congenital which is very rare
- the second is autoantibodies against Ach receptors, leading to muscles that cannot contract resulting in weakness and collpase. often associated with thymus disease/thymoma, cand this disease can lead to aspiration penumonia
what kind of ticks cause tick paralysis?
Dermacentor and Ixodes
a benign tumor of muscle is called:
a malignant tumor of muscle is called: _______, and the place it likes to originate from is ______
rhabdomyoma
rhabdomyosarcoma, urinary bladder
muscle is not a common site of metastasis for neoplasia, EXCEPT….
in horses with melanoma
what is equine polysaccharide storage myopathy? grossly what does it look like? how do you diagnose this?
abnormal glycogen accumulation in muscles of mostly warmbloods and drafts, likely causing decreased energy in myofibers. these animals are prone to exertional rhabdomyolysis and hind limb pain
gross: pale muscles esp the hind limbs, dark red kidneys from myoglobin, myoglobinuria
have to diagnose using muscle biopsy
what is hypokalemic myopathy?
a disease of cows, usually with a history of post partum ketosis. anorexia leads to lowpotassium which can cause myonecrosis. the cow may be weak or recumbent with low serum potassum and high CK/AST
briefly describe the pathogenesis of milk fever/hypocalcemia in cows and how it causes muscle damage
abnormal post partum calcium hemostasis–> hypocalcemia–>weakness and recumbency–>muscle damage from recumbency
what is porcine stress syndrome/,alignant hyperthermia? grossly what does it look like?
a genetic condition in pigs that are bred for increased muscle and low fat. an abnormal ryanodine receptor leads to excessive muscle contraction. cliniclly they are normal until they are either exposed to halothane anesthesia OR experience high stress, leading to muscle rigidity and high body temperature which progresses to death
gross: muscles are pale, swollen, and appear cooked
what is the name of the parasite in dogs that infects young animals in utero and infects the peripheral nervous system and skeletal muscles resulting in denervation atrophy of hinf limb muscles and myositis?
neosporum caninum
define musular dystrophy
inherited, progressive condition with myofibere degernation and necrosis with regeneration
what is X linked muscular dystrophy?
a genetic condition affecting dogs, defective dystrophin gene, leads to progressive weakness and muscle atrophy, eventually cardiac fibrosis
true or false: hypothyroidism in dogs causes skeletal muscle weakness and atrophy
true! it is a similar presentation to hypercortisolism
what is masticatory myositis?
an immune mediated inflammation against type 2 myofibers of the masticatory muscles leading to bilateral swelling, pain, and inability to open the mouth acutely, or symmetrical atrophy of mastication muscles and fibrosis chronically. to diagnose you must do serology to test for the antibody
this is jack. what is wrong with poor jack?
he has chronic masticatory myositis (can see atrophy of the temporalis and masseter muscles)
what is immune mediated polymositis and how it it different from masticatory myositis?
it is an immune mediated inflammation that targets the myofibers causing necrosis in MULTIPLE muscles, so all muscles can be affected. with masticatory myositis only the masication muscles are affected
what virus in cats may cause an immune mediated myositis?
FIV, feline immunodeficinecy virus
true or false: cats with hypothyroidism can experience muscle weakness due to hypokalemia
false. HYPERTHYROIDISM in cats an cause hypokalemia and resulting muscle weakness, as well as chronic renal disease!
