Muscle and Tendon Flashcards
The capillary network that supports the myofiber is carried in the :
endomysium
A muscle fascicle, or bundle, is surrounded by the :
perimysium
Resting cells that lie between the basal lamina and the sarcolemma are:
satellite cells
The Z band contains contractile/noncontractile elements.
non-contractile
Besnoitia darlingi is a common apicomplexan of what species?
opossum, infects fibroblasts and endothelial cells (Opossums are about the least darling things on earth)
Type I muscle fibers are red/white, oxidative/glycolytic and fast/slow.
red, slow and oxidative. (On day 1 of exercise you are SOR (slow, oxidative, red)).
Laryngeal hemiplagia results from denervation atrophy after axonal degeneration of the ________?
left recurrent laryngeal nerve
Muscle atrophy due to cachexia is mediated through?
TNF (AKA cachectin)
Primary myopathies affect which type of muscle fiber?
Type I (1=primary)
Denervation atrophy affects what type of muscle fiber?
both Type I and Type II (no nerve = no muscles regardless of type)
Disuse and cachexia atrophy of muscles primarily affects what types of muscle fibers?
Type II (On day 2 of exercise, you don’t want to use your muscles anymore = disuse)
Double muscling is the result of the absence of what regulatory muscle protein?
myostatin. Lack of myostatin allows for unregulated hypertrophy of muscle
What is the most sensitive and specific indicator of skeletal muscle injury? A. Myoglobin B. Troponin T C. Serum Creatine kinase D. Serum AST
Serum CK is the most sensitive and specific. Myoglobin and AST are also used clinically, but CK is the most specific. Troponin T is specific for myocardial injury.
Muscle necrosis is mediated by the influx of what into the cytosol from the ECF? A. Sodium B. Potassium C. Calcium D. Hydrogen ions
Calcium causes irreversible damage as a result of initiation of Ca-dependent processes in the cytosol and overload of Ca within the mitochondria leading to energy failure, membrane damage and necrosis.
Polysaccharide storage myopathy in Quarterhorses is the result of a defect in which gene? A. GBE1 B. GYS1 C. Dystrophin D. HYPP
Glycogen synthase 1 (GYS1) is the defective gene in polysaccharide storage myopathy. GBE1 is for glycogen branching defect in horses, Dystrophin is for X-linked muscular dystrophy, and HYPP is for hyperkalemic periodic paralysis in the Impressive line of horses.
What breeds of dogs are affected by phosphofructokinase deficiency?
SPANIELS!! English springer and American Cocker
Myophosphorlyase deficiency affects what breed of cattle?
Charolais
Exercise-induced collapse affects Labrador Retrievers with a defective gene ________?
Dynamin 1
Myostatin is associated with what clinical presentation
double muscling in beef cattle and whippets
Porcine stress syndrome leading to PSE meat is associated with a defective gene ______?
Ryanodine receptor
Malignant hyperthermia in Quarter horses and dogs is associated with what defective gene?
ryanodine receptor 1
The histologic finding of pigs with splayleg is:
myofibrillar hypoplasia: reduction in muscle fiber diameter and an abnormally small mass of myofibrils within muscle fibers. Also stains very lightly with eosin. but PAS shows accumulation of cytoplasmic glycogen.
Double muscling affects the:
A. size of the myofiber
B. structure of the myofiber
C. number of fibers
the number of muscle fibers
The breed of dog best known for X-linked muscular dystrophy is:
Golden Retriever
Histologic findings in a dog with X-linked muscular dystrophy include:
Dogs with X-linked muscular dystrophy have multifocal, polyphasic myonecrosis and mineralization, numerous swollen and dark staining fibers (AKA large dark fibers), empty sarcolemmal tubes, nemaline rods on Gomorri’s trichrome or T Blue stains, fat infiltration, and subepicardial changes leading to progressive degenerative cardiomyopathy. Dystrophin anchors cytoskeletal actin to extracellular laminin and is believed to maintain myocyte membrane integrity during contraction. Absence of dystrophin allows gaps to develop in the myocyte membrane; resulting in calcium influx and hypercontraction, degeneration, and necrosis
Centronuclear myopathy is associated with what breed?
Labrador retriever
Degenerative polymyopathy is assocated with what breed of dog?
Bouvier des Flandres
Canine dermatomyositis of Collies, Shelties and Corgis has what skin and muscular histologic lesions?
skin: basal cell degeneration, subepidermal clefts
muscle: essentially none that is primary.
Myotonia in dogs is over-represented in what breeds?
ChowChow, Staffordshire Terrier, Min. Schnauzer
Congenital myotonia in goats (“fainting goats”) is due to a defective?
voltage-dependent chloride channel, CIC-1, in the skeletal muscle
The defect in HYPP horses is due to:
Mutation in the muscle sodium channel leading to increased open time. Allows influx of excess sodium and efflux of excess potassium. (HYPP = lets out too much PotassiumPotassium, therefore hyperkalemic)
What are the gross and microscopic lesions of HYPP?
NONE!
Glycogen branching enzyme deficiency occurs in what species?
Horses and Norwegian Forest cats
Polysaccharide storage myopathy is characterized by glycogen (within lysosomes/distributed in the cytoplasm)
distributed in the cytoplasm
The PAS-positive, amylase resistant material characteristic of GBE deficiency is?
amylopectin
The primary histologic finding in malignant hyperthermia is:
severe acute rhabdomyolysis secondary to a sudden increase in myoplasmic calcium concentration, myofiber contraction, tachycardia, hyperthermia.
The species most sensitive to monensin toxicity is:
horses, cardiac toxicity predominates over skeletal muscle
The histologic lesions associated with monensin toxicity are
monophasic multifocal myonecrosis (compare to polyphasic multifocal myonecrosis of nutritional myopathy)
A plant origin cause for monophasic mutlifocal myonecrosis in cattle, horses, goats and pigs is:
senna, coffee senna (Cassia sp. )
Exertional rhabdomyolysis is characterized by all of the following except:
A. underlying metabolic disorder of the muscle
B. preferential effects in the hindlimb muscles
C. elevations in CK and AST
D. poor diet management and excessive exercise
E. myoglobinuria
D. poor diet management and excessive exercise are not well-established in the pathogenesis, and the disease is most likely due to underlying metabolic disorders in the muscles (so forget Monday morning disease)
Exertional rhabdomyolysis affects which populations of muscle fibers?
Type 2A (oxidative-glycolytic) and 2B (glycolytic). Nutrional myopathies affect the type 1 fibers (oxidative).
Masticatory myositis is characterized by:
A. primary myofiber necrosis with secondary inflammation
B. atrophy of only the masseter muscles
C. antibodies directed against the 2M isoform of myoglobin
D. over-representation in Labrador Retrievers
E. a primarily eosinophilic, B cell and CD8+ T cell infiltrate
C. antibodies directed against the 2M isoform of myoglobin which are only found in the masticatory muscles. The inflammation in masticatory myositis is due to an autoimmune disease, and myofiber necrosis is secondary to the inflammation and not the other way around, although additional inflammatory infiltrates will be present to clean up necrotic fibers. The masseter, temporal and pterygoid muscles are all involved, and bilaterally. German Shepherd Dogs are over-represented. It is primarily a lymphocytic infiltrate composed of mostly CD4+ lymphocytes, B cells and
+/- eosinophils. Eosinophils, if present, will always be admixed with lymphocytes.
Polymyositis can be distinguished from masticatory myositis when both are present in the temporal muscles by:
polymyositis is primarily a CD8+ T cell infiltrate while masticatory myositis is primarily a CD4+ T cell infiltrate. Poly= many (more). 8 is more than 4.
A useful clinical pathology marker for masticatory myositis which may rule out polymyositis is:
serum antibodies to 2M myosin, although some PM cases will have some circulating 2M myosin antibodies
Which breed of dog has the best genetic association with polymyositis?
Newfoundlands have a breed association
SLE-induced polymyositis can be detected by what clinical marker?
positive ANA titer
Invasion of otherwise intact skeletal muscle fibers by lymphocytes is characteristic of what type of disorder?
immune-mediated myositis (masticatory, polymyositis).
Acquired myasthenia gravis occurs from:
circulating antibodies to motor end plate acetylcholine receptors bind and form immune complexes at the neuromuscular junction. The cross-linking of bound Ab leads to endocytosis of Ach receptors and therefore reduction in receptor density
What type of neoplasia is associated with acquired myasthenia gravis:
thymoma
What endocrinopathy is associated with myasthenia gravis?
hypothyroidism
A common sequela of myasthenia gravis is:
megaesophagus
Myasthenia gravis is best diagnosed by:
A. detection of circulating anti-2M myoglobin antibodies
B. detection of a diminishing response in action potential during electrodiagnostic testing
C. detection of circulating antiacetylcholine receptor antibodies
C. Detection of circulating antiacetycholine receptor antibodies is the best test for myasthenia gravis. Electrodiagnostic testing is also a standard test but is not the gold standard. A. detects masticatory myositis.
The histologic lesion associated with myasthenia gravis is:
NONE!
Pigeon fever in horses is due to abscessation of the pectoral muscles from infection with:
Corynebacterium pseudotuberculosis
Blackleg caused by C. chauveoi differs in its pathogenesis from C. septicum or C. perfringens in that:
the spores are latent in the muscle and not introduced from the external environment from wound infection
Blackleg differs from pseudo-blackleg in its diagnostic confidence by:
C. chauveoi is never a wound contaminant, while C. septicum can be and culture needs to be done immeadiately after death to prevent contamination of the site.
What is the Sarcocystis life cycle?
Predator releases sporocysts in feces –> Ingestion of sporocysts on grass by prey animal–> spoozoites released –> invasion of tissues –> schizogeny in endothelial cells –> schizonts develop in striated muscle fibers as thin-walled cysts containing metrocytes –> metrocytes become banana-shaped bradyzoites in cysts within the muscle –> muscle ingested by predator and cycle starts over
Sarcocystis cruzi is considered the most clinically important sarcocystis of what species?
cattle
Sarcocystis cruzi-related clinical disease causes what clinical signs?
hemolysis –>icterus, petechiae of mucous membranes, fever, abortion, drooling
Myositis with mononuclear leukocytic infiltration, myofiber necrosis, myofiber atrophy and polyradiculoneuritis is characteristic of what type of infection?
Toxoplasma gondii
Trichinella enter the intestinal crypts and then travel systemically via the:
lymphatics, then blood
Trichinella is consumed most often by humans eating what kind of meat?
horsemeat and bear meat
Taenia solium develops in what two species?
humans and pigs
What is the larval form of Taenia soium called?
Cysticercus cellulosae
What is the larval form of Taenia saginata called?
Cysticercus bovis
Hepatozoon americanum causes myositis in what species?
dog
Histologic lesions of dogs infected with Hepatozoon amercanum include?
multiple acute granulomas interspersed with rows of neutrophils between muscle fibers, multiple stages of the parasite, secondary amyloidosis and glomerulonephritis
Leishmania infantum has characteristic histologic lesions of?
myocarditis and glomerulonephritis, also causes skeletal myonecrosis with a lymphohistiocytic infiltrate
What IHC markers would best confirm skeletal muscle origin in a poorly differentiated rhabdomyosarcoma?
A. myogenin and myoD
B. Desmin and actin
C. Myoglobin and sarcomeric actin
A. myogenin and myoD are the best IHC markers for poorly differenatiated tumors of skeletal muscle origin, followed by myoglobin and sarcomeric actin which are specific for skeletal muscle but routinely are expressed only in well-differentiated tumors. Desmin and actin are specific for all muscle a.s well as myofibroblasts, not just skeletal muscle
Cardiac rhabdomyomas are most common in which species and in what anatomic location?
left ventricular wall of pigs (red wattle breed predisposed)
Cardiac rhabdomyomas in pigs are of what tissue origin?
Purkinje cells, hence purkinjeoma as a potential replacement term
Laryngeal rhabdomyomas are common in what species?
dogs
The most common form of rhabdomyosarcoma is:
botryoid variant of embryonal rhabdomyosarcoma
Embryonal rhabdomyosarcomas express what two markers reliably?
the myogenic regulatory factors: myogenin and myoD
Where does the botryoid variant of embryonal rhabodmyosarcoma most often occur?
the trigone area of the bladder in dogs
Where do embryonal rhabdomyosarcomas most often occur?
head and neck of young animals
Which two transcription factors are involved in the development of muscle cells?
PAX3 and PAX7
A neoplasm in the tongue of a dog with closely packed round cells demonstrating PAS-positive, amylase-resistant intracytoplasmic granules should warrant what diagnosis?
granular cell tumor
The granules in a granular cell tumor are actually what?
secondary lysosomes
Parasites found in tendons are usually from what family?
Onchocerca, a filarial nematode
A worm nest or worm nodule found in the brisket or hindlimb connective tissue in cattle is what species?
Onchocerca gibsoni
Musculoaponeurotic fibromatosis (or desmoid tumor) in the horse is characterized by:
perimysial and endomyseal connective tissue dissecting between muscle bundles and myofibers.
Fibrodysplasia ossificans progressiva is a progressive fibrosing and ossifying lesion of tendons and muscle associated aponeuroses that occurs in which species?
cats
