Lecture 16 Muscle Pathology Flashcards Preview

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Flashcards in Lecture 16 Muscle Pathology Deck (84):

What (4) types of neoplasms are derived from skeletal muscle?

  1. Rhabomyoma
  2. Rhabdomyosarcoma
  3. Fibrosarcoma
  4. Lipoma


Which is more common, rhabdomyoma OR rhabdomyosarcoma?



True or Flase:

  1. Infiltrating lipomas are harder to totally remove becuase of their quick growth rate.
  2. Infiltrating lipomas do NOT metastasize.

  1. FALSE: infiltrating lipomas are harder to totally remove, so they do tend to recur after surfical removal, but their growth is SLOW
    1. TRUE: lipomas do NOT metastasize


Which type of collagen are tendons primarily composed of?

Type I


True or False:

Tendons have an impaired ability to heal when injured, dispite a heafty blood supply.


Tendons have an impaired ability to heal becuase of a MEAGER BLOOD SUPPLY


How are tendon sheaths similar to a joint?

Both are lined by synovium, which allows for the same lubricating effect


What is the condition called when tendons are shorter than normal?

Contracted tendons


Are contracted tendons a congential defect OR genetic defect?



When contracted tendons are severe, what other developmental abnormality might you find grossly?

Hypoplastic muscle development 




What is the lesion most commonly found in tendons?

Tears or ruptures due to traumatic injury


An animal is presented to you with a ruptured tendon.  What might you inform the owner of regarding this animal's healing process?

When a tendon ruptures, the healing that occurs is usually via fibrosis, producing a TYPE III COLLAGEN, which does not have the same tensile strength as tpye I.  The healed tendon will be more prone to break down again!!!


What is a term used for the inflammation of a tendon and the sheath around it?



What is your diagnosis?

Q image thumb

Ruptured tendon

A image thumb

Which muscles are involved in EOSINOPHILIC MYOSITIS in dogs?

Muscles of mastication: masseter, temporalis, and pterygoid muscles


What is believed to be the cause of eosinophilic myositis in dogs?

The muscles it affects (muscles of mastication) are composed of a unique type 2M muscle fiber.  It is believed that this is an immune-mediated myositis in which autoantibodies are produced against a protein specific to the type 2M fibers.  


You are presented with a dog that has intermittent episodes where he does not want to eat.  What muscle condition might you want to heavily consider?

Eosinophilic myositis

(This condition causes inflammation in the muscles of mastication during actue, intermittent episodes)


What might eosinophilic myosiitis of a dog progress to?

The inflammation can result in fibrosis and atrophy of the muscles of mastication


What is the term for end stage myositis?

Atrophic myositis 


Neosporosis, due to infection with Neospora caninum, will cause ____ ____ in dogs.

Neosporosis, due to infection with Neospora caninum, will cause NECROTIZING MYOSITIS in dogs.


How might a dog become infected with NEOSPOROSIS?

By eating bovine fetuses aborted due to neosporosis


What is myasthenia gravis?


Myasthenia gravis is general muscle weakness due to a decrease in acetylcholine (ACH) receptors at myoneural junctions


How might an animal get myasthenia gravis?

  1. Congenital
    • Overall low number of ACH receptors at the myoneural junction
  2. Acquired
    • Autoimmune disease - antibodies attack the ACH receptors


A dog presents to you for resent episodes of regurgitation.  After running radiographs, you diagnose megaesophagus.

What other condition might you want to check for now?

Myasthenia gravis


  1. What is the common name of Equine Rhabdomyolysis?
  2. What type of change in the muscle is this condition associated with?
  3. Is this monophasic OR polyphasic?

  1. "Monday morning disease"
  2. Acute myodegeneration
  3. Monophasic


What might the recent history of a horse that presents with Equine Rhabdomyolysis?

AKA : exertional myopathy

A working horse on a high grain diet, housed on over the weekend (not worked), and put back to heavy work on Monday.


  1. Acute myodegeneration associated with Equine Rhabdomyolysis causes the liberation of what substance?
  2. How can this be tested clinically?


  1. Myoglobin is liberated from damaged muscle
  2. Causes myoglobinuria - test the urine, will be darkened in color


Horses who come down with Equine Rhabdomyolysis may likely have what other condition?

Equine polysaccharide storage myopathy


Equine polysaccharide storage myopathy is the accumulation of _____ aggregates in ____ ___ ____.

Equine polysaccharide storage myopathy if the accumulation of polysaccharide aggregates in type 2 myocytes.


True or False:

Equine polysaccharide storage myopathy (EPSM) is a congenital defect.



EPSM is a GENETIC defect



Equine polysaccharide storage myopathy can result in muscle atrophy; why?

Due to repeated bouts of myodegeneration


Hyperkalemic periodic paralysis is a defect in what?

Explain how this defect causes hyperkalemia.

Defect in sodium channels --> causes sodium channels to be more permeable than normal --> this causes polarization abnormalities --> myotonia --> hyperkalemia


Which of the following diseases is caused by an autosomal dominant trait? :

  • Exertional myopathy
  • Equine polysaccharide storage myopathy
  • Hyperkalemic periodic paralysis

Hyperkalemic periodic paralysis


These samples are from a horse.

  1. Based on the color change in the urine and the kidney, what is your most likely diagnosis?
  2. What causes this color change?

Q image thumb

  1. Equine rhabdomyolysis ( with myoglobinuria and myoglobin nephropathy)
  2. Myoglobin

A image thumb

  1. The visible changes you see with Equine rhabdomyolysis are similar to the changes you would see with what in sheep?
  2. What causes the color change in that condition?

  1. Copper toxicity
  2. Hemoglobin


  1. What is the arrow pointing to?
  2. What condition is this associated with?

Q image thumb

  1. Arrow is pointing to a polysaccharide aggregate
  2. These aggregates will develop in Equine Polysaccharide Storage Myopathy (EPSM)

A image thumb

True or False:

Equine polysaccharide storage myopathy is an inflammatory disease associated with atrophy of the muscle.


EPSM does cause atrophy of muscle

BUT EPSM is NOT inflammatory 


  1. What are the gross characteristics of nutritional myopathy?
  2. Is this monophasic degeneration OR polyphasic degeneration?

  1. Swollen, pale muscles ("white muscle disease")
  2. Polyphasic degeneration

A image thumb

What is the cause of nutritional myopathy in foals?

Dietary deficiency of vitamin E and/or selenium


What type of lesion do you get with ionophore toxicosis?

Acute myodegeneration & necrosis


What types of changes might a toxicity cause in a muscle?

Degeneration & necrosis


  1. What type of toxin is monensin?
  2. If given monensin, what ultimately causes the death of a horse, for example?


  1. Iodophore
  2. Myodegeneration of the cardiac muscle --> conduction defects


Which of the following can be due to a vitamin E/selenium deficiency? :

Nutritional myopathy

Ionophore toxicosis

Lower motor neuron disease

Clostridial myositis

Nutritional myopathy


Lower motor neuron disease


  1. Lower motor neuron disease will develop into ____ atrophy of muscles.
  2. This condition will manifest as ____.

  1. Lower motor neuron disease will develop into denervation atrophy of the muscles.
  2. This condition will manifest as ataxis.


This is a leg muscle from a steer:

  1. What is the proper name of this condition?
  2. What is the common name of this condition?
  3. What causes the cavitations in the muscle?

Q image thumb

  1. Clostridial myositis
  2. Black leg
  3. Gas production

A image thumb

What are the characteristics of Clostridial myositis?

Serohemorrhagic exudate


Muscle emphysema


  1. What condition is this lesion most likely associated with?
  2. What are the circled areas?

Q image thumb

  1. Clostridial myositis
  2. Areas of emphysema where gas has been produced

A image thumb

Which of the following might you see in a pig?

Myasthenia gravis

Nutritional myopathy

Polysaccharide storage myopathy


Malignant hyperthermia

Nutritional myopathy


Malignant hyperthermia


  1. Malignant hyperthermia is an inherited defect in what?
  2. Explain the pathway on how this defect causes hyperthemia.


  1. Calcium channel regulation
  2. Defect in Ca channel regulation between T tubules and sarcoplasmic reticulum --> increase Ca release into the sarcoplasm --> excessive myofiber contraction --> increase in body temperature


What type of gross lesion might you see with malignant hyperthemia in a pig?

Acute myodegeneration


Explain how trauma to a muscle (bruising) can cause clostridial myositis.

Ingestion of spores --> absorbed by the intestine --> distributed to muscle --> trauma to muscle --> prodcues a focal area that is anaerobic --> spores germinate --> produce toxins --> destroy tissue


This is a muscle from a cow that suffered a penetrating wound.  There is a serofibrinous exudate, lots of neutrophils, and these "bubbles".

What is your diagnosis?

Q image thumb

Necrohemorrhagic myositis due to Blackleg


The bacteria present within these muscle cells are gram +, club-shaped rods.

  1. What bacteria is infecting this muscle?
  2. What is this condition called?

Q image thumb

  1. Clostridium
  2. Clostridial myositis

A image thumb

This is muscle from a cow with a nutritional myopathy.

  1. Which nutrients were likely missing from the diet?
  2. What type of myodegeneration does this cause?

Q image thumb

  1. Vitamin E and/or selenium
  2. Polyphasic myodegeneration


  1. Which condition might cause these white striations in the muscle?
  2. What changes are occurring that cause these visible striations?

Q image thumb

  1. Nutritional myopathy
  2. Myodegeneration & mineralization

A image thumb

This is tissue from an animal with a nutritional myopathy.

  1. What cellular change is being outlined in yellow?
  2. What other cellular change most likely will be occurring?

Q image thumb

  1. Mineralization
  2. Cellular swelling


If a muscle undergoes myodegeneration & regeneration, what do we call that?

Polyphasic degeneration


True or False:

  1. Neurons are long-lived cells.
  2. Neurons are organized into layers and clusters.
  3. Neurons lie within the white matter.

  1. TRUE
  2. TRUE
  3. FALSE : Neurons are within the GRAY matter


  1. Which cells of the CNS respond to injury?
  2. Which cells of the CNS are part of the blood brain barrier?

  1. Astrocytes
  2. Astrocytes


When you look at the brain of say an NFL football player, it will be shruken.  What cellular changes will have taken place?





Which cells produce the myelin sheaths around axons?



Which cells of the CNS help regulate the microenvironment?





Where would you find oligodendrocytes within the CNS?

Within white matter tracks


  1. What are the phagocytic cells of the brain?
  2. What are they derived from?

  1. Microglial cells
  2. Monocytes


Based on their function, when might you see a population of microglial cells?

Under certain conditions of necrosis and inflammatory processes


  1. Which cells are involved in the production of cerebral spinal fluid?
  2. What else do you know about those cells?

  1. Ependymal cells
  2. These cells line the ventricles (single cell layer) & are ciliated (helping circulate the CSF)


  1. Which layer of the meninges is the vascular layer?
  2. Which layer of the meninges is tough and fibrous?
  3. What is the pia mater bound to?

  1. Arachnoid
  2. Dura mater
  3. Neuropil


This is a section of the cerebellum.

  1. What are the two visible layers here?
  2. What is the name of the cell circled in red ink?

Q image thumb

  1. Granular layer (left) & molecular layer (right)
  2. Perkinje cell

A image thumb

What are these cell types?

Yellow = ____

Red = ____

What type of protein is unique to the red cell?

Q image thumb

Yellow = neuron

Red = astrocyte

Astrocytes contain an intermediate filament protein called GLIAL FIBRILLARY ACIDIC PROTEIN

A image thumb

  1. Red cell = ____
  2. Yellow cells = ____
  3. Around the cell circled in red is a myelin sheath.  What cell type is this formed by?

Q image thumb

  1. Red cell = axon
  2. Yellow cells = oligodendrocytes
  3. Myelin sheaths around the axons are formed by oligodendrocytes

A image thumb

  1. What cell type is outlined in red?
  2. How many layers do these cells typically make?
  3. Are they cuboidal or columnar?

Q image thumb

  1. Ependymal cells
  2. Single cell layer
  3. Cuboidal cells

A image thumb

  1. What is the prefix used to denote gray matter?
  2. What is the prefix used to denote white matter?

  1. Polio - (polioenchphalomalacia is necrosis of the gray matter of the brain)
  2. Leuko - (leukoencephalomalacia is necrosis of the white matter of the brain)


This is an image of the meningeal layers.

1.  What is this layer?

2.  What is this layer?

3.  What is the space called around the vasculature?

Q image thumb

  1. Dura mater
  2. Arachnoid
  3. Virchow-robin space

A image thumb

  1. What is the space called outlined in yellow?
  2. What is the tissue denoted by red?
  3. What is the tissue denoted by blue?

Q image thumb

  1. Yellow = subarachnoid space
  2. Red = pia mater
  3. Blue = brain

A image thumb

This is a cross section of the cerebral cortex:

  1. What is the tissue layer denoted by blue?
  2. What is the tissue layer denoted by yellow?

Q image thumb

  1. Blue = arachnoid
  2. Yellow = pia mater

A image thumb

Red = ____

Yellow = ____

Blue = ____

Q image thumb

Red = astrocyte foot processes fused together to form the glial limitans

Yellow = capillary

Blue = endothelial cells

A image thumb

Under what does the glial limitans lie?

Under the pia mater






Q image thumb

  1. Pia mater
  2. Glial limitans
  3. Virchow-robins space

A image thumb

What makes up the blood brain barrier?

  1. Endothelium (with tight junctions)
  2. Basement membrane
  3. Astrocytes


This is a cross section of a peripheral nerve:

  1. What cells are heavily represented in this histiologic slide?
  2. What is the white space around these cells?
  3. What makes up that white space?

Q image thumb

  1. Axons
  2. Myelin sheaths of the axons
  3. Oligodendrocytes


  1. Where are the cell bodies of the upper motor neurons?
  2. Where are the cell bodies of the lower motor neurons?

  1. Within the brain
  2. Within the ventral horms of the spinal cord (which go out and innervate skeletal muscle) & motor nuclei of cranial nerves of the brain 


  1. When you have damage to the UMNs, what type of paralysis would you see?
  2. Why?
  3. When you have damage to the LMNs, what type of paralysis would you see?

  1. Spastic paralysis
  2. Without upper motor neurons, there is no inhibitory stimuli acting on the lower motor neurons
  3. Flaccid paralysis


`What produces myelin sheath around axons of the peripheral nervous system?

Schwann cells


  1. Around a bundle of axons there is the _____.
  2. Around the whole nerve is the _____.

  1. Around a bundle of axons there is the perinerurium.
  2. Around the whole nerve is the epinerurium.


  1. What type of degeneration happens when you damage an axon?
  2. What will happen down stream from the damage?
  3. What will happen proximal to the damage?

  1. Wallerian degeneration
  2. Downstream will deteriorate
  3. Proximal part will swell