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Pathology II > Lecture 18: Skeletal Muscle Pathology I > Flashcards

Lecture 18: Skeletal Muscle Pathology I Flashcards

1
Q

Which of the following is heart vs skeletal muscle

A

Left: heart- single centrally located nucleus
Right: skeletal muscle- multiple nuclei on periphery

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2
Q

identify 1-6

A
  1. Mitochondria
  2. Glycogen
  3. Z line
  4. I band
  5. M line
  6. A band
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3
Q

what are myofibers

A

long and multinucleated cells, little to no regenerative capacity

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4
Q

what are satellite cells

A

run along length of myofibers and have full capacity of division, fusion, and can restore mature myofibers

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5
Q

what are the physiologic and morphological characteristics of type 1 muscle fibers

A

Phys: slow twitch, oxidative fatigue resistant, “red muscle” aerobic

Morph: high mitochondria and fat, low glycogen

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6
Q

what are the physiologic and morphological characteristics of type 2A muscle fibers

A

Phys: fast twitch, oxidative and glycolytic fatigue resistant

Morph: intermediate mitochondria, fat and glycogen

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7
Q

what are the physiologic and morphological characteristics of type 2B muscle fibers

A

fast twitch, fatigue sensitive, glycolytic “white muscle” anaerobic

Morph: low mitochondria and fat, high glycogen

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8
Q

which muscle fibers are used for long distance

A

type 1

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9
Q

which muscle fibers are used for short distance, high intensity

A

2B

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10
Q

how does the percentage of type 1 and type 2 muscle fibers differ in the fore and hindlimbs

A

more type 1 muscle fibers (postural) in forelimbs
More type 2 muscle fibers (locomotive) in hind limbs

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11
Q

what are the functions of muscle

A
  1. Posture and movement including respiration
  2. Homeostasis- glucose metabolism and body temp
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12
Q

the function of muscles is intimately related to the function of __

A

PNS

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13
Q

what is a neuropathic change in myofibers

A

effect of absence of nerve supply

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14
Q

what is a myopathic change in myofibers

A

primary changers are within muscle cells/fibers

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15
Q

neuromuscular diseases involve __

A

lower motor neurons, peripheral nerves, NMJ, and muscle

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16
Q

what is the epimysium

A

surrounds whole muscle

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17
Q

what is perimysium

A

surrounds fascicle

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18
Q

what is endomysium

A

around each muscle fiber

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19
Q

what are some clinpath findings that indicate skeletal muscle injury

A
  1. Elevated CK (muscle specific)
  2. Elevated LDH and AST
  3. Deficient carbonic anhydrase III
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20
Q

carbonic anhydrase III is critical for ___

A

acetylcholine receptor homeostasis in NMJ

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21
Q

carbonic anhydrase deficiency induces __ leading to __

A

accelerated degradation of AChR leading to myasthenia gravis

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22
Q

what is wrong in pallor muscle

A

necrosis, denervation, anemia, young animals

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23
Q

what is wrong in pale streaking muscle

A

necrosis and mineralization

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24
Q

what is wrong in dark red mottling muscle

A

congestion, hemorrhagic necrosis, inflammation, myoglobin staining and hypostatic congestion

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25
Q

what is wrong with green muscle

A

eosinophilic inflammation or putrefaction

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26
Q

what is wrong with lipofuscin (tan-brown) muscle

A

old animals

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27
Q

what is wrong with black muscle

A

melanoma

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28
Q

What wrong and what cause

A

Eosinophilic myositis- green discoloration due to abundant eosinophils in inflammation

Histo: tons of eosinophils

inflammation secondary to sarcocystis

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29
Q

from dog: what wrong and what could have caused this

A

pale streaks- necrosis and mineralization
Cause: Canine X-linked muscular dystrophy (Duchenne;s type)- dystrophin gene defect

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30
Q

what is dystrophin

A

structural link between muscle cytoskeleton and ECM to maintain muscle integrity

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31
Q

from horse- what wrong and what could have caused

A

Yellow streaks- denervation atrophy

Cause: equine motor neuron disease

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32
Q

type 1 postural muscle samples are best for what equine disorder

A

equine motor neuron disease

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33
Q

type 2 locomotive muscle samples are best for what equine disorder

A

equine polysaccharide storage myopathy

34
Q

what muscles are best to submit for masticatory myositis in dogs

A

temporal and masseter

35
Q

describe how to prepare muscle sample

A
  1. Collect muscle strip not larger than 1cm with myofibers running length wise
  2. Place on rigid surface (tongue depressor) to avoid contraction band artifacts after placing in fixative
36
Q

how does the skin, subcutis and fascia act as defense mechanism of skeletal muscle

A

form structural barrier to protect from external injury

37
Q

how does vasculature act as defense mechanism for skeletal muscle

A

collateral circulation protects against ischemia
Recruitment of monocytes, macrophages, neutrophils
Capillary endothelium resistant to tumor metastasis

38
Q

what can cause disturbances of circulation and lead to a degenerative myopathy

A
  1. Occlusion of major blood vessel
  2. External pressure on muscle
  3. Compartment syndrome- swelling impedes blood- ischemia
  4. Vasculitis/vasculopathies
39
Q

nutritional deficiency is a result in loss of __mechanism

A

Antioxidant defense

40
Q

what are common nutritional deficiencies and is the result

A

vitamin E or selenium deficiency—> necrosis and pale—> oxidative injury—> white muscle disease

41
Q

selenium is vital in __ system which protects against ___

A

glutathione perioxidase, oxidative injury

42
Q

how do ionophore cause toxic myopathies

A

overdose—> disruption of ionic equilibrium—> calcium overload—> skeletal and cardiac muscle necrosis

43
Q

what are some clinical signs of ionophore toxicity

A

anorexia, diarrhea, weakness

44
Q

__ and __ are extremely high with ionophore toxicity

A

CK and AST

45
Q

what is the most common degenerative myopathy in cows and what is cause

A

Plant toxicity due to senna occidentalis

46
Q

horse that lived with cows suddenly became very weak, off feed, colic signs, arrhythmias. This histo was taken- what wrong and what likely cause

A

Necrosis and fragmented muscle fibers
Cause: ionophore toxicity

47
Q

what is exercise induced myonecrosis known as and what are some causes

A

capture myopathy
Causes: extreme stress, struggle or exertion

48
Q

what are some signs of equine exertional rhabdomyolsis

A

sudden onset stiff gait, reluctance to move, swelling over muscles, especially gluteals

49
Q

what blood work sign is consistent with equine exertional rhabdomyolysis

A

high CK and AST

50
Q

what causes equine exertional rhabdomyolysis

A

high grain feeding and lack of regular exercise

51
Q

what wrong here and identify 1

A

myositis ossificans
1. Osseous metaplasia

52
Q

what is myositis ossificans

A

focal lesion of fibrosis with osseous metaplasia caused by muscle trauma

53
Q

what is muscle dystrophy

A

inherited progressive, degenerative primary disease of myofibers characterized by ongoing necrosis and regeneration

54
Q

what is myotonia/ channelopathies

A

inability of myofibers to relax, resulting in spasmodic contractions. Abnormal ion channel function

55
Q

what wrong

A

congenital muscle steatosis- pale muscles, replace of muscles by adipocytes

Denervation atrophy

56
Q

what wrong and cause

A

congenital muscular hyperplasia caused by genetic defect causing inactivation myostatin gene which regulates number and size of myofibers

57
Q

what is malignant hyperthermia and cause

A

Cause: defect in ryanodine receptor triggered by anesthesia (halothene) or stress

Causes unregulated release of Ca2+ from SR leading to increased contraction that generates heat, severely increased body temp

58
Q

in pigs what is malignant hyperthermia also called

A

Porcine stress syndrome or pork/pale soft exudative

59
Q

what are metabolic myopatheis characterized by

A

reduced muscle cell energy production

60
Q

what is type IV glycogen storage disease

A

glycogen branching enzyme deficiency

61
Q

what does glycogen branching enzyme typically produce

A

alpha 1-6 branches in glucose

62
Q

glycogen branching enzyme is necessary to build __

A

glycogen

63
Q

what happens with deficient GBE

A

Glycogen lacks normal branched structure—> can’t effectively utilize glycogen as energy source—> tissues become weak and unable to function properly

64
Q

in GBE deficiency what abnormal form of glycogen accumulates in cells

A

amylopectin

65
Q

Foal born, very weak, no energy, can’t stand. Perform histopath and this is result what wrong and what stain was used

A

purple clumps are amylopectin which increase in glycogen storage disease type IV: GBE deficiency

Stain: PAS

66
Q

from patient with GBE deficiency, what is arrow pointing at

A

hyaline inclusion

67
Q

what is the cause of acquired myasthenia gravis

A

immune mediated disordered caused by circulating autoantibodies that target skeletal muscle acetylcholine receptor

68
Q

autoantibodies in myasthenia gravis damage receptor due to __ or __

A
  1. direct effect on NMJ
  2. Formation of cross-linked antibodies that lead to receptor internalization
69
Q

Why type of tumor has been associated with myasthenia gravis and what does it cause

A

thymoma- secondary loss of self tolerance to acetylcholine receptors (myoid cells involved)

70
Q

how do you dx myasthenia gravis

A

detection of autoantibodies to acetylcholine receptor in blood

71
Q

botulinum toxicity is characterized by profound __

A

flaccid paralysis

72
Q

How does botulinum cause flaccid paralysis

A

toxin causes cleavage of SNARE proteins that are responsible for release of acetylcholine from pre synaptic vesicles

73
Q

What botulism toxin type are dogs, ruminants and horses sensitive to

A

dogs: type C
Ruminants: type C and D
Horses: type C and B

74
Q

what is the cause of tick paralysis

A

toxins produced by dermacentor or ixodes ticks that block acetylcholine release at axon terminal

75
Q

Rhabdomyoma and rhabdomyosarcomas arise from ___

A

intramuscular pluripotent cells

76
Q

what is a rhabdomyoma, where do they occur and in who

A

benign, smooth, pink, nodular, unencapsulated. Occur commonly inn larynx of adult dogs

77
Q

what is a rhabdomyosarcoma, where do they occur and in who

A

malignant tumor, occur at young age most commonly in the neck, oral cavity, tongue

78
Q

what is the most common primary neoplasm of skeletal muscle

A

hemangiosarcoma

79
Q

5yr old dog presents with SQ mass, histo shows the following. Which is abnormal mass vs control. IHC was done- what does that tell you

A

left: rhabdomyosarcoma- Desmin +

Right: normal control

80
Q

what are infiltrative lipomas

A

variant of lipoma that recurs if not completely excised, but does not metastasize, make muscle pale and weak

81
Q

what causes vaccine associated sarcomas

A

IM vaccine sites or extended into underlying muscle from SQ injections

Pathology II (19 decks)

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