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Module 7 > Muscle Pathology > Flashcards

Muscle Pathology Flashcards

1
Q

what are the types of muscle fibres

A

type 1 and type 2

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2
Q

how many mitochondria do type 1 and type 2 have

A

1: many
2: fewer

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3
Q

what is the metabolism of type 1 and 2 muscle fibres

A

1: oxidative (aerobic)
2. glycolytic (anaerobic)

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4
Q

what type of contraction do type 1 and 2 muscle fibres have

A

1: slow
2: fast

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5
Q

which muscle fibres fatigue more easily

A

1: slow
2: more easily

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6
Q

which type of muscle is 1 and 2 fibres

A

1: postural
2: propulsive

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7
Q

what colour are type 1 and 2 muscle fibres

A

1: red
2: white

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8
Q

what are the fibres like in type 1 and 2

A

1: smallest
2: 2B is largest (fast-contracting, fast-fatiguable, glycolytic) 2A: mixed oxidative-glycolytic; fast-contracting, slow-fatigueing (intermediate)

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9
Q

what is the mixed mosiac pattern

A

most muscles contain both type 1 and 2 fibres

proportion varies dependent on muscle function

determined by motor neuron

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10
Q

which muscle fibre do dogs not have

A

type 2B

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11
Q

what is rigor mortis

A

sustained muscle contraction after death

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12
Q

what causes rigor mortis

A

absence of adequate ATP production –> actin and myosin cannot be released from eachother

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13
Q

how is rigor mortis stopped

A

muscle breakdown (autolysis)

variable onset and resolution depending on intrinsic and extrinsic factors (temp, etc)

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14
Q

what is a motor unit

A

myofibres innervated by a single axon

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15
Q

how are fine movements produced

A

small motor units –> 1-4 myofibres per axon

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16
Q

how are large forces generated

A

large motor units –> 100-150 myofibres per axon

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17
Q

how are muscles examined using clinical pathology

A

CK, ALT (AST, LDH less specific)

myoglobin

integrity not function

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18
Q

how can muscles be examined using electrophysiology

A

electromyography

electroneurography

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19
Q

what are gross examination features of muscle ex vivo

A
  1. size
  2. colour
  3. texture
  4. histological examination
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20
Q

what changes colour changes of muscles indicate

A
  1. pale pink/white: anemia, young animal, ischemic necrosis, mineralization, collagen, fat
  2. red: congestion, hemorrhage, hemorrhagic, necrosis, inflammation, myoglobin staining
  3. green: eosinophils, severe putrefaction
  4. tan-brown: lipofuscin
  5. black: melanosis in calves
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21
Q

what texture changes occur in muscles

A

soft: fat, necrosis
firm: fibrosis
hard: mineralization

22
Q

what needs to be considered when muscles are biopsied

A

certain muscles easier to sample due to longitudinal orientation

  1. type of muscle: proximal/distal
  2. certain muscle/muscle groups: ex. masticatory muscle myositis
  3. type of myofibre
  4. fresh vs. fixed muscle
23
Q

what are response to insult

A
  1. hypertrophy (addition of myofilaments)
  2. atrophy
  3. degeneration and necrosis
  4. regeneration
  5. chronic myopathic change: alterations in myofibre diameter, fibrosis, fat infiltration, aetiology: chronic inflammation, deneration, degenerative myopathy

often cause for changes not clear on histology –> history and ancillary tests required

24
Q

what is atrophy

A

usually reversible

reduced myofibre diameter

25
Q

what is hyaline degeneration

A

homogenously eosinophilic fibres, loss of striations

26
Q

what does regeneration of muscle depend on

A

muscle is post mitotic tissue

regeneration depends on intact satellite cells and extent of damage to basal lamina

27
Q

what are the steps of regeneration in muscle

A

basal lamina intact

  1. macrophages entre and remove debris
  2. satellite cells become myoblasts
  3. myoblasts fuse to form myotubes
  4. essential structures reformed
  5. nuclei move to peripheral position
28
Q

what occurs when the basal lamina is destroyed

A

if satellite cells survive mutlinucleate muscle giant cells develop

29
Q

what are the types of muscle pathology

A
  1. vascular
  2. inflammatory (infectious/immune-mediated)
  3. traumatic
  4. anomaly/congenital
  5. metabolic/toxic
  6. idiopathic/iatrogenic
  7. neoplastic
  8. degenrative
30
Q

what occurs during vascular damage

A

ischemia

  1. occlusion of large blood vessel
  2. external pressure on a muscle (downer cow, anaesthesia)
  3. internal pressure on a muscle (compartment syndrome)
  4. vasculitis/vasculopathy
31
Q

how does inflammatory damage occur

A
  1. penetrating wounds
  2. spread from adjacent sites
  3. hematogenous
32
Q

what bacteria causes inflammatory damage to muscle

A

clostridia –> myonecrosis

CI. perfringens, CI. chauvoei, CI. septicum, CI. novyi

33
Q

how does bacteria cause inflammatory damage

A

toxins –> damage to myofibrils and vessels leads to necrosis

34
Q

what is pyogenic bacteria

A

abscesses

35
Q

what parasites cause inflammatory damage

A

protozoa: Neospora caninum
nematode: trichinella spiralis (pigs), larval migrans (dogs)
cestode: larval form

36
Q

what are the causes of immune-mediated muscle damage

A

primarily dogs

usually cytotoxic T cells

37
Q

what is masticatory muscle myositis

A

antibodies againts type 2M myosin and myositigen

focal myositis of masticatory muscles

38
Q

what are traumatic injuries

A

crushing

lacterations

tearing or ruptures

39
Q

what is the most common muscle to undergo traumatic injury

A

diaphragm

40
Q

what do traumatic injuries normally cause

A

damage to basement membrane –> fibrosis

41
Q

what is X-linked muscular dystrophy

A

absence of membrane associated cytoskeletal protein dystrophin

repeated necrosis and regeneration of fibres

progressive weakness and skeletal muscle atrophy beginning within days of birth

42
Q

what is labrador centronuclear myopathy

A

mutation in gene encoding cell surface protein

weakness, gait abnormalities, exercise intolerance

43
Q

what is hyperkalemic periodic paralysis

A

membrane instability and continuous myofibre activity

muscle spasm followed by paralysis

44
Q

what is equine polysaccharide storage myopathy

A

carbohydrate metabolic disorder

recurring exertional rhabdomyolysis, unexpected pelvic limb lameness

45
Q

what are metabolic injuries to muscle

A

oxidative injury due to loss of antioxidant defense mechanisms

46
Q

what are examples of metabolic injuries

A

selenium deficiency

vit E deficiency

“white muscle disease”

47
Q

what are examples of toxic damage to muscle

A
  1. ionophores (monensin in horses)
  2. plants

multifocal and monophasic/polyphasic necrosis

48
Q

what is exertional (iatrogen) damage

A

capture myopathy in highly strung wild animal

more often: underlying pre-existing conditions (Se deficiency, muscular dystrophy, electrolyte depletion, glycogen storage dx)

49
Q

what is primary neoplasm damage

A

rhabdomyoma

rhabdomyosarcoma

50
Q

what is secondary neoplasm

A

injection site sarcoma

round cell tumours: lymphoma, mast cell tumour

infiltrative lipoma

carcinoma

Module 7 (50 decks)

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