Muscle pathology I

What are myofibers

Long multi-nucleated cells w/ little to no regenerative capacities

What does a satellite cell do?

Stem cells to regenerate a bit of damage muscles

What are type 1 skeletal muscle Fibers?

Slow twitching oxidatie red muscles - aerobic

Type 1 skeletal muscle will have ____ mitochondria

Many

What are type 2A SK muscle fibers?

Fast twitch oxidative glycolytic - fatigue resistant

Type 2A SK muscle fibers will have ___ mitochondria?

Intermediate

What are Type 2b SK muscle fibers?

Fast twitch

Fatigue sensitive

White muscle

Anaerobic

Type 2B SK muscle fibers will have ___ mitochondria?

Few

What are functions of muscles?

Posture / movement

homeostasis

The function of SK muscles wil lbe related to the function of the ___?

Peripheral nervous system

What is a neuropathic?

Effect/ absence of nerve supply

What are myopathics?

Changes w/in muscle cell fibers

Neuromuscuar dz will involve what?

Lower motor neurons and peripheral nerves

Expalin the healing process of muscles?

Necrosis cleaned up by macrophages

satellite cells enlarge and develope into myoblasts

Myoblasts start proliferating and regenerate myofibers

What kind of necrosis does SK muscle go through?

Coagulation necrosis

What are clinpath findings of SK muscle inj?

Creatine kinase elevation

AST/ LDH elevation

Carbonic anhydrase III

What does carbonic anhydrase III insufficiency suggest?

Myasthenia gravis - acetylocholine receptor degredation

Pallor suggests ____?

Necrosis - anemia

Pale streaking suggests?

Necrosis and mineralization

What does dark red molting suggest?

Congestion/ hemorrhagic necrosis

Green muscle suggests?

Eosinophilic inflammation / putrefaction - Sarcocystis - parasitic

What is an example of pale streaks in SK muscles in dogs?

Canine X - linked muscular dystrophy - duchenne's type

What is dystrophin?

A structural link between muscle cytoskeletins

What is going to cause canine x linked muscular dystrophy?

Defected dystrophin genes

What are causes of localized pallor?

Inj site necrosis

What pathological changes can we see in equine motor neuron dz?

Collagen and fat infiltration due to denervation atrophy

What muscle biopsy would we take for a horse of w/ Equine motor neuron dz?

Type 1 postural

What muscle biopsy would we take for equine polysaccharide storage myopathy?

Type 2 SK muscle - Locomotory

What sample would we take for masticatory myositis of dogs?

Temporal or masseter

What is the ideal muscle biopsy?

1cm myofibers running lengthwise - avoid contracting band artifact

What are direct inj to muscle?

Penetrating wounds/ IM Inj

bone fractures causeing trauma adjacent muscle

External pressure

Name some defense mechanisms of muscle?

Skin - structural barriers

Vasculature - collateral circulation

Immunologic responses

Name a few disturbances of circulation?

Occlusions

Pressure

Swelling impeding blood supply

What is an example of external pressure causing circulation disturbances?

Downers cow syndrome

What is white muscle dz?

A nutritional deficiency - vit E/ Selenium deficiency

What does Ionophore toxicity do?

Calcium overload causing too much contraction leading to muscle necrosis

Ionophore is most common toxicity in what animals?

Horses

What is the most common myotoxic in cattle?

Senna occidentalis

What is capture myopathy?

Exercise induced myonecrosis

What is tying up?

Equine exertional rhabdomyolysis

-stiff gait - high grain feeding - lack of regular exercise

What is myositis ossificans?

Focal lesions of fibrosis w/ osseous metaplasia caused my muscle trauma

How do you treat myositis ossificans?

Painful - sx excision

Ducheene's muscular dystrophy in cats and dogs is an example of what?

Inherited progressive degenerative primary dz of myofibers

What is myotonia?

A channelopathy due to abnormal ion channel function

What is neonatal calf denervation atrophy?

Muscles replaced by fat,

What is congenital muscle hyperplasia?

Double muscling - autosomal recessive

- inactivation of the myostatin gene

- IM fat are reduced - large bulky muscles

What is malignant hyperthermia?

Unregulated release of calcium leading to increased temp due to defect in ryanodine receptors

What is malignant hyperthermia called in pigs?

Porcine stress syndrome - pale soft exudative

What is the most common type of metabolic myopathies?

Glycogenosis - glycogen storage dz - Type 4 Glycogen branching enzyme deficiency

What does a Glyogen branching enzyme deficiency going to do?

Less branching - cant utilize glycogen and leads to muscle necrosis

What stain will highlight Glycogen branching enzyme deficiency?

PAS stain

What is Myasthenia gravis?

Immune-mediated disorder attacking acetylcholine rexeptors

Myasthenia gravis has an associated w/ what?

Thymic abnormalities - thymoma

Botulism will cause a ___ paralysis most common in ___?

Flaccid paralysis - Blocks acetylcholine

Horses

What ticks cause tick paralysis?

Dermacentor and Ixodoes

What does tick paralysis cause?

Toxin Blocks acetylcholine - Flacid paralysis

What is neoplasia of the muscles?

Rhabdomyomoa/Rhabdomyosarcoma

Hemangiosarcoma

What is an infiltrative lipoma?

A lipoma that makes the muscle pale and weak

What is animals do vax associated sarcomas related in?

Cats - IM vax sites