Week 1 lesson 6: Pathogenesis of muscle injury

What plays an important role in muscle regeneration?

Satellite cells

What are the 7 clinical signs of muscle disease?

1. Muscle atrophy

2. Muscle hypertrophy

3. Muscle swelling

4. Weakness

5. Muscle spasms

6. Abnormal gait

7. Esophageal dysfunction

What can be add or delete sarcomeres to cause elongation or shortening of the entire muscle?

Myofibers

What are the 6 ways that muscles respond to injury?

1. Myofibers adding or deleting sarcomeres

2. Necrosis

3. Regeneration

4. Alteration in myfiber size

5. Splitting

6. Cytoarchitectural alterations

What are the two ways that myofibers change in size?

atrophy

hypertrophy

What are the three different alterations of cytoarchitectural?

Vacuolar change

Internal nuclei

Whorled and ring fibers

What are the 6 pathologic changes resulting in pale skeletal muscle?

1. pale streaks

2. overall pallor

3. necrosis

4. mineralization

5. enlargement

6. steatosis

What type of muscle injury has large, dark red fibers, hyaline degeneration, loss of striations, and fragmentation? There is also an increase in intracellular calcium and macrophage infiltration.

Myofiber necrosis

Due to increased intracellular calcium during myofiber necrosis, what can happen inside the cell?

Mineralization causing chalky white streaks

In myofiber necrosis there is macrophage infiltration, this causes the activation of what cells?

Satellite cells allowing for regeneration

How well tissue is able to regenerate will depend on what layer?

Basal lamina

What happens to the regeneration when the basal lamina is damaged?

If its damaged it creates a fibrosis

What are the 5 different types of chrontic myopathic changes when muscles respond to injury?

1. Excessive fiber-size

2. Internal nuclei

3. Fiber splitting

4. Fibrosis

5. Fat infiltration

What are they two types of portals of entry into the muscular system?

Direct

Hematogenous

What are the 4 types of direct portals of entry into the muscular system?

1. penetration wounds

2. Intramuscular injections

3. Bone fracture causing trauma to adjacent muscle

4. External pressure causing crush injury

What are the three types of hematogenous portals of entry into the muscular system?

1. blood born pathogens, toxins, autoantibodies

2. Cytotoxic lymphocytes causing immune-mediated damage

3. Other inflammatory cells

What are the 3 main defense mechanism of skeletal muscle?

1. Skin, subcutis, and fascia

2. Vasculature

3. Immunologic response

How does skin, subcutis, and fascia act as a defense mechanism of skeletal muscle?

Forms structural barriers to protect against external injury

How does vasculature act as a defense mechanism of skeletal muscle?

• Collateral circulation to protect against ischemia

• Recruitment of monocytes and neutrophils

• Capillary endothelium resistant to tumor metastasis

How does Immunologic responses act as a defense mechanism of skeletal muscle?

Innate humoral and cellular immunologic responses

What does DICE2N3 stand for?

• Dengenerative

• Inflammatory

• Congenital

• Endocrine

• Electrolyte

• Neuropathic

• Neurojunctions

• Neoplasms

What are the 5 different degenerative causes of muscle disease?

1. Ischemia

2. Nutritional

3. toxic

4. exertional

5. traumatic

What are the 4 different inflammatory causes of muscle disease?

1. Bacterial

2. Viral

3. Parasitic

4. Immune-mediated

What are the 6 different congenital causes of muscle disease?

1. Anatomic defects

2. Muscular dystrophy

3. Congenital myopathy

4. Myotonia

5. Metabolic

6. Malignant hyperthermia

What are the 2 different endocrine causes of muscle disease?

1. Hypothyroidism

2. Hypercortisolism

What are the 3 different electrolyte causes of muscle disease?

1. Hypokalemia

2. Hypernatremia

3. Other electrolyte imbalance

What are the 2 different neuropathic causes of muscle disease?

1. peripheral neuronopathy

   1. motor meuronopathy

What are the 3 different neuromuscular junction causes of muscle disease?

1. Myasthenia gravis

2. Botulism

3. Tick paralysis

What are the 3 different neoplasia causes of muscle disease?

1. Primary tumors (rhabdomyoma)

2. Secondary tumors (hemangiosarcoma)

3. Metastatic tumors

A puppy diagnosed with a mutation in dystrophin exhibits progressive muscle degeneration with cycles of necrosis and attempted regeneration. Which category does this disease fall into?

Degenerative myopathy

What are the 3 types of bacterial myopathies in horses?

1. Clostridal myositis

2. Cornybacterium pseudotuberculosis

3. Streptococcal-associated myopathies

What bacterial myopathies causes hemorrhagic myositis and muscle necrosis?

Clostridial myositis

What is the bacterial myopathy that cause purpura hemorrhagica, streptococcal-associated phabdmyolysis and muscle atrophy?

Streptococcal-associated myopathie

What is another name for Corynebacterium pseudotuberculosis?

Pigeon fever

What are the two types of parasitic myopathies in the horse?

Protozoal myopathy (sarcocystis)

Ear tick associated muscle spasms (otobius megnini)

What are the three different types of nutitional toxic myopathies in a horse?

1. Nutritional myopathy (selenium or Vit. E def.)

2. Ionophore toxicity

3. Plant toxicities

How does ionophore toxicity (monensin) cause segmental necrosis?

Facilitate the movement of ions across cell membranes disrupting the intracellular pH causing segmental necrosis

What are the two plants that cause plant toxicities in horses?

Cassia occidentalis (coffee senna) and Thermopsis

How do plant toxicities cause muscle damage?

Mitochondrial dysfunction which

Which toxicity causes myofibrillar degeneraton, lipid accumulation, multifocal myofiber necrosis and fragmentation due to mitochondrial dysfunction?

Plant toxicities

What are the tow main congenital myopathies in horses?

Hyperkalemic periodic paralysis

Equine Polysaccaride storage myopathy

anWhat congenital disease in horses is a underlying CHO metabolic disorder that causes an abnormal accumulation of intracytoplasmic glycogen?

Equine polysaccharide storage myopathy

What are 3 main exertional rhabdomyolysis another type of equine myopathy?

Tying up

Azoturia

Monday morning dz

Black water

By which mechanism does ionophore toxicity result in muscle damage?

Facilitating ion transport across membranes

Which electrolyte abnormality is most characteristic of hyperkalemic periodic paralysis (HYPP) in horses?

Hyperkalemia

What are the 5 bacterial myopathies for cattle?

1. Clostridial Myositis

2. Botulism

3. Pyogenic Bacteria

4. Actinobacillus lignieresii

5. Actinomyces bovis

What is another name for Clostridial Myositis?

Black leg

What is another name for actinobacillus lingnieresii?

Wooden tongue

What is another name for actinomyces bovis?

Lumpy jaw

What protozoal myopathy causes pale, white nodules of myofiber necrosis and granulomas?

Sarcocystis spp.

What are the two types of protozoal myopathies in cattle?

Sarcocystis and neopora caninum

What are the three different types of nutritional and toxic myopathies in cattle?

Selenium or Vit E deficiency

Coffee senna

Monensin

What are the two main congenital disorders in cattle?

Steatosis

Congenital muscular hyperplasia

What is an abnormal accumulation of fat within muscle tissue replacing normal muscle fibers in cattle?

Steatosis

What is the problem with downer cow syndrome (ischemic necrosis)?

It ecludes blood vessels not allowing for oxygen to flow into muscle tissue

What is the hallmark of clostridial muscle disease?

Gas bubbles in muscle

Which myopathy in cattle results in muscle necrosis due to oxidative damage?

Nutritional myopathy

What are the three types of bacterial myopathies in sheep and goats?

Clostridial Myositis

Botulism

Tentanus

How does botulism cause flaccid paralysis?

Botulism toxin → disruption of neurotransmitter vesicle exocytosis at myoneural junctions → flaccid paralysis

How does tetanus cause spastic paralysis?

tetanospasmin toxin → disruption of neurotransmitter vesicle exocytosis at neural-neural junctions → spastic paralysis

What muscle in camelids can cause megaesophagus, which contains a large amount of skeletal muscle?

Tunica muscularis

Adult llamas and alpacas are prone to develop abnormal motility and megaesophagus which can can cause what?

Lose body condition

Abnormal rumination of feed boluses

Atrophy of type 1 and 2 fibers

At what location does tetanus toxin act to explain the associated clinical signs?

Neural-neural junction

What is the cuase of canine Duchenne-type muscular dystrophy?

Dystrophin deficiency

What component is affected in myasthenia gravis?

Neuromuscular junction ACh receptors

What is the most common parasitic myopathies in pigs?

Trichinosis (trinchinella spiralis)

What does trichinosis cause in pigs?

0.5 - 1 mm white nodule and myositis

What is the main congenital in pigs that causes muscle injury?

Myofibrillar hypoplasia (splay legs)

What is the 2 main congenital disorders that cause muscle injury in dogs?

X-linked Muscular Dystrophy (Duchenne’s Type)

Labrador Retriever centronuclear myopathy

What congenital disorder in dogs is from the absence of dystrophin which causes repeated bouts of necrosis and regeneration?

Duchenne’s Types

What congenital disease can cause atrophy, hypertrophy, and internal nuclei in dogs?

Labrador Retriever Centromuclear myopathy

What are the two main immune-mediated myopathies in dogs?

Polymyositis

Masticatory myositis

What is the main disorder of the neuromuscular junction in dogs?

Myathenia gravis

What is the main congenital disorder that causes muscle injury in cats?

X-linked muscular dystrophy