Muscle

• Shown below is the throat muscle in a horse, state the name of the abnormality and its cause

  Denervation atrophy

  Cause: partial nerve damage

  Specifically Right Laryngeal hemiparesis in a horse.

  
• Shown below is the muscle of the limb of a horse. What is probable abnormality and its cause?

  Disuse atrophy – Caused by restricted movement in a limb

  
• What is the abnormality below called

  • Atrophy due to cachexia – Marked malnutrition or neoplasia – Typically postural muscles less affected

  
• Hypertrophy can either be pathological and physiological. State a cause of each

  Physiologic - exercise

  Pathologic - Due to loss of function of contralateral limb
• What is myotonia? (cause and common in what animal breed)

  A protein is produced that controls Cl- channels hence Involuntary contraction of a muscle group

  common in saanen goats
• What is steatosis in the context of congenital muscle disease?

  Replacement of myocytes with adipose tissue
• Congenital muscle hypertrophy

  Normal in some cattle breeds eg Belgium blue

  The muscle contains reduced adipose tissue
• Congenital muscular dystrophy

  Caused by a cytoskeletal protein (dystrophin) defect

  Common in people, rarely seen in dogs and cats Eg labradors

  Death is usually due to heart failure as cardiac myocytes are also affected
• What does congenital muscular dystrophy cause in dogs

  Diaphragm atrophy which can lead to a hernia , the Diaphragm gets very thin.
• What does congenital muscle dystrophy cause in cats

  Multiple muscle hypertrophy
• Malignant hyperthermia / porcine stress syndrome 


  Triggered by stress or halothane

  Caused by: defect in ryanodine receptor which leads to uncomtrolled sustained contraction

  Sequel: produces excessive heat and lactic acid resulting in myocyte necrosis

  Multi focal monophasic necrosis
• Congenital storage disease

  -Most common in polysaccharide myopathy

  -most common in draft breed horses

  -predisposed to exertional rhabdomyolysis

  • Muscle biopsy shows high levels of intracellular carbohydrate
  • If this condition persist it results in fibrosis and weakness
• What is exertional rhabdomyolysis in a horse characterized by?

  Pale swollen (necrotic) lumbar muscles
• What does myoglobinuric nephrosis indicate in a horse?

  It indicates kidney damage due to myoglobin in the urine
• How can animals die from capture myopathy?

  They can die quickly due to metabolic acidosis or later from myoglobinuric nephrosis
• What is shown below, state its cause, and signs

  Black leg

  Cause : C. Chauvoei

  Signs: emphysematous necrosis, rancid butter smell, crepitus

  
• What is the problem caused by this wound Gas gangrene

  Gas gangrene

  C. Septicum

  emphysema, odor , no inflammation

  
• Name the problem in sheep in the muscle, it’s cause and a problem that it may lead too

  Big head

  C. Novyi

  Tissue damage from head butting

  
• What is the problem seen below, what can it turn into and what is it caused by

  Wooden tongue

  can lead to glossal myositis

  cause: actinobacillus lignieresii

  
• What is seen below

  Cystercys ovis

  measles

  
• What is masticatory myositis associated with?

  Autoimmunity against type II masticatory myosin
• What is the significance of type II masticatory myosin in masticatory myositis?

  This protein is restricted to masticatory muscles
• What are the consequences of masticatory myositis?

  Eosinophilic myositis followed by fibrosis and atrophy
• What condition is characterized by muscle swelling and exophthalmus?

  Extraocular myositis
• What metabolic imbalances can alter muscle function?

  Loss of homeostasis of glucose, calcium, potassium, magnesium, and phosphate
• How do Cushing’s disease and hypothyroidism affect muscles?

  They result in muscle weakness and atrophy
• What is white muscle disease also known as?

  Nutritional myopathy

  
• Who is usually affected by white muscle disease?

  Neonatal or young animals
• What is the consequence of a lack of free-radical scavenging in muscles?

  It results in oxidative muscle necrosis
• Which muscles are more affected by oxidative muscle necrosis?

  More active muscles produce more free radicals and have more severe lesions
• What visible sign indicates muscle pallor in vitamin E/Selenium deficiency?


  Visible pallor in the tongue, diaphragm, and heart in young animals
• What can cause death in animals affected by vitamin E/Selenium deficiency?

  Heart failure or respiratory failure caused by costal muscle damage
• What is a notable histological feature of white muscle disease?

  Multifocal multiphasic necrosis with marked calcification
• What is the role of iron in muscle pathology?

  Iron is a pro-oxidant that predisposes to oxidative muscle necrosis
• How does monensin toxicity affect muscle cells?

  It prevents muscle cells from producing ATP
• What are the symptoms of monensin toxicity in horses?

  Diarrhea, colic, and death after 24 hours
• What happens to muscles in cases of monensin toxicity?

  Muscles are pale and swollen
• What types of tumors are classified as benign in skeletal muscle neoplasia?

  Laryngeal rhabdomyoma in dogs and cardiac rhabdomyoma in pigs, cattle, and sheep
• What are rhabdomyosarcomas?

  Uncommon aggressive tumors in all species
• What is a unique feature of botryoid rhabdomyosarcomas?

  They involve the bladder in young dogs and resemble bunches of grapes