Musculoskeletal Pathology III Flashcards
Name three cytoarchitectural changes of degeneration
- Vacuolar change
- Internal nuclei
- Whorled and ring fibres
What is the chronic myopathic change?
- Excessive fibre size
- fat infiltration and fibrosis
What is segmental necrosis?
- Sarcoplasm begins to fragment
- Fragmented cytoplasm can mineralise
- Circulating monocytes infiltrate and mature to macrophages
In what animals does true muscular dystrophy occur?
Golden Retriever, Rottweilers
What is myotonia?
inability of skeletal muscle to relax
What causes malignant hyperthermia?
defective ryanodine receptor
What does malignant hyptherthermia look like?
fatal, produces pale, soft, ‘parboiled’ looking muscle
What does toxic myopathy cause?
causes monophasic or polyphasic necrosis
What is ionophore toxicity?
class of antibiotics used as feed additives
What is exertional myopathy?
- ionic and physical events associated with myofibre contraction can lead to myofibre necrosis in certain conditions
What is bacterial myosistis?
fairly common in livestock, response similiary
What occurs when there is decreased muscle loading?
atrophy
What is cachexia
weakness and wasting of the body due to insufficient dietary energy
What causes the hypercortisolism ‘pot belly’?
abdominal muscle atrophy
What is physiological hypertrophy?
normal response to exercise
What is compensatory hypertrophy?
occurs due to conditions that decrease the number of working mycofibres
What can compensatory hypertrophy lead to?
fibre splitting, which reduces diffusion distance
What is chronic myopathic change
- excessive fibre size
- fat infiltration and fibrosis- may result in increased muscle size
What is dystrophic
calcification?
A type of mineralisation that occurs in damaged or necrotic tissue in the body
e.g Ca2+ entering the sarcolemma
What is an innervation based anatomic defect
failure of innervation
congenital defects in lower motor neurons
such as arthrogryposis
What is the most common genetic defect?
defect in the myostatin gene
Congenital muscle hyperplasia due to increased number of myofibres
What are the most common failures of muscle development?
- Myofibrils fail to develop
- Congenital defects in diaphragmatic muscle
What is myotonia?
inability of the skeletal muscle to relax
results in spasmodic contraction
hyperkalemic periodic paralysis in quarter horses
What causes malignant hyperthermia?
defective ryanodine receptor
What is occlusion of a major artery?
aortilliac thrombosis
How does a nutritional deficiency cause muscle damage?
high metabolic activity of muscle makes it sensitive to free radical damage, needs antioxidants as a defence mechanism
What is the most common nutritional deficiency?
Selenium
Selenium protects cells from oxidative injury
What does muscle affected by nutritional deficiency look like?
Pale ‘white muscle disease’
When are livestock most prone to ingesting toxins
pasture, hay or processed feed
What is ionophore toxicity?
class of antibiotics used as feed alternatives
What is exertional myopathy?
ionic and physical events associated with myofibre contraction leads to myofibre necrosis in certain conditions
What is bacterial myositis?
fairly common in livestock, the response is similiar to response in bacterial infection anywhere else in the body
diffuse infection without an abscess
What do endocrine diseases lead to?
type 2 myofibre atrophy
What can electrolyte abnormalities cause?
profound weakness and myofibre necrosis
What is the definition of a neuromuscular disease?
Conditions with clinical signs primarily of muscle dysfunction
What can happen with compensatory hypertrophy?
Fibre splitting in order to reduce diffusion distance
What is global necrosis?
Necrosis of the entire fibre
What is segmental necrosis?
Necrosis of part of the muscle fibre
What mineral usually causes necrosis of muscle fibres
Ca2+ which can also go on to trigger necrosis in all cell types
* as a result, muscles are prone to mineralisation
What is an example of a disease caused by failure to innervate?
arthrogryposis in ruminants
severe alteration in myofibre innervation
What does a defect in the myostatin gene cause?
Congenital muscle hyperplasia due to an increased number of myofibres
What is the pathogenesis of true muscular dystrophy in dogs?
- Defect in the dystrophin gene allows gaps in the sarcoplasm
- Causes Calcium to enter the cell
- regulated necrosis and regeneration
- progressive cardiomyopathy and skeletal muscle wasting
What causes fainting goats?
Chloride Channel defect
What is exertional myopathy?
ionic and physical events that are associated with myofibre contraction that lead to myofibre necrosis
* often there is also a pre-existing condition
What does exertional myopathy relate to in horses?
Equine Polysaccharide storage myopathy
What introduces bacterial myositis?
- Direct penetration from wounds
- Haematogenous spread
- Spread from mearby cellulitis
What does Haemorrhagic myonecrosis look like?
- Red/ black areas with gas bubbles
- Clostridial species release toxins that are often acute, often fatal
What does pyogenic bacteria muscle disease look like?
- Localised suppurative and necrotising myosistis
- may resolve completely or become an abscess
What occurs in immune-mediated myositis?
Cytotoxic T lymphocytes damage myofibres
What does endocrine disease lead to?
Endocrine disease leads to type II myofibre atrophy
* neuropathy and denervation atrophy (resulting altered fibre type pattern)
What do electrolyte abnormalities cause?
- Profound weakness, sometimes myofibre necrosis
