Musculoskeletal Pathology III

Question 1

Name three cytoarchitectural changes of degeneration

Answer 1

1. Vacuolar change
2. Internal nuclei
3. Whorled and ring fibres

Question 2

What is the chronic myopathic change?

Answer 2

• Excessive fibre size
• fat infiltration and fibrosis

Question 3

What is segmental necrosis?

Answer 3

• Sarcoplasm begins to fragment
• Fragmented cytoplasm can mineralise
• Circulating monocytes infiltrate and mature to macrophages

Question 4

In what animals does true muscular dystrophy occur?

Answer 4

Golden Retriever, Rottweilers

Question 5

What is myotonia?

Answer 5

inability of skeletal muscle to relax

Question 6

What causes malignant hyperthermia?

Answer 6

defective ryanodine receptor

Question 7

What does malignant hyptherthermia look like?

Answer 7

fatal, produces pale, soft, ‘parboiled’ looking muscle

Question 8

What does toxic myopathy cause?

Answer 8

causes monophasic or polyphasic necrosis

Question 9

What is ionophore toxicity?

Answer 9

class of antibiotics used as feed additives

Question 10

What is exertional myopathy?

Answer 10

• ionic and physical events associated with myofibre contraction can lead to myofibre necrosis in certain conditions

Question 11

What is bacterial myosistis?

Answer 11

fairly common in livestock, response similiary

Question 12

What occurs when there is decreased muscle loading?

Answer 12

atrophy

Question 13

What is cachexia

Answer 13

weakness and wasting of the body due to insufficient dietary energy

Question 14

What causes the hypercortisolism ‘pot belly’?

Answer 14

abdominal muscle atrophy

Question 15

What is physiological hypertrophy?

Answer 15

normal response to exercise

Question 16

What is compensatory hypertrophy?

Answer 16

occurs due to conditions that decrease the number of working mycofibres

Question 17

What can compensatory hypertrophy lead to?

Answer 17

fibre splitting, which reduces diffusion distance

Question 18

What is chronic myopathic change

Answer 18

• excessive fibre size
• fat infiltration and fibrosis- may result in increased muscle size

Question 19

What is dystrophic
calcification?

Answer 19

A type of mineralisation that occurs in damaged or necrotic tissue in the body

e.g Ca2+ entering the sarcolemma

Question 20

What is an innervation based anatomic defect

failure of innervation

Answer 20

congenital defects in lower motor neurons

such as arthrogryposis

Question 21

What is the most common genetic defect?

Answer 21

defect in the myostatin gene

Congenital muscle hyperplasia due to increased number of myofibres

Question 22

What are the most common failures of muscle development?

Answer 22

1. Myofibrils fail to develop
2. Congenital defects in diaphragmatic muscle

Question 23

What is myotonia?

Answer 23

inability of the skeletal muscle to relax

results in spasmodic contraction

hyperkalemic periodic paralysis in quarter horses

Question 24

What causes malignant hyperthermia?

Answer 24

defective ryanodine receptor

Question 25

What is occlusion of a major artery?

Answer 25

aortilliac thrombosis

Question 26

How does a nutritional deficiency cause muscle damage?

Answer 26

high metabolic activity of muscle makes it sensitive to free radical damage, needs antioxidants as a defence mechanism

Question 27

What is the most common nutritional deficiency?

Answer 27

Selenium | Selenium protects cells from oxidative injury

Question 28

What does muscle affected by nutritional deficiency look like?

Answer 28

Pale 'white muscle disease'

Question 29

When are livestock most prone to ingesting toxins

Answer 29

pasture, hay or processed feed

Question 30

What is ionophore toxicity?

Answer 30

class of antibiotics used as feed alternatives

Question 31

What is exertional myopathy?

Answer 31

ionic and physical events associated with myofibre contraction leads to myofibre necrosis in certain conditions

Question 32

What is bacterial myositis?

Answer 32

fairly common in livestock, the response is similiar to response in bacterial infection anywhere else in the body | diffuse infection without an abscess

Question 33

What do endocrine diseases lead to?

Answer 33

type 2 myofibre atrophy

Question 34

What can electrolyte abnormalities cause?

Answer 34

profound weakness and myofibre necrosis

Question 35

What is the definition of a neuromuscular disease?

Answer 35

Conditions with clinical signs primarily of muscle dysfunction

Question 36

What can happen with compensatory hypertrophy?

Answer 36

Fibre splitting in order to reduce diffusion distance

Question 37

What is global necrosis?

Answer 37

Necrosis of the entire fibre

Question 37

What is segmental necrosis?

Answer 37

Necrosis of part of the muscle fibre

Question 38

What mineral usually causes necrosis of muscle fibres

Answer 38

Ca2+ which can also go on to trigger necrosis in all cell types * as a result, muscles are prone to mineralisation

Question 39

What is an example of a disease caused by failure to innervate?

Answer 39

arthrogryposis in ruminants | severe alteration in myofibre innervation

Question 40

What does a defect in the myostatin gene cause?

Answer 40

Congenital muscle hyperplasia due to an increased number of myofibres

Question 41

What is the pathogenesis of true muscular dystrophy in dogs?

Answer 41

* 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

Question 42

What causes fainting goats?

Answer 42

Chloride Channel defect

Question 43

What is exertional myopathy?

Answer 43

ionic and physical events that are associated with myofibre contraction that lead to myofibre necrosis * often there is also a pre-existing condition

Question 44

What does exertional myopathy relate to in horses?

Answer 44

Equine Polysaccharide storage myopathy

Question 45

What introduces bacterial myositis?

Answer 45

* Direct penetration from wounds * Haematogenous spread * Spread from mearby cellulitis

Question 46

What does Haemorrhagic myonecrosis look like?

Answer 46

* Red/ black areas with gas bubbles * Clostridial species release toxins that are often acute, often fatal

Question 47

What does pyogenic bacteria muscle disease look like?

Answer 47

* Localised suppurative and necrotising myosistis * may resolve completely or become an abscess

Question 48

What occurs in immune-mediated myositis?

Answer 48

Cytotoxic T lymphocytes damage myofibres

Question 49

What does endocrine disease lead to?

Answer 49

Endocrine disease leads to type II myofibre atrophy * neuropathy and denervation atrophy (resulting altered fibre type pattern)

Question 50

What do electrolyte abnormalities cause?

Answer 50

* Profound weakness, sometimes myofibre necrosis