58 - Diseases of the musculoskeletal system 2 Flashcards Preview

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Flashcards in 58 - Diseases of the musculoskeletal system 2 Deck (26):
1

Components of muscle fibre

Basal lamina
Plasma membrane
Mitochondria
Sarcoplasmic reticulum
Myofibrils
Myonuclei

2

Functional systems of a myocyte

Ion fluxes
Neuromuscular transmission
Excitation-contraction coupling
Oxidative phosporylation
mRNA transport

3

Neurogenic atrophy

Two populations of small and large f
Small angulated f
Group atrophy
Fibre grouping
Target f
Pyknotic nuclear clumps

4

Most common muscle biopsy site

quadriceps

5

Sarcolemma

Basal lamina - links muscle fibres to endomyseal connective tissue, survives muscle fibres necrosis and acts as a platform for satellite cell proliferation.

Plasma membrane forms a barrier between extra and intracellular space

6

DMD

Rarely biopsied as can test genes.
Chair-bound by 12 years old

7

Diseases of myonucleus

Limb girdle muscular dystrophy 1B or Emery-Dreifuss muscular dystrophy

Centronuclear myopathies (should be at the side) causing myotubular myopathy.

8

Emery-Dreifuss

XL
Weakness of proximal arm and distal leg muscle
Early contactures
Cardiomyopathy

9

Limb girdle muscular dystrophy

Heterogenous
Phenotypic overlap with spinal muscular atrophy and BMD
Histochemistry needed

10

Core disease

not detected until child has started walking
AD
Central core is a well demarkated zone in the central of the muscle fibre devoid of NADH. Cores only occur in type I fibres.

Issue is malignant hyperthermia (can die from resp. paralysis)

11

Nemaline myopathy

AR
Children
Problem with sarcomere
Resp. insufficiency
High arched palate
Kyphoscoliosis
Loss of cell structure

12

Ion channel disorder

Cl- ad Na+ is associated with malignant hyperthermia also

13

Malignant hyperthermia

Abnormal susceptibility to certain anaesthetic agents.

Prolonged rise in intracellular Ca2+ ions
Rigid contractions and elevation in body temperatures

14

Complex molecular defects

Repeat expansion disease -> myotonic dystrophy, oculopharyngeal muscular dystrophy

Large telomeric deletion disease -> facioscapulohumeral dystrophy

15

Myotonic dystrophy

AD
Myotonia and progressie weakness of facial muscle
Onset - 20-30 yrs
Cardiac conduction defects

16

Myotonic dystrophy histology

Selective atrophy of type I fibres
Type II hypertrophy
Paucity of type IIb fibres
Central nuclei are an early feature
Motheaten and targetoid fibres
Ring fibres common

17

Facioscapulohumeral dystrophy

AD
Affects myocardium
Associated with progressive deafness
Retinal vasculopathy

18

Developed disorders

XL myotubular myopathy
Congenital fibre-type disproportion

19

Disorders of catabolic mechanisms

Lysosomal disorders
Proteolytic disturbances

20

Neuromuscular transmission defects

Neurogenic muscle disease
Myasthenia gravis
Lambert-eaton myasthenic syndrome
Congenital myasthenic syndrome

21

Myasthenia gravis

Autoimmune diseases with antibodies IgG against Ach receptor. Do not get any muscle contraction due to no Ach binding.
Muscle biopsy not an appropriate diagnostic test because it cannot be tested. Needs to be clinically diagnosed.

22

Eaton-Lambert myasthenic syndrome

Rare non-metastatic manifestation of malignancy, usually oat-cell carcinoma of the bronchus
Gives you atrophic fibres

23

Dermatomyositis

Inflammatory myopathy responsible for chronic debilitating disease
Associated with a scaly rash

24

Dermatomyositis histology

mononuclear infiltration of muscle with fibre necrosis and replacement fibrosis

25

Drug induced myopathies

Statin myopathy
Steroid induced

Most severe causes necrotising myopathy causing rhabomyolysis, myoglobinuria and renal failure - caused by heroin and renal failure

26

Motor neuron disease

Progressive disease of middle to old age
Widespread degeneration of motor neurons
Involves ant. horn cells, brain stem nuclei and Betz cells.
Upper and lower motor neuron signs with wasting

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