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| − | ===Regeneration===
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| − | [[Image:Muscle regeneration.jpg|right|thumb|100px|<small><center>Muscle regeneration (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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| − | *Skeletal muscle myofibres have substantial regenerative ability
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| − | *Success depends on:
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| − | **An intact '''sarcolemmal tube''' - to act as a support and guide
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| − | **Availability of '''satellite cells''' - to act as progenitor cells for new sarcoplasm production
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| − | **Macrophages to clear up cell debris
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| − | **If these conditions are not met (e.g. severe thermal damage) '''fibrosis''' will occur
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| − | *Stages:
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| − | #Nuclei in [[Muscles - degenerative#Necrosis|necrotic segement]] disappear, hyalinased sarcoplasm due to loss of normal myofibrillar structure, may separate from adjacent normal myofibrils and/or [[Muscles - degenerative#Calcification|mineralise]]
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| − | #Monocytes from capillaries -> macrophages in necrotic portion, satellite cells swell -> vesicular with prominent nucleoli -> mitosis (within 1-4 days after initial injury)
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| − | #Satellite cells move to centre
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| − | #Macrophages clear the sacrolemmal tube, plasmalemma disappears, shape maintained by basal lamina
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| − | #Satellite cells -> myoblasts (contain myosin) -> fuse forming myotubes with row of central nuclei; cytoplasmic processes fusing
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| − | #Growing and differentiating fibre, striations appear - formation of sarcomeres
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| − | #Nuclei move to peripheral position (2-3 weeks after initial injury)
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| − | *Regeneration by '''budding'''
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| − | **When conditions are not optimal, disrupted sacrolemma
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| − | **E.g. injection of irritating substance, trauma, [[Muscles - degenerative#Ischaemia|infarction]]
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| − | **Myoblasts proliferate -> sacrolamma bulges from cut part -> club-shaped with numerous central nuclei = muscle giant cells
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| − | *Monophasic lesions - all at same phase above
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| − | **Damage occured at one time, e.g. trauma or one toxin exposure
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| − | *Multiphasic lesions - different stages as described above
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| − | **Ongoing damage, e.g. vitamin E - selenium deficiency, continuous exposure to toxin
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