Difference between revisions of "Muscles - Anatomy & Physiology"

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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
 
  
  

Revision as of 11:10, 18 July 2008

BACK TO MUSCULOSKELETAL ANATOMY AND PHYSIOLOGY


Introduction

  • Skeletal muscle includes muscles of:
    • Posture
    • Movement
    • Respiration


  • Two basic types of skeletal myofibre:
    • Type I
      • Grossly red
      • High myoglobin level
      • Slow rate of contraction
      • High oxidative activity
      • Function - postural
    • Type II
      • Grossly white
      • Low myoglobin level
      • Fast rate of contraction
      • High glycolytic activity
      • Function - exercise


  • Each muscle is composed of multiple fascicles
    • Each fascicle is composed of multiple polygonal myofibres




Rigor Mortis

  • Muscles remain biochemically active after the death of an animal
  • Following a period of relaxation, contraction and stiffening occurs
  • Due to deficiency of ATP releasing myosin heads from their binding sites at end of power stroke
  • Onset faster in ATP deprived animals (starvation, hunting, tetanus...)
  • May be absent in cachetic animals
  • Disappears due to autolysis or putrefaction
  • See general pathology


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