Lecture: Muscles and Muscle Tissue 4

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  1. Female and Male
    female skeletal muscle makes up 36% of body mass

    male skeletal muscle makes up 42% of body mass

    muscle strength per unit is the same in both sexes
  2. With Age...
    With age, connective tissue increases and muscle fiber decreases

    By age 30, loss of muscle mass (sarcopenia) begins

    regular exercise reverses sarcopenia

    Atheroscerosis may block distal arteries, leading to intermittent claudication and sever pain in leg muscles
  3. Muscular Dystrophy
    Group of inherited muscle-destroying diseases

    Muscles enlarge due to fat and connective tissue deposits

    Muscle fibers astrophy
  4. Duchenne Muscular Dystrophy (DMD)
    Most common and sever type

    Inherited, sex linked, carried by femailed and expressed in males (1/3500) as lack of dystrophin

    Victims become clumsy and fall frequently; usually die of respiratory failure in their 20s

    no cure, but Viral gene therapy or infusion of stem cells with correct dystrophin genes show promise
  5. Regeneration
    Cardiac and Skeletal cells become amitotic, but can lengthen and thickn

    Myoblast like skeletal muscle cells have limited regenerative ability

    Injured heart muscle is mostly replaced by connective tissue

    -Smooth muscle regenerates throughout life
  6. Development and formation
    All muscle tissue develop from embryonic myoblasts

    Multinucleated skeletal muscle cells form by fusion

    Growth factor agrin stimulates clusting of ACh receptors at neuromuscular junctions

    Cardiac and smooth muscle myoblasts develop gap junctions
  7. Developmental Aspects
    muscular development reflects neuromuscular coordination

    Development occurs head to toe, and promixmal to distal

    peak natural neural control occurs by mid-adolescence

    Athletics and training can improve neuromuscular control
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Lecture: Muscles and Muscle Tissue 4
Developmental aspects
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