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Jun 28 2010, 4:09 AM EDT (current) AndyC
Jun 28 2010, 4:04 AM EDT AndyC 1 word added

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Muscle

  • Consists predominantly of contractile cells and produces the movements of various parts of the body by contraction.
  • Occurs in three types: skeletal, cardiac and smooth

Skeletal Muscle

  • Is voluntary and striated; makes up about 40% of the total body mass; and functions to produce movement of the body, generate body heat, and maintain body posture.
  • Has two attachments, an origin (which is usually the more fixed and proximal attachment), and an insertion (which is the more movable and distal attachment).
  • Is enclosed by epimysium , a thin layer of connective tissue. Smaller bundles of muscle fibers are surrounded by perimysium. Each muscle fiber is enclosed by endomysium.

Cardiac Muscle
  • Is involuntary and striated and forms the myocardium , the middle layer of the heart.
  • Is innervated by the autonomic nervous system but contracts spontaneously without
    any nerve supply.
  • Includes specialized myocardial fibers that form the cardiac conducting system.

Smooth Muscle
  • Is involuntary and nonstriated, and generally arranged in two layers, circular and longitudinal , in the walls of many visceral organs.
  • Is innervated by the autonomic nervous system, regulating the size of the lumen of
    a tubular structure.
  • Undergoes rhythmic contractions called peristaltic waves in the walls of the
    gastrointestinal (GI) tract, uterine tubes, ureters, and other organs.



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