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Location Muscles associated with the skeleton (are connected to
bones by tendons).
Platisma and mimic muscles
Voluntary sphincters of
inner organs
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SKELETAL MUSCLE --- is innervated by the somatic nervous
system – voluntary!! ---- consists of very long tubular
cells (also called muscle fibres).
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SKELETAL MUSCLE Skeletal muscle fibers run the full length
of a muscle.
The average length of skeletal muscle
cells in humans is about 3 cm (sartorius muscle up to 30 cm, stapedius muscle only about 1 mm). Their diameters vary from 10 to 100 µm.
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Nuclei: Skeletal muscle fibres contain many nuclei (up to several
hundred ) placed beneath the plasma membrane
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Myofibrils
Mechanism of contraction:
Sliding filaments model
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Myofibrils has some bands and lines depending on
the distribution and interconnection of myofilaments -- : I-band
- actin filaments only, A-band - myosin filaments which may overlap with actin filaments T or Z-line -- band of connections between actin filaments; zone of apposition of actin filaments belonging to two neighboring sarcomeres; M-line - band of connections between myosin filaments. H-band - zone of myosin filaments only (no overlap with actin filaments) within the A-band