Soft tissue tumors - Skeletal muscle-normal

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Soft tissue tumors

Skeletal muscle

Skeletal muscle-normal

Reviewer: Vijay Shankar, M.D. (see Reviewers page)
Revised: 18 February 2013, last major update November 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

Definition
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● Normal skeletal muscle arises from mesectoderm in head and neck and from myotomes (group of skeletal muscles supplied by a specific segmental spinal nerve), and elsewhere via formation of myoblasts and myotubes (muscle fibers)
● Contains myofibrils composed of thin (actin) and thick (myosin) filaments

Terminology
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● Skeletal muscle cells are also called myofibers or myocytes

Embryologic images
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Various images

Diagrams
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Various images

Section of myofibrils with sarcoplasmic reticulum (SR) and T-tubules (T)

Various images

Micro description
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● Long cylindrical cells, unbranched and striated
● Multinucleated syncytia, formed by fusion of single cells
● Nuclei are peripheral to the myofiber

Micro images
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Various images

Longitudinal and transverse sections

Skeletal muscle vasculature

Normal striated muscle

Electron microscopy description
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● Electron microscopy reveals structural components:
● I (isotropic) band: thin filaments only
● A (anisotropic) band: overlapping thin and thick filaments
● H band: thick filaments only
● Z line: divides center of I band; serves as attachment site for the sarcomere, the repeating individual unit of the muscle fiber

Electron microscopy images
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Various images

Additional references
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● Wikipedia, Slideshow of the sliding filament model (ppt)

End of Soft tissue tumors > Skeletal muscle > Skeletal muscle-normal

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