Skeletal Muscle Fiber Location and Arrangement

Author: Scott A. Sheffield MS

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Skeletal muscle fibers are located inside muscles, where they are organized into bundles called image descriptionfascicles (= fasciculi).

Cross-section of the thigh showing muscle bundles and their surrounding sheaths.
Cross-section of the thigh showing muscle bundles and their surrounding sheaths.
Cross-section of the thigh showing muscle bundles and their surrounding sheaths.
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  • image descriptionThe epimysium is the connective tissue layer that covers the outer surface of the muscle
Cross-section of the thigh showing muscle bundles and their surrounding sheaths.
Cross-section of the thigh showing muscle bundles and their surrounding sheaths with the epimysium labelled.
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Surrounding and holding together each fascicle is a layer of connective tissue known as image descriptionperimysium.

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Cross-section of the thigh showing muscle bundles and their surrounding sheaths with the epimysium labelled.
Cross-section of the thigh showing muscle bundles and their surrounding sheaths with the epimysium and perimysium labeled.
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Portions of the perimysium extend into the fascicle and merge with the image descriptionendomysium, a thin layer of areolar connective tissue that covers each muscle fiber.

Cross-section of the thigh showing muscle bundles and their surrounding sheaths with the epimysium and perimysium labeled.
Cross-section of the thigh showing muscle bundles and their surrounding sheaths with the epimysium, perimysium and endomysium labeled.
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In the deep fascia around the muscles are several large image descriptionarteries, veins, and nerves. Branches of these vessels and nerves penetrate each muscle close to its midpoint, then extend into the epimysium and perimysium layers. In the endomysium, individual muscle fibers (cells) are supported by nearby capillaries and nerve cells.

Cross-section of the thigh showing muscle bundles and their surrounding sheaths with the epimysium, perimysium and endomysium labeled.
Cross-section of the thigh showing muscle bundles and their surrounding sheaths with the epimysium, perimysium and endomysium labeled.
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Skeletal Muscle Fiber Location and Arrangement