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9.6E: Arrangement of Fascicles

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    7557
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    Skeletal muscles are grouped into fascicles, which are bunches of muscle fibers surrounded by a perimysium.

     

    LEARNING OBJECTIVES

     

    Outline the construction of a muscle fascicle

     

    KEY TAKEAWAYS

    Key Points

     

    • Skeletal muscle is surrounded by a thick connective sheet termed the fascia
    • Underneath this is another layer of connective tissue called the epimysium, which extends inwards as the perimysium into the muscle, splitting fibers into bundles termed fascicles.
    • Each fascicle is surrounded by another layer of connective tissue termed the endomysium.
    • This structure separates and protects the muscle and also acts to spread force throughout the muscle, preventing damage.

     

    Key Terms

     

    • perimysium: The continuation of the epimysium into the muscle, splitting fibers into fascicles.
    • epimysium: A sheet of connective tissue lying below the fascia, also surrounding a muscle.
    • fascia: A sheet of thick connective tissue which surrounds a muscle.
    • endomysium: A sheet of connective tissue which wraps each fascicle.
    • fascicle: A group of muscle of fibers surrounded by the perimysium.

     

    Muscle Fascia

    This diagram depicts the organization of connective tissue in the structure of the muscle. Terms include skeletal muscle, epimysium, muscle fascicles, perimysium, endomysium, muscle fibers, sarcolemma.

     

     

    Muscle Structure: Skeletal muscle is surrounded by a thick outer layer of connective tissue termed the fascia. Within this is a layer termed the epimysium which splits inwards into the muscle as the perimysium dividing muscle fibers into groups termed fascicle. Each fascicle is surrounded by another layer of connective tissue termed the endomysium.

    Skeletal muscle tissue is composed of numerous muscle fibers which are separated from adjacent muscles and other tissues by a layer of dense, elastic connective tissue termed the fascia. This fascia can project beyond the end of the muscle and attach to bones, other muscles, and other tissues. Key muscle groups and the associated vascular and nervous systems can also be separated from other tissue, such as in the upper arm. These groupings are called fascial compartments.

    This fascia is interlinked with a serious of fascia found throughout the body, including the superficial fascia which is the lowermost layer of the skin and the visceral fascia which surrounds internal organs. The fascia surrounding a muscle or muscle group does not contain many blood vessels, but is rich with sensory receptors.

    Muscle fascia is predominately composed of cross-linked collagen and elastin fibers oriented parallel to the direction of muscle force, making them able to resist high-tension forces while remaining somewhat elastic.

     

    Fascicles

     

    Beneath the fascia in skeletal muscle is another layer of connective tissue termed the epimysium which is closely associated with the fascia. It extends inwards and becomes the perimysium, then into the muscle separating muscle fibers into small bundles termed fascicles. Fascicles can be arranged in a variety of anatomical positions within a muscle, producing different movements.

    Each individual fiber within a fascicle is surrounded by a thin connective layer termed the endomysium, which helps maintain close association between the muscle fiber and associated vascular and nervous systems.

    The organization of connective tissue throughout and around a muscle provides strength and flexibility while distributing the force evenly. It also maintains the close association of the vascular and nervous system with the muscle, which is required to deliver necessary metabolites and nerve impulses.

     

    Cardiac and Smooth Muscle Tissue

     

    Whilst both cardiac and smooth muscles are also wrapped in connective tissue, they are not differentiated in the same way as skeletal muscles.

     

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