describe the structure of striated muscle

Straited muscles:
se have striped appearance under the microscope. Therefore, they are called striated muscles. For example skeletal muscle.

  • Each skeletal muscle in the body is made of muscle bundles or fascicles. Each fascicle is held together by fascia (collagenous connective tissue layer).

  • Muscle bundle: A collection of many muscle fibres

  • Muscle fibre: Has sarcoplasm lined by sarcolemma (plasma member). It has the sarcoplasmic reticulum (endoplasmic reticulum) which is a storehouse for calcium ions.

  • Myofibrils or myofilaments (parallel arrangement of filaments) are present inside the sarcoplasm of muscle fibre.

  • Structure of Myofibril:

    • Each myofibril has alternate light and dark bands on it (striated appearance).

    • Light band: Contains the protein actin and is called the I band (Isotropic band)

    • Dark band: Contains the protein myosin and is called the A band (anisotropic band)

    • Actin: Thin filament; Myosin: Thick filament

    • Actin and myosin are arranged parallel to each other as rod-like structures.

    • Z line: An elastic fibre which bisects the I band. Portion between two Z lines represents a functional sarcomere.

    • In resting state, the thick filament partially overlaps the free ends of the thin filament.

    • H zone: The zone where the thick filaments are not overlapped by the free ends of the thin filament

    • M line: Holds the dark band at the centre; thus, it bisects the H zone. 

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