Structure of Skeletal Muscle -
- Each organised skeletal muscle in our body is made of a number of muscle bundles or fascicles held together by a common collagenous connective tissue layer called fascia or epimysium.
- Each muscle bundle or fascicle is surrounded by a perimysium.
- Each muscle bundle or fascicle contains a number of muscle fibres or myofibers. These are the muscle cells.
- The myofibres are covered with endomysium.
- Each myofiber is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm.
- The muscle fibre is a syncytium as the sarcoplasm contains many nuclei.
- The endoplasmic reticulum, i.e., the sarcoplasmic reticulum of muscle fibres is the storehouse of calcium ions.
- A characteristic feature of the muscle fibre is the presence of a large number of parallelly arranged filaments in the sarcoplasm called myofilaments or myofibrils.
- Each myofibril has alternate dark and light bands on it.
- A detailed study of the myofibril has established that the striated appearance is due to the distribution pattern of two important proteins – Actin and Myosin.
- The light bands contain actin and are called I-band or Isotropic bands, whereas the dark band called ‘A’ or Anisotropic band contains myosin.
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Each myofiber is lined by the plasma membrane called sarcolemma enclosing the sarcoplasm. Hence, the correct option is sarcolemma
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