Muscle Fibres

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•  Skeletal muscle fibres are multinucleate and contain specialised endoplasmic reticulum

•  Muscle fibres contain many myofibrils

Organisation of Skeletal Muscles

  • Skeletal muscles consist of tightly packaged muscular bundles (fascicles) surrounded by connective tissue (perimysium)
  • Each bundle contains multiple muscle fibres, which are formed when individual muscle cells fuse together
  • Muscle fibres contain tubular myofibrils that run the length of the fibre and are responsible for muscular contraction
  • The myofibrils can be divided into repeating sections called sarcomeres, each of which represent a single contractile unit 

Structural Arrangement of Skeletal Muscles

muscle organisation

Muscle Fibre Structure

Each individual muscle fibre has the following specialised features designed to facilitate muscle contraction:

  • They are multinucleate (fibres form from the fusion of individual muscle cells and hence have many nuclei)
  • They have a large number of mitochondria (muscle contraction requires ATP hydrolysis)
  • They have a specialised endoplasmic reticulum (it is called the sarcoplasmic reticulum and stores calcium ions)
  • They contain tubular myofibrils made up of two different myofilaments – thin filament (actin) and thick filament (myosin)
  • The continuous membrane surrounding the muscle fibre is called the sarcolemma and contains invaginations called T tubules

Components of A Skeletal Muscle Fibre

   Component:         Labelled             Nucleus             Mitochondria           Myofibril            Sarcoplasmic Reticulum        Sarcolemma