T Tubules

T Tubules, a term abbreviated from the their full name Transverse Tubules, are tunnel-like extensions of sarcolemma that pass through muscle cells (which are also called 'muscle fibres' and 'muscle fibers') from one side of the cell to the other.

It is due to the side-to-side, i.e. across the muscle, orientation of these structures that they are referred to as "transverse".


The functions of T-tubules

T tubules play an important role in the physiology of muscle contraction:

  • Muscle action potential, which is the movement of electrical charge, travelling along T tubules triggers the release of calcium(2+) ions from the sarcoplasmic reticulum.
  • This allows the calcium (2+) ions to flood into the sarcoplasm,
  • ... which causes actions and movements of proteins (including actin, myosin, troponin, and tropomyosin) within the myofibrils that eventually result in muscle contraction.


See also more about the types of muscle contraction.


This section consists of short summaries about the structures that form the muscles of the body. This list is not exhaustive but is intended to be appropriate for students of A-Level Human Biology, ITEC courses in massage and related subjects, and other courses in health sciences. For more general information about muscles see the pages about:

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