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Figure 38 04 02.jpg
Sarcoplasm shown with a muscle fiber
LocationCytoplasm of muscle cell
Anatomical terms of microanatomy

Sarcoplasm is the cytoplasm of a muscle cell. It is comparable to the cytoplasm of other cells, but it contains unusually large amounts of glycogen (a polymer of glucose), myoglobin, a red-colored protein necessary for binding oxygen molecules that diffuse into muscle fibers, and mitochondria.[1][2][3] The calcium ion concentration in sarcoplasma is also a special element of the muscle fiber; it is the means by which muscle contractions take place and are regulated.[4][5] The sarcoplasm plays a critical role in muscle contraction as an increase in Ca2+ concentration in the sarcoplasm begins the process of filament sliding. A decrease in Ca2+ in the sarcoplasm subsequently ceases filament sliding.[6] The sarcoplasm also aids in pH and ion balance within muscle cells.[3]

It contains mostly myofibrils (which are composed of sarcomeres), but its contents are otherwise comparable to those of the cytoplasm of other cells. It has a Golgi apparatus near the nucleus, mitochondria just inside the cell membrane (sarcolemma), and a smooth endoplasmic reticulum (specialized for muscle function and called the sarcoplasmic reticulum).[7]

While sarcoplasm and myoplasm, viewed etymologically, might seem to be synonyms, they are not. Whereas sarcoplasm is a type of cytoplasm, myoplasm is the entire contractile portion of muscle tissue.[4][5][7]


  1. ^ Douplik, A (2013) The response of tissue to laser light. Woodhead Publishing. pp. 47–109. ISBN 9780857092373.
  2. ^ Toumanidou, Themis (2018). Chapter 9 - Spinal Muscles. Academic Press. pp. 141–166. ISBN 9780128128510.
  3. ^ a b Roberts, Michael D.; Haun, Cody T.; Vann, Christopher G.; Osburn, Shelby C.; Young, Kaelin C. (2020). "Sarcoplasmic Hypertrophy in Skeletal Muscle: A Scientific "Unicorn" or Resistance Training Adaptation?". Frontiers in Physiology. 11. doi:10.3389/fphys.2020.00816. ISSN 1664-042X. PMC 7372125. PMID 32760293.
  4. ^ a b Mescher, Anthony L. (22 February 2013). Junqueira's basic histology : text and atlas. Junqueira, Luiz Carlos Uchôa, 1920- (Thirteenth ed.). New York. ISBN 9780071807203. OCLC 854567882.
  5. ^ a b Ross, Michael H. (2011). Histology : a text and atlas : with correlated cell and molecular biology. Pawlina, Wojciech. (6th ed.). Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins Health. ISBN 9780781772006. OCLC 548651322.
  6. ^ Shahinpoor, Mohsen (2013). Muscular Biomimicry. Elsevier. pp. 139–160. ISBN 9780124159952.
  7. ^ a b Trovato, Francesca Maria; Imbesi, Rosa; Conway, Nerys; Castrogiovanni, Paola (22 July 2016). "Morphological and Functional Aspects of Human Skeletal Muscle". Journal of Functional Morphology and Kinesiology. 1 (3): 289–302. doi:10.3390/jfmk1030289.

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