Sarcoplasm is the cytoplasm of a myocyte (muscle fiber, muscle cell). It is comparable to the cytoplasm of other cells, but it contains unusually large amounts of glycosomes (granules of stored glycogen) and significant amounts of myoglobin, an oxygen-binding protein. 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.[1][2]

Muscle system
LocationCytoplasm of myocyte
Anatomical terms of microanatomy

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).[3]

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.[1][2][3]


  1. Mescher, Anthony L. Junqueira's basic histology : text and atlas. Junqueira, Luiz Carlos Uchôa, 1920- (Thirteenth ed.). New York. ISBN 9780071807203. OCLC 854567882.
  2. 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.
  3. 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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