• A fine reticular network of membrane-limited elements that pervades the sarcoplasm of a muscle cell; continuous over large portions of the cell and with the nuclear envelope; that part of the endoplasmic reticulum specialized for calcium release, uptake and storage.
  Gene Ontology Dictionary
  Gene Ontology Consortium, 2021
• A network of tubules and sacs in the cytoplasm of SKELETAL MUSCLE FIBERS that assist with muscle contraction and relaxation by releasing and storing calcium ions.
  NLM Medical Subject Headings
  U.S. National Library of Medicine, 2025
• Special form of agranular reticulum found in the sarcoplasm of striated muscle and comprising a system of smooth surfaced tubules forming a plexus around each myofibril.
  CRISP Thesaurus
  National Institutes of Health, 2006
• The endoplasmic reticulum of striated muscle, specialised for the sequestration of calcium ions that are released upon receipt of a signal relayed by the T tubules from the neuromuscular junction.
  NCI
  U.S. National Cancer Institute, 2021
• Sarcoplasmic reticulum, intracellular system of closed saclike membranes involved in the storage of intracellular calcium in striated (skeletal) muscle cells. Each segment of the sarcoplasmic reticulum forms a cufflike structure surrounding a myofibril, the fine contractile fibres that extend the...
  Encyclopedia Britannica
  Encyclopedia Britannica, Inc., 2025