myofibril

Myofibrils (obsolete term: sarcostyles) are cylindrical organelles, found within muscle cells. They are bundles of actomyosin filaments that run from one end of the cell to the other and are attached to the cell surface membrane at each end. Actomyosin motors are important in muscle contraction (relying in this case on "classical myosins") as well as other processes like retraction of membrane blebs, filiopod retraction, and uropodium advancement (relying in this case on "nonclassical myosins").
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Noun
1. one of many contractile filaments that make up a striated muscle fiber
(synonym) myofibrilla, sarcostyle
(hypernym) fibril, filament, strand
(part-holonym) striated muscle cell, striated muscle fiber
(part-meronym) sarcoplasm