One of the fine longitudinal fibrils occurring in a skeletal or cardiac muscle fiber comprising many regularly overlapped ultramicroscopic thick and thin myofilaments. SYN: muscular fibril, myofibrilla. [myo- + Mod. L. fibrilla, fibril]
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myo·fi·bril .mī-ō-'fīb-rəl, -'fib- n one of the longitudinal parallel contractile elements of a muscle cell that are composed of myosin and actin
myo·fi·bril·lar -rə-lər adj
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n.
one of numerous contractile filaments found within the cytoplasm of striated muscle cells. When viewed under a microscope myofibrils show alternating bands of high and low refractive index, which give striated muscle its characteristic appearance.
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myo·fi·bril (mi″o-fiґbril) muscle fibril: one of the slender threads that can be made visible in a muscle fiber by maceration in certain acids. They run parallel with the long axis of the fiber, and are composed of numerous myofilaments (q.v.). See Plate 32. myofibrillar adjMedical dictionary. 2011.