myofilaments

my·o·fil·a·ments

(mī'ō-fil'ă-ments), The ultramicroscopic threads of filamentous proteins making up myofibrils in striated muscle. Thick ones contain myosin and thin ones mostly actin; thick and thin myofilaments also occur in smooth muscle fibers but are not regularly arranged in discrete myofibrils and thus do not impart a striated appearance to these cells.

my·o·fil·a·ments

(mī'ō-fil'ă-mĕnts) The ultramicroscopic threads of filamentous proteins making up myofibrils in striated muscle. Thick ones contain myosin and thin ones, actin; thick and thin myofilaments also occur in smooth muscle fibers but are not regularly arranged in discrete myofibrils and thus do not impart a striated appearance to these cells.