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(cell and molecular biology)
Any of the fibrils converging on desmosomes in epithelial cells.



a filamentous formation in the epithelial cells of animals. While tonofibrils were previously thought to extend from one cell to another, electron-microscope investigations have disproved the notion that such formations are continuous. It has been shown that they converge in the region of the desmosomes, where they bend and reenter the core of the cell. The usual diameter of a tonofibril is approximately 60 angstroms. It is likely that tonofibrils ensure the mechanical stability of cells.

References in periodicals archive ?
The reported ultrastructural features of PCE include the presence of microvilli, lacy cytoplasm, and abundant tonofibrils.
The exact percentage of glassy cells needed to make the diagnosis of GCC is not well established, but it may range from 30% to 100%[1,9] Ultrastructurally, glassy cells may show intermediate filaments, polyribosomes, tonofibrils, and desmosomes.
Few primitive desmosomes and sparse tonofibrils were rarely observed.