what are tonofilaments
tonofilament[tonâ²Å-filâ²Ä-ment] 1. A structural cytoplasmic protein, of a class known as intermediate filaments, bundles of which together form a tonofibril; a tonofilament is made up of a variable number of related proteins, keratins, and is found in all epithelial cells, but is particularly well developed in the epidermis.