INTERMEDIATE FILAMENTS
Intermediate filaments are one of three kinds of filaments (cytoplasmic fibrillous (thread-like) protein structures). They are 10 nm in diameter. Various proteins (like, for example, pre-keratin, vimentin, desmin) form intermediate filaments in cells of various tissues. Intermediate filaments cannot contract. Intermediate filaments of pre-keratin are characteristic for epithelial cells. They often form dense fascicles. In connective tissue cells they consist of vimentin and lay as rather loose reticulum in cytoplasm. Their functional role in the most cases is unknown. In neurons intermediate filaments participate in axonal transport.