Intermediary Filaments-the Tonofilament System

In addition to actin filaments and microtubules, intermediary filaments (tonofilament) are the third system making up the intracellular cytoskeleton of eukaryotic cells. Their diameter is 7–11 nm. This makes them thicker than microfilaments (5–7 nm) and thinner than microtubules (20–25 nm). Currently, five subclasses of intermediary filaments are define d: the cytokeratin filaments in epithelial cells; desmin filaments, the characteristic structures in smooth cells and striate d muscle fibers; glia filaments, glia acidic fibrillary protein ( GAFP) in astrocytes; neurofilament in neurons from the central and peripheral nervous system; and vimentin filaments , which are characteristic of cells of mesenchymal origin (fibroblasts, chondrocytes, macrophages, endothelial cells, etc.). This figure shows vimentin-type intermediary filaments (Tonofilaments) in human endothelial cells from the umbilical vein. Staining was done using a fluorescence-labeled antibody against vimentin .

References

Kuehnel, W.(2003). Color Atlas of Cytology, Histology, and Microscopic Anatomy. 4^th edition . Institute of Anatomy Universitätzu Luebeck Luebeck, Germany . Thieme Stuttgar t · New York .