Microtubules

Microtubules exist in all cells and consist of extended non-contractile tubes, which are several micrometers long and have no branches. Their outer diameter is 21–24 nm, the inner diameter is 14–16 nm. The tubule wall is about 8 nm thick and densely structured. It is built from globular, helical proteins ( tubulin), which themselves are compose d of 13 lengthwise running protofilaments. Microtubules not only maintain the geometry of cells (cytoskeleton ), they also participate in the construction of kinocilia, centrioles, kinetosomes and the mitosis spindles. Another of their many functions is the regulated intracellular transport of materials and organelles. Microtubules in an epithelium cell from the endometrium.

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 .