The basic structure of the centriole is nine groups of three microtubules arranged as a cylinder. The two illustrations below show this structure. This drawing shows the three-dimensional structure of the nine groups of three microtubules and the right angle orientation of the two centrioles. Each animal cell has two of these centrioles. In a cell that is not in the process of dividing these centrioles are aligned at right angles to each other.
Longer microtubules project outward from the area around the centrioles.
These microtubules form part of the cytoskeleton . Function As animal cells prepare for cell division these two centrioles separate and go to opposite ends of the cell. The spindle fibers that pull the chromosomes apart during mitosis form from the vicinity of the centrioles. Because of this behavior it was long felt that centrioles were necessary for animal cell division. However, some animal cells can divide when the centrioles have been removed.