centriole /sen″trē·ōl′/ [Gk, kentron] , an intracellular organelle, usually a component of the centrosome. Often occurring in pairs, centrioles are associated with cell division and can be closely studied only with an electron microscope. They are tiny cylinders positioned at right angles to each other, with walls consisting of nine bundles of fine tubules, three tubules to a bundle. Numerous centrioles occur in some large cells, such as the giant cells in bone marrow. The precise function of centrioles is still unknown, but they appear to aid in the formation of the spindle that develops during mitosis.
