Also found in: Dictionary, Thesaurus, Medical.
an intracellular formation found at the base of each flagellum or cilium in unicellular organisms as well as in the cells of multicellular organisms and in spermatozoa. Usually cylindrical, about 0.5 microns (μm) long, 0.1–0.2 μm in diameter. Basal granules appear to be of centriolar origin (for example, in spermatids it is possible to trace the transformation of centrioles into basal granules, and in some flagellates the same basal granule may bear a flagellum and, like the centriole, take part in the formation of a spindle in cell division). Basal granules are sometimes called blepharoplasts.