Figs. 309 & 310 from Don Fawcett's Chapter 12 (Centrioles). The plane of a thin section only rarely happens to coincide with the long axis of both members of a pair of centrioles. It is more common for one to be cut longitudinally and the other transversely, as in the accompanying micrographs. In both of these examples, the centrioles are oriented at right angles even though they are some distance apart. The pair of centrioles in the upper micrograph on the facing page is closely associated with the Golgi apparatus and occupies a concavity in the nucleus. This is a common relationship in the hemopoietic cell line and in other cell types as well. The lower figure illustrates the special character of the pericentriolar cytoplasm which often contains numerous satellites. The labeled microtubules end in one of the satellites. A copy of the chapter is available on the ASCB's BioEDUCATE website.