Protoplasmic astrocytes range in size from 10 to 40 μm, frequently are located in gray matter in relation to capillaries and have a clearer cytoplasm than do fibrous astrocytes (Fig. 1-12). Within the perikaryon of both types of astrocyte are scattered 9-nm filaments and 24-nm microtubules (Fig. 1-13); glycogen granules; lysosomes and lipofuscin-like bodies; isolated cisternae of the rough ER; a small Golgi apparatus opposite one pole of the nucleus; and small, elongated mitochondria, often extending together with loose bundles of filaments along cell processes. A centriole is not uncommon. Characteristically, the nucleus is ovoid and the nucleochromatin homogeneous, except for a narrow, continuous rim of dense chromatin and one or two poorly defined nucleoli. The fibrous astrocyte occurs in white matter (Fig. 1-13). Its processes are twig-like, being composed of large numbers of 9-nm glial filaments arranged in tight bundles. The filaments within these cell processes can be distinguished from neurofilaments by their close packing and the absence of side-arms (Figs. 1-13 and 1-14). Desmosomes and gap junctions occur between adjacent astrocytic processes.