Astrocytes

ASTROCYTES (from Greek aster- star and ky-tos- cell), star-shaped or spider-like cells, one of the forms of neuroglia cells, found in the central nervous system by the Golgi method and recognized by some authors (Ramon y Cajal) as independent elements. They are distinguished into 1) long-rayed and 2) short-rayed astrocytes. Both have a small cell body with numerous processes; the former have very long, usually smooth processes, while the latter have short, uneven processes that sometimes take on a hairy appearance. These processes, intertwining but apparently not anastomosing with each other, form an isolating and supportive framework for nerve elements; they end freely or attach to the surface of nerve elements and blood vessels, sometimes enveloping them with their processes. Long-rayed astrocytes are found predominantly in the white matter of the central nervous system of higher vertebrates, while short-rayed ones are found in the gray matter. According to the views of most modern authors and according to data obtained by the Weigert method, astrocytes are merely perinuclear accumulations of protoplasm of a continuous syncytium and the site of fiber crossing. For details, see Neuroglia.