Common classes of animal glycans found in the extracellular environment of the brain. The glycans are depicted as parts of hypothetical glycoconjugates. The representative sugars are depicted by colored symbols as described in the legend. GalNAc, N-acetylgalactosamine; GlcNAc, N-acetylglucosamine; Gal, galactose; Glc, glucose; Man, mannose; Fuc, fucose; Xyl, xylose; GlcA, glucuronic acid; IdoA, iduronic acid. (Figure modified and reprinted with permission from Chapter 1 from Essentials of Glycobiology, 2nd edition).