A
brush border (
striated border or
brush border membrane) is the
microvilli-covered surface of
simple cuboidal epithelium and
simple columnar epithelium cells found in certain locations of the body. Microvilli are approximately 100 nanometers in diameter and their length varies from approximately 100 to 2,000 nanometers in length. Because individual microvilli are so small and are tightly packed in the brush border, individual microvilli can only be resolved using
electron microscopes; with a
light microscope they can usually only be seen collectively as a fuzzy fringe at the surface of the epithelium. This fuzzy appearance gave rise to the term
brush border, as early anatomists noted that this structure appeared very much like the bristles of a paintbrush.