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a bounding line, edge, or surface.
brush border a specialization of the free surface of a cell, consisting of minute cylindrical processes (microvilli) that greatly increase the surface area.
vermilion border the exposed red portion of the upper and lower lips.
the apical epithelial surface bearing closely packed microvilli about 2 mcm long, such as occur on the cells of the proximal tubule of the nephron.
Synonym(s): limbus penicillatus
brush borderPhysiology A specialized portion of the free or apical aspect of certain epithelial cells–eg, of the GI tract, consisting of closely packed microvilli that facilitate absorption; brush border cells line the luminal surface of the intestine and proximal convoluted tubules of the kidneys; the BB contains absorptive microvilli and glycocalyx–which is rich in hydrolytic enzymes
brush bor·der(brŭsh bōr'dĕr)
An epithelial surface bearing closely packed microvilli about 2 mcm long, such as occurs in the proximal tubule of the nephron.