(粘液川 Mucus(化学屏障) Mucin(粘蛋白) igh molecular weight, heavily glycosylated proteins produced by epithelial tissues v key characteristic is their ability to form gels v At least 19 human mucin genes have been distinguished by CDNA cloning v Function: lubrication, chemical barriers, cell signaling 13Mucin（粘蛋白）：  high molecular weight, heavily glycosylated proteins produced by epithelial tissues  key characteristic is their ability to form gels  At least 19 human mucin genes have been distinguished by cDNA cloning  Function: lubrication, chemical barriers, cell signaling 13 (粘液)Mucus（化学屏障）