ABSTRACT
Intestinal mucins form a viscous, hydrated blanket on the surface of the intestinal mucosa that presumably protects the delicate columnar epithelium by excluding and entrapping foreign particles, microorganisms, and macromolecules. The mucous blanket is constantly renewed by the secretion of high molecular weight glycoproteins from individual goblet cells throughout the epithelium. Goblet cells differentiate in the lower portion of the crypts of both small and large intestine and gradually migrate onto the villi or mucosal surface The slow continuous release of mucin under "baseline" conditions is accomplished by exocytosis, involving the intermittent fusion of the membrane of a single secretory granule with the luminal plasma membrane of the cell. The goblet cell is unique, in that its intracellular mucous granules are stored in a tightly packed mass at the apical pole of the cell, and this mass is surrounded by a filament-rich, cup-shaped sheath of peripheral cytoplasm that gives the cell its characteristic shape and name.
