Coordinated regulation of colonic fluid and mucus secretion.

The human colon, unlike the small intestine which is relatively sterile, contains a diverse microbiome which contributes to host metabolism. The luminal environment is constantly changing and responds to epithelial absorption and secretion which occurs as motility is regulated by longitudinal and circular smooth muscle. Mucous gels are crucial to lubrication and maintenance of an unstirred layer which separate the epithelium from the lumen. Gel-forming mucins are produced and released by goblet cells and become hydrated, although the source of water is not definitively understood. The purpose of this review is to summarize regulation of water movements across the colonic epithelium, goblet cell secretion of mucus and to consider how these distinct processes are functionally coupled.