Chapter 8 - Structure and Function of Intestinal Mucosal Epithelium

Abstract

This chapter describes the absorptive mucosa and the gut-associated lymphoid tissue (GALT) mucosa. The mucosal epithelial layer forms the interface between the luminal contents of the intestines and the tissue compartments of the gastrointestinal tract. This area is the site for digestion and absorption of various essential nutrients. Protecting the layer against harmful agents and infectious pathogens is carried out by many nonimmunologic factors like: gastric acid, pancreatic juice, bile, motility, mucus, glycocalyx, and cell turnover. In addition to these physiologic barriers, an immunologic barrier is created and maintained by the immune defense system, which includes—the GALT-immunoreactive cells distributed throughout the intestinal tract and the systemic immune system. In the intestinal lumen, pancreatic and biliary juice, mucus, glycocalyx, intestinal motility, and resident microflora interact to limit the colonization by enteropathogens. Pancreatic and biliary juices, along with S-IgA and lysozyme, have antibacterial activities in some species. Turnover of crypt cells increases the rate of epithelial renewal in response to the invasion of harmful pathogens that damage the surface cells.