Gastroduodenal mucosal defense: coordination by a network of messengers and mediators.

Gastroduodenal mucosal defense is composed of structural features of the mucosa, cellular monitors of pending or actual injury, and a web of effector cells that protect the mucosa from damage and govern its recovery from injury. By virtue of these systems, the gastroduodenal mucosa can cope with the harmful ingredients of ingested food and the potentially deleterious effects of gastric acid and pepsin. It is increasingly appreciated that a network of chemical messengers coordinates the alarm, defensive, and healing mechanisms. This article highlights some of the advances from the past year that have furthered our understanding of the regulatory systems that govern gastroduodenal mucosal homeostasis. Particular emphasis is given to control of the mucous and epithelial phospholipid barriers, the mucosal microcirculation, and the epithelial, neural, immune, and inflammatory mediators of the mucosal repair mechanisms.