ABSTRACT
Peptic ulcers are the result of an imbalance between mucosal insults and mucosal defense mechanisms. Several protective mechanisms can keep peptic ulcers from developing in the healthy state. These include the surface mucus and bicarbonate layer, the epithelial barrier, tight intercellular junctions, mucosal blood flow-mediated removal of back-diffused acid, and cell restitution and epithelial renewal (Fig. 2). When these mechanisms are interrupted or are nonfunctioning, the mucosa is vulnerable to various insults. This is likely why certain disease states, such as shock or cardiovascular disease, liver disease, or renal failure, are predisposing conditions for the development of PUD.
