AP BIOLOGY

Detailed explanation-1: -THE STOMACH does not digest itself because it is lined with epithial cells, which produce mucus. This forms a barrier between the lining of the stomach and the contents. Enzymes, which make up part of the digestive juices are also secreted by the stomach wall, from glands with no mucus barrier.

Detailed explanation-2: -The stomach is protected from self-digestion by the mucosal barrier. This barrier has several components. First, the stomach wall is covered by a thick coating of bicarbonate-rich mucus. This mucus forms a physical barrier, and its bicarbonate ions neutralize acid.

Detailed explanation-3: -The stomach normally does not digest itself because of a mechanism which regulates gastric secretion. This checks the secretion of gastric juice before the content becomes sufficiently corrosive to damage the mucosa. Pure gastric juice can destroy the mucosa and produce a peptic ulcer.

Detailed explanation-4: -The intestinal mucus is an efficient system for protecting the epithelium from bacteria by promoting their clearance and separating them from the epithelial cells, thereby inhibiting inflammation and infection.