AP BIOLOGY

Detailed explanation-1: -The inner surface of the stomach is lined by a mucous membrane known as the gastric mucosa . The mucosa is always covered by a layer of thick mucus that is secreted by tall columnar epithelial cells.

Detailed explanation-2: -The stomach has a two-layered mucus system, composed of an inner, attached mucus and an outer, unattached, loose mucus layer, both built by the MUC5AC mucin produced by the superficial epithelium. Glands in the stomach and duodenum secrete the gel-forming mucin MUC6.

Detailed explanation-3: -The mucus layer provides an essential first host barrier to inhaled pathogens that can prevent pathogen invasion and subsequent infection. Respiratory mucus has numerous functions and interactions, both with the host and with pathogens.

Detailed explanation-4: -The production of mucus is conducted by stomach surface epithelial cells and foveolar cells. The mucus itself is around 95 per cent water, with the remaining five per cent made up of polymers that give the mucus its gel-like viscosity.