Stomach mucus

Mucus is produced by the mucus neck cells and by the surface epithelial cells of the stomach wall. A thick layer of mucus adheres to the wall of the stomach, forming the gastric mucosal barrier. The function of this barrier is to protect the gastric mucosa from injury — specifically, from the corrosive actions of HCl and pepsin. Together with bicarbonate ion released into the lumen of the stomach, mucus neutralizes the acid and maintains the mucosal surface at a nearly neutral pH. 

The bilberry (Vaccinium myrtillus) has traditionally been used to treat ulcers, because bilberry might stimulate the production of the stomach mucus and... 

Mil. Masamune, H., Hakotnori, S., and Masamune, O., Biochemical studies on carbohydrates. CLXXXIX. N-glyoside- and acetal-linkage in the molecule of the group mucopolysaccharide from pig stomach mucus. Tohoku ]. Exptl. Med. 64, 281-295 (1956). 

M18. Masamune, H., Shinohara, H., Abe, S., and Kaketa, H., Chemical nature of toxohormone (Nakahara) Sixth report The group mucopolysaccharide from pig stomach mucus acts as a weak toxohormone. CCXXIII. Biochemical studies on Carbohydrates. Tohoku J. Exptl. Med. 69, 53-57 (1959). 

Y5. Yosizawa, Z, Biochemical studies on carbohydrates. CXCV. Digestion of the group O and AO mucopolysaccharides from pig stomach mucus by Ihe O enzyme from B. fulminans. Tohoku. Exptl. Med. 65, 177-185 (1957). 

The protecting effect of hot pepper and capsaicin on stomach mucus was proven in animal tests, and it is also known that vanilloid receptors are activated in the process. The protecting effect is pronounced at low doses, much higher amounts are harmful. At low levels, capsaicin causes the formation of a substance beneficial for... 

V. cholerae is a gram-negative bacillus. Vibrios pass through the stomach to colonize the upper small intestine. Vibrios have filamentous protein extensions that attach to receptors on the intestinal mucosa, and their motility assists with penetration of the mucus layer.2 The cholera enterotoxin consists of two subunits, one of which (subunit A) is transported into the cells and causes an increase in cyclic AMP, which leads to a deluge of fluid into the small intestine.20 This large volume of fluid results in the watery diarrhea that is characteristic of cholera. The stools are an electrolyte-rich isotonic fluid, the loss of which results in blood volume depletion followed by low blood pressure and shock.2 Of note, the diarrheal fluid is highly infectious. 

The formation of antibodies is only one mechanism by which an animal may protect itself from substances or microorganisms that are potentially harmful. A mechanical protection against infection is provided by the presence of an intact skin surface and membranes together with the secretion of mucus from many internal membrane surfaces. The acids secreted by the stomach and skin have a bactericidal effect as does the presence in many body fluids of certain enzymes, particularly lysozyme. 

The chemical barriers are also important but are sometimes neglected in discussions of defence. To some extent they are specific for each tissue or organ and examples are as follows. Enzymes, such as lysozyme, which digests part of the bacterial coat, are present in many secretions (e.g. tears, milk) acid in the stomach, in the vagina, on the surface of the skin alkali in the small intestine mucus in the intestine, respiratory tract and vagina. 

Vomiting and diarrhoea remove pathogens from the stomach and intestine and urination eliminates them from the bladder. Mucus in the lumen of the intestine, in the vagina and in the bronchioles of the lung not only restricts access of pathogens to the epithelial cells but also localises them for attack by inununoglobulin-A. 

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