![]() In healthy patients, there is always a thick mucus layer to protect the stomach from auto-digestion. The cells respond to external factors such as mechanical stress and elements of the cephalic and gastric digestion phases by increasing mucus productions as required. An increase in mucus production is signalled by a stimulation of the Vagus nerve (Cranial nerve 10) and is mediated by prostaglandins. Much like the control of salivary secretions, the gastric secretions (including mucus secretion) is largely controlled by neural influences. The bicarbonate ions are then pumped into the mucus layer by exchanging them with chloride ions. These bicarbonate ions are formed in the mucus-secreting cells by reacting carbon dioxide with water, using the enzyme carbonic anhydrase. ![]() The bicarbonate element of the mucus is important as it allows an increased pH local to the epithelial cells, protecting them from the highly acidic stomach environment. The viscosity of mucus is dynamic and can be altered by the rate of secretion from glandular cells or rate of breakdown by proteolytic enzymes within the stomach lumen. 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. The production of mucus is conducted by stomach surface epithelial cells and foveolar cells. Note that mucus cells are at the neck of the gastric pits Gastric Mucus production Fig 2 - Diagram showing different types of cells in the gastric pits. This is why patients on chronic intakes of NSAIDs are at a much higher risk of peptic ulcers. This makes the mucus layer less effective at protecting the stomach epithelium as well as less effective at managing any subsequent damage to the epithelium. When prostaglandins are blocked, less gastric mucus is secreted, cellular junctions become less tight and mucosal blood flow is less adequately maintained. NSAIDs work by blocking the synthesis of prostaglandins, which play an important role in both pain sensation and mucosal maintenance. Drugs such as ibuprofen and aspirin have revolutionised the immediate management of pain and inflammation but can have adverse effects on the gastrointestinal mucosa. The effect of NSAIDs on gastric mucus secretion has been known for around 40 years. By Y_tambe (Y_tambe's file), via Wikimedia Commonsįig 3 – Diagram showing how damage occurs during an H.
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