“The stomach secretes HCl into the stomach lumen, while the pancreas secrete NaHCO3 into the duodenal lumen. Both secretions take place via similar mechanisms.
In the stomach, parietal cells lining glands secrete H+ and Cl– ions in response to protein, caffeine or alcohol present in the stomach, or simply an expanded stomach may also stimulate the parietal cells. On stimulation, parietal cells take up Cl– ions from the interstitium and secrete them into the stomach lumen. Simultaneously, they also pump intracellular H+ ions into the stomach lumen through the H+/K+ ATPase. In the lumen, H+ ions combine with Cl– ions to generate HCl. Since H+ and OH– ions are in equilibrium with H2O molecules in every cell, the loss of H+ ions from parietal cells would result in excessive amounts of free OH– ions. Intracellularly these OH– ions combine with CO2 molecules to generate HCO3– ions.
The normal pH of the stomach lumen ranges from 1.5 to 4.
In the pancreas, cells lining ducts secrete HCO3– ions in response to hormone secretin. On stimulation, OH– ions combine with CO2 molecules to generate HCO3– ions inside the pancreatic duct cells. HCO3– ions are secreted by the pancreatic duct cells into the duodenal lumen, where they combine with Na+ ions to generate NaHCO3.
Community acquired pneumonia (CAP) is a group of lung infections that can be transmitted between members of a community by normal social contact. One of the most common bacterial cause of pneumonia is streptococcus pneumonia, a neutrophile (can only survive in pH ranging from 6.5 to 8.3) that enters via the nasal passageway to infect the lungs. However, streptococcus pneumonia is also a natural flora of the mouth and pharynx and has the potential to invade the stomach, rest and multiply there. If this happens, the proliferating streptococci, from the stomach may spread into the esophagus and pharynx. From the pharynx, they may enter the respiratory passageways and infect the lungs to cause pneumonia.”
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