pH regulation of the stomach

pH regulation of the stomach

Overview of Stomach pH Regulation

  • The stomach uses a delicate balance of acids and bases to regulate pH, which allows for the effective digestion of food.
  • Hydrochloric acid (HCl) produced by stomach cells lowers the stomach’s pH to around 1-2, creating an extremely acidic environment.

Role of Hydrochloric Acid in Stomach

  • Hydrochloric acid enables the protease enzyme, pepsin, to function. Pepsin is not active in a less acidic environment and therefore requires a low pH.
  • Hydrochloric acid also kills many potentially harmful bacteria ingested with food, thus, providing a protective effect.

Regulation of HCl Production

  • Production of HCl is carefully regulated by a combination of neural, hormonal and paracrine mechanisms.
  • Gastrin, a hormone secreted when food enters the stomach, stimulates the parietal cells to produce HCl.
  • At the same time, the secretion of another chemical, somatostatin, inhibits the production of HCl when the pH gets too low.
  • It is this careful balance that maintains the stomach’s pH at a level that facilitates digestion but also minimises the chance of harmful effects.

Buffering System

  • The stomach also has a buffering system to prevent the pH from becoming too low.
  • Bicarbonate ions (HCO3-) are secreted by the stomach lining cells to neutralise the excess acid.
  • The reaction of HCO3- and HCl forms carbonic acid (H2CO3) which quickly breaks down to produce carbon dioxide (CO2) and H2O. The CO2 is then exhaled, and water remains harmless in the stomach.
  • When the stomach’s pH balance is disrupted, several conditions may arise.
  • Acid reflux, characterised by the movement of stomach acid into the oesophagus, can cause heartburn and discomfort.
  • Production of too much stomach acid can lead to peptic ulcers, sores on the lining of the stomach or the small intestine.
  • The treatment of these conditions often involves drugs such as proton pump inhibitors and antacids, which help balance the stomach’s pH levels.

Drug Action in pH Regulation

  • Antacids neutralise stomach acid by providing a source of base to react with the HCl, forming a salt and water.
  • Proton pump inhibitors work by blocking the action of the proton pumps in the parietal cells, reducing the production of stomach acid.

Remember that a thorough understanding of these processes and reactions helps in understanding how different drugs can manage stomach acid related conditions.