How is the stomach protected from acid?

The stomach is protected from the acidic environment it creates to digest food through several mechanisms:

1. Mucous Layer: The stomach lining is covered with a thick layer of mucus produced by specialized cells called gastric mucous cells. This mucus forms a protective barrier that shields the stomach wall from direct contact with the acidic gastric juices.

2. Epithelial Cell Tight Junctions: The stomach's epithelial cells are tightly connected by specialized structures called tight junctions. These junctions create a barrier that prevents the backflow of acidic stomach contents into the surrounding tissues.

3. Bicarbonate Secretion: The stomach lining also secretes bicarbonate ions (HCO3-) to help neutralize the acidic environment. These ions react with hydrochloric acid (HCl), the primary component of gastric juice, to form water and carbon dioxide.

4. Prostaglandins: The stomach produces prostaglandins, hormone-like substances that play a role in protecting the gastric mucosa. Prostaglandins help maintain the integrity of the mucosal lining and stimulate the production of mucus.

5. Cell Renewal: The stomach lining undergoes constant renewal, with new cells continuously replacing old ones. This process ensures that damaged cells are replaced, maintaining the stomach's ability to withstand acidic conditions.

These protective mechanisms work together to create a highly acidic environment in the stomach while preventing damage to its own tissues. However, certain conditions, such as excessive acid production or a breakdown in these protective mechanisms, can lead to stomach ulcers and other gastrointestinal problems.