The stomach secretes hydrochloric acid (HCl). This acid, also known as gastric acid, is a crucial component of gastric juice and plays a vital role in digestion.
How Hydrochloric Acid is Produced
Hydrochloric acid is produced by specialized cells within the stomach lining called parietal cells. These cells secrete the hydrogen (H+) and chloride (Cl-) ions separately. The hydrogen ions are pumped out via hydrogen/potassium ATPase pumps, while chloride ions are released through chloride channels. The combination of these ions in the stomach lumen creates the hydrochloric acid. [17-Jul-2023]
Function of Hydrochloric Acid in Digestion
The highly acidic environment created by HCl in the stomach (pH approximately 1-3) is essential for:
- Activating pepsin: Pepsin is a digestive enzyme that breaks down proteins. HCl activates its precursor, pepsinogen. [Merck Manual Professional Edition]
- Killing bacteria: The low pH of the stomach acts as a defense mechanism against harmful bacteria ingested with food. [In brief: How does the stomach work?]
- Denaturing proteins: HCl helps unfold proteins, making them more accessible to pepsin's action.
Regulation of Hydrochloric Acid Secretion
The secretion of hydrochloric acid is tightly regulated by various factors, including:
- Gastrin: A hormone that stimulates acid secretion. [Physiology, Gastrin - StatPearls]
- Histamine: A chemical messenger that also promotes acid production. [Discuss the hormones secreted by the stomach]
- Acetylcholine: A neurotransmitter that enhances acid secretion. [Discuss the hormones secreted by the stomach]
In contrast, several substances inhibit acid secretion, maintaining a balanced approach to digestion. [Physiology of gastric acid secretion]
Location of Acid Secretion
Acid secretion primarily occurs in the proximal two-thirds (body) of the stomach. [Merck Manual Professional Edition] The strongly acidic environment (pH) generated in the gastric lumen is directly a result of the secreted HCl. [The Physiology of the Gastric Parietal Cell]
