Stomach acid is a fluid in the stomach of humans or animals that consists of several components and is largely responsible for the digestion of food. The low pH dissolves the protein chains in the food, and the enzymes in the stomach further break down the proteins. If the production of gastric acid is disturbed, infections of the digestive tract can occur, and too much production of gastric acid leads to heartburn or stomach ulcers.
What is stomach acid?
Infographic on the anatomy and structure of the stomach with gastric ulcer. Click to enlarge. Gastric acid is a digestive fluid produced in the stomach. It has a pH of 1.5 – 3.5 and consists of hydrochloric acid (about 0.5%), large proportions of potassium chloride and sodium chloride. Gastric acid plays a major role in the breakdown of proteins by digestive enzymes. It breaks down the digested proteins to such an extent that the enzymes can completely decompose the long amino acid chains. The production of gastric acid is regulated by cells at the edge of the stomach. Other cells regulate the production of bicarbonate, a basic fluid that dampens the concentration of stomach acid when necessary. In addition, these cells form a mucus layer to protect the stomach wall from attack by the acid.
Anatomy and structure
Gastric acid is produced by parietal cells in the stomach. Secretion is a complex and energetically costly process. Parietal cells act in a dense network through which acid is secreted into the lumen of the stomach. These cells are part of a glandular tissue (epithelium) in the gastric mucosa. The result is a highly acidic environment within the stomach. Protein chains in food ingested by humans lose their basic structure here and are broken down into individual components. Peptide compounds are exposed. The potassium chloride acid activates pepsinogen into the pepsin enzymes. This is another step in digestion, as it cuts the links in the protein chains. This process is called proteolysis. In addition, the growth of many microorganisms is inhibited in stomach acid; a fact that prevents infections.
Functions and tasks
There are three phases of gastric acid secretion. In the basal phase, a small amount of gastric acid is always released into the stomach to break down ingested food. In the cephalic phase, 30% of gastric acid is produced and released through activities related to the ingestion of food (e.g. taste and smell). From the brain, these signals are relayed to the vagus nerve, a complex nerve cord that controls taste sensations. The parietal cells are stimulated and release gastric acid. In the gastric phase, about 50% of the gastric acid needed to digest food is produced. This is caused by the expansion of the stomach and the arrival of protein chains inside the stomach. Caffeine and calcium can also promote the production of gastric acid. After the chyme (mixture of acid and decomposed food) enters the anterior tract of the intestine in the intestinal phase, the last 10% of gastric acid is formed.
Diseases
A common complaint many people have with stomach acid is heartburn. Heartburn occurs when stomach acid enters the esophagus too high and irritates the areas there. Normally, stomach acid is kept from rising too high by gravity and a sphincter muscle. The muscle only opens when food is ingested. However, if it opens too frequently, or does not close properly, acid can escape and cause a painful irritation at the level of the sternum. Too much food or pressure in the stomach can also cause heartburn, as can a reaction to certain foods. These include: Tomatoes, citrus fruits, onions, garlic, caffeine, or alcohol. One treatment for heartburn or chronic reflux is medication through pH neutralizing agents, as well as a prudent diet. In addition, disorders in the production of gastric acid can lead to infections in the digestive tract, as microorganisms cannot be adequately killed. Too much production of gastric acid, in turn, can lead to ulcers in the stomach. The acid then penetrates the protective stomach lining and attacks the stomach wall behind it. These symptoms can also be treated with medication.
Typical and common stomach disorders
- Heartburn
- Reflux disease
- Inflammation of the gastric mucosa (gastritis)
- Stomach acidity
- Duodenal ulcer
- Irritable stomach
- Crohn’s disease (chronic inflammation of the intestine)
- Ulcerative colitis
- Appendicitis
