Health Conditions

The function of the stomach is to store, dissolve and partially digest the contents of a meal and deliver this partially digested food to the small intestine in quantities that optimize digestion and absorption. In the stomach, food is digested and sterilized by gastric acid that consists of a mixture of hydrochloric acid and digestive enzymes like pepsin. This highly acidic mixture is produced by parietal cells within gastric glands in the folds of the stomach wall. Gastric acid is secreted by parietal cells in the stomach in response to three different substances: acetylcholine, histamine, and gastrin. Acetylcholine is released in response to chewing. Gastrin is released by G cells in the stomach in response to both swelling of the stomach wall and acetylcholine. High gastrin levels cause histamine to be released from mast cells in the tissues of the digestive tract.

Hydrochloric acid (H+) production is stimulated by three substances: gastrin, acetylcholine, and histamine.

During a meal, the rate of acid production greatly increases. Sensations like seeing, smelling, tasting and chewing food send signals via the vagus nerves to the parietal cells, causing them to increase acid production. More nerve messages follow as the stomach stretches, hydrogen ion concentration increases, and as a result of the presence of peptides. This increases release of gastrin, which in turn increases production of hydrochloric acid. On average, the stomach produces 2 liters of hydrochloric acid daily.

The cells of the stomach and duodenum have two defenses against their acidic environment. They multiply quickly and they secrete a protective layer of mucus.

An ulcer starts when the protective barrier that lines the gastrointestinal tract is injured, exposing the underlying tissue to the strong stomach acids and enzymes that are responsible for disinfecting and digesting the food that we eat. In the absence of a protective barrier, prolonged contact with acid leads to inflammation, erosion, and ulceration of the stomach's or duodenum's lining.

H. pylori thrives in the harsh chemical environment of the stomach by secreting an enzyme that neutralizes the acid in the area where the bacteria are growing. This allows the bacteria to become established and to grow within the epithelial tissue. The bacteria are often found in grooves between cells under a stable layer of mucus that shields the organisms from gastric acid. Once it is established in the stomach wall, H. pylori produces substances that cause tissue damage. The body's immune system reacts with an inflammation to fight the infection, and this causes further local tissue damage. After a time, the damaged tissue no longer can secrete mucous properly, which allows the acid and enzymes to also begin to attack the tissue. Eventually, the mucosal cell layer wears away in an ulcer, exposing the underlying tissue to the harsh digestive chemicals. When a blood vessel is exposed the acid and digestive enzymes can open up the blood vessel making it a bleeding ulcer.

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Note: The above information is intended to supplement, not substitute for, the expertise and judgment of your physician, pharmacist, or other healthcare professional. It is not intended to diagnose a health condition, but it can be used as a guide to help you decide if you should seek professional treatment or to help you learn more about your condition once it has been diagnosed.