Gastroesophageal Refiux In some people, the gastroesophageal sphincter at the entrance to the stomach does not close properly or opens when it should not. The result is gastroesophageal reflux. Acidic chyme splashes back into the esophagus, causing a burning pain commonly called heartburn or acid indigestion. Occasional acid reflux can be treated with over-the-counter antacids, but a chronic problem should be discussed with a doctor. Repeated exposure to acid can damage the tissue of the esophagus and raise the risk of esophageal cancer.
Stomach Ulcers When something disrupts the stomach's protective mucus layer, gastric fluid and enzymes can erode the stomach lining, causing an ulcer. Most ulcers occur after an acid-loving species of bacteria (Helicobacter pylori) makes its way through gastric mucus and infects cells of the stomach lining. H. pylori releases chemicals that increase gastrin secretion, thus making the stomach more acid. The extra acidity stresses cells of the stomach lining so the infection spreads more easily. Antibiotics halt the infection and allow healing to occur.
Continual use of nonsteroidal anti-inflammatory drugs such as ibuprofen or aspirin can also cause a stomach ulcer. These drugs interfere with chemical signals that maintain the health of the stomach lining.
Disorders That Affect Digestion in the Small Intestine
Lactose Intolerance To be able to digest lactose, a person must have functional lactase at the surface of their brush border cells. In many people, including most Asians and African Americans, expression of the gene for lactase declines in adulthood. As a result, lactose is not broken down in the small intestine. When lactose enters the large intestine, resident bacteria break it down in reactions that produce hydrogen gas as a by-product. The result is flatulence, a feeling of bloating, and cramps.
Disorders That Affect Digestion in the Large Intestine
Appendicitis—an inflammation of the appendix— requires prompt treatment. It often occurs after a bit of feces lodges in the appendix and infection sets in. Removing an inflamed appendix prevents it from bursting and releasing bacteria into the abdominal cavity. Such a rupture could cause a lifc-threatcninc infection.