The stomach is an organ of the digestive system, located in the abdomen just below the ribs. Swallowed food is mixed with gastric juices containing enzymes and hydrochloric acid. The lining of the stomach called the epithelium is layered with multiple folds. The epithelium is coated with mucus (gastric mucosa) secreted by special glands. Inflammation caused by gastritis occurs in this lining.
Gastritis occurs when a bacterium, Helicobacter pylori, or the chronic use of drugs or certain medications weakens the protective mucous coating of the stomach and duodenum, allowing acid to get through to the sensitive lining beneath. Helicobacter pylori bacterium is also responsible for most peptic ulcers.
However, gastritis is not just one disease but a group of conditions, all of which result in the inflammation of the stomach lining. Inflammation of the stomach means that white blood cells move into the wall of the stomach as a response to an injury to the stomach. Commonly, the inflammation results from infection with the same bacterium that causes most stomach ulcers. Yet other factors such as traumatic injury and regular use of certain pain relievers can also contribute to gastritis.
Gastritis may be caused by many factors including infection, alcohol, particular medications and some allergic and immune conditions. It can be either acute, with severe attacks lasting a day or two, or chronic, with long term appetite loss or nausea. In many cases, gastritis has no symptoms (asymptomatic). But, common symptoms may include:
Copied with permission from: http://plrplr.com/79747/gastritis-more-than-just-a-grumbling-stomach/