What is Stomach?
{{one source|}} [[File:Stomach diagram.gif|thumb|right|The stomach in the gastrointestinal system]] [[Image:Stomach blood supply.svg|thumb|240px|Schematic image of the blood supply to the human stomach: [[left gastric artery|left]] and [[right gastric artery]], [[left gastroepiploic artery|left]] and [[right gastroepiploic artery]] and [[short gastric arteries]]<ref name=Moore150>{{cite book |author1=Anne M. R. Agur |author2=Moore, Keith L. |title=Essential Clinical Anatomy (Point (Lippincott Williams & Wilkins)) |url=https://archive.org/details/essentialclinica0000moor_c2o8 |publisher=Lippincott Williams & Wilkins |location=Hagerstown, MD |year= 2007|isbn=978-0-7817-6274-8 |oclc= 172964542}}; p. 150</ref>]] The '''stomach''' is part of the [[digestive system]]. It is an internal organ between the [[esophagus]] and the [[small intestine]]s. The stomach is the third stage in the digestive process. It holds [[food]] after ingestion. Food in the stomach then passes through to the [[small intestine]] where most of the food's [[nutrition]] is absorbed. The stomach contains [[hydrochloric acid]] of [[pepsin]] made by stomach [[cell]]s. As a useful side-effect, the acid kills [[bacteria]] in the food. However, its main function is to help the protein-digesting [[enzymes]] called [[protease]]s work. In general, the food is churned, squeezed and mixed. This prepares it for digestion. The partially digested food is called chyme. The stomach acid may cause problems. It can make [[peptic ulcer]]s worse. It can also cause [[heartburn]]—pain in the chest when acid from the stomach ''refluxes'' (backs up into) the oesophagus. These can usually be treated by neutralizing the acid. [[Vomit]]ing occurs when food goes back up the oesophagus and out the mouth. Vomiting can be a [[symptom]] of disease. Stomachs of other mammals work differently to human stomachs. [[Ruminant]]s, for example, have a stomach with multiple compartments. In that system, food goes through the first part of the digestive system twice, and the work of