The stomach is surrounded by parasympathetic (stimulant) and sympathetic (inhibitor) plexuses (networks of blood vessels and nerves in the anterior gastric, posterior, superior and inferior, celiac and myenteric), which regulate both the secretory activity of the stomach and the motor (motion) activity of its muscles. Because it is a distensible organ, it normally expands to hold about one litre of food. The stomach of a newborn human baby will only be able to retain about 30 millilitres. The maximum stomach volume in adults is between 2 and 4 litres. Sections
In classical anatomy the human stomach is divided into four sections, beginning at the cardia. The cardia is where the contents of the oesophagus empty into the stomach. The fundus (from Latin bottom) is formed in the upper curved part. The body is the main, central region of the stomach. The pylorus (from Greek gatekeeper) is the lower section of the stomach that empties contents into the duodenum.The cardia is defined as the region following the "z-line" of the gastroesophageal junction, the point at which the epithelium changes from stratified squamous to columnar. Near the cardia is the lower oesophageal sphincter. Research has shown that the cardia is not an anatomically distinct region of the stomach but a region of the oesophageal lining damaged by reflux. Anatomical proximity
The stomach bed refers to the structures upon which the  stomach rests in mammals.
These animals all consume diets that require little storage of food, no predigestion with gastric juices, or both.The gastric lining is usually divided into two regions, an anterior portion lined by fundic glands and a posterior portion lined with pyloric glands. Cardiac glands are unique to mammals, and even then are absent in a number of species. The distributions of these glands vary between species, and do not always correspond with the same regions as in humans. Furthermore, in many non-human mammals, a portion of the stomach anterior to the cardiac glands is lined with epithelium essentially identical to that of the oesophagus. Ruminants, in particular, have a complex stomach, the first three chambers of which are all lined with oesophageal mucosa.In birds and crocodilians, the stomach is divided into two regions. Anteriorly is a narrow tubular region, the proventriculus, lined by fundic glands, and connecting the true stomach to the crop. Beyond lies the powerful muscular gizzard, lined by pyloric glands, and, in some species, containing stones that the animal swallows to help grind up food.In insects there is also a crop. The insect stomach is called the midgut. Information about the stomach in echinoderms or molluscs can be found under the respective articles. Additional images
See also
Gastroesophageal reflux disease
Human gastrointestinal microbiota
Proton-pump inhibitor

References
External links

Stomach at the Human Protein Atlas
"Stomach" article from the Encyclopedia of Nursing & Allied Health, from enotes.com
Digestion of proteins in the stomach or tiyan
Site with details of how ruminants process food
Control of Gastric Emptying Archived 2019-11-12 at the Wayback Machine