The glands contains a number of cells, with the function of the glands changing depending on their position within the stomach.Within the body and fundus of the stomach lie the fundic glands. In general, these glands are lined by column-shaped cells that secrete a protective layer of mucus and bicarbonate. Additional cells present include parietal cells that secrete hydrochloric acid and intrinsic factor, chief cells that secrete pepsinogen (this is a precursor to pepsin- the highly acidic environment converts the pepsinogen to pepsin), and neuroendocrine cells that secrete serotonin.Glands differ where the stomach meets the esophagus and near the pylorus. Near the junction between the stomach and the oesophagus lie cardiac glands, which primarily secrete mucus. They are fewer in number than the other gastric glands and are more shallowly positioned in the mucosa. There are two kinds - either simple tubular with short ducts  or  compound racemose resembling the duodenal Brunners glands. Near the pylorus lie pyloric glands located in the antrum of the pylorus. They secrete mucus, as well as gastrin produced by their G cells. Gene and protein expression
About 20,000 protein coding genes are expressed in human cells and nearly 70% of these genes are expressed in the normal stomach. Just over 150 of these genes are more specifically expressed in the stomach compared to other organs, with only some 20 genes being highly specific. The corresponding specific proteins expressed in stomach are mainly involved in creating a suitable environment for handling the digestion of food for uptake of nutrients.
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