The stomach is a muscular organ in the upper abdomen that is part of the digestive system. Various cells in the stomach secrete digestive enzymes and hydrochloric acid. These substances break down food so the body can absorb nutrients.
The cells of the stomach are constantly exposed to digestive juices and the stomach’s contents. Therefore, to protect themselves, the cells produce a layer of mucus and constantly regenerate to keep the stomach lining healthy.
This article looks at the types of cells of the stomach, their purpose, and how they work.
The stomach has four regions:
- Fundus: the upper rounded part of the stomach
- Cardia: the part nearest the esophagus
- Body: the main central part
- Pylorus: the lower narrow part
Besides different regions, the stomach also has
- Serosa: The serosa is the outermost layer of the stomach. It consists of a thin layer of connective tissue that helps anchor the stomach in place.
- Muscularis: The muscularis layer consists of smooth muscle. Muscle contractions help mix and churn the food.
- Submucosa: The submucosa layer is beneath the mucosa. It consists of connective tissue and blood vessels, which provide nutrients to the mucosa.
- Mucosa: The innermost layer is the mucosa. It is in contact with food as it enters the stomach and is responsible for secreting digestive enzymes and hydrochloric acid. The mucosa has folds to increase the surface area available for nutrient absorption.
The mucosa further subdivides into the surface epithelium, lamina propria, and muscularis mucosa.
The epithelium folds into the lamina propria, forming the gastric pits and glands, which contain the
- surface mucous cells (foveolar cells)
- parietal cells
- chief cells
- neuroendocrine cells
The gastric mucosa lines the stomach and contains the gastric glands, which secrete different substances. The surface of the stomach and opening of the gastric pits have a single layer of columnar epithelial cells, known as surface mucous cells or foveolar cells.
These cells secrete a thick layer of mucus that covers the stomach lining and protects it from the digestive juices. The mucus also provides a slippery surface that helps food move through the stomach.
The surface mucous cells constantly regenerate, so the stomach lining is always protected.
Parietal cells are present in the gastric pits that
In addition to secreting hydrochloric acid, these cells secrete a protein known as intrinsic factor. Intrinsic factor helps the body absorb vitamin B12 in the small intestines.
Chief cells are present in the base of gastric glands, which are in the fundus. They secrete digestive enzymes that help break down food.
The chief cells secrete pepsinogen. It converts to pepsin in the presence of hydrochloric acid. Pepsin helps digest proteins into small units known as polypeptides.
Neuroendocrine cells occur in the gastric pits of the stomach. There are several subtypes that secrete various hormones:
- G-cells: These sit in the stomach’s pylorus region and produce the hormone gastrin. Gastrin can increase hydrochloric acid production by stimulating ECL-like cells to release histamine.
- ECL-like cells: These cells secrete histamine when gastrin stimulates them. Histamine binds to receptors on the parietal cells and increases hydrochloric acid secretion. These cells exist mainly in the fundus of the stomach.
- D-cells: These cells are in the pylorus of the stomach. They secrete an inhibitory molecule called somatostatin. When the stomach reaches a certain level of acidity, D-cells release somatostatin, which then suppresses gastrin and the overall production of gastric acid.
- EC-cells: These cells secrete serotonin. Serotonin is involved in regulating gastrointestinal motility and fluid secretion.
- P/D1 cells: These cells secrete the hormone ghrelin. Ghrelin is a hunger hormone that increases appetite and promotes fat storage.
The cells of the stomach are highly specialized with different and varied functions.
The surface mucous cells secrete a layer of mucus that protects the stomach lining. Parietal cells secrete hydrochloric acid that helps break down food and intrinsic factor that aids in the absorption of vitamin B12.
Chief cells secrete enzymes that support digestion. Neuroendocrine cells secrete various hormones that regulate stomach acidity, hunger, and gastrointestinal motility.
Each cell type works together to ensure that the stomach can effectively digest food and protect itself from harmful substances.