Gastric mucosa
The gastric mucosa (Latin tunica mucosa gastric ) is the inner lining ( mucosa ) of the stomach. It consists of an epithelium, an intrinsic layer (lamina propria ) and a bonding layer ( submucosa, the submucosa ) for further external smooth muscle of the stomach wall.
The gastric mucosa is the stomach acid and the substances involved in the digestive process pepsinogen and Intrinsic factor and various hormones. It also causes the lining of the stomach with a thick slime layer which protects the stomach wall from the gastric acid.
The mucous membrane of the stomach is set depending on the state in filling wrinkles. The mucosa shows a fielding these " fields " are as areae gastricae called. From the crater-like depressions of mucous go for self layer as " gastric pits " ( foveolae gastricae ) are referred to.
Epithelium
The epithelium of the gastric mucosa consists of only one cell layer of high prismatic ( taller than wide ) cells ( single-layered columnar epithelium ). The cells ( Epitheliocyti superficiales gastris ) are connected firmly by so-called tight junctions. In many epithelial mucus -producing subsidiary cells are interspersed. Of these cells and the mucus of the gastric glands (see below) protects the epithelium before the produced hydrochloric acid in the stomach.
Lamina propria mucosae
The intrinsic layer consists of connective tissue, blood vessels, lymph vessels, cells of the immune system ( partly as lymphoid follicles ) and glands. The gastric glands open into the gastric pits. It is tubular ( tubular ) glands. Depending on the stomach region, these are designed differently and perform different functions. We distinguish cardia, fundus and pyloric glands. In the epithelium of the gastric glands are also integrated alongside endocrine cells operating exocrine cells belonging to the diffuse neuroendocrine system ( DNES ).
For the submucosa toward the self layer has a layer of smooth muscle, the lamina muscularis mucosae. At the transition to the submucosa are ganglia of Meissner plexus ( submucosal plexus ).
Kardiadrüsen
The Kardiadrüsen ( Glandulae cardiacae ) extend to the area of the cardia ( cardia ), only at pigs they take up almost half of the stomach. In horses, they are formed on an edge region at the transition from the actual cutaneous mucosa.
The tubular glands are branched and tortuous. Their wall consists of the actual gland cells ( Epitheliocyti cardiaci ), mucins, an alkaline mucous secretion secrete.
Fundic gland
Fundus or self glands ( glands gastricae propriae ) constitute the primary gastric juice. They extend to the stomach bottom ( fundus ) and body ( corpus ulcer ). It is stretched tube gland with different cell types. These tubes are divided into three sections:
- Isthmus: the bottleneck at the transition from the gastric pits ( gastric foveola ) for glands hose
- Neck ( cervix ) of the glands hose
- Main part ( pars principalis ): lower section and glands basic
The cells of the isthmus are partly composed of epithelial cells. They form, as the rest of the epithelium, mucus ( mucus ) and bicarbonate ions which have as bases a buffer effect against the free protons. This alkaline mucus protects the epithelium from the acidic environment of the stomach. Next in depth are stem cells that divide continuously and replace the dying epithelial cells.
In the glandular neck especially secondary and parietal cells occur. In the main part are the main cells and some parietal cells.
The subsidiary cells ( Mucocyti cervicales ) are iso -to high- prismatic and have a basal nucleus. They also secrete alkaline mucus to protect the epithelium.
The parietal cells ( Exocrinocyti parietal, and parietal cells ) are between the other cells or outside of them. They secrete protons extracellularly store together with chloride ions to form hydrochloric acid and for cobalamin absorption ( vitamin B12) necessary intrinsic factor. The cells form intracellular secretion channels with microvilli. These channels are incorporated in the active state of the cells in the luminal ( facing the stomach cavity ) plasma membrane, thus increasing the contact and release area. Here are proton- potassium pump, the proton transport in exchange for potassium ions out of the cell. Parietal cells are relatively large and eosinophilic ( with eosin dyeable and therefore reddish).
The enterochromaffin -like cells ( ECL cell and or H- ) cells are endocrine cells, which are often located in the vicinity of the parietal cells. They produce histamine, which stimulates acid production of parietal cells.
The principal cells ( Exocrinocyti principales ) in the body of the gastric glands are highly prismatic with a basally located nucleus. They form pepsinogens, the precursors of various enzymes collectively known as pepsin ( in ruminants the Lab). They are latched in so-called zymogen granules in the cells. Principal cells are characterized by the large proportion of rough-surfaced endoplasmic reticulum basophilic ( with basophilic dyes dyeable, so bluish).
Pyloric
The pyloric glands ( glands pyloricae ) lie on the stomach outlet ( pylorus ). You but, similar to the Kardiadrüsen, an alkaline mucous secretion. You are isoprismatisch, the nucleus is partially strongly flattened. In contrast to the more orally (ie towards the esophagus ) lying gastric glands have the glandulae pyloricae no principal and no parietal cells. In the epithelium of the pyloric glands in addition to the exocrine gland cells ( Exocrinocyti pyloric ) that produce mucus, endocrine cells integrated, form the hormones and release to the surrounding blood vessels:
G- cells form the hormone gastrin stimulates the acid production in the parietal cells. This is done directly ( by stimulation of acid-forming parietal cells ) and indirectly, by stimulating the release of histamine in ECL cells.
The D- cells make somatostatin. They are stimulated by gastric acid in the stomach lumen. Somatostatin inhibits the Gastrinausschüttung in G cells and histamine in ECL cells (which has a negative effect on acid production ) and also directly the acid production in parietal cells. D- cells are also present in the gastric fundus and body as well as in the duodenum ( and in other organs of the body, such as the pancreas).
Submucosa
The submucosa represents a displacement layer