Layers and structure of the stomach wall

The stomach wall shows a characteristic layered structure under the microscope.

From the inside, the stomach wall is lined by mucosa (tunica mucosa). The stomach mucosa is divided into three sublayers.
The uppermost layer is a covering tissue (Lamina epithelialis mucosae), which forms a tough neutral mucus that protects the stomach mucosa from mechanical, thermal and enzymatic damage. This is followed by a shifting layer (Lamina propria mucosae), in which the stomach glands (Galandulae gastricae) are embedded. Finally, there is a very narrow layer of autologous muscle (lamina muscularis mucosae), which can change the relief of the mucosa.
The gastric mucosa is followed by a loose layer of shifting tissue (Tela submucosa), which consists of connective tissue and in which a dense network of blood and lymph vessels runs, as well as a network of nerve fibers, the plexus submucosus (Meissen plexus), which controls the activity of the stomach glands (secretion).
This plexus works independently of the central nervous system (CNS), but can be influenced by it via the autonomic nervous system.
This is followed by a strong gastric muscle layer (tunica muscularis). It is divided into three sublayers, each of which has fibers that run in different directions: First, an inner layer of small oblique muscle fibers (fibrae obliquae), then a circular stratum (stratum circulare), and on the very outside an outer longitudinal stratum (stratum longitudinale). These muscles are responsible for the wave-like movement of the stomach (peristalsis), which is responsible for the constant mixing of the chyme with the gastric juice.Between the ring and longitudinal muscle layer runs a network of nerve fibers, the plexus myentericus (Auerbach plexus), which controls the function of the muscles.
Just like the submucosal plexus, this plexus works largely independently (autonomous), but is regularly influenced by the autonomic nervous system.
A new connective tissue shifting layer (Tela subserosa) follows.
The end is a coating of the peritoneum which lines all organs. This coating is also called tunica serosa.

The stomach glands (Glandulae gastricae) are located in the lamina propria mucosae and can be found in the fundus and the body of the stomach. Up to 100 glands are located on 1mm2 of the mucosal surface.

In the wall of the glandular tube there are various cells:

Mucus cells:They produce the same neutral mucus as the surface mucus cells (epithelial cells).
Secondary cells:These cells are located rather superficially in the gland and secrete an alkaline mucus, i.e. the pH value is high due to the hydrogen carbonate (OH) ions contained in them. This property is important to control and, if necessary, regulate the pH of the stomach. The mucus coats the stomach mucosa and thus protects against self-digestion by the aggressive hydrochloric acid (HCl) and enzymes (self-digesting proteins).
This type of cell is particularly abundant in the cardia and in the fundus of the stomach.
Main cells:These cells produce the inactive precursor enzyme pepsinogen, which is converted into the active enzyme pepsin by hydrochloric acid (HCl) after release and is responsible for the digestion of proteins. Since the enzyme only comes into contact with the hydrochloric acid on the surface of the gland, it prevents the glands from digesting the pepsinogen themselves. This cell form is mainly located in the corpus of the stomach.
Proof cells:These cells, which are found in the stomach corpus, produce abundant hydrogen ions (H+ ions), which are needed for the formation of hydrochloric acid (HCL).
The hydrochloric acid has a very low pH value of 0.9-1.5. In addition, the cells form the so-called intrinsic factor. This substance forms a complex with vitamin B12 in the intestine, which can then pass through the wall of the small intestine. This vitamin is of particular importance in the formation of blood cells (erythropoiesis), which is why patients who have had their stomachs removed can develop anemia.
G-cells:These cells, which are preferentially located in the antrum of the stomach, have the ability to produce the hormone gastrin. This hormone causes an increase in the formation of HCl in the peripheral cells.