Stomach
The stomach is a hollow muscular organ located in the epigastric region. Its volume on an empty stomach is about 50 ml, but when filled it can stretch up to 1.5 liters. The main function is mechanical and chemical processing of food.
Sections of the stomach
- Cardial region - area of the entrance to the esophagus, contains the cardiac sphincter
- Bottom (vault) - dome-shaped part, usually filled with gas (air bubble on x-ray)
- Body - the main part where the main digestion occurs
- Pyloric (pyloric) section - tapers to the duodenum, contains the pyloric sphincter
Stomach wall
The wall consists of four layers:
- Mucous membrane - forms folds, contains gastric pits and glands
- Submucosa - loose tissue with vessels and nerves
- Muscular membrane - three layers of smooth muscle (longitudinal, circular, oblique)
- Serous membrane - visceral peritoneum
Three layers of muscle (instead of the usual two) provide powerful mixing - the stomach makes 3 peristaltic waves per minute.
Secretion
The glands of the stomach produce 2–3 liters of gastric juice per day:
- Parietal cells - hydrochloric acid (pH 1.5–2.0) and intrinsic Castle factor (necessary for the absorption of vitamin B12)
- Chief cells - pepsinogen, converted into pepsin under the influence of acid
- Accessory cells - mucus and bicarbonates to protect the wall
Hydrochloric acid is so aggressive that it dissolves metal. But the mucous-bicarbonate barrier creates a neutral zone 0.5 mm thick on the surface of the mucosa - thanks to this, the stomach does not digest itself.
Clinical significance
An imbalance between aggressive (acid, pepsin) and protective (mucus, bicarbonates) factors leads to peptic ulcer. The discovery of the bacterium Helicobacter pylori in 1982 made a revolution: it turned out that most ulcers are infectious in nature and can be treated with antibiotics.
You can view the stomach and its parts in three-dimensional format in the Humio application - the interactive model allows you to study the wall and surrounding structures layer by layer.