- Clinical science
The stomach is a hollow intraperitoneal organ in the left upper quadrant of the abdomen, between the and the in the . It is supplied with arterial blood from the and its branches. The veins of the stomach drain into the , and the lymphatics eventually drain into the . It is innervated by the sympathetic and parasympathetic nervous system, as well as the myenteric plexus and submucous plexus of the enteric nervous system. The stomach has four histological layers: the mucosa, submucosa, muscularis propria, and serosa. The mucosa is lined with numerous glands containing specialized cells that produce various secretions: e.g., , which secrete and , and gastric chief cells, which secrete pepsinogen. ( ), , and are the main stimulators of gastric secretions. , ( ), , and ( ) are the main inhibitors.
- LUQ of the abdomen
- Abdominal regions: epigastric, left hypochondriac, and umbilical
- Anterior to the stomach
- Posterior to the stomach
Sections of the stomach
- Cardia: the part of the stomach that lies immediately distal to the
- Gastric fundus: the dome-shaped region of the stomach just lateral to the cardia
- Body (stomach): the main portion of the stomach; lies between the fundus and the pylorus
- Pylorus: the terminal conical narrowing of the stomach; further subdivided into the proximal antrum and the distal
- Curvatures of the stomach
Sphincters of the stomach
- Gastroesophageal sphincter (lower esophageal sphincter)
- A muscular ring located in the
- Controls the movement of gastric contents into the duodenum
The stomach is an intraperitoneal organ.
- Omentum: extends from stomach (and proximal duodenum) to other abdominal organs
Peritoneal ligaments of the stomach
|Lesser curvature||Superior part|| |
|Inferior part|| || |
|Greater curvature||Superior part|| || |
|Inferior part|| || |
|Posterior gastric wall|
|Names||Drainage into||Important feature|
|Autonomic nervous system||Sympathetic|| |
|Parasympathetic|| || |
|Enteric nervous system|| || |
| || |
- The stomach's four histological layers are the same as the .
- The mucosa of the stomach is specialized in the following ways:
- It contains millions of gastric pits that are lined by mucous-secreting cells (foveolar cells) and open into ; one or more gastric glands.
- Gastric glands in the lamina propria contain; various specialized cells and vary; in composition and thickness depending on their location in the stomach.
- Stem cells ; located at the necks of the gastric glands proliferate and differentiate to replace gastric cells.
- Enteroendocrine cells ; are located throughout ; the gastric mucosa and secrete various .
|Specialized cells of the gastric glands|
|Region||Cell type||Secretory product or function|
|Fundus and body|
|Pylorus and antrum|| || |
| || |
Types of digestion
- Mechanical digestion: peristalsis of the stomach against a closed → breakdown of food into smaller particles
Chemical digestion: : enzymatic breakdown of food into chyme by and enzymes
- See for more information.
Mechanism of gastric acid secretion
- Gastric acid is secreted by the parietal cells.
- H+/K+-ATPase pump on the apical cell membrane of parietal cells secretes H+ ions into the lumen.
- parietal cell cytoplasm converts CO2 into H+ and . in
- Intracellular HCO3- is exchanged for Cl- through the basolateral membrane.
- H+ and Cl- are secreted into the gastric lumen as HCl.
Gastric acid contains high amounts of hydrochloric acid (HCl). Repeated vomiting can therefore cause metabolic alkalosis due to the loss of acid (H+).
|Phase||Stimuli||Main mediators||Effect on acid secretion||Mechanism||Effect on gastric pH|
|Cephalic phase|| || || |
|Gastric phase|| || || || |
|Intestinal phase|| || |
Disturbances of gastric secretions
- Helicobacter pylori : ↑ acid secretion and ↓ protective factors/mucous production
- ( syndromegastrinoma): ↑↑ gastrin secretion → parietal cell hyperstimulation → ↑↑ gastric acid secretion
- Pharmacologically-induced alterations in gastric acid secretion
- The stomach is a derivative of the primitive foregut.
- See .