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 that lies between the fundus and the pylorus
- Pylorus: the terminal conical narrowing of the stomach that can be 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
Vasculature, lymphatics, and innervation of the stomach 
|Arteries of the stomach|
|Lesser curvature||Superior part|| |
|Inferior part|| |
|Greater curvature||Superior part|| |
|Inferior part|| |
|Fundus|| || |
|Posterior gastric wall|| |
- Veins of the stomach
- Drain into
- The anastomosis between the left gastric vein and the esophageal vein is a site of portosystemic anastomosis.
|Innervation of the stomach|
|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 mucus-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 (a semifluid mixture of digested food and digestive enzymes) by and enzymes
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.
|Phases of gastric acid secretion |
|Stimuli||Main mediators||Mechanism||Effect on acid secretion||Effect on gastric pH|
|Cephalic phase|| || |
|Gastric phase|| || |
|Intestinal phase|| || |
Disturbances of gastric secretions
|Most important conditions that cause disturbances in gastric acid secretion|
|Increased gastric acid secretion|| |
| || |
|Decreased gastric acid secretion (achlorhydria)|| |
- The stomach is a derivative of the primitive foregut.
- See “.”