Stomach is a muscular, hollow organ of the gastrointestinal tract, the continuous passage through which food travels during digestion. It lies mainly in the upper left abdomen, beneath the diaphragm, between the oesophagus and duodenum. It temporarily holds food, mixes it with gastric secretions and releases it into the small intestine.
Where is the stomach located, and what surrounds it?
The stomach occupies mainly the epigastric region, the upper central part of the abdomen, and the left hypochondriac region, beneath the left ribs. Its position and shape vary with filling, posture and body build. The oesophagus, the muscular tube carrying swallowed food, enters it from above; the duodenum, the first part of the small intestine, continues from its outlet.
In front, the stomach relates to the diaphragm, the muscular partition between chest and abdomen, the left lobe of the liver and the anterior abdominal wall. The spleen lies to its left. The transverse colon, the section of large intestine crossing the abdomen, lies below it.
Behind the stomach is the lesser sac, a space within the peritoneal cavity. This cavity is the potential space between the layers of the peritoneum, the membrane lining the abdominal cavity and covering many abdominal organs. Beyond the lesser sac lie the pancreas, left kidney, left adrenal gland, splenic artery and diaphragm, which contribute to the stomach’s posterior relations.
What are the main parts and surfaces of the stomach?
The stomach has anterior and posterior surfaces, facing forwards and backwards. Its lesser curvature is the shorter, concave border on the right, while its greater curvature is the longer, convex border extending around the left and lower sides.
| Region | Position | Main anatomical feature |
|---|---|---|
| Cardia | Around the oesophageal opening | Surrounds the entry of the oesophagus |
| Fundus of stomach | Above and to the left of the cardia | Forms the rounded upper dome |
| Body of stomach | Between the fundus and pyloric part | Forms the main central region |
| Pyloric part | Towards the duodenum | Narrows towards the stomach outlet |
The pyloric part comprises the pyloric antrum, its wider initial portion, and the pyloric canal, its narrower terminal portion. It ends at the pylorus, where thickened circular muscle forms the pyloric sphincter, a ring controlling the outlet into the duodenum.
The lesser omentum, a double layer of peritoneum, connects the lesser curvature to the liver. The greater omentum is a peritoneal fold that descends from the greater curvature before folding back towards the transverse colon. Other peritoneal folds connect the stomach to the spleen and diaphragm.
What layers make up the stomach wall?
From the inside out, the stomach wall has the following layers:
- Mucosa: the inner lining, containing glands that produce mucus, acid and digestive substances.
- Submucosa: supporting connective tissue containing blood vessels, lymphatic vessels and nerves.
- Muscular layer: smooth muscle, which contracts without voluntary control, arranged in inner oblique, middle circular and outer longitudinal layers.
- Serosa: the outer covering formed by visceral peritoneum, the layer of peritoneum covering an organ.
The mucosa and submucosa form rugae, folds that become less prominent as the stomach expands. Small openings called gastric pits lead into glands within the mucosa. The oblique muscle fibres are particularly characteristic of the stomach and help its wall mix the contents.
What supplies the stomach with blood and drains its lymph?
Arteries carry blood to the stomach through branches of the celiac trunk, a major artery supplying the upper abdominal digestive organs. The left gastric artery and right gastric artery run along the lesser curvature. The right gastric artery usually arises from the proper hepatic artery, which also supplies the liver.
The left and right gastro-omental arteries follow the greater curvature, while the short gastric arteries supply the upper stomach. These vessels form connections with one another along the curvatures. The left gastro-omental and short gastric arteries arise from the splenic artery; the right gastro-omental artery arises from the gastroduodenal artery.
Veins carry blood away from the stomach and generally accompany the arteries. The right gastric vein and left gastric vein drain into the portal vein, which carries blood from digestive organs towards the liver. Other gastric veins reach this system through the splenic vein or superior mesenteric vein.
Lymph, fluid collected from tissues by lymphatic vessels, follows routes alongside the gastric arteries. It passes through regional lymph nodes, small organs that filter lymph, and ultimately reaches the celiac lymph nodes around the celiac trunk.
How is the stomach innervated?
The stomach receives autonomic nerves, which regulate involuntary activity. Parasympathetic fibres reach it through the anterior and posterior vagal trunks, bundles derived from the vagus nerves. They promote gastric movement and secretion.
Sympathetic fibres reach the stomach through the celiac plexus, a network of nerves around the celiac trunk. They generally reduce gastric activity and constrict blood vessels. Nerve networks within the stomach wall also coordinate local muscle contractions and glandular secretion.
What does the stomach do during digestion?
The stomach stores a meal while its wall contracts to mix food with gastric juice, the fluid secreted by its glands. Acid provides the conditions in which pepsin, a protein-digesting enzyme, acts. Mucus helps protect the lining from the contents.
Mixing produces chyme, a semifluid mixture of food and gastric secretions. Contractions move it towards the pylorus, and the pyloric sphincter helps regulate its passage into the duodenum. Gastric glands also produce intrinsic factor, a protein needed for vitamin B12 absorption later in the small intestine.
How can you find the stomach in the 3D model?
In the 3D model next to this article, rotate and zoom towards the upper left abdomen, then select and isolate the stomach. Hide or fade selected structures, or pull parts apart, to explore their spatial relationships. Cut a section along the sagittal, coronal or transverse plane to view the model from a different perspective. Switch layers on and off to examine its position relative to surrounding structures.