- Clinical science
The stomach is a hollow intraperitoneal organ that lies in the LUQ of the abdomen, between the esophagus and the duodenum. The stomach has two curvatures, two sphincters (i.e., the gastroesophageal sphincter and the pyloric sphincter), and four parts (i.e., the cardia, fundus, body, and pylorus). As part of the foregut, the arterial supply of the stomach is derived from the celiac trunk and its branches. The veins of the stomach drain into the portal vein and the lymphatics eventually drain into the celiac lymph nodes. The stomach is innervated by the autonomic nervous system as well as the enteric nervous system (Auerbach and Meissner plexuses). Histologically, the stomach has four layers: the mucosa, submucosa, muscularis propria, and the serosa. The mucosa is lined by columnar epithelium and has numerous glands containing specialized cells which produce various secretions, such as parietal cells that secrete gastric acid and intrinsic factor, and chief cells that secrete pepsinogen. Gastric secretions are regulated neurohormonally and occur in three distinct phases: cephalic, gastric, and intestinal. Acetylcholine (ACh), gastrin, and histamine are the main mediators that stimulate gastric secretions. Somatostatin, cholecystokinin (CCK), secretin, and gastric inhibitory peptide (GIP) are the main inhibitors.
- Location: the stomach bed, which is formed by the spleen, pancreas, left kidney and adrenal gland, transverse colon and mesocolon, and the diaphragm
- Superficial anatomy: epigastric and left upper quadrant (hypochondrium) region
- Epithelium: simple columnar epithelium
- Begins digestion process
- Holds chyme while digestion progresses in the intestines
- Kills bacteria (except Helicobacter pylori)
- Denatures proteins before being acted on by pepsin
Regions of the stomach
- Formed by the upper curvature of the stomach
- Body (stomach)
- Connects the body and pylorus of the stomach
- Extends from the greater curvature; covers the intestines
- Lesser omentum
The blood supply of the stomach arises from the celiac artery (trunk).
- From the anterior surface of the aorta, at the level of T12-L1
- Travels along the superior border of the pancreas
- Lesser curvature
- Greater curvature
- Gastric fundus
- Posterior gastric wall
- In most cases, the course of the veins is similar to the course of the arteries.
- Venous drainage into the portal vein
- Lymphatics: drains into the celiac lymph nodes, along with the liver, spleen, pancreas, and upper duodenum
- Fundus and body
- Mucosa: rugae with deep pits and shallow glands
- Contains the pyloric sphincter: circular smooth muscle
The gastric secretory response is divided into 3 phases:
- Cephalic phase: Mediated by vagal (cholinergic) mechanisms, which get activated by sight, smell, and taste of food as well as swallowing.
- Gastric phase: Mediated by gastrin, which is released in response to gastric distension and chemical stimulation (amino acids).
- Intestinal phase: Occurs in response to entry of acidic chyme into the duodenum, feedback regulatory hormones, such as somatostatin from D cells, decrease acid secretion.
- Produced by parietal cells
- Increased intracellular HCO3- → Cl- secretion
- Gastric acid contains high amounts of hydrochloric acid (HCl), K+
- Stimulated by
Overview of secretions
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Disturbances of stomach secretions
Helicobacter pylori gastritis
- ↑ Acid secretion
- ↓ Protective factors/mucus production
- Pernicious anemia
- NSAIDs: ↓ protective prostaglandins
- Proton pump inhibitors (PPIs)
- H2 antihistamines: reduce production of stomach acid
See the section on embryology in.