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Stomach

Last updated: May 5, 2021

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The stomach is a hollow intraperitoneal organ in the left upper quadrant of the abdomen, between the esophagus and the duodenum in the gastrointestinal tract. It is supplied with arterial blood 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. 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., parietal cells, which secrete gastric acid and intrinsic factor, and gastric chief cells, which secrete pepsinogen. Acetylcholine (ACh), gastrin, and histamine are the main stimulators of gastric secretions. Somatostatin, cholecystokinin (CCK), secretin, and gastric inhibitory peptide (GIP) are the main inhibitors.

Overview [1]

Anatomical parts

  • Sections of the stomach
    • Cardia: the part of the stomach that lies immediately distal to the gastroesophageal sphincter
    • 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 pyloric canal
  • Curvatures of the stomach
  • Sphincters of the stomach

The antrum and lower lesser curvature are the most common sites for peptic stomach ulcers.

Peritoneal attachments

The stomach is an intraperitoneal organ.

Vasculature, lymphatics, and innervation of the stomach [1]

Arteries

Arteries of the stomach
Structure Origin Important features
Lesser curvature Superior part
  • Left gastric artery
Inferior part
  • Right gastric artery
Greater curvature Superior part
  • Left gastroepiploic artery (also known as the left gastro-omental artery)
Inferior part
  • Right gastroepiploic artery (also known as the right gastro-omental artery)
Fundus
  • Short gastric arteries
Posterior gastric wall
  • Posterior gastric artery

Veins

Esophageal varices develop in portal hypertension due to the portosystemic shunting of blood from the left gastric vein (portal system) into the esophageal veins (caval system).

Lymphatics

Innervation

Innervation of the stomach
Name Effects
Autonomic nervous system Sympathetic
  • ↓ Glandular secretion
  • Peristalsis
  • ↑ Sphincter tone
Parasympathetic
  • ↑ Glandular secretion
  • Peristalsis
  • ↓ Sphincter tone (i.e., sphincter relaxation)
Enteric nervous system
  • Controls local gastrointestinal secretion and nutrient absorption
  • Controls inherent myogenic motility of the GIT

The left vagus nerve is anterior to the stomach, and the right vagus is posterior to it. This can be remembered with the mnemonic LARP: Left Anterior, Right Posterior.


Specialized cells of the gastric glands
Region Cell type Secretory product or function
Fundus and body
  • Pepsinogen
  • Parietal cell
    • Large eosinophilic cells with a circular nucleus (fried egg appearance)
    • Typically located in the middle of the gastric glands
Pylorus and antrum

Types of digestion

  • Mechanical digestion: peristalsis of the stomach against a closed pyloric sphincter → breakdown of food into smaller particles
  • Chemical digestion: enzymatic breakdown of food into chyme (a semifluid mixture of digested food and digestive enzymes) by gastric acid and enzymes

See “Secretory and regulatory products of the gastrointestinal tract.”

Mechanism of gastric acid secretion

Gastric acid contains high amounts of hydrochloric acid (HCl). Repeated vomiting can therefore cause metabolic alkalosis due to the loss of acid (H+).

Phases

Phases of gastric acid secretion [3]
Stimuli Main mediators Mechanism Effect on acid secretion Effect on gastric pH
Cephalic phase
  • Increase in acid secretion
  • Decreases
Gastric phase
  • Distention of the stomach by food
Intestinal phase
  • Decrease in acid secretion
  • Decreases (food moves into the duodenum buffering of acid by food decreases)

Disturbances of gastric secretions

Most important conditions that cause disturbances in gastric acid secretion
Condition Pathomechanism
Increased gastric acid secretion
  • Gastrin secretion
  • ↓ Protective factors/mucous production
Decreased gastric acid secretion (achlorhydria)

  1. Olszewski PK, Li D, Grace MK, Billington CJ, Kotz CM, Levine AS. Neural basis of orexigenic effects of ghrelin acting within lateral hypothalamus.. Peptides. 2003; 24 (4): p.597-602.
  2. Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences ; 2016
  3. Vakil BN. Physiology of gastric acid secretion. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/physiology-of-gastric-acid-secretion.Last updated: September 24, 2018. Accessed: January 30, 2019.