• Clinical science

Stomach

Abstract

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.

Gross anatomy

Overview

Regions of the stomach

  • Cardia
    • Located below the diaphragm
    • Originates at the z-line
    • Forms the gastroesophageal junction
  • Fundus
    • Formed by the upper curvature of the stomach
  • Body (stomach)
  • Antrum
    • Connects the body and pylorus of the stomach
  • Pylorus
    • Connects to the duodenum
    • Divided into pylorus antrum and pyloric canal
    • Contains the pyloric sphincter:
      • Contraction prevents passage of chyme into the duodenum
        • Contraction is stimulated by secretin, CCK, and GIP

Omentum

Vasculature

  • 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

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

Microscopic anatomy

Gastric cells and secretory products

Gastric secretions

The gastric secretory response is divided into 3 phases:

  1. Cephalic phase: Mediated by vagal (cholinergic) mechanisms, which get activated by sight, smell, and taste of food as well as swallowing.
  2. Gastric phase: Mediated by gastrin, which is released in response to gastric distension and chemical stimulation (amino acids).
  3. 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.

Gastric acid

Overview of secretions

Cell type Function Control
Stimulation Inhibition
Intrinsic factor
  • Binds to Vitamin B12
  • Required for absorption in the terminal ileum
Gastric acid
  • Decreases stomach pH
  • Activates pepsinogen to pepsin
Pepsin
  • Secreted as pepsinogen
  • Activated by acidic gastric pH (H+)
  • Protein digestion
  • Inactivated by high pH
  • -
Bicarbonate
  • Mucosal cells
  • Secretin
  • -
Gastrin
  • -
Ghrelin
  • Stomach
  • Fasting
  • Sleep deprivation
  • Intake of food (stretching of stomach)

Disturbances of stomach secretions

References:[1][2]

Diseases of the stomach

Embryology

See the section on embryology in overview of the gastrointestinal tract.

  • 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): pp. 597–602. pmid: 12860204.
  • 2. Liddle RA. Ghrelin. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/ghrelin. Last updated July 7, 2017. Accessed November 24, 2018.
  • 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.
  • Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences; 2015.
last updated 02/18/2019
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