8th February 2024

Overview

Gastric motility is controlled by smooth muscle cells and allows mixing of food. This is mediated by the smooth muscle cells, and the parasympathetic nervous system stimulates increased contractility, while reduced contractility is seen with increased sympathetic stimulation. 

The stomach also relaxes and distends to receive ingested food, and CCK stimulates this. Gastric emptying is stimulated by stomach distension and gastrin while it is reduced by fatty acids, secretin, CCK and acidic environments in the duodenum. 

The stomach also produces gastric acid, mediated by the parietal cells. Secretion is stimulated by vagal stimulation, gastrin, and histamine (H2 receptors are found on parietal cells). Secretion is inhibited by low pH (<3), small intestine peptide/hormone (e.g., secretin, CCK, GIP), anticholinergics (e.g., atropine), H2 receptors antagonist (e.g., Cimetidine), proton pump inhibitors(e.g., omeprazole). The parietal cells also produce an intrinsic factor that is vital in the absorption of vitamin B12. 

Other cells within the stomach include:

• Mucosal cells (located in stomach antrum): produce mucous and HCO3-
• Chief cells (located in the stomach body): produce pepsinogen
• G cells (located in the stomach antrum): produce gastrin
• Neuroendocrine cells: produce multiple secretory products, e.g., somatostatin