Phases of Gastric Secretion
  • Similarly to Salivary secretion, gastric secretion can be divided into three phases:

Cephalic phase
  • accounts for around 30% of the response to a meal
  • controlled by the brain
  • stimulated by senses - taste, smell, vision but also by thoughts.
  • Vagal impulses releases ACh in main body of the stomach
  • apart from directly stimulating secretion of acid it stimulates histamine release
  • histamine stimulates release of gastrin from parietal G cells
  • the three compounds initiate the cascade for production and release of HCl
Gastric phase
  • accounts for around 60% of the response
    involves both neural and humoral reflexes
  • initiated by:
  • distension of the stomach
  • the presence of polypeptides in the antrum stimulate G cells to secrete gastrin
  • low pH at antral mucosa inhibits gastric phase through the release of somatostatin from endocrine cells
  • an important negative feedback regulation of gastric HCl secretion
Intestinal phase
  • accounts for less than 10%
  • principle feedback via hormones from duodenum
  • fats in the duodenum cause the release of Cholecystokinin (CCK) and Gastric Inhibitory Peptide (GIP)
  • CCK stimulates chief cells to release pepsinogen
  • GIP releases somatostatin- inhibits acid production
  • secretin release from the duodenum also causes a release of stomatostatin
  • acid in the duodenum acts by negative feedsback via intrinsic nerves