Gastric Secretions

• Nervous and hormonal mechanisms control the secretion of digestive juices
• The volume and content of gastric secretions are controlled by nervous and hormonal mechanisms
• The secretion of digestive juices is controlled by both nervous and hormonal mechanisms
• Nervous and hormonal mechanisms control both the volume of secretions produced and the specific content (e.g. enzymes, acids, etc.)
• Nervous Mechanism:

  • The sight and smell of food triggers an immediate response by which gastric juice is secreted by the stomach pre-ingestion
  • When food enters the stomach, it causes distension, which is detected by stretch receptors in the stomach lining
  • Signals are sent to the brain, which triggers the release of digestive hormones to achieve sustained gastric stimulation
• Hormonal Mechanism:

  • Gastrin is secreted into the bloodstream from the gastric pits of the stomach and stimulates the release of stomach acids
  • If stomach pH drops too low (becomes too acidic), gastrin secretion is inhibited by gut hormones (secretin and somatostatin)
  • When digested food (chyme) passes into the small intestine, the duodenum also releases digestive hormones: Secretin and cholecystokinin (CCK) stimulate the pancreas and liver to release digestive juices
  • Pancreatic juices contain bicarbonate ions which neutralise stomach acids, while the liver produces bile to emulsify fats