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Bio& 242 Unit 1 / Lecture 4. Hormonal control in the Digestive system: Gastric hormones. GASTRIN : Secretion: By enteroendocrine (G) cells in gastric pits of the mucosa. Stimulus: Stomach distention and acid pH of chyme causes Gastrin. Action: 1. increases HCl production in stomach

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hormonal control in the digestive system gastric hormones
Hormonal control in the Digestive system: Gastric hormones

GASTRIN:

Secretion: By enteroendocrine (G) cells in gastric pits of the mucosa.

Stimulus: Stomach distention and acid pH of chyme causes Gastrin.

Action:

  • 1. increases HCl production in stomach
  • 2. increases gastric motility
  • 3. stimulates growth of gastric mucosa
  • 4. contract lower esophageal sphincter
  • 5. relaxes pyloric sphincter
  • 6. relaxes ileocecal sphincter
hormonal control in the digestive system gastric hormones1
Hormonal control in the Digestive system: Gastric hormones

Somatostatin:

Secretion: By enteroendocrine (D) cells in gastric pits of the mucosa in the pylorus.

Stimulus: continuously released, overridden by Gastrin and nerves

Action:

  • Inhibition of Gastrin production
hormonal control in the digestive system small intestinal hormones
Hormonal control in the Digestive system: Small Intestinal hormones

SECRETIN:

Secretion: By Enteroendocrine (S) cells in the Crypts of Lieberkuhn of small intestine.

Stimulus: Acid chyme in small intestine causes secretion of Secretin:

Actions:

  • stimulate secretion of pancreatic juice and bile that is rich in bicarbonate ions.
  • inhibit production of HCl in stomach
  • promote growth and maintenance of the pancreas
  • enhance effects of Cholecystokinin (CCK)
  • Increases rate of bile secretion by hepatocytes
hormonal control in the digestive system small intestinal hormones1
Hormonal control in the Digestive system: small intestinal hormones

CHOLECYSTOKININ (CCK):

Secretion: Enteroendocrine (CCK) cells in the small intestine mucosa Crypts of Lieberkuhn

Stimulus: Chyme rich in amino acids, triglycerides and fatty acids enter the small intestine.

Actions:

  • increases secretion of pancreatic juice rich in digestive enzymes
  • opens the Sphincter of Oddi
  • contracts the gallbladder
  • Inhibits gastric secretion and motility
  • May reduce hunger
hormonal control in the digestive system small intestinal hormones2
Hormonal control in the Digestive system: small intestinal hormones

Gastric Inhibitory Peptide (GIP):

Secretion: Enteroendocrine cells in the small intestine mucosa Crypts of Lieberkuhn

Stimulus: Chyme rich in triglycerides, fatty acids, and glucose enter the small intestine.

Actions:

  • Stimulates release of insulin by beta cells
  • Inhibits gastric secretion and motility
  • Stimulates lipogenesis by adipose tissue
  • Stimulates glucose use by skeletal muscle cells
hormonal control in the digestive system small intestinal hormones3
Hormonal control in the Digestive system: small intestinal hormones

Vasoactive Intestinal Peptide (VIP):

Secretion: Enteroendocrine cells in the small intestine mucosa Crypts of Lieberkuhn

Stimulus: Chyme entering the small intestine.

Actions:

  • Stimulates buffer secretion
  • Inhibits gastric secretion
  • Dilates intestinal capillaries
hormonal control in the digestive system pancreas and islets of langerhans
Hormonal control in the Digestive system Pancreas and Islets of Langerhans

Endocrine cells make up 1% of the pancreas and are observed as Islets of Langerhans:

1. Alpha Cells: Secrete Glucagon (increases blood sugar)

2. Beta Cells: Secrete Insulin (decreases blood sugar)

3. Delta Cells: Secretes Somatostatin (inhibits secretion of both glucagon and insulin and prolongs rate of nutrient absorption / decrease depletion)

4. F-Cells: Secrete Pancreatic Polypeptide (inhibit secretion of digestive enzymes and inhibits contraction of the gallbladder)