Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.
Gastric Secretion
and
Its Regulation
Part II
Learning Objectives ….
•Gastric Hormones
•Pancreatic secretions
•Intestinal secretions
•Regulation
GI Hormones are broadly classified into 3 categories:
I. Gastrin family that includes cholecystokinin and gastrin.
II. Sec...
Gastrin
Source:
• Produced by G cells in the stomach located mainly in antral region
with apex projecting towards the lume...
• Major hormone that stimulates gastric acid secretion.
• Gastrin G34 and G17,- two major forms of gastrin.
• Most gastrin...
Products of protein digestion
(peptides and amino acids)
Vagal stimulation
Releasing GRP
Food in stomach
(gastric distensi...
2. Tropic action
3. Stimulates gastric motility
4. Stimulates insulin secretion and exocrine pancreatic secretion.
5. Colo...
Cholecystokinin
Source:
• Produced by I cells of the small intestine.
Functions
• Contraction of Gall Bladder.
• Stimulates pancreatic secretion rich in enzymes.
• Relaxation of Sphincter of O...
Regulation :
Cholecystokinin
Contact of intestinal mucosa with fatty acids and peptides
Stimulation of I cells
Secretion o...
Secretin
First hormone to be discovered
• Selectively expressed in specialized enteroendocrine cells of the
small intestin...
Functions
1. It increases secretion of pancreatic juice rich on bicarbonate.
2. It also increases alkaline bile secretion....
Regulation of
secretin
Contact of intestinal mucosa with acidic chyme and peptides
Stimulation of S cells
Secretion of sec...
Glucagon
• Synthesized and released from pancreatic alpha cells and from
intestinal L cells of the ileum and colon.
• Gluc...
Somatostatin
• Found in almost every organ in the body and throughout the GI
tract.
• In the gut, somatostatin is produced...
Somatostatin has broad inhibitory actions:
• Reduces gastric acid production and pepsinogen secretion
• Inhibits pancreati...
Vasoactive Intestinal Polypeptide (VIP)
• VIP secreted from mucosal cells of entire GIT
• Found in nerves of GIT, other au...
• Markedly increases intestinal secretion rich in electrolytes and water; in excess
produces watery diarrhea.
• Decreases ...
Glucose-dependent Insulinotropic Polypeptide (GIP)
• K cells present in the mucosa of duodenum and jejunum.
• Inhibits gas...
Motilin
• Endocrine cells of the duodenal epithelium.
• Contraction of intestinal smooth muscle  increases GI motility,
e...
Leptin
secreted :
• Adipocytes
• the chief cells of the stomach
• Placenta,
• Breast milk.
• Blood leptin levels reflect t...
• Leptin's ability to reduce food intake occurs within the brain
• Decreasing NPY a potent stimulant of food intake
• Incr...
Ghrelin
gastric fundus
• Intestine
• Pancreas
• Pituitary
• Kidney
• Placenta.
• Strong orexigenic that play a central rol...
Guanylin
• Paneth cells (endocrine cells: crypts of Lieberkuhn of small
intestine)
• Stimulate guanylyl cyclase  increase...
Pancreatic Secretions
• Bicarbonate
• Enzymes (amylase, trypsin, chymotrypsin, elastase,
carboxypeptidase, A and B, lipase...
Intestinal secretions
• Villi
• Microvilli: 1) Increase surface area,
2) Seat for attachment of enzymes
for terminal diges...
What we learned ….
•Gastric Hormones
•Pancreatic secretions
•Intestinal secretions
•Regulation
THANK YOU
gastric secretion and its regulation
gastric secretion and its regulation
Upcoming SlideShare
Loading in …5
×

gastric secretion and its regulation

1,724 views

Published on

discusses on hormonal secretions, pancreatic and intestinal secretions

Published in: Education
  • Be the first to comment

gastric secretion and its regulation

  1. 1. Gastric Secretion and Its Regulation Part II
  2. 2. Learning Objectives …. •Gastric Hormones •Pancreatic secretions •Intestinal secretions •Regulation
  3. 3. GI Hormones are broadly classified into 3 categories: I. Gastrin family that includes cholecystokinin and gastrin. II. Secretin family that includes GIP, Glucagon, secretin and VIP III. Other polypeptides.
  4. 4. Gastrin Source: • Produced by G cells in the stomach located mainly in antral region with apex projecting towards the lumen.
  5. 5. • Major hormone that stimulates gastric acid secretion. • Gastrin G34 and G17,- two major forms of gastrin. • Most gastrin in the circulation during fasting is G34, whereas after a meal it is G17. • Antral G cells are primary source of G17, whereas duodenal G cells are primary source of G-34. • Metabolized: kidney (primarily), intestine and liver.
  6. 6. Products of protein digestion (peptides and amino acids) Vagal stimulation Releasing GRP Food in stomach (gastric distension) G cells of stomach Secretion of gastrin Parietal cells of stomach HCl Secretion High acidic gastric content (autoregulation of gastrin secretion) Acidic duodenal chyme (secretes hormones) Intestinal hormones (GIP,VIP,, Somatostatin, secretin and glucagon) (-)(-) (-) Control of HCl Secretion
  7. 7. 2. Tropic action 3. Stimulates gastric motility 4. Stimulates insulin secretion and exocrine pancreatic secretion. 5. Colonic contraction that initiates gastrocolic reflex after a meal, thus activating defecation after meal. 6. Stimulates histamine secretion of ECL (enterochromaffin like cells)
  8. 8. Cholecystokinin Source: • Produced by I cells of the small intestine.
  9. 9. Functions • Contraction of Gall Bladder. • Stimulates pancreatic secretion rich in enzymes. • Relaxation of Sphincter of Oddi • Augments the action of Secretin to produce alkaline pancreatic secretion. • Inhibits gastric acid secretion and gastric motility delays gastric emptying. • Stimulates growth of pancreas. • Enhances motility of small intestine and colonic movement. • In brain, acts as anorexigenic neurotransmitter i.e inhibits food intake.
  10. 10. Regulation : Cholecystokinin Contact of intestinal mucosa with fatty acids and peptides Stimulation of I cells Secretion of CCK Increased release of bile and pancreatic secretion Digestion of protein and fat Fatty acids and peptides Positive feedback (+)
  11. 11. Secretin First hormone to be discovered • Selectively expressed in specialized enteroendocrine cells of the small intestine called S cells • Mechanism of action: secretin acts on adenylate cyclase on the cell membrane and increases cytosolic formation of cAMP.
  12. 12. Functions 1. It increases secretion of pancreatic juice rich on bicarbonate. 2. It also increases alkaline bile secretion. 3. Augments the action of CCK to produce pancreatic secretion rich in enzymes. 4. Decreases gastric acid secretion and motility. 5. Causes contraction of pyloric sphincter.
  13. 13. Regulation of secretin Contact of intestinal mucosa with acidic chyme and peptides Stimulation of S cells Secretion of secretin Stimulation of pancreatic secretion rich in water and bicarbonate H2O AND HCO3 floods duodenum Neutralization of acid in duodenum(increase duodenal pH) (-)
  14. 14. Glucagon • Synthesized and released from pancreatic alpha cells and from intestinal L cells of the ileum and colon. • Glucagon is released from pancreas in response to a meal and binds to G protein–coupled receptors on skeletal muscle and the liver to exert its glucoregulatory effects. • Regulates glucose homeostasis via gluconeogenesis, glycogenolysis, and lipolysis and is counter regulatory to insulin.
  15. 15. Somatostatin • Found in almost every organ in the body and throughout the GI tract. • In the gut, somatostatin is produced by • D cells in the gastric and intestinal mucosa • islets of the pancreas, • enteric neurons.
  16. 16. Somatostatin has broad inhibitory actions: • Reduces gastric acid production and pepsinogen secretion • Inhibits pancreatic enzyme, fluid, and bicarbonate secretion and reduces bile flow. • Its effects on gut motility are largely inhibitory • Reduces intestinal transport of nutrients and fluid, • Inhibitory effects on tissue growth and proliferation.
  17. 17. Vasoactive Intestinal Polypeptide (VIP) • VIP secreted from mucosal cells of entire GIT • Found in nerves of GIT, other autonomic nerves, blood and also in brain. • VIP is a potent vasodilator that • Increases blood flow in the GI tract • Smooth muscle relaxation
  18. 18. • Markedly increases intestinal secretion rich in electrolytes and water; in excess produces watery diarrhea. • Decreases GI motility. • neuromodulator of sphincters of the GI tract: • LES • Sphincter of Oddi
  19. 19. Glucose-dependent Insulinotropic Polypeptide (GIP) • K cells present in the mucosa of duodenum and jejunum. • Inhibits gastric secretion and motility: Gastric inhibitory peptide (GIP). • Stimulates insulin secretion.
  20. 20. Motilin • Endocrine cells of the duodenal epithelium. • Contraction of intestinal smooth muscle  increases GI motility, esp in interdigestive phase. • It is a major regulator of migrating motor complex(MMC) that sweeps and cleans the intestine and thus, prepares the intestine for next meal.
  21. 21. Leptin secreted : • Adipocytes • the chief cells of the stomach • Placenta, • Breast milk. • Blood leptin levels reflect total body fat stores. • Reduce food intake.
  22. 22. • Leptin's ability to reduce food intake occurs within the brain • Decreasing NPY a potent stimulant of food intake • Increasing (α−MSH), an inhibitor of food intake. • Peripherally, leptin acts synergistically with cholecystokinin to reduce meal size.
  23. 23. Ghrelin gastric fundus • Intestine • Pancreas • Pituitary • Kidney • Placenta. • Strong orexigenic that play a central role in the neurohormonal regulation of food intake and energy homeostasis.
  24. 24. Guanylin • Paneth cells (endocrine cells: crypts of Lieberkuhn of small intestine) • Stimulate guanylyl cyclase  increase conc. of cGMP  increases activity of chloride channels  increases chloride secretion into the intestine regulates fluid movement across intestinal tract.
  25. 25. Pancreatic Secretions • Bicarbonate • Enzymes (amylase, trypsin, chymotrypsin, elastase, carboxypeptidase, A and B, lipase, colipase, cholesterol esterase, phospholipase, ribonuclease) Regulation: i. Hormones: Secretin and CCK ii. Neural : Parasympathetic and sympathetic
  26. 26. Intestinal secretions • Villi • Microvilli: 1) Increase surface area, 2) Seat for attachment of enzymes for terminal digestion of CHO+proteins 3) Stirring mechanism Brush Border Enzymes: Maltase, dextrinase, lactase Enterokinase, dipeptidyl peptidase, aminopeptidase
  27. 27. What we learned …. •Gastric Hormones •Pancreatic secretions •Intestinal secretions •Regulation
  28. 28. THANK YOU

×