GI HORMONES & THEIR ROLE
IN SECRETOMOTOR
FUNCTION OF THE GUT
RK Goit, Lecturer
Department of Physiology
 GI Hormones - secreted from the endocrine cells
 especially in stomach & small intestine
 endocrine cells
 Enteroendo...
1. Gastrin family-gastrin & CCK
2. Secretin family-secretin, glucagon, GLI, VIP &
GIP
3. Other polypeptides
Gastrin
 pyloric glands (G Cells)-antral portion of the
stomach
 also found in the pancreatic islets in fetal life
 ant...
 a polypeptide hormone
 heterogeneity
 Macroheterogeneity-peptide chains of various length
 Microheterogeneity-differe...
Functions
 stimulation of gastric acid & pepsin secretion
 stimulates growth of gastric mucosa & mucosa of
intestine
 ↑...
Stimulate that ↑ gastrin secretion
 Luminal
 Peptides & amino acids
 Distension
 Neural
 ↑ vagal discharge via GRP
 ...
Stimulate that ↓ gastrin secretion
 Luminal
 Acid
 Somatostatin
 Blood-borne
 Secretin, GIP, VIP, Glucagon
Cholecystokinin-Pancreozymin
(CCK-PZ or CCK)
 I cells in the upper intestine
 nerves in the distal ileum & colon
 neuro...
 polypeptide hormone
 heterogeneity
 CCK 58, CCK 39, CCK 33, CCK 12, CCK 8, CCK 4
 Duodenum & jejunum CCK 12, CCK 8
 ...
Functions
 pancreatic secretion rich in enzymes
 augments the action of secretin to produce
alkaline pancreatic secretio...
 causes contraction of gall bladder
 ↑ secretion of enterokinase
 enhance motility of small intestine
 stimulates colo...
Secretin
 S cells located in the mucosa of the upper part of
small intestine (duodenum & jejunum)
 polypeptide hormone (...
Functions
 ↑ secretion of pancreatic juice rich in bicarbonate
 ↑ alkaline bile secretion
 augments the action of CCK t...
Glucagon & Glicentin
Preproglucagon (179 AA)
A cells L cells
pancreatic islets lower GIT
upper GIT
Glucagon Glicentin
 pr...
VIP
 polypeptide containing 28 AA
 nerves in the GIT
 also found in blood
 also found in the brain & autonomic nerves
Functions
 ↑ intestinal secretion rich in electrolytes & water
 causes vasodilation
 ↓ GI motility
 potentiates the ac...
GIP
 polypeptide hormone containing 42 AA
 K cells present in the mucosa of duodenum &
jejunum
 inhibits gastric acid s...
Motilin
 polypeptide hormone containing 22 AA
 enterochromaffin cells & Mo cells present in the
mucosa of GIT
 ↑ GI mot...
Neurotensin
 a polypeptide hormone containing 13 AA
 neurons & mucosal cells of ileum
 inhibits gastric acid secretion ...
Substance P
 Endocrine & nerve cells in the GIT
 ↑ intestinal motility of the small intestine
Somatostatin
 a polypeptide containing either SS 14 or SS 28
 D cells in GIT, hypothalamus, D cells of pancreas
 inhibi...
GRP
 polypeptide containing 27 AA
 vagal nerve endings that terminate on G cells
 ↑ gastrin secretion
Guanylin
 polypeptide hormone containing 15 AA
 secreted form the paneth cells
 ↑ secretion of Cl- into the intestinal ...
Peptide YY
 entire GIT (ileum & colon)
 inhibits the food intake
 inhibits gastric acid secretion & motility
Ghrelin
 polypeptide (28 AA)
 oxyntic cells of stomach (intestine)
 ↓ when food is eaten & ↑ during fasting
References
Ganong Review of Medical Physiology, 22/E
THANK YOU
Gastrointestinal hormomes & their role in secretomotor fuction of the gut
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Gastrointestinal hormomes & their role in secretomotor fuction of the gut

  1. 1. GI HORMONES & THEIR ROLE IN SECRETOMOTOR FUNCTION OF THE GUT RK Goit, Lecturer Department of Physiology
  2. 2.  GI Hormones - secreted from the endocrine cells  especially in stomach & small intestine  endocrine cells  Enteroendocrine - GI hormones  Enterochromaffin - serotonin  APUD – amines & polypeptides (neuroendocrine cells)  Carcinoid tumors originate from neuroendocrine cells.
  3. 3. 1. Gastrin family-gastrin & CCK 2. Secretin family-secretin, glucagon, GLI, VIP & GIP 3. Other polypeptides
  4. 4. Gastrin  pyloric glands (G Cells)-antral portion of the stomach  also found in the pancreatic islets in fetal life  anterior & intermediate lobes of the pituitary gland, in the hypothalamus, medulla oblongata, & in the vagus & sciatic nerves
  5. 5.  a polypeptide hormone  heterogeneity  Macroheterogeneity-peptide chains of various length  Microheterogeneity-differences in molecular structure  G 34, G 17, G 14 (depending on number of AA)  G 17- principal gastrin secreted from the stomach
  6. 6. Functions  stimulation of gastric acid & pepsin secretion  stimulates growth of gastric mucosa & mucosa of intestine  ↑ gastric motility  contraction of muscles at the gastro-esophageal junction  exocrine pancreatic secretion  insulin secretion  stimulates mass movement of large intestine  colonic contraction that initiates gastrocolic reflex after a meal
  7. 7. Stimulate that ↑ gastrin secretion  Luminal  Peptides & amino acids  Distension  Neural  ↑ vagal discharge via GRP  Blood-borne  Calcium  Epinephrine
  8. 8. Stimulate that ↓ gastrin secretion  Luminal  Acid  Somatostatin  Blood-borne  Secretin, GIP, VIP, Glucagon
  9. 9. Cholecystokinin-Pancreozymin (CCK-PZ or CCK)  I cells in the upper intestine  nerves in the distal ileum & colon  neurons in brain ( cerebral cortex) & in nerves in many part of the body  peptides & amino acids, & long chain fatty acids
  10. 10.  polypeptide hormone  heterogeneity  CCK 58, CCK 39, CCK 33, CCK 12, CCK 8, CCK 4  Duodenum & jejunum CCK 12, CCK 8  Enteric & pancreatic nerves CCK 4  Brain CCK 58, CCK 8  half-life of CCK is about 5 minutes
  11. 11. Functions  pancreatic secretion rich in enzymes  augments the action of secretin to produce alkaline pancreatic secretion  relaxation of sphincter of Oddi  stimulate growth of pancreas  inhibits gastric acid secretion  inhibits gastric motility-delays gastric emptying
  12. 12.  causes contraction of gall bladder  ↑ secretion of enterokinase  enhance motility of small intestine  stimulates colonic movements  augments contraction of pyloric sphincter  stimulates glucagon secretion
  13. 13. Secretin  S cells located in the mucosa of the upper part of small intestine (duodenum & jejunum)  polypeptide hormone (27 AA)  acid chyme (↓ 4.5-5.0)- secretin
  14. 14. Functions  ↑ secretion of pancreatic juice rich in bicarbonate  ↑ alkaline bile secretion  augments the action of CCK to produce pancreatic secretion rich in enzymes  ↓ gastric acid secretion & motility  contraction of pyloric sphincter
  15. 15. Glucagon & Glicentin Preproglucagon (179 AA) A cells L cells pancreatic islets lower GIT upper GIT Glucagon Glicentin  produces hyperglycemia
  16. 16. VIP  polypeptide containing 28 AA  nerves in the GIT  also found in blood  also found in the brain & autonomic nerves
  17. 17. Functions  ↑ intestinal secretion rich in electrolytes & water  causes vasodilation  ↓ GI motility  potentiates the action of acetylcholine on salivary glands  inhibits gastric acid secretion
  18. 18. GIP  polypeptide hormone containing 42 AA  K cells present in the mucosa of duodenum & jejunum  inhibits gastric acid secretion & motility  stimulate insulin secretion
  19. 19. Motilin  polypeptide hormone containing 22 AA  enterochromaffin cells & Mo cells present in the mucosa of GIT  ↑ GI motility (interdigestive phase)  a major regulator of MMC
  20. 20. Neurotensin  a polypeptide hormone containing 13 AA  neurons & mucosal cells of ileum  inhibits gastric acid secretion but ↑ ileal blood flow
  21. 21. Substance P  Endocrine & nerve cells in the GIT  ↑ intestinal motility of the small intestine
  22. 22. Somatostatin  a polypeptide containing either SS 14 or SS 28  D cells in GIT, hypothalamus, D cells of pancreas  inhibits secretion of gastrin, VIP, GIP, secretin & motilin  inhibits pancreatic exocrine secretion; gastric acid secretion & motility; gall bladder contraction; & absorption of glucose, amino acids & triglycerides
  23. 23. GRP  polypeptide containing 27 AA  vagal nerve endings that terminate on G cells  ↑ gastrin secretion
  24. 24. Guanylin  polypeptide hormone containing 15 AA  secreted form the paneth cells  ↑ secretion of Cl- into the intestinal lumen
  25. 25. Peptide YY  entire GIT (ileum & colon)  inhibits the food intake  inhibits gastric acid secretion & motility
  26. 26. Ghrelin  polypeptide (28 AA)  oxyntic cells of stomach (intestine)  ↓ when food is eaten & ↑ during fasting
  27. 27. References Ganong Review of Medical Physiology, 22/E
  28. 28. THANK YOU

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