2. OBJECTIVES
INTRODUCTION.
HISTORY.
CLASSIFICATION.
COMMON DESCRIPTION.
CELLS PRODUCING – SOURCE.
CLASSIFICATION.
LOCATION.
STIMULUS.
MECHANISM OF ACTION.
ACTIONS.
APPLIED.
3. INTRODUCTION
Earlier ---Believed Regulatory mechanisms were
controlled by the nervous system
Later numerous chemicals in the name of
hormones were found
Hormones -- Play an integral role in most of the
regulatory mechanisms in our body
Main objective of learning this topic in detail
4. INTRODUCTION. (Cont….)
Largest endocrine organ
Enteric endocrine system.
Total about 30 GIT hormones.
These are biologically active
polypeptide & act in a paracrine
fashion.
Main function is:
1. To regulate the git secretion
2. To regulate the movement of GI
tract.
PARACRINE HORMONES.
6. HISTORY.
BAYLISS & STARLING (1902) discovered the first
GIT hormone secretin.
GREGORY AND TRACY (1964) --chemical
definition of Gastrin.
YALOW AND BENSON (1966) invented RIA to
estimate quantity .
JORPES AND MUTT (1996) chemical nature of
secretin and cholecystokinin and a group of other
hormones.
8. Endocrine cells - GIT
“Enteroendocrine cells”
More than 15 types present
Spread all over --stomach, small
intestine,
colon
Many cells secrete only one
hormone
eg. G cells, S cells, K cells, M
cells
Cells that manufacture Serotonin
in addition to polypeptides –
Entero- chromaffin cells.
9. APUD cells or Neuroendocrine cells
(Amine Precursor Uptake and
Decarboxylase).
Cells that manufacture amines in addition
to polypeptides
Found in lungs and other organs in
addition to GIT
Can form carcinoid tumors
13. G.I. HORMONES
Structure ofStructure of SecretinSecretin (27 AA)(27 AA)
(comparison with other GI hormones)(comparison with other GI hormones)
Gastrin (17 AA)Gastrin (17 AA)
Cholecystokinin (CCK (33 AA))Cholecystokinin (CCK (33 AA))
19. Mode of action
Gastrin Receptor (parietal cells)
Intracellular
calcium(IP3)
H+
-K+
ATPase Ca++ activates
protein kinase
Acid secretion
20. Function of gastrin.
Stimulate Gastric Acid and pepsin
secretion
Trophic action – growth of gastric
mucosa and intestinal mucosa
Stimulate Gastric Motility
Contraction of muscle at gastro
esophageal junction cardiac
sphincter prevents reflux
oesophagitis Peristaltic
contraction
21. Functions of Gastrin.
Stimulate Exocrine pancreas secretion
Stimulate Insulin secretion
Stimulate mass movement of large
intestine
Colonic contraction that initiates Gastro-
colic reflex – defecation after meal
Stimulate Histamine secretion from ECL
cells
22. Food in the stomach
(gastric distension)
Products of protein digestion
(peptides and amino acids)
Vagal stimulation
(Non – cholinergic)
G cells of stomach
Secretion of gastrin
Parietal cells of stomach
HCI secretion
High acidic gastric content
(auto regulation of
gastrin secretion
Acidic duodenal chyme
(secrete hormones)
Intestinal hormones
(GIP, VIP, somatostatin, secretin
& glucagon)
REGULATION
23. CHOLECYSTOKININ-pz.
GREEK –
chole, "BILE"; cysto, "SAC"; kinin, "MOVE"; so MOVE
THE BILE-SAC
Source: I cells – Granular mucosal cells of
duodenum & jejunum.
Also – cerebral cortex, somatic nerves,
distal ileum, colon.
24. STRUCTURE:
CCK 58 39 33 12 8 4
Stimuli: Acid, protein, fat
Digested products in duodenum
Initially considered 2 hormones later found to be
one
25. Functions of CCK-pz
Contraction of gall bladder –
increased bile release
Stimulate pancreatic secretion
rich in enzyme
Augments the action of secretin
Inhibit gastric acid secretion
Inhibit gastric motility
Delay gastric emptying
26. Regulation of secretions.
•CCK-PZ –
• Increased by
Acid in duodenum
Products of carbohydrates, fats, & proteins
digestion.
Mainly peptides & amino acids
Positive feedback–
27. SECRETIN.
Bayliss & Starling (1902)
discovered the first gastro
intestinal hormone SECRETIN
SOURCE : S cells – upper SI
(Argentaffin cells)
Structure : 27 AA
Stimuli : Acid in duodenum
28. Function of secretin.
Stimulate secretion of pancreatic juice rich
in HCO3
-
Stimulate bile secretion.
Augment action of CCK to produce pancreatic
secretion rich in enzymes
Reduces the gastric acid secretion and
motility
Contraction of pyloric sphincter
30. GASTRIC INHIBITORY
PEPTIDE( GIP)
Source: K cells – jejunum & duodenum
Initially called Enterogastrone.
Discovered as a factor in extracts of
intestine that inhibited gastric motility
and secretion of acid.
31. GASTRIC INHIBITORY
PEPTIDE( GIP)
Another activity of GIP is its ability to Enhance
the release of insulin in response to infusions of
glucose. -- Glucose-dependent insulinotropic
peptide.
Regulation – Increases by fat in duodenum
Monday, April 27, 2015
33. Stimulate Intestinal secretion of electrolytes &
water.
Vasodilatation – decreases BP
Induce smooth muscle relaxation (lower
esophageal sphincter, stomach, gallbladder)
Stimulate secretion of water into pancreatic
juice and bile.
Inhibition of gastric acid secretion and
absorption from the intestinal lumen.
Decreases the GI motility.
ACTIONS.
34. ENTEROGLUCAGON ANDENTEROGLUCAGON AND
GLUCAGON-LIKE PEPTIDES.GLUCAGON-LIKE PEPTIDES.
Source : Terminal SI and LI - L cells.
Given the name "Enteroglucagon",
"Proglucagon-derived Peptides".
In both pancreas and gut, 3 types of products are
generated:
• Glucagon-like Peptide-1 (GLP-1)
• Glucagon-like Peptide-2 (GLP-2)
• Glucagon-like Peptide-3 (GLP-3)
Monday, April 27, 2015
35. GLP-1GLP-1
Inhibit gastric
emptying,
Inhibit gastric
secretion and
Inhibit pancreatic
secretion,
Decreases food
intake.
Glucagon-like
peptide-2
It stimulates
proliferation of
intestinal epithelial
cells.
Monday, April 27, 2015
36. SOMATOSTATIN (GHIH).
Source -- S Cells or δ cells
GIT MUCOSA.
Structure– SS14, SS28 (more active)
Somatostatin is also secreted by the Hypothalamus &
pancreas.
Stimuli –
Acid in stomach
stimuli which increases insulin secretion
Monday, April 27, 2015
38. MOTILIN
• Source -- Endocrinocytes (Mo Cells) in
the mucosa of the proximal Small Intestine.
• Based on 22 AA sequence,
39. MOTILIN participates in controlling the pattern of
smooth muscle contractions in the upper GI tract that
increases the MIGRATING MYOELECTRIC COMPLEX
("Housekeeping contractions“).
It sweep the stomach and SI clear of undigested
material and stimulates the production of PEPSIN.
40. GHRELIN-28 AA
’Ghre’’ – Growth ---- Europian name.
Source -- Endocrine cells in the stomach,
especially when one is hungry;
Action-- acts on the hypothalamus to stimulate
feeding;
This action counteracts the inhibition of feeding
by leptin and Pyy 3-36.
Monday, April 27, 2015
42. GUANYLIN
15 amino acid residues
Source:
Cells of the intestinal mucosa
Stimulant:
Stimulation of Guanylin
Function:
It increase Cl- movement to intestine
43. Other hormones
HormonesHormones sourcesource EffectsEffects
NeurotensinNeurotensin Neurons & ilealNeurons & ileal
epitheliumepithelium
Inhibit GI motility - ilealInhibit GI motility - ileal
blood flowblood flow
GRPGRP Vagal nerveVagal nerve Gastrin releaseGastrin release
GuanylinGuanylin Paneth cellsPaneth cells Secretion of chloride ionsSecretion of chloride ions
ChymodeninChymodenin Duodenal mucosaDuodenal mucosa Selective secretion ofSelective secretion of
chymotrypsinogen fromchymotrypsinogen from
pancreatic acinar cellspancreatic acinar cells
Substance PSubstance P Entire GITEntire GIT Increases the motility of SIIncreases the motility of SI
Increases local vasodilationIncreases local vasodilation
Perception of pain sensationPerception of pain sensation
BombesinBombesin Entire GITEntire GIT Increases gastric secretionIncreases gastric secretion
Increases motility of gallIncreases motility of gall
bladderbladder
Increases motility of SIIncreases motility of SI
48. Zollinger-Ellison Syndrome
(Gastrinoma)
Caused by a tumor (or tumors) called
Gastrinoma gastrin stomach acid.
SIGNS & SYMPTOMS:
Pain in the stomach and esophagus,
Nausea
Vomiting of blood,
Difficulty in swallowing
Sore throat, coughing, and
wheezing
Sour or bitter taste in the mouth
Blood in the stool
49. VERNER MORRISON SYNDROME
( VIPOMAS)
VIP Cause profound and chronic
WDHA-syndrome (or) pancreatic
cholera syndrome
Watery Diarrhoea and resultant
Dehydration,
Hypokalemia,
Achlorhydria,
Acidosis,
vasodilation (flushing and
hypotension),
Hypercalcemia
Hyperglycemia.
51. CARCINOID TUMORS( APUDOMAS)
Carcinoid tumors originate from the diffuse
neuroendocrine system, specifically the
enterochromaffin (EC) cells (submucosa of the
intestine)
