Download large intestine

GIT HORMONES
Lecture Physiology
Dr. Mujeeb Ahmed Shaikh
Dr.Mohammed Sharique Ahmed Quadri
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2. OVERVIEW OF GASTRO-INTESTINAL
HORMONES
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We will discuss the following hormones:
Gastrin
Secretin
CCK
Motilin
Somatostatin
GIP
VIP
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GASTRIN
• Produced by G-cells in the stomach.
• Stimulates the release of HCL and Pepsinogen in
the stomach.
• Increases gastric motility.
• Increases ileal motility .
• Relaxes Ileocecal Sphincter.
• Induces mass movements in colon [because to
help the contents moving through GIT on arrival
of new meal in the stomach].
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SECRETIN
• Secretin is released from small intestine when
stomach acid contents come to duodenum.
 Functions
• It inhibits gastric emptying to delay the acid
contents of stomach to enter in the duodenum.
• It inhibits gastric secretion.
• It acts on pancreatic duct to produce large
volume of watery, NaHCO3 secretion.
• It stimulates the secretion of NaHCO3 rich bile in
the liver by acting on the bile ducts.
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CCK [Cholecystokinin]
• CCK is released from the duodenum in response
mainly to fat, to a lesser extent to protein
products.
• Actions of CCK
I. Inhibition of gastric motility and secretion
II. Stimulates pancreatic Acinar cells to secrete
pancreatic enzymes [amylase, lipase, Trypsinogen,
Chymotrypsinogen].
III. It causes contraction of gall-bladder and relaxation
of sphincter of Oddi.
IV. Regulator of food intake (key role in satiety)
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MOTILIN
• It is polypeptide and secreted by
entrochromaffin cells and Mo cells in the
stomach, small intestine and colon.
• It causes contraction of smooth muscles in the
stomach and intestine.
• It level increases during inter-digestive state
and controls GIT motility between the meals.
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SOMATOSTATIN
• It is secreted by D-Cells in pancreatic islets and
by similar D-cells in GIT mucosa.
• Somatostatin inhibits secretion of Gastrin, VIP,
GIP, Secretin and Motilin.
• Somatostatin secretion is stimulated by acid in
the lumen of intestine.
• It acts probably in a paracrine fashion.
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GIP [Glucose Dependent Insulinotorphic
Peptide]
• GIP is released from the duodenum.
• GIP stimulates release of insulin.
– Stimulated by presence of meal specially glucose
GIP stimulates insulin release .
• Inhibits gastric motility
– before it was called Gastric Inhibitory Peptide [this
role is minimum].
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VIP [Vasoactive Intestinal Peptide]
• VIP is found in nerves in the GIT.
• It stimulates intestinal secretion of electrolytes
and water.
• Other action – relaxation of intestinal smooth
muscle including sphincters.
• Inhibition of gastric acid secretion.
• It potentiates the action of acetylcholine in
salivary glands.
• VIP is also found in brain, blood, autonomic
nerves.
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REMINDER REGARDING GIT ENZYMES
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Thank you
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References
• Human physiology by Lauralee Sherwood,
seventh edition
• Text book physiology by Guyton &Hall,11th
edition
• Text book of physiology by Linda .s
contanzo,third edition
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