Phsyiological basis of heath and disease BBMS2006 (BBMS2006)
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Endocrine Pancreatic Hormones
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Phsyiological basis of heath and disease BBMS2006 (BBMS2006)
Institution
The University Of Hong Kong
Pancreatic cell types and their functions, secretions, as well as the pancreatic hormones and their stimulation, synthesis, release, action and regulation, and description of different forms of diabetes
Phsyiological basis of heath and disease BBMS2006 (BBMS2006)
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Pancreatic Endocrine
Functions
Friday, 19 November 2021 9:31 AM
The pancreas
- An organ located in the abdominal cavity behind the stomach
- Receives blood from
○ Head
§ Superior mesenteric artery and pancreaticoduodenal
artery
○ Tail / body / neck
§ Splenic artery
- Exocrine gland
○ 99% of cells arranged into acini
○ Secrete pancreatic juice
§ Enzymes and bicarbonate ions which flow into GIT
through network of ducts
§ Flows through pancreatic duct
○ Function to digest food
- Endocrine gland
○ Scattered among acini are islets of Langerhans
§ Tiny clusters of endocrine tissue
§ Secrete peptide hormones into blood stream
§ Function in regulating carbohydrate, protein and fat
metabolism
○ 4 major cell types according to histological staining
§ B (beta) cells
□ Centrally located within the islet and constitute
70% of the islet mass
□ Secrete
® Insulin
® amylin
§ located in periphery of the islet
□ PP (gamma)
® 1-2%
® Pancreatic polypeptide producing PP cell
□ A(alpha) cells
® 15-20%
® Glucagon
□ D(delta)
® 3-10%
, ®
□ A(alpha) cells
® 15-20%
® Glucagon
□ D(delta)
® 3-10%
® Somatostatin
○ Other cell types
§ Nerve cells
□ Produce vasoactive intestine polypeptide (VIP)
which induces glycogenolysis and
hyperglycemia
® Stimulates water secretion from the
pancreas
§ Enterochromaffin cells
□ Synthesize serotonin for modulation of
gastrointestinal neurons and thereby make the
gut contract around the food
§ Gastrin cells
□ Occasionally in the pancreas with produce
gastrin to stimulate secretion of gastric acid
(HCL) from the stomach
Insulin
- Plasma half life about 6 minutes
- Degraded by insulinase mainly in the liver and to a lesser extent
in the kidneys and muscles
- Synthesis
○ Translation of the insulin RNA by ribosomes attached to
the ER to form an insulin preprohormone
○ Preproinsulin contains a 24-residue signal peptide which
directs the nascent polypeptide chain to the rough ER
○ The signal peptide is cleaved as the polypeptide is
translocated into the lumen of the rough ER
○ The molecule is then folded and the disulfide bonds are
formed to make proinsulin
○ Proinsulin becomes active insulin in the golgi apparatus
through the action of endopeptidases which detach the
peptide segment connecting the A and B chains
§ C peptide
- Insulin receptor
○ Consists of alpha and beta sections
○ Process
§ Binding of insulin to receptor proteins
§ Phosphorylation of receptor
□ Tyrosine kinase now active
§ Phosphorylation of signal molecules
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