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
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
