The endocrine pancreas Flashcards
What is the embryology of the pancreas?
At junction of foregut and midgut 2 pancreatic buds (dorsal and ventral) are generated and eventually fuse to form the pancreas
Exocrine functions begin after birth
Endocrine (hormone ) functions from 10-15 weeks
Which two buds fuse to form the pancreas in the embryo?
What small clusters make up the pancreas?
Formed of small clusters of glandular epithelial cells
98%-99% of cells are clusters called acini
How is the exocrine activity of the pancreas performed?
Acinar cells
They manufacture and secrete fluid and digestive enzymes, called pancreatic juice, which is released into the gut
How is the endocrine activity of the pancreas performed?
By islet cells
Manufacture and release several peptide hormones into the portal vein
How much of the pancreas is the islets of Langerhans?
only 2-3% of total volume of the pancreas
What are the different cells in the Islets of Langerhans and what do they secrete?
a-cell secretes glucagon
b-cell secretes insulin
d-cell secretes somatostatin
What is insulin?
What is its function?
Polypeptide, 51 amino acids
Reduces glucose output from the liver
Increases storage of glucose, fatty acids, amino acids
What is glucagon?
What is its function?
Peptide - 29 amino acid
Mobilises glucose, fatty acids, amino acids from stores
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What does insulin supress?
What does insulin increase?
What does glucagon increase?
What does glucagon reduce?
What are other counterregulatory hormones the have similar effects to glucagon?
Describe mechanism behind insulin secretion?
Glucose enters b-cell by GLUT2 glucose transporter
incomplete
What is insulin released as initially?
Proinsulin
A and B chains of insulin joined by a C-peptide
Disulphide bridges link A and B chains
presence of C peptide implies endogenous insulin production
What is biphasic release of insulin?
B-cells sense rising glucose
First phase response - rapid release of stored product
Second phase response - slower, release of newly synthesised hormone
What action does insulin have in muscle and fat cells?
What are the numeric boundaries of a normal blood glucose?
> 6(mmol/mol) too high
~5 is normal
<4 too low
What is the short term response to blood glucose of >6?
What is the long term response?
Make glycogen (glycogenesis)
Make triglyceride (lipogenesis)
What is the short term response to a blood glucose of <4 mmol/mol?
What is the long term response?
Split glycogen (glycogenolysis)
Make glucose from amino acids/lactate (gluconeogenesis)
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What is CHO metabolism?
Metabolism of carbohydrates
Best way to eat a meal?
Chatting with family or friends over a meal - feel fuller quicker from smaller portions
What are insulins most important mechanisms?
Getting glucose out of the bloodstream
Letting the body know it doesn’t have to produce MORE glucose - e.g. doesn’t have to produce ketones
No hepatic insulin effect - unrestrained glucose + ketone production - more glucose enters the blood
No muscle/fat insulin effect? - impaired glucose clearance + muscle/fat breakdown - less glucose enters peripheral tissues
How is CHO metabolism regulated during fasting?
Glucose from the liver - glycogenolysis, gluconeogenesis
Glucose delivered to insulin independent tissues - brain and red blood cells
Insulin levels low
Muscles use free fatty acids for fuel
