Endocrine pancreas

Question 1

Which week of gestation are the islets of Langerhans distinguishable?

Answer 1

12 weeks

Question 2

From which embryological origin is the pancreas derived?

Answer 2

Endoderm of the foregut

Question 3

Describe the microscopic appearance of the Islets of Langerhans

Answer 3

1-2% of cell mass in pancreas

Clusters of ~1000 cells

Surrounded by rosettes of acinar cells (exocrine cells)

Stain paler than acinar cells (lower protein content)

Spaces in-between the endocrine cells - capillary networks

Question 4

Different cell types of islets observed with what technique? What do they each secrete?

Answer 4

Immunohistochemistry reveals presence of different cell types, namely:

• Alpha cells -> glucagon
• Beta cells -> insulin
• Delta cells -> somatostatin
• Epsilon cells -> ghrelin
• PP cells -> pancreatic polypeptide

Question 5

Blood supply to pancreas

Answer 5

inferior pancreaticoduodenal artery

splenic arteries

Question 6

Innervation of pancreas

Answer 6

S - celiac ganglion

Ps - vagus nerve branch

Question 7

Insulin secretion stimulated by:

Answer 7

• Raised blood glucose, amino acid and fatty acid
• Hormones (like glucagon, glucagon-like peptide, glucose-dependant insulinotrophic peptide hormone etc.)
• Parasympathetic stimulation

Question 8

Insulin secretion inhibited by:

Answer 8

• Sympathetic stimulation

- Somatostatin

Question 9

Insulin main actions

Answer 9

Inhibits glucagon effect on liver, promoting glycogen storage/glycolysis

Promotes glucose absorption by muscles and adipose

Question 10

Organ(s) of glucagon action and mechanism of action

Answer 10

Only acts on liver

Gs-protein coupled receptor - cAMP to promote glycogenolysis and gluconeogenesis to raise blood glucose levels

Question 11

Role of somatostatin

Answer 11

Inhibits insulin release

Question 12

Main effects of insulinoma

Answer 12

Hypoglycaemia

Tumorous beta cells are no longer regulated by glucose so there is an over-secretion of insulin, lowering blood glucose