1. Unit 2 – Endocrine Module Histology of the endocrine pancreas
Safaa El Bialy (MD, PhD)

2. Objectives
Describe the histology of the hormone producing cells and their molecular signaling pathways.

3. main pancreatic duct (duct of Wirsung)
liver
pancreas
gall bladder
stomach
duodenum
main pancreatic duct (duct of Wirsung)

4. Pancreas
endocrine pancreas -
islet of Langerhans 4

5. Pancreas Parenchyma is formed by 2 types of glands: exocrine component
secretes an alkaline fluid rich in digestive enzymes into the duodenum
endocrine component
primary products of secretion are hormones that affect carbohydrate (and lipid and protein) metabolism 5

6. Endocrine pancreas < 5% of the pancreas
innervated by autonomic nerve fibres
endocrine cells are grouped into islets of Langerhans
islets contain numerous capillaries
islets are more numerous in the tail of the pancreas
endocrine cells are small, pale, round and arranged in cords 6

7. Endocrine Pancreas Endocrine cells Smaller than exocrine cells
Polygonal or round with pale cytoplasm

9. Endocrine pancreas main endocrine cells of the islets of Langerhans:
alpha
produce glucagon
second most common cell
acidophilic
beta
produce insulin
most common cell (> 60%)
Large sperical , pale and central
delta
produce somatostatin
-- F cells (PP cells)
produce pancreatic polypeptide ( inhibits action of exocrine cells ) 9

10. Pancreas endocrine

12. Immunohistochemistry
Alpha cells ßcells

13. Endocrine pancreas – immunohistochemistry
Anti-glucagon antibodies
Anti-somatostatin antibodies
Anti-insulin antibodies 13

14. Insulin and glucagon - - Hypoglycemia Hyperglycemia + + Cells 
Maintain glycémia

15. Medical application Diabetes: 1. Type 1 diabetes
Starts in infancy or adolescence
Autoimmune
Insulin deficiency
2. Type 2 diabetes
Resistance of cells targeted by insulin

16. Autonomic Innervation of the Pancreas
The islets of Langerhans receive autonomic innervation via 2 neurones (preganglionic in the SNC and postganglionic in the autonomic ganglia
The parasympathetic stimulation of insulin secretion is part of the cephalic phase. It refers to sensory stimuli and neural inputs that are activated when food is first eaten. There is an activation of the parasympathetic preganglions
Those will activate the postganglionic neurones and stimulate the secretion of insulin even before the elevation of the blood glucose levels in the blood. An example of feedforward regulation.
The sympathetic stimulation inhibits insulin secretion and stimulates glucagon secretion

17. Local retroaction of the pancreatic cells
Glucagon stimulates or modulates the local secretion of insulin
Insulin inhibits glucagon secretion
Negative/positive feedback between insulin and glucagon so between A and B cells.
Somatostatin (cells D) inhibits secretion of cells A et B and glucagon the secretion of D cells.
A paracrine effect which regulates homeostasis