Endocrine & Exocrine Pancreas Function (Bolton)

Question 1

Endocrine versus Exocrine cells of the pancreas

Answer 1

Endocrine: Islets of Langerhans (alpha cells [glucagon] & beta cells [insulin]

Exocrine: Acinar cells & Ductal cells

everything outside of black box = exocrine pancreas

Question 2

What do acinar cells secrete and how do they function?

Answer 2

Secrete inactive digestive enzymes (trypsin, chymotrypsin, carboxypolypeptidase), which then enter the pancreatic duct -> duodenum -> trypsin becomes activated by enterokinase, and then activates the other 2 enzymes. Then, they go on to digest CHOs, fats, protein.

Question 3

What do ductal cells secrete and why

Answer 3

Secrete bicarbonate after acinar cells secrete the digestive enzymes -> neutralize the acidic gastric contents from the stomach in the duodenum so that the acinar cells’ secretions can function

Question 4

Pancreatitis

Answer 4

inappropriate or early activation of digesting enzymes (trypsin, chymotrypsin, carboxypolypeptidase) within the pancreas is what causes the inflammation -> digestion of pancreas and not the food itself in duodenum (auto-digestion of the pancreas)

Question 5

Process of stimulating acinar cells to secrete digestive enzymes

Answer 5

Presence of amino acids and fat in the duodenum -> ACh and CCK are stimulated -> stimulate acinar cells to secrete digestive enzymes in the duodenum

Question 6

Process of stimulating ductal cells to secrete bicarbonate.

Answer 6

Presence of gastric acid (HCl) in duodenum -> Secretin is stimulated -> Stimulate ductal cells to secrete bicarbonate to neutralize HCl in the duodenum

Question 7

Exocrine Pancreatic Insufficiency

Answer 7

Acinar cells fail to produce digestive enzymes -> food in duodenum does NOT get digested.

• hallmark clinical sign: weight loss with diarrhea despite ravenous appetite

young german shepherds

Question 8

Two most common exocrine pancreatic diseases in dog/cat

Answer 8

EPI and pancreatitis

Question 9

Most common disease of endocrine pancreas + clinical signs

Answer 9

Diabetes melitus - failure of beta cells of endocrine pancreas to secrete insulin -> no formation of glycogen, protein and triglyceride

• elevated blood glucose levels -> glucose from circulation spills into the urine -> PU/PD
• weight loss despite good appetite (unable to store glucose, AAs and fat -> animal’s body feels like it’s starving)

Question 10

Role of insulin

Answer 10

Present in high amounts after a meal // elevated levels of glucose in the blood (fed state): promotes cellular nutrient uptake & storage

1. Stimulates glycogenesis (formation of glycogen) in the liver & skeletal muscle, proteogenesis (formation of protein) in skeletal muscle, and lipogenesis (formation of triglyceride) in adipose tissue

Question 11

Role of glucagon

Answer 11

Functions in between meals (fasted state):
1. glucagon breaks down stored CHOs in the liver & skeleteal muscle, and fat in adipose tissue (glycogen & triglycerides) via glycogenolysis and lipolysis
2. end-products = glucose+glucose, and glycerol + fatty acids -> body utilizes them for energy

glucagon has little-to-no effect on protein

Question 12

What are the stored versions of the macronutrients?

Answer 12

• CHOs: glucose + glucose -> glycogen
• Proteins: AA + AA -> protein
• Fats: glycerol + fatty acid -> triglyceride

Question 13

What hormone stimulates gluconeogenesis and what hormone inhibits it?

Answer 13

Stimulates = glucagon
Inhibits = insulin

gluconeogenesis = creation of glucose

Question 14

In a fasted state, why does glucagon stimulate insulin?

Answer 14

• in a fasted state, we need glucagon to break down glycogen in order to release glucose into the blood (to maintain normal blood glucose levels)
• also, we need a some insulin present to help move systemic glucose from the blood into the cells elsewhere in the body that need it to function properly

insulin is reqired to move nutrients into cells from blood

While glucagon is prominent in fasted state, there is still a little bit of insulin released as well

Question 15

Why does insulin inhibit glucagon in a fed state?

Answer 15

In a fed state, insulin = predominate hormone.
- Insulin inhibits glucagon because it is trying to store glucose and fat (glycogen & triglyceride), and it does NOT need glucagon to break down what is being stored

Question 16

Delta cells and somatostatin

Answer 16

Somatostatin = hormone released by delta cells (δ) of endocrine pancreas // Islets of Langerhans
- moderates the release of alpha and beta cells’ hormones (glucagon and insulin)