Physiology-Pancreas

Question 1

What cells are contained in the region indicated below?

Answer 1

The lighter staining region in the pancreatic parenchyma are Islets of Langerhans, which contain the endocrine cells of the pancreas.

Question 2

What is the function of the different cell types found in the region of the pancreas indicated below?

Answer 2

In the Islet of Langerhans you have 1) Beta Cells: interior of islet, secrete alcohol-soluble insulin granules. 2) Alpha Cells: periphery of islet, secrete alcohol-insoluble glucagon granules. 3) Delta cells: paracrine secretion of somatostatin. 4) F (or PP) cells: make pancreatic polypeptide.

Question 3

What structures are found in the interlobular connective tissue of the pancreas?

Answer 3

Large excretory ducts, blood vessels and nerves.

Question 4

What kind of capillaries run through the Islets of Langerhans?

Answer 4

Fenestrated capillaries

Question 5

How does the pancreatic acinus differ from that in the submandibular gland?

Answer 5

No striated ducts in the pancreas, only serous cells in pancreas, no myoepithelial cells in the pancreas, and centroacinar cells mark the beginning of the intercalated ducts in the pancreas.

Question 6

Where are the granules located on the exocrine cells of the pancreas?

Answer 6

Zymogen granules are located on the apical side of the cells

Question 7

Identify the different structures labeled below.

Answer 7

1) Pancreatic acinus, note eosinophilic at base b/c nucleus is on basal side of cell and granules are at apical side 2) Intercalated duct 3) Centroacinar cell

Question 8

What role do centroacinar cells play in pancreatic secretions?

Answer 8

They express high levels of carbonic anhydrase and play a role in secretion of bicarbonate.

Question 9

What cells are critical in determining the ionic composition of the fluid that leaves the pancreas?

Answer 9

Intercalated duct epithelium. They are the main secreters of fluid in the pancreas.

Question 10

Proteolytic enzymes secreted by the pancreas

Answer 10

Endopeptidases (Trypsinogen, chymotrypsinogen, proelastase) and exopeptidases (procarboxypeptidase A/B, proaminopeptidase)

Question 11

Nucleolytic enzymes secreted by the pancreas

Answer 11

Ribonuclease and deoxyribonuclease

Question 12

Lipolytic enzymes secreted by the pancreas

Answer 12

Procolipase, lipase, prophospholipase A2 and carboxyl ester hydrolase

Question 13

Amylolytic enzyme secreted by the pancreas

Answer 13

Alpha-amylase

Question 14

In addition to secretion of hydrolytic enzymes, what else do acinar cells produce to protect the pancreas?

Answer 14

Trypsin inhibitor. It prevents the conversion of trypsinogen to trypsin before secretions reach the duodenum.

Question 15

What triggers secretion of hydrolytic enzymes from the acinar cells?

Answer 15

CCK and ACh -> PKC signaling.

Question 16

What triggers secretion of Na, K, HCO3 and Cl from the acinar cells? From the interlobular ducts?

Answer 16

Acinar cells = spontaneous. Interlobular ducts = secretin or VIP -> cAMP signaling, note that these secretions are more rich in bicarbonate.

Question 17

What happens to fluid Cl levels are secretory rate increases?

Answer 17

It decreases. HCO3 is let out and HCO3 concentration increases by taking Cl back into the cell via the CFTR.

Question 18

What cells secrete secretin?

Answer 18

Enteroendocrine (S) cells when the chyme enters the small intestine.

Question 19

Where do duct cells get all that bicarb from?

Answer 19

CO2 + H2O + Carbonic anhydrase. Na/HCO3 basal cotransporter.

Question 20

Where does VIP come from?

Answer 20

Vasoactive intestinal peptide is a hormone release by the vagus nerve.

Question 21

What cells secrete CCK?

Answer 21

Enteroendocrine (I) cells when the fatty acids and peptides in the chyme enter the small intestine

Question 22

How does sympathetic stimulation affect pancreatic secretions?

Answer 22

Inhibits vagal and secretion induced secretions.

Question 23

4 phases of pancreatic secretion

Answer 23

1) Resting phase: vagal stimulation -> ACh (zymogen release) and VIP (fluid release) 3) Gastric phase: stomach distention -> vagal stimulation and gastrin release -> additional secretion of alkaline fluid 4) Intestinal phase: chyme enters duodenum -> secretin release -> 70-80% of pancreatic secretion into duodenum occurs

Question 24

What do activated proteases in the duodenum do besides break down food?

Answer 24

Inhibit acinar cell zymogen release

Question 25

What substance suppresses vagal stimulation of acinar cell zymogen release?

Answer 25

Pancreatic polypeptide (PP)

Question 26

What hormone is released in presence of fat in lower intestine that also inhibits pancreatic secretions?

Answer 26

NPY

Question 27

What hormones are present after food has been absorbed into circulation that inhibit pancreatic secretions?

Answer 27

Glucagon, somatostatin and PP

Question 28

Why does pancreatic fluid need to be alkaline?

Answer 28

Hydrolytic enzymes are only activated at higher pH

Question 29

Common causes of acute pancreatitis?

Answer 29

Alcohol or blockage of common bile duct. Consquence is pancreatic enzymes digestion pancreatic tissue.

Question 30

Pancreatitis without pain.

Answer 30

Cystic fibrosis, pancreatitis due to decreased HCO3 secretion from loss of CFTR.