Physiology of the pancreas

Question 1

Which arteries supply the pancreas?

Answer 1

celiac and SMA

Question 2

What percent of the pancreas makes up the exocrine/endocrine portions?

Answer 2

80% exocrine

2% endocrine

Question 3

The ventral pancreatic bud in embryology becomes:

Answer 3

The uncinate process. The dorsal bud=body, tail, and head

Question 4

What forms the pancreatic duct?

Answer 4

The ventral duct anastamoses with the dorsal duct. When these systems fail to fuse, it is called pancreas divisum

Question 5

What are the components of the langerhans cells and what do each of these secrete?

Answer 5

A cells: glucagon
PP cells: Pancreatic polypeptide
D cells: Somatostatin

Question 6

Acinar cells have receptors for which hormones/neurotransmitters?

Answer 6

CCK (hormone)
Gastrin-releasing peptide
Acetylcholine
VIP. 
-->All of these stimulate pancreatic digestive enzymes

Question 7

How does the hormone CCK stimulate pancreatic secretion?

Answer 7

Primarily through a vagal afferent/efferent pathway.

The vagal efferents release GRP, Ach, and VIP

Question 8

What hormone is the primary stimulant of ductal cell secretion?

Answer 8

Secretin. It works by increasing cAMP, which inactivates the Cl channel, causing increased secrecretory flow, high [Cl], turning on the Cl/HCO3 antiport system and thus alkalinization of pancreatic juices

Question 9

What stimulates secretin release?

Answer 9

Acidity of stomach contents

Question 10

What potentiates secretin’s effects?

Answer 10

Acetylcholine.

Question 11

How does the cephalic phase mediate its effects? List the stimulus, mediator, and response.

Answer 11

STIMULUS - sight and smell of food
MEDIATOR - vagus efferents enteric nervous system GRP, Ach, VIP
PRIMARY RESPONSE - enzyme secretion

Question 12

How does the gastric mediate its effects? List the stimulus, mediator, and response

Answer 12

STIMULUS - gastric distention
MEDIATOR - vagus efferents enteric nervous system GRP, Ach, VIP
RESPONSE - enzyme secretion

Question 13

How does the intestinatl phase mediate its effects (there are two)

Answer 13

STIMULUS - fatty acids, amino acids in the duodenum
MEDIATOR – CCK vagus enteric nervous system –> GRP, Ach, VIP
Also direct CCK stimulation thru receptor on Acinar cell
RESPONSE - enzyme secretion

STIMULUS - H+ in duodenum
MEDIATOR - Secretin
RESPONSE - Bicarbonate and water secretion

Question 14

What happens when the pancreas is stimulated by secretin?

Answer 14

Bicarb concentration increases and Cl concentration decreases

Question 15

Most of the digestive enzymes of the pancreas digest what substance?

Answer 15

They’re proteolytic

Question 16

What are the important proteolytic enzymes from the pancreas?

Answer 16

Trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase, and prophospholipase A2

Question 17

How are these proenzymes converted into enzymes?

Answer 17

Enterokinase converts trypsinogen to trypsin in the duodenum. Then trypsin converts more trypsinogen and other proenzymes to their active forms.

Question 18

Aside from sequestration of enterokinase in the duodenum, what other mechanisms prevent pancreatic autodigestion?

Answer 18

1. Membrane enclosed compartments
2. Trypsin inhibitor in the acinar cell prevents the small amount of activated trypsin from harming the pancreas
3. Acidic pH in zymogen granules inactivates trypsin
4. Tight ductal epithelium

Question 19

What are the three lipases secreted by the pancreas?

Answer 19

Lipase
PhospholipaseA2
Carboxylesterase

Question 20

What else do you need for the full activity of pancreatic lipase

Answer 20

bile acids and colipase