Gastrointestinal Tract 4 - Pancreas

Question 1

The pancreases contains two types of glands

Answer 1

Exocrine and endocrine

Question 2

Exocrine pancreas

Answer 2

• produce digestive enzymes (in excess) and secretions

- secrete HCO3 into duodenum for the neutralization of stomach acid- critical for enzyme function

Question 3

Endocrine pancreas (non-digestive)

Answer 3

Produces hormones that regulate entire body (e.g., insulin)

Question 4

Exocrine-secretion of substances into

Answer 4

ducts that drain onto an epithelial surface (apical surface).

Question 5

Endocrine-

Answer 5

ductless gland, secretion occurs across epithelial basolateral surface for diffusion into blood

Question 6

Main pancreatic duct joins common bile duct just before entering the

Answer 6

duodenum

Question 7

Pancreatic ducts

Answer 7

• Acinar cells produce and secrete digestive enzymes- exocytosis
• Duct cells secrete H2O and HCO3-

Question 8

Pancreatic juices

Answer 8

• isotonic, alkaline

Contains electrolytes:

• High HCO3-, low Cl-
• Na+, K+ same as in plasma
• HCO3- and H2O secreted mainly by duct cells
• HCO3- neutralizes gastric acid in duodenum

Contains digestive enzymes

Question 9

The digestive enzymes in pancreatic juice secreted by

Answer 9

Acinar cells

Question 10

Proteolytic enzymes stored and secreted in inactive forms; activation occurs in the

Answer 10

Duodenum

Question 11

Ductular Cell Secretion of HCO3-

Answer 11

1. Chloride channel (CFTR) opens
   - Allows diffusion of Cl- into duct lumen
2. Cl- in lumen is exchanged for HCO3- in cell
3. H2O and Na+ follow paracellularly in response to electrochemical gradient across epithelium
4. Neutral pH of cytosol is maintained by exchange of H+ (exported from cell) for Na+ (imported).(in combination with carbonic anhydrase)
   - Secondary active transport dependent upon the electrochemical gradient generated by the Na+/K+-ATPase

Question 12

Ductular Cell Secretion of HCO3- results in watery alkaline secretion that neutralizes

Answer 12

gastric acid and washes digestive enzymes through

Question 13

Parietal cells in stomach are producing lots of

Answer 13

Acid

Question 14

Duct cells in pancreas are producing and secreting

Answer 14

HCO3- (base)

Question 15

Alkaline tide.

Answer 15

Large amount of HCO3- pumped across basolateral surface into blood stream.

• by parietal cells in stomach

Question 16

Acid tide.

Answer 16

Large amounts of H+ being pumped across the basolateral surface into
blood stream

• by duct cells in pancreas

Question 17

HCO3- from stomach and H+ from pancreas eventually

Answer 17

meet up in the portal vein. Maintain acid base balance

Question 18

Pancreas the source of majority of

Answer 18

Digestive enzymes

• proteases
• amylolytic enzymes
• lipases
• nucleases

Question 19

Without the pancreas, ______ would occur

Answer 19

Starvation

Question 20

Proteases

Answer 20

digest proteins into peptides and amino acids

Question 21

Amylolytic enzymes

Answer 21

digest starch into sugars

Question 22

Lipases

Answer 22

digest triglycerides into free fatty acids and monoglycerides

Question 23

Nucleases

Answer 23

digest nucleic acids into free nucleotides

Question 24

Acinar cells synthesize and package pro-enzymes into zymogen granules that are stored at the

Answer 24

apical pole of the cell

Question 25

Are enxymes secreated activated or inactivated

Answer 25

Inactivated, activate them in the duodenum

Question 26

Enterokinase-

Answer 26

enzyme embedded in the luminal membrane of the duodenum. | - Cleaves trypsinogen to trypsin (protease)

Question 27

Trypsin is a

Answer 27

protease and also activates other proteases

Question 28

Pancreas also secretes a variety of trypsin inhibitors to

Answer 28

antagonize any prematurely activated trypsin

Question 29

Digestive enxymes are stored in

Answer 29

Inactive form, not activated until they reach the intestine

Question 30

Trypsin can degrade itself if activated

Answer 30

prior to reaching the intestine

Question 31

In cystic fibrosis, which channel is mutated ?

Answer 31

The Cl- channel involved in HCO3- secretion in the pancreas

Question 32

CF patients can suffer from “pancreatic insufficiency”

Answer 32

- Still produce all of the digestive enzymes - HCO3- and H2O secretion is minimal and enzymes do not get flushed from ducts and therefore do not reach the intestine - Retained proteolytic enzymes = pancreatic autodigestion

Question 33

How are patients with cystic fibrosis treated?

Answer 33

Must receive supplements of digestive enzymes and antacids to allow for adequate nutrition

Question 34

The major proteases secreted by pancreas

Answer 34

Inactive enzyme: - trypsinogen (actvdd by enterokinase) - Chymotrypsinogen (actvtd by trypsin) - pro-elastase (actvtd by trypsin) - pro-carboxy peptidase (actvtd by trypsin) Activate enzyme: - trypsin - Chymotrypsin - elastase - carboxypeptidase A and B

Question 35

The action of trypsin, Chymotrypsin, elastase ?

Answer 35

Endopeptidases (hydrolyze interior peptide bonds of proteins and polypeptides)

Question 36

Action of carboxypeptidase A and B ?

Answer 36

Exopeptidases (hydrolyze bonds at C- terminal end)

Question 37

Amylolytic enzyme secreted by pancreas action is

Answer 37

Cleaves starches to sugars (same as salivary amylase) End products: Maltose, maltotriose & α- limit dextrins

Question 38

Lipolytic enzyme

Answer 38

Inactive enzyme: - Prephospholipase A2 (trypsin) Activate enzyme: - Lipase (hydrolysis triglycerides) - Phospholipase A2 (hydrolyzes phospholipids) - Cholesterol esterase (hydrolyzes cholosterol-esters)

Question 39

End product of Lipase

Answer 39

Free fatty acids & 2-monoglycerides

Question 40

End product of Phospholipase A2

Answer 40

Free fatty acids and lysophospholipids

Question 41

End product of Cholesterol esterase

Answer 41

Free fatty acids & cholesterol

Question 42

Circulating CCK stimulates:

Answer 42

Pancreas to increase digestive enzyme secretion Gall bladder contraction: - Release of bile acids for fat breakdown - Relaxation of the sphincter of Oddi

Question 43

Fatty acids and amino acids in the small intestine triggers

Answer 43

CCK secretion from cells in small intestine into blood.

Question 44

How is release of CCK stopped?

Answer 44

Fats and amino acids are absorbed and stimulation of CCK release is stopped-due to their removal

Question 45

Secretin regulation of pancreatic HCO3-secretion

Answer 45

- Acid enters the duodenum from the stomach - Reduced pH triggers secretin secretion from cells in small intestine into blood. Circulating secretin stimulates: - Pancreas (duct cells) to increase HCO3- secretion. - Liver (duct cells) to increase HCO3- secretion.

Question 46

When is secretion of secretin stopped

Answer 46

When Stomach acid is neutralized

Question 47

Secretin and CCK both:

Answer 47

Inhibit gastrin secretion

Question 48

The inhibition of gastrin secretion results in:

Answer 48

- Reduced stomach motility-slows stomach emptying | - Reduced acid secretion

Question 49

Phases of pancreatic secretion

Answer 49

1) Cephalic phase: Minor. Sight, smell, taste = stimulate pancreatic secretion via the parasympathetic nerves. 2) Gastric phase: Minor. Distension of stomach = stimulate pancreatic secretion via the parasympathetic nerves. 3) Intestinal phase Major. - Acid from stomach in duodenum = secretin release - Digested fat and protein in duodenum = CCK release