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Phsyiology 210 B > Gastrointestinal Tract 4 - Pancreas > Flashcards

Gastrointestinal Tract 4 - Pancreas Flashcards

1
Q

The pancreases contains two types of glands

A

Exocrine and endocrine

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2
Q

Exocrine pancreas

A
  • produce digestive enzymes (in excess) and secretions

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

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3
Q

Endocrine pancreas (non-digestive)

A

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

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4
Q

Exocrine-secretion of substances into

A

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

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5
Q

Endocrine-

A

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

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6
Q

Main pancreatic duct joins common bile duct just before entering the

A

duodenum

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7
Q

Pancreatic ducts

A
  • Acinar cells produce and secrete digestive enzymes- exocytosis
  • Duct cells secrete H2O and HCO3-
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8
Q

Pancreatic juices

A
  • 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

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9
Q

The digestive enzymes in pancreatic juice secreted by

A

Acinar cells

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10
Q

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

A

Duodenum

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11
Q

Ductular Cell Secretion of HCO3-

A
  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
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12
Q

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

A

gastric acid and washes digestive enzymes through

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13
Q

Parietal cells in stomach are producing lots of

A

Acid

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14
Q

Duct cells in pancreas are producing and secreting

A

HCO3- (base)

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15
Q

Alkaline tide.

A

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

  • by parietal cells in stomach
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16
Q

Acid tide.

A

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

  • by duct cells in pancreas
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17
Q

HCO3- from stomach and H+ from pancreas eventually

A

meet up in the portal vein. Maintain acid base balance

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18
Q

Pancreas the source of majority of

A

Digestive enzymes

  • proteases
  • amylolytic enzymes
  • lipases
  • nucleases
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19
Q

Without the pancreas, ______ would occur

A

Starvation

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20
Q

Proteases

A

digest proteins into peptides and amino acids

21
Q

Amylolytic enzymes

A

digest starch into sugars

22
Q

Lipases

A

digest triglycerides into free fatty acids and monoglycerides

23
Q

Nucleases

A

digest nucleic acids into free nucleotides

24
Q

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

A

apical pole of the cell

25
Q

Are enxymes secreated activated or inactivated

A

Inactivated, activate them in the duodenum

26
Q

Enterokinase-

A

enzyme embedded in the luminal membrane of the duodenum.

- Cleaves trypsinogen to trypsin (protease)

27
Q

Trypsin is a

A

protease and also activates other proteases

28
Q

Pancreas also secretes a variety of trypsin inhibitors to

A

antagonize any prematurely activated trypsin

29
Q

Digestive enxymes are stored in

A

Inactive form, not activated until they reach the intestine

30
Q

Trypsin can degrade itself if activated

A

prior to reaching the intestine

31
Q

In cystic fibrosis, which channel is mutated ?

A

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

32
Q

CF patients can suffer from “pancreatic insufficiency”

A
  • 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
33
Q

How are patients with cystic fibrosis treated?

A

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

34
Q

The major proteases secreted by pancreas

A

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
35
Q

The action of trypsin, Chymotrypsin, elastase ?

A

Endopeptidases (hydrolyze interior peptide bonds of proteins and polypeptides)

36
Q

Action of carboxypeptidase A and B ?

A

Exopeptidases (hydrolyze bonds at C- terminal end)

37
Q

Amylolytic enzyme secreted by pancreas action is

A

Cleaves starches to sugars (same as salivary amylase)

End products: Maltose, maltotriose & α- limit dextrins

38
Q

Lipolytic enzyme

A

Inactive enzyme:
- Prephospholipase A2 (trypsin)

Activate enzyme:

  • Lipase (hydrolysis triglycerides)
  • Phospholipase A2 (hydrolyzes phospholipids)
  • Cholesterol esterase (hydrolyzes cholosterol-esters)
39
Q

End product of Lipase

A

Free fatty acids & 2-monoglycerides

40
Q

End product of Phospholipase A2

A

Free fatty acids and lysophospholipids

41
Q

End product of Cholesterol esterase

A

Free fatty acids & cholesterol

42
Q

Circulating CCK stimulates:

A

Pancreas to increase digestive enzyme secretion

Gall bladder contraction:

  • Release of bile acids for fat breakdown
  • Relaxation of the sphincter of Oddi
43
Q

Fatty acids and amino acids in the small intestine triggers

A

CCK secretion from cells in small intestine into blood.

44
Q

How is release of CCK stopped?

A

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

45
Q

Secretin regulation of pancreatic HCO3-secretion

A
  • 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.
46
Q

When is secretion of secretin stopped

A

When Stomach acid is neutralized

47
Q

Secretin and CCK both:

A

Inhibit gastrin secretion

48
Q

The inhibition of gastrin secretion results in:

A
  • Reduced stomach motility-slows stomach emptying

- Reduced acid secretion

49
Q

Phases of pancreatic secretion

A

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

Phsyiology 210 B (24 decks)

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