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GI > Phys: Pancreas > Flashcards

Phys: Pancreas Flashcards

0
Q

What are the most plentiful cells in the pancreas?

A

Acinar cells (84%).

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1
Q

J: This refers to the condition in which the major and accessory pancreatic ducts do not fuse.

A

What is pancreas divisum?

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2
Q

What are ways in which the endocrine pancreas influences the exocrine?

A

Venous blood from the islets perfuse neighboring acini before entering the portal vein, exposing them to hormones:

(1) insulin stimulates enzyme synthesis and secretion
(2) somatostatin and glucagon inhibit enzyme secretion

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3
Q

What is the major stimulus for water and bicarbonate secretion by pancreatic duct epithelial cells?

A

Secretin.

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4
Q

What is the MoA of secretin?

A

It activates adenylate cyclase in pancreatic duct cells, which opens apical chloride channels (CFTR). Bicarbonate is exchanged for luminal chloride.

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5
Q

What disease impairs the secretion of water and bicarbonate by pancreatic duct cells?

A

Cystic fibrosis.

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6
Q

What are the functions of secretin?

A

(1) Retards gastric emptying
(2) Promote mesenteric blood flow
(3) Stimulates secretion of bicarbonate from the pancreas

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7
Q

What stimulates secretin release?

A

Presence of acid in the intestine.

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8
Q

How does the storage and release of amylases, lipases and proteases differ?

A

Amylases and lipases are stored and secreted in their active form, whereas proteases are kept as inactive proenzymes.

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9
Q

How is trypsin activated?

A

The trypsinogen released by the pancreas is activated to trypsin by enterokinases on the intestinal brush border.

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10
Q

What is PSTI?

A

Also called SPINK1, it is a peptide inhibitor of trypsin in the cytoplasm of pancreatic acinar cells.

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11
Q

Where is most amylase produced?

A

Pancreas (though salivary glands do as well).

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12
Q

What does amylase do?

A

It cleaves 1,4-glycoside linkages.

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13
Q

What are the products of amylase digestion?

A

(1) maltose
(2) maltotriose
(3) limits dextrin containing 1,6-linkages

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14
Q

What are causes of maldigestion?

A

(1) excess gastric acid
(2) inadequate enzyme or bicarbonate excretion
(3) poor bile flow
(4) intestinal dysmotility

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15
Q

What are causes of malabsorption?

A

Mucosal disease.

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16
Q

Can a change in diet affect the proportions of enzymes synthesized by the pancreas?

A

Yes.

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17
Q

What hormones increase the free cytoplasmic calcium in pancreatic acinar cells?

A

(1) CCK
(2) ACh
(3) GRP
(4) substance P

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18
Q

What hormones increase cAMP in pancreatic acinar cells?

A

(1) VIP

(2) secretin

19
Q

What is the major stimulus for the secretion of pancreatic enzymes?

A

Cholecystokinin (CCK).

20
Q

What does CCK do?

A

(1) Contracts gallbladder
(2) Relaxes the hepatopancreatic sphincter of Oddi
(3) Delays gastric emptying

21
Q

Where is CCK primarily produced?

A

Discrete upper intestinal cells (though also in CNS and peripheral nerves of the intestine).

22
Q

What stimulates the release of CCK?

A

Presence of peptides, amino acids, fatty acids in intestine.

23
Q

What are the stimulatory phases of pancreatic secretion?

A

(1) cephalic
(2) gastric
(3) intestinal

24
Q

By what is the cephalic phase of pancreatic secretion mediated?

A

The vagus nerve.

25
Q

J: This refers to the act of chewing and expectorating.

A

What is sham feeding?

26
Q

J: This substance inhibits the cephalic phase of pancreatic secretion.

A

What is atropine?

27
Q

What occurs in the gastric phase of pancreatic secretion?

A

Distention of the stomach sends a vagovagal response to the pancreas, triggering release of pancreatic enzymes.

28
Q

What can inhibit the release of CCK?

A

(1) intraluminal trypsin that isn’t complexed to meal protein
(2) IV amino acids and glucose

29
Q

J: The presence of this substance in the terminal ileum and colon can inhibit gastric emptying and pancreatic secretion.

A

What is oleic acid?

30
Q

What are some tests for pancreatic function?

A

(1) 72 hr fecal fat
(2) Sudan stain of stool (for fat)
(3) analysis of duodenal secretion after meal, CCK, or secretin stimulation
(4) endoscopic ultrasound
(5) MRI
(6) CT

31
Q

What percentage of lipase output must be lost in order to see a noticeable increase in fecal fat?

A

90%.

32
Q

What are the functions of bile?

A

(1) Excretion of metabolites of lipid waste, like bilirubin
(2) Fat and fat-soluble vitamin absorption
(3) Excretion of cholesterol
(4) Secretion of IgA

33
Q

What is a bile salt that increases canalicular flow? Decreases?

A

(1) ursodeoxycholic acid

(2) lithocholic acid

34
Q

What is the rate-limiting step in the secretion of bile?

A

Secretion into the canaliculus, as its against a concentration gradient.

35
Q

How is the intracellular bile salt concentration controlled?

A

A nuclear receptor, farnesoid X factor (FXR), senses intracellular bile salt. Its stimulation suppresses bile salt synthesis and increases canalicular secretion.

36
Q

What is the rate-limiting step in bile salt synthesis?

A

Cholesterol synthesis from acetate by HMGCoA reductase.

37
Q

What is the difference between primary and secondary bile salts?

A

Primary bile salts are synthesized in the liver, whereas secondary salts are later manipulated by bacteria in the colon.

38
Q

What is the purpose of the conjugation of bile salts?

A

It makes stronger acids which ionizes the upper small intestine, preventing back diffusion into bile ducts. Also, ileal receptors only bind conjugated bile salts.

39
Q

What does it mean for a bile salt to be conjugated?

A

Its carboxyl side chain is conjugated with taurine or glycine.

40
Q

What is the role of lecithin in micelles?

A

It increases the ability to solubilize cholesterol.

41
Q

What value is equal to the amount of bile synthesized by the liver?

A

The amount of fecal bile.

42
Q

What are 3 causes of bacterial overgrowth in the small bowel?

A

(1) motility disorders
(2) surgical blind loops
(3) small bowel diverticuli

43
Q

Why is bacterial overgrowth in the small bowel a concern?

A

It causes premature deconjugation of bile salts leading to precipitation of bile acids and inadequate micelle formation.

44
Q

What is a possible role of cholesterol and phospholipids in a mixed micelle?

A

To protect the GI mucosa from the toxic effects of the bile salts.

GI (39 decks)

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