Physiology Part 1 > Lec 20 GI Secretory Function > Flashcards

Lec 20 GI Secretory Function Flashcards

(47 cards)

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1
Q

What 3 things in salivary secretion?

A
  • bicarbonate
  • salivary amylase
  • lingual lipase
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2
Q

is saliva isotonic, hypotonic, or hypertonic?

A

hypotonic

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3
Q

What happens to salivary bicarbonate concentration as salivary flow increases?

A

bicarbonate concentration increases

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4
Q

What are the two organs and functions of the stomach?

A

fundus and body: secretion reservoir

antrum: mixing and grinding

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5
Q

What 3 things are first secreted in stomach when food enters?

A
  • Vagus/parasympathetic secretes acetylcholine
  • ECL cells secrete histamine
  • G cells secrete gastrin
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6
Q

What 4 things are responsible for turning on parietal and chief cell secretions?

A
  • vagal activity [ACh]
  • gastric distension
  • gastrin
  • histamine
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7
Q

What 2 things do parietal cells secrete?

A

Acid [H+]

Intrinsic Factor [IF]

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8
Q

What cells secrete gastrin?

A

G cells in antrum

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9
Q

What do chief cells secrete?

A

pepsinogen

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10
Q

What are two sources of lipase

A

lingual –> saliva

gastric: cells in fundus

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11
Q

What cells in glands in proximal stomach vs distal?

A

proximal: ECL cells, chief cells, parietal cells
distal: G and D cells
both: mucous cells

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12
Q

How many layers of muscle in stomach? What are they?

A
  • circular
  • oblique
  • longitudinal
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13
Q

What type of action is histamine [hormone, paracrine, autocrine, etc]?

A

paracrine –> released from ECL cells and activates parietal cells at local level

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14
Q

What are foveolar cells?

A

mucus secreting cells

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15
Q

what type of cells in mucous neck?

A

gastric stem cells

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16
Q

In parietal cell – what happens to H+, Cl-, HCO3-, K+?

A
  • K enters cell via Na/K ATPase on basolateral side
  • K exits via K channel on lumen and reenters via H/K ATPase that pumps H+ out into lumen
  • Positive charge in lumen attracts Cl- that exits cell via Cl channel passively
  • HCO3- produced as by-product of acid exits basolateral side into blood stream
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17
Q

What is mech by which parietal cell activated?

A
  • ACh to M3, Histamine to H2, or Gastrin to CCK-B
  • at activation, increase cellular Ca [in case of ACh or gastrin] or AMP [via histamine] which causes H/K ATPase to migrate to luminal cell surface
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18
Q

What 2 things activate ECL cell to release histamine?

A
  • Acetylcholine

- Gastrin

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19
Q

How does gastrin act on parietal cell [direct and indirect]?

Study These Flashcards
A
  • activates parietal cell to secrete HCl

- activates ECL to secrete histamine that then induces further HCl secretion by parietal

20
Q

How does vagus/ACh act on parietal cell [direct and indirect]?

Study These Flashcards
A
  • activates parietal cell to secrete HCl

- activates ECL to secrete histamine that induces further HCl secretion by parietal

21
Q

How does somatostatin act on parietal cell [direct and indirect]?

Study These Flashcards
A
  • inhibits parietal cell HCl secretion
  • inhibits G cell gastrin secretion [main function, paracrine]
  • inhibits ECL cell histamine secretion
22
Q

What activates somatostatin release from D cell?

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A
  • HCl produced in proximal stomach travels down to distal stomach where D cell senses the low pH and releases SST
23
Q

What does D cell secrete?

24
Q

What is GRP?

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A
  • a peptide released by parasympathetic nerves in response to distention
  • causes G cell to release gastrin
25
what happens to gastrin if no acid in stomach
its elevated
26
what does gastrin do? what does it act on?
- hormone released from G cell - activates ECL cell to release histamine - activates chief cell to release pepsinogen - activates parietal cell to release H
27
What does distention of stomach do?
- can turn on acid production
28
what is the functional unit of the pancreas
gland lined by acinar cells
29
What do pancreatic duct cells secrete?
- release HCO3 into lumen via Cl/HCO3 exchanger | - release Cl via CFTR channel
30
How does CAMP affect pancreatic duct cell secretion?
- CAMP causes increased Cl secretion via CFTR into lumen
31
What 3 things in pancreatic duct cell are stimulated by hormone secretin?
- more Cl secreted out to lumen via CFTR - increased activity Cl/HCO3 exchanger [Cl into cell from lumen, HCO3 out to lumen] - increased activity NBC [exchanges HCO3 into cell from basolateral side, Na out basolateral to blood stream]
32
How does pancreatic flow affect pancreatic bicarbonate conc?
- increased pancreatic flow --> increased pancreatic bicarbonate concentration
33
What causes s cells to produce secretin?
acid coming into lumen
34
What do pancreatic acinar cells secrete? What 5 things activate their secretion [via what 2 secondary messengers]
- enzymes released from granules into duodenum release activated by: - GRP, ACh [m3], CCK [CCK] via Ca - VIP, Secretin via cAMP PRIMARY TRIGGER = CCK
35
What are bile acids formed from?
cholesterol
36
How are primary bile acids formed from cholesterol? where are they secreted? where reabsorbed?
formed: via dehydroxylase and conjugation with glycine/taurine to make them soluble secreted: into bile reabsorbed: in terminal ileum
37
How are secondary bile acids formed from cholesterol? where are they secreted? where reabsorbed?
formed: via dehydroxylase primary bile acids [by bacteria] by bacteria reabsorbed: by colon, conjugated by liver, secreted back into bile
38
What are major effects of bile acid conjugation?
- lowers pKa to enhance hydrophilicity [makes more water soluble] - reduces passive diffusion across cell membranes in transit in biliary tree
39
Where are conjugated bile acids reabsorbed?
- in terminal ileum | - circulate back to liver via enterohepatic circulation
40
What are micelles? function?
- bile acids form sphere with hydrophobic part in center, hydrophilic part on outside - hydrophobic interior allows to package that fats while still staying soluble - transport lipids for absorption
41
What are components of human bile?
- 2/3 primary and secondary bile salts | - some phospholipids, cholesterol, protein, bilirubin, electrolytes
42
Where does fat absorption occur?
jejunum and ileum
43
What is possible consequence of getting rid of ileum?
- mess up enterohepatic circualtion - don't get enough reabsorption of bile salts - liver can't make enough to compensate so get bile salt deficiency
44
What 4 things tell bile duct to make HCO3?
- secretin - CCK - gastrin - vagal stimulation [ACh]
45
What do VIP/NO do to sphincter of oddi?
- relax sphincter so allow stuff to come through when gall bladder contracted above
46
What 2 things tell gall bladder to secrete bile salts?
- CCK | - ACh [vagal]
47
What is responsible for vagal afferent signal to tell vagus to induce bile salt secretion?
CCK
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