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GI/GU Exam > Secretions of GI Tract and Pancreas > Flashcards

Secretions of GI Tract and Pancreas Flashcards

1
Q

How does the saliva composition compare to plasma?

A

Saliva is hypotonic compared to plasma

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2
Q

What all is in saliva?

A
  • water
  • electrolytes (K+ and HCO3- especially)
  • alpha amylase
  • lingual lipase
  • kallikrein
  • mucus
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3
Q

What are the parts of the salivary ducts? (4)

A
  • acinus
  • myoepithelial cells
  • intercalated duct
  • striated duct
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4
Q

What is the acinus?

A

the blind end that secretes the inital saliva

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5
Q

What do myoepithelial cells do?

A

Have motile extensions, when stimulated contract to eject saliva into mouth

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6
Q

What does the intercalated duct do?

A

Is just a channel. Saliva here has composition similar to plasma

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7
Q

What does the striated duct do?

A

Is lined w/ductal cells that modify comp of saliva by altering electrolyte concentration

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8
Q

What are the pre and post synaptics that are part of the parasympathetics of secretion?

A

pre - start at CN VII, XI

post - autonomic ganglia innervating individual glands

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9
Q

What increases firing of parasympathetics and thus saliva production? (4)

A
  • food
  • nausea
  • smells
  • conditioning
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10
Q

What decreases firing of parasympathetics (saliva production)? (3)

A
  • dehydration
  • fear
  • sleep
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11
Q

What are the steps of parasympathetic stimulation? (4)

A
  1. stimulus stimulates ANS, sends signal
  2. Ach released
  3. ACh attaches to mAchR
  4. IP3, Calcium increase, leading to saliva
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12
Q

What are the pre and post synaptics that are part of the sympathetics of secretion?

A

pre - originate at cervical ganglion (T1-T3)

post - extends to glands in periarterial space

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13
Q

What does stimulation of sympathetics lead to, saliva-wise? (3)

A
  • increased saliva production
  • increased bicarb and enzyme secretions
  • contraction of myoepithelial cells
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14
Q

Which system is saliva under the control of?

A

the ANS only

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15
Q

What are the main components of gastric juice? (5)

A
  • water
  • hydrogen ions (for HCl)
  • Pepsinogen
  • Mucus
  • Intrinsic factor
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16
Q

What does hydrochloric acid do?

A

Initiates protein digestion by activating pepsinogen to pepsin
kills lots of bacteria that enter the stomach

17
Q

What is pepsinogen?

A

The inactive precursor to pepsin

18
Q

What is the purpose of mucus?

A

Lines stomach to protect it from gastric acid, lubricates the mucosa, maintains neutral stomach pH, it and HCO3 neutralize acid

19
Q

What is the purpose of intrinsic factor?

A

Binds to vitamin B12, is required for its absorption

20
Q

Where is vitamin B12 absorbed?

A

Ileum

21
Q

What is the purpose of water in gastric juice?

A
  • Is medium for HCl and enzyme action

- solubilizes ingested material

22
Q

Regarding parietal cells:

  • what do they secrete?
  • Where are they located?
A
  • Parietal cells secrete HCl and Intrinsic factor

- Are located mainly in the body of the stomach

23
Q

How does HCl get pumped into the stomach lumen?

A
  • Hydrogen ions generated w/in parietal cell from dissociation of water, done by carbonic anhydrase (makes bicarb, hydrogen)
  • bicarb transported out of basolateral membrane in exchange for Cl-
  • H+ pumped into lumen in exchange for K+ through proton pump
24
Q

Regarding chief cells:

  • what do they secrete?
  • where are they located?
A
  • Secrete pepsinogen

- Found in body of stomach

25
Q

Regarding G cells:

  • What do they secrete?
  • Where are they located?
A
  • Produce gastrin

- Located in antrum

26
Q

Regarding Mucus cells:

  • What do they secrete?
  • Where are they located?
A
  • Secrete mucus, HCO3 and pepsinogen

- Located in the antrum

27
Q

What is the direct path of gastric secretion?

A

Vagus nerve → ACh → parietal cells

  • vagus stimulation stimulates M3 receptor
  • Gq activated
  • IP3/Calcium released
  • H-K ATPase activated, secretes H+
28
Q

What is the indirect path of gastric secretion?

A

Vagus → GRP → G cells

29
Q

How does gastrin activate parietal cells?

A 
G cells normally inhibited by somatostatin. Gastrin stimulates CCKb receptor: 
- Gq activated
- IP3/Ca2+ released
- H-K ATPase activated
ALSO ACTIVATES ECL CELLS
30
Q

How does histamine effect gastric secretions?

A

Stimulates it by:

  • ECL release histamine
  • acts on H2 receptor
  • Gs activated
  • increase in cAMP
  • H-K ATPase activated
31
Q

How does somatostatin effect gastric secretions?

A

Decreases?

GI/GU Exam (21 decks)

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