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PHSL233 > Lecture 27 - GI Secretion > Flashcards

Lecture 27 - GI Secretion Flashcards

1
Q

What does the endocrine secretion do in GI secretions?

A

(Hormones)
Regulation of motility and secretion
- gastrin stimulation of stomach motility and gastric acid secretion
- CCK and secretin inhibition: stomach motility, stimulation: pancreatic secretion

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2
Q

What does exocrine secretion do in GI secretions?

A

Prepare food for digestion by:
- diluting it to the osmolality of the plasma
- altering pH for optimal digestion
- digesting food
- protection/lubrication

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3
Q

What are the major components of GI secretion?

A

mucus, enzymes, electrolytes or serous solutions

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4
Q

Where is the exocrine or serous secretions in GI tract produced?

A

Produced by Epithelial cells lining GI tract and associated organs

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5
Q

What are the roles of saliva?

A

Oral hygiene
- xerostomia (dry mouth, lack of saliva)
Aids in:
- talking
- chewing and swallowing by moistening and dissolving food
Assists in rendering food isosmotic
Amylase - starch digestion

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6
Q

What are the three main pairs of salivary glands?

A

Parotid (serous)
Submandibular (mixed mucous/serous)
Sublingual (mucous)

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7
Q

What are the types of acinus cell in the salivary glands?

A

Serous acinar cells - zymogen granules
Mucous acinar cells

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8
Q

What are the types of duct cells in the salivary glands?

A

Intercalated ducts
Striated ducts

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9
Q

What do the duct cells do in salivary glands?

A

Drain into mouth
Reabsorption from primary fluid
- dilute solution
- limited further secretion

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10
Q

What do the acinus cells do in salivary glands?

A

Site of primary secretion
- isotonic NaCl solution

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11
Q

What is the volume of saliva produced per day?

A

1.5L

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12
Q

What is the basal rate of saliva production?

A

0.5 mL/min

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13
Q

What are the main components of saliva?

A

Mucus
Digestive enzymes
Serous secretion

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14
Q

What produces the mucus found in saliva?

A

Sublingual & submandibular & buccal glands

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15
Q

What produces the digestive enzymes found in saliva?

A

a-amylase - parotid gland
salivary glands of tongue - lingual lipase

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16
Q

What produces the serous secretion found in saliva?

A

Primarily parotid, lesser extent submandibular

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17
Q

What is the serous secretion in saliva?

A

Hypo-osmotic solution of NaCl with slightly elevated K+ and HCO3
- composition varies with rate of secretion

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18
Q

What osmolarity is saliva?

A

Saliva is always hypo-osmotic
- Osmolarity increases as rate of secretion increases

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19
Q

What is the conc of ions in saliva vs plasma?

A

[Na+] & [Cl-] < in plasma
[K+] higher than plasma
[HCO3-] higher than plasma
- Na+ in saliva goes up when flow rate increases, not to point as what it is in plasma

20
Q

What is the constant and variable in saliva secretion rate?

A

Rate of secretion by acini variable
Rate of absorption by duct is constant

21
Q

What happens when there are slow rates of saliva secretion?

A

Primary fluid in contact with duct epithelium for extended period of time
Greater absorption of NaCl
- when we don’t eat: fluid more time to be absorbed

22
Q

What happens when there are high rates of saliva secretion?

A

Primary fluid passes through ducts rapidly
Limited absorption of NaCl

23
Q

Saliva
A. is hypertonic during stimulation of secretion.
B. helps digesting starch.
C. contains enzymes such as pepsin.
D. contains less bicarbonate than plasma.

A

B. helps digesting starch.

A - Always hypotonic regardless of stimulation
C - contains amylase and lipase
D - Higher than plasma

24
Q

Which salivary duct produces primary fluid?

A

Acini salivary duct

25
Q

What salivary duct modifies fluid?

A

Striated and excretory ducts

26
Q

What do the salivary striated and excretory ducts do?

A

Modification of fluid by reabsorption of Na+ and Cl- without water
- Limited amount of K+ and HCO3- secretion depending on species
- Mucus

27
Q

Describe the primary fluid produced by salivary acini ducts

A

Isotonic NaCl
- amylase
- mucus

28
Q

What is the difference in duct cell epithelium in salivary glands vs pancreas?

A

Pancreas - leaky epithelium in ducts
Saliva - tight epithelium in ducts

29
Q

What can move paracellularly in salivary acinus cells?

A

Na+ and H2O

30
Q

What channels are found in the basolateral membrane of salivary acini cells?

A

Na/K-ATPase
K channel
NKCCI
H2O channel

31
Q

What channels are found in the apical membrane of salivary acini cells?

A

Cl- channel
H2O channel

32
Q

What is the duct cell mechanism in saliva secretion?

A

Isotonic primary saliva
-> Na+ reabsorbed
-> K+ secreted
-> HCO3- secreted
=> hypotonic saliva

33
Q

What channels are found in the apical membrane of salivary duct cells?

A

ENaC
K+ channel
CFTR (Cl- channel)
Cl-/HCO3- exchanger

34
Q

What channels are found in the basolateral membrane of salivary duct cells?

A

Na+/HCO3- cotransporter
NHE

35
Q

What type of epithelium is found in salivary duct cells?

A

Tight epithelia

36
Q

What nervous pathway is the main system in salivary secretion regulation?

A

Parasympathetic

37
Q

What is the parasympathetic regulation of salivary secretion?

A

Main system
Acetylcholine
Stimulate blood flow
High amount of serous saliva

38
Q

What is the sympathetic regulation of salivary secretion?

A

Noradrenalin (α1,B2)
Inhibits blood flow
Low amount of mucous saliva

39
Q

What is the regulation of salivary secretion?

A

mainly nervous – both branches ANS regulate secretion

40
Q

What is saliva secreted in response to?

A
  • thought of food
  • approach of food
  • food in the mouth
  • parasympathetic nervous system
41
Q

What are the two reflexes involved in saliva secretion?

A

Conditioned reflex
Unconditioned reflex

42
Q

What is the conditioned reflex of saliva secretion?

A

Due to sight and smell of food
Learned response – Pavlov

43
Q

What is the unconditioned reflex of saliva secretion?

A

Due to presence of food in mouth and response to taste receptors

44
Q

Secretion of a hypotonic salivary solution
A. depends on sympathetic activation.
B. requires a basolateral chloride and bicarbonate channel in acini.
C. requires para-cellular re-absorption of Na+ in acini.
D. requires leaky acinar epithelium.

A

D. requires leaky acinar epithelium.

A - Parasympathetic
B - Channel found in duct cell apical membrane, transporter not channel

45
Q

What is the only salivary cell that secretes enzymes?

A

Acinar cells

PHSL233 (32 decks)

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