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W/Physiology > Topic 6.3 > Flashcards

Topic 6.3 Flashcards

1
Q

3 types of secretors in the GI

A
  • Exocrine glands (pancreas, salivary)
  • Gland formed by the gut wall itself (Bruner, Lieb)
  • Intestinal mucosa
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2
Q

2 main functions of GI secretion

A

Protection, and promotion of digestion + absorption

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3
Q

What are the 2 types of GI secretion?

A

Organic, inorganic

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4
Q

What are secretagogues?

A

Ligands which can act on secretory cells. Can be either endocrine or paracrine.

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5
Q

How much secretion / day?

A

9-10L day / secretion

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6
Q

Daily production of saliva

A

800-1500mL / day

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7
Q

7 main functions of saliva

A
  1. Disrupts the food into smaller particles
  2. Lubrication for swallowing and speaking
  3. Initiation of starch and lipid (kids) digestion
  4. Cleansing function
  5. Antimicrobial effect
  6. Neutralization of gastric content
  7. Calcium binding proteins for teeth
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8
Q

How does the saliva have an antimicrobial effect?

A

Contains IgA and lysozymes

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9
Q

What are the major salivary glands? (3)

A

Parotid, sublingual, submandibular

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10
Q

What are the minor salivary glands? (3)

A

Tongue, lips, palate

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11
Q

What is the general structure of the salivary glands?

A

Tubuloalveolar

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12
Q

What are the 2 types of acinar cells and their difference?

A
  • Mucous : produce mucin

- Serous : have zymogen granules (amylase and lipase)

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13
Q

What type of gland is parotid?

A

Mostly serous

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14
Q

What type of gland is sublingual?

A

Mainly mucous / mixed

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15
Q

What type of gland is submandibular?

A

Mixed

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16
Q

What type of gland is buccal?

A

Mucous

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17
Q

4 proteins produced in the acinar cells?

A
  • Amylase
  • Ig
  • Mucin
  • R protein (haptocorin)
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18
Q

What is haptocorin useful for?

A

B12 absorption : protects it from acidity of the stomach

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19
Q

how is the primary secretion compared to the plasma?

A

Isoosmotic, with similar electrolyte concentration to blood plasma

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20
Q

What type of epithelium is the acinar epithelium?

A

leaky epithelium

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21
Q

What inhibits ENaC?

A

amiloride

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22
Q

What upregulates ENaC?

A

Aldosterone

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23
Q

How is the resulting saliva?

A

Hypoosmotic, and alkaline compared to its surroundings

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24
Q

How is salivary secretion regulated?

A

Mostly parasympathetic, neural regulation

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25
Q

What is VIP coupled to and what does it result in?

A

Gs coupled, causes “atropine resistant” vasodilation, which increases secretion

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26
Q

What is Ach couples to and what does it result in?

A

Gq coupled (M3) on acinar cells, causes exocytosis and constriction of acinar cells, which increases secretion

27
Q

What effect does the sympathetic system have on salivary secretion? (2)

A
  • B2 : increases mucin secretion

- A1 : constricts vessels

28
Q

What is the external way of salivary secretion?

A

Unconditioned stimuli activates CN, for example : seeing food, smell…

29
Q

What type of cells are in the midline of the gastric mucosa?

A

proliferative cells (regenerate the mucosa)

30
Q

What do surface epithelial cells produce? (2)

A

mucin, bicarbonate

31
Q

What do parietal cells secrete? (2)

A

the gastric acid + intrinsic factor through exocytosis

32
Q

What do chief cells secrete?

A

digestive enzymes

33
Q

Which cells of the gastric mucosa can be found everywhere in the stomach?

A

the surface epithelial cells

34
Q

What is the daily production of gastric juice?

A

1-1.5L / day

35
Q

How is the gastric juice osmotically?

A

isoosmotic

36
Q

What are the 4 main constituents of gastric juice?

A

Water, electrolytes (H, Cl), bicarbonate, proteins (mucin, digestive enzymes)

37
Q

What are the 3 functional regions of the stomach?

A
  • Cardia / LES
  • Fundus / body
  • Antrum / pylorus
38
Q

Which is the only region of the stomach to produce gastric juice / acid?

A

The fundus / body, the rest only secrete mucin and bicarbonate

39
Q

What is the role of the cardia / LES?

A

prevent reflux, entry of food

40
Q

What is the role of the fundus / body?

A

reservoir + secretion of gastric juice

41
Q

What is the role of the antrum / pylorus?

A

mixing, grinding, regulation of emptying

42
Q

Which cells secrete the intrinsic factor?

A

parietal cells

43
Q

How do parietal cells increase their surface and energy?

A

With the canaliculi and the mitochondria

44
Q

What are the 2 forms of the parietal cell?

A
  • Resting / inactive

- Active / secreting (has canalicul)

45
Q

Which drugs can inhibit the K+ / H+ pump? (2)

A

omeprazol, pantoprazol

46
Q

What is the H+ source for gastric acid?

A

Parietal cell metabolism

47
Q

How is the H+ gradient in parietal cell / lumen?

A

The gradient is a million-fold : 10^6 : from pH = 7.2 to pH = 1-2

48
Q

What is the most important regulator of gastric acid secretion?

A

parasympathetic nervous system through vagal nerve stimulation

49
Q

What are the 6 ways of activating G cells?

A
  1. Ach
  2. GRP (gastrin releasing peptide) : para sympathetic NT
  3. Mechanical stimuli : wall tension
  4. Alcohol, soda, cola
  5. Helicobacter pilori
  6. Sympathetic system : B2 receptor
50
Q

What is the G cell inhibitor?

A

Somatostatin

51
Q

How is the release of somatostatin triggered?

A

If GA secretion is too high, pH is too low, which activates the D cells - which produces somatostatin

52
Q

What type of receptor is somatostatin coupled to?

A

Gi receptor

53
Q

ON which cells can somatostatin act?

A

On g cells mostly, or directly on parietal cells

54
Q

On which cells can gastrin act to regulate GA secretion?

A

On parietal cell directly or on ECL cells, which then release histamine to the parietal cells

55
Q

What are the 2 phases of GA secretion?

A 
Cephalic phase (smelling, tasting)
Gastric phase (presence of protein breakdown product)
56
Q

Which molecule can decrease GA secretion (on top of somatostatin)

A

prostaglandins

57
Q

What produces prostaglandins?

A

COX enzymes

58
Q

How do prostaglandins decrease GA?

A

Gi signaling, reduce cAMP signal and decrease secretion

59
Q

How does GA composition change based on the rate of secretion?

A
  • Basal secretion : ++ NaCl, low H+

- High secretion : ++ H+ and Cl

60
Q

What can we use to measure the H+ content of GA?

A
  • BAO (basal acid output)

- PAO (peak acid output)

61
Q

What is the basal acid output?

A

1.5 - 2.5 mmol H+ / hour

62
Q

What is the peak acid output?

A

Women : 25 mmol H+ / hour

Men : 35 mmol H+ / hour

63
Q

What protects the gastric mucosa from high acidity?

A

2mm sticky mucin layer produced by surface epithelial cells

64
Q

What can regulate Chief cell secretion? (4)

A
  • Acetylcholine (vagus stimulation after meal)

- Gastrin, secretin, CCK

W/Physiology (31 decks)

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