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PHYS Exam 6 > GI 2: Gastric Function > Flashcards

GI 2: Gastric Function Flashcards

1
Q

What is the function of the stomach?

A

➢ Temporary storage of ingested material
➢ Production of Chyme (Mechanical digestion and mixing)
➢ Meter delivery of chyme to duodenum
➢ Partially sterilize meal
➢ Initiates protein digestion
➢ Produce Specialized Secretions

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2
Q

What are the specialized secretions by the stomach?

A
  • HCl acid
  • Pepsinogen
  • Intrinsic factor
  • Mucus
  • Hormones/Paracrines
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3
Q

What are the four sections of the stomach?

A
  • cardia
  • fundus
  • body
  • antrum
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4
Q

What are the four types of gastric motility in the stomach?

A
  • receptive relaxation
  • peristalsis (trituration/homogenization)
  • emptying (pyloric sphincter)
  • migrating motility complex (MMC)
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5
Q

What is the function of gastric receptive relaxation?

A

➢ Accommodate the volume of the meal
➢ Reduce pressure increases preventing gastric reflux and premature gastric emptying

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6
Q

What is the function of gastric peristalsis in the stomach?

A

➢ Chyme production
➢ Trituration: Mix ingested nutrients with gastric secretions, breakdown large particles and increase SA for digestion

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7
Q

What is the function of emptying the stomach?

A

➢ ≈ 200 kcal/hr released into small intestine
➢ Important not to overload Small Intestine

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8
Q

What is the function of the migrating motility complex (MMC)?

A

➢ Sweep ingested solids that cannot be digested out of stomach and through intestinal tract
➢ Occurs during fasting
➢ Takes approximately 90 min to go from stomach to colon

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9
Q

What initiates the gastric receptive relaxation?

A
  • stretch of gastric/duodenal walls
  • protein or fat in duodenum (CCK)
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10
Q

Which of these is short and which is long…

ENS
Vago-vagal

A

ENS - short
Vago-vagal - long

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11
Q

What hormone causes gastric receptive relaxation?

A

inhibitory signals (NO, VIP) from enteric nervous system

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12
Q

What is gastric peristalsis generated by?

A

interstitial cells of cajal (pacemaker cells)

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13
Q

What is the frequency of basic electrical rhythm (BER) of the stomach?

A

3/minute

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14
Q

What influences the rate of gastric emptying?

A
  • solid vs liquid
  • nutrient content
  • force of gastric contractions
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15
Q

____% of stomach contents emptied 2.5 to 3 hours

A

50%

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16
Q

Transit through the colon ___________ hours

A

8 to 15 hours

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17
Q

Total emptying of the stomach ________ hours

A

4 to 5 hours

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18
Q

Total emptying of the small intestine _______ hours

A

3 to 5 hours

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19
Q

What increases the force of antral contractions and causes increased gastric emptying?

A
  • gastrin
  • distension of stomach
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20
Q

What decreases the force of antral contractions and causes decreased gastric emptying?

A

contents of duodenum

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21
Q

What are enterogastrones and what are examples?

A
  • hormones secreted by duodenum in response to nutrients and acid in chyme.
    1. CCK (Fat, Protein)
    2. Secretin (Acid)
    3. GIP (Carbohydrate)
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22
Q

What hormone is used during the migrating motility complex (MMC)?

A

motilin

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23
Q

What is the migrating motility complex (MMC)?

A

➢ Occurs in between meals (fasting state) approximately every 90 minutes
➢ Intervals of strong propulsive contractions
➢ Sweep stomach and small intestine of indigestible material
➢ Intrinsic to ENS and involves hormone Motilin.
➢ Continue until meal ingested.

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24
Q

What cell makes HCl?

A

parietal cell (oxyntic)

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25
Q

What cell makes intrinsic factor?

A

parietal cell (oxyntic)

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26
Q

What cell makes pepsinogen?

A

chief cell

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27
Q

What cell makes mucus, HCO3-, and trefoil factors?

A

surface mucous cell

28
Q

What cell makes histamine?

A

ECL cells

29
Q

What cell makes gastrin?

A

G cells

30
Q

What cell makes somatostatin?

A

D cells

31
Q

What cells make ghrelin?

A

Gr cells

32
Q

What cells are part of the oxyntic gland (corpus)?

A

abundant parietal and chief cells

33
Q

What cells are part of the pyloric gland (antral)?

A

mucus-secreting cells

34
Q

What is the alkaline tide that occurs during parietal cell function?

A

blood is more basic for a couple of hours due to excess HCO3- in basolateral membrane

35
Q

What hormones activates the oxyntic cells (acid producing)?

A

gastrin
histamine
ACh

36
Q

What hormone inhibits the oxyntic cells (acid producing)?

A

somatostatin

37
Q

What side of the membrane are the proton pump inserted into on oxyntic cells?

A

apical membrane

38
Q

What is synergism of oxyntic cell function?

A

– combination of factors creates a greater level of acid secretion than just additive

39
Q

The short and long neural control of oxyntic cells result in what being secreted when the stimulus is stretch?

A

Acid
pepsin
intrinsic factor
gastrin

40
Q

What neurotransmitters cause the short and long neural control mechanisms to stimulate oxyntic cells?

A

ACh
GRP (gastrin releasing peptide)

41
Q

Stretch on the gastric walls causes what to be secreted?

A

ACh
GRP (gastrin releasing peptide)
gastrin

42
Q

What does somatostatin do to parietal cells?

A

inhibits parietal cells directly and by inhibiting gastrin and histamine

43
Q

What stimulates D cells to secrete somatostatin?

A

HCl

44
Q

What does somatostatin inhibit?

A

G cells = gastrin
ECL cells = histamine
Parietal cells = HCl (acid)

45
Q

What are the three phases of GI activation?

A
  • cephalic phase (via vagus)
  • gastric phase (local, vagal, and gastrin-histamine stimulation)
  • intestinal phase (nervous and hormones)
46
Q

What is the stimulus for cephalic phase of acid secretion?

A

Sight of food
Smell of food
Taste of food
Thoughts of food

47
Q

What is the cephalic phase of acid secretion?

A
  • acid secretion goes up
  • somatostatin levels go up
  • acid levels are kept low because of somatostatin
48
Q

What is the gastric phase of acid secretion?

A
  • food in stomach buffers the acid and prevents somatostatin secretion (= more acid)
  • distension of stomach causes acid secretion
  • peptides stimulate G cells which produce gastrin (= more acid)
49
Q

What is the intestinal phase of acid secretion?

A

increased H+
distension
osmolarity
fats in duodenum

50
Q

What is the intestinal phase of acid secretion?

A
  • intestinal stimuli cause release of enterogastrones (CCK, secretin, GLP1, GIP)
  • enterogastrones inhibit G cells, ECL cells, and parietal cells (= less acid in stomach)
  • increase parasympathetics
51
Q

What do enterogastrones (CCK, secretin, GLP1, GIP) do to acid secretion?

A

inhibit acid secretion

52
Q

How do you regulate acid during the interdigestive period (fasting)?

A

➢ Acid is secreted at low levels
➢ Lack of buffer (no food) causes low pH in stomach (3)
➢ Basal secretions stimulated by Histamine and Ach
➢ Gastrin low due to low pH in gastric lumen
➢ Function: Possibly to sterilize gastric lumen

53
Q

What do PPIs (proton pump inhibitor) do?

A

➢ Binds to and inhibits H+/K+ pump
➢ Produces nearly 100% inhibition.
➢ May have side effects related to functions of acid.

54
Q

What is the funciton of acid?

A

➢ Facilitates digestion of proteins.
➢ Protects against some pathogens.
➢ Increases absorption of B12, iron, calcium.

55
Q

What is required for Vitamin B12 absorption?

A

intrisic factor

56
Q

What can deficiency of vitamin B12 via low intrinsic factor cause?

A

pernicious anemia

57
Q

What is the function of a chief cell?

A

Secretes pepsinogen to initiate digestion of protein

58
Q

How is pepsinogen activated into pepsin?

A
  • low pH (less than 5)
  • HCl
59
Q

What is the main activation of chief cells?

A

local and vagal reflexes that release Ach

60
Q

How do chief and parietal cells work together to create pepsin for protein breakdown?

A
61
Q

What is the only known appetite stimulant?

A

ghrelin

62
Q

What hormone may partly account for the anorexia and weight loss seen in some patients following gastric resection?

A

ghrelin

63
Q

What ghrelin level increase following decrease in body fat what happens?

A
  • increase in hunger/eating
  • decrease in metabolism
64
Q

What is the gastric mucosal barrier?

A

➢ Two hydrophilic layers separated by hydrophobic barrier
➢ Mucus is secreted by mucous cells onto surface of epithelium
➢ Contains long chains of oligosaccharides that expand and retain water
➢ Viscoelastic substance that coats surface of gastric epithelial cells
➢ Limit diffusion of acid through the plane of the gel via a mechanism known as viscous fingering
➢ Micro-climate with high pH produced by surface cell secretion of HCO3

65
Q

What is mucus secretion stimulated by in the gastric mucosal barrier?

A

prostaglandins

(NSAIDS decrease prostaglandins)

66
Q

What protein helps stabilize the gastric mucosal barrier?

A

trefoil

67
Q

What are the causes of ulcers?

A

– “No acid, no ulcer”
* Helicobacter pylori-bacterial infection destroys the
gastric diffusion barrier
* Zollinger-Ellison Syndrome-G Cell tumor

PHYS Exam 6 (4 decks)

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