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D1 Spring - Physiology Exam 6 > 4/25: Gastric Function > Flashcards

4/25: Gastric Function Flashcards

1
Q

What are the 3 main functions of the stomach?

A
  1. Temporary storage of ingested material
  2. Production of chyme (mechanical digestion and mixing)
  3. Meter delivery of chyme to duodenum
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2
Q

What special secretions does the stomach produce?

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

What is the function of the fundus and body?

A

Secretion reservoir

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4
Q

What is the function of the antrum?

A

Mixing
Grinding

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5
Q

What are the 4 types of gastric motility?

A
  1. Receptive relaxation
  2. Peristalsis (trituration/homogenization)
  3. Emptying
  4. Migrating motility complex (MMC)
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6
Q

What does receptive relaxation accomodate for?

A

The volume of the meal

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7
Q

What does receptive relaxation reduce?

A

Pressure increases preventing gastric reflux and premature gastric emptying

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8
Q

What does peristalsis produce?

A

Chyme

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9
Q

What is the function of peristalsis?

A

Trituration/homogenization

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10
Q

What is trituration?

A

Mix ingested nutrients with gastric secretions, breakdown large particles and increase SA for digestion

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11
Q

What sphincter controls emptying?

A

Pyloric sphincter

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12
Q

What does the migrating motility complex do?

A

Sweep ingested solids that cannot be digested out of stomach and through intestinal tract

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13
Q

What does migrating motility complex occur?

A

During fasting

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14
Q

What is gastric receptive relaxation initated by?

A
  • stretch of gastric or duodenal wall
  • protein or fat in duodenum (CCK)
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15
Q

What reflexes are associated with gastric receptive relaxation?

A

ENS (short) and Vago-vagal (long) reflexes

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16
Q

What is gastric receptive relaxation caused by?

A

Inhibitory signals (NO, VIP) from ENS

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17
Q

What is the function of the gastric receptive relaxation?

A

Accommodates increased volume of food and slows emptying

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18
Q

What is gastric peristalsis/trituration generated by?

A

Pacemaker cells (interstitial cells of cajal) located in GI smooth muscle

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19
Q

What do smooth muscle cells undergo?

A

spontaneous phases of
depolarizations and repolarizations = slow waves
or Basic Electrical Rhythm (BER) of stomach

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20
Q

What are the functions of gastric peristalsis/trituration?

A

Acts to mix and break down (triturate) gastric contents (retropulsion)

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21
Q

What does gastric peristalsis/trituration regulate?

A

Gastric emptying

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22
Q

What does peristaltic wave force?

A

Chyme through pyloric sphincter

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23
Q

What does gastric peristalsis/trituration cause?

A

Pyloric sphincter to contract reducing volume released to small intestine

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24
Q

What is rate of gastric emptying influenced by?

A

Solid vs. Liquid
Nutrient content
Force of gastric contractions

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25
Q

What do factors that increase force of antral contraction do to gastric emptying?

A

Increases it
- gastrin (gastric hormone)
- distension of stomach

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26
Q

What do factors that decrease force of antral contractions do to gastric emptying?

A

Decrease it
- contents of duodenum

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27
Q

What are enterogastrones?

A

Hormones secreted by duodenum in response to nutrients and acid in chyme

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28
Q

What are the three enterogastrones?

A
  1. CCK (fat, protein)
  2. Secretin (acid)
  3. GIP (carbohydrate)
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29
Q

Where does migrating motility complex occur?

A

In between meals (fasting state) approx. every 90 minutes

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30
Q

What is MMC intervals of?

A

Strong populsive contractions

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30
Q

What does MMC sweep?

A

Stomach and small intestine of indigestible material until meal is ingested

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31
Q

MMC is ______ to ENS and involves hormone _________

A

Intrinsic; motilin

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32
Q

What is the cell type, source, and function of HCl?

A

Exocrine
Parietal cell
Activation of pepsinogen, sterilization of meal

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33
Q

What is the cell type, source, and function of intrinsic factor?

A

Exocrine
Parietal cell
Vit B12 absorption

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34
Q

What is the cell type, source, and function of pepsinogen?

A

Exocrine
Chief cell
Protein digestion

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35
Q

What is the cell type, source, and function of mucous, HCO3?

A

Exocrine
Surface mucous cells
Gastroprotection

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36
Q

What is the cell type, source, and function of trefoil factors?

A

Exocrine
Surface mucous cells
Gastroprotection

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37
Q

What is the cell type, source, and function of histamine?

A

Paracrine
ECL cells
Regulation of gastric secretion

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38
Q

What is the cell type, source, and function of gastrin?

A

Endocrine
G cells
Regulation of gastric secretion

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39
Q

What is the cell type, source, and function of gastrin-releasing peptide?

A

NS
nerces
Regulation of gastric secretion

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40
Q

What is the cell type, source, and function of Ach?

A

NS
Nerces
Regulation of gastric secretion

41
Q

What is the cell type, source, and function of somatostatin?

A

Paracrine
D cells
Regulation of gastric secretion

42
Q

What is the cell type, source, and function of ghrelin?

A

Endocrine
Gr cells
Stimulate hunger

43
Q

What gland is found in the fundus/body?

A

Oxyntic gland (corpus)

44
Q

What does the oxyntic gland have abundant amounts of?

A

Parietal and chief cells

45
Q

What does the pyloric gland have?

A

Abundant mucus secreting cells
Hormones that regulate gastric functions

46
Q

What is alkaline tide?

A

pH of blood rises due to acid into lumen and abosrbtion of base into blood

47
Q

What is alkaline tide neutralized by?

A

Acid thats secreted by pancreas

48
Q

What are oxyntic cells activated by?

A

Gastrin, histamine, acetylcholine

49
Q

What are oxyntic cells inhibited by?

A

Somatostatin

50
Q

What do cells secrete?

A

Up to 2L/day of HCl
Intrinsic factor (IF)

51
Q

Where are protein pumps inserted?

A

Apical membrane

52
Q

What is synergism?

A

Combination of factors creates a greater level of acid secretion than just additive

53
Q

Pharmacologically, inhibiting the activity of any one factors greatly _______ acid secretion

A

Reduces

54
Q

What does Ach do with the oxyntic gland?

A

Stimulates it to release acid

55
Q

What does GRP (gastrin releasing peptide) do with the oxyntic gland?

A

Stimulates gastrin secretion from G cells into blood

56
Q

What are neurotransmitters involved in oxyntic cells?

A
  1. ACh
  2. GRP (gastrin releasing peptide)
57
Q

What is the stimulus for the oxyntic gland?

A

Stretch of the gastric wall

58
Q

What does the stretch of the gastric wall cause?

A

Short and long reflexes to be initiated

59
Q

What does the short and long reflexes stimulate?

A

Oxyntic glands to secrete acid and intrinsic factor

60
Q

What does somatostatin inhibit?

A

Parietal cells

61
Q

What are the three phases of GI activation?

A

Cephalic phase
Gastric phase
Intestinal phase

62
Q

What are stimulants of the cephalic phase?

A

Outside GI tract-
Sight of food
Smell of food
Taste of food
thoughts of food

63
Q

What is the cephalic phase mediated by?

A

PNS - vagus nerve

64
Q

What is the gastric phase mediated by?

A

Signals from lumen
Food in stomach

65
Q

What happens during the gastric phase when food is in the stomach?

A

Buffers acid which increases pH to prevent stimulation of somatostatin secretion

66
Q

When does the intestinal phase occur?

A

When there is content in the small intestine -
Increased H+, distension, osmolarity, fats in duodenum

67
Q

What do the intestinal stimuli in the intestinal phase cause the release of?

A

Enterogastrones

68
Q

What are examples of enterogastrones?

A

CCK
Secretin
GLP-1
GIP

69
Q

What happens with a rise of the enterogastrones?

A

Inhibit gastrin secretion
inhibit PNS function
inhibit parietal, ECL, and G cells
decrease acid secretion

70
Q

What levels is acid secreted?

A

Low levels

71
Q

What does a lack of buffer (no food) cause?

A

Low pH in stomach (3)

72
Q

What are basal secretions stimulated by?

A

Histamine and Ach

73
Q

Why is gastrin low?

A

Due to low pH in gastric lumen

74
Q

What are the functions of acid in the stomach?

A
  1. Facilitates digestion of proteins
  2. Protects against some pathogens
  3. Increases absorption of B12, iron, calcium
75
Q

What are PPIs?

A

Proton pump inhibitor

76
Q

What do PPIs bind to and inhibit?

A

H-K pump
**may be side effects due to functions of acids

77
Q

What is intrinsic factor?

A

Glycoprotein secreted by oxyntic cells
Exocytosis
- secretion activated by same secretagogues that activate HCl secretion

78
Q

What is the mechanism for secretion of intrinsic factor?

A

Unknown but different than acid secretion (inhibitors or proton pump do not inhibit intrinsic factor secretion, but does reduce its function)

79
Q

What is intrinsic factor required for?

A

Vitamin B12 absorption
Red cell production

80
Q

What does a deficiency in intrinsic factor cause?

A

Pernicious anemia

81
Q

What do chief cells secrete?

A

Pepsinogen to initiate digestion of protein
Exocytosis

82
Q

When is pepsinogfen activated?

A

To pepsin by low pH (inactivated by pH >5)

83
Q

What are chief cells mainly activated by?

A

Local and vagal reflexes that release ACh

84
Q

What is ghrelin produced by?

A

Endocrine cells located in oxyntic glands

85
Q

What is ghrelin known as?

A

Appetite stimulant

86
Q

What does ghrelin stimulate?

A

Hypothalamic NT neuropeptide Y

87
Q

What does grehlin account for in patients following gastric resection?

A

Anorexia and weight loss

88
Q

What is the flow chart of grehlin?

A
89
Q

Why doesn’t the stomach digest itself?

A

Two hydrophilic layers separated by hydrophobic barrier

90
Q

What is mucus secreted by in gastric mucosal barrier?

A

Mucous cells onto surface of epithelium

91
Q

What does the gastric mucosal barrier contain long chains of?

A

Oligosaccharides that expand and retain water

92
Q

What coats the surface of gastric epithelial cells?

A

Viscoelastic substances

93
Q

What is viscous fingering?

A

Limit diffusion of acid through the plane of the gel

94
Q

What is mucus secretion stimulated by?

A

Prostaglandins (NSAIDs)

95
Q

What do trefoil proteins help with?

A

Stabilizing barrier

96
Q

Where can ulcers be located?

A

Gastric
Duodenal
Esophagus

97
Q

No acid =

A

No ulcer

98
Q

What are causes of ulcers?

A

Helicobacter pylori-bacterial infection that destroys the gastric diffusion barrier
Zollinger-ellison syndrome-G cell tumor

99
Q

What is mucosal destruction?

A

“gastritis”, mostly oxyntic gland mucosa damage

100
Q

What are examples of emptying?

A

Obstruction
Gastroparesis
Dumping

D1 Spring - Physiology Exam 6 (6 decks)

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