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

4/25: Gastric Function Flashcards

(101 cards)

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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
What do factors that increase force of antral contraction do to gastric emptying?
Increases it - gastrin (gastric hormone) - distension of stomach
26
What do factors that decrease force of antral contractions do to gastric emptying?
Decrease it - contents of duodenum
27
What are enterogastrones?
Hormones secreted by duodenum in response to nutrients and acid in chyme
28
What are the three enterogastrones?
1. CCK (fat, protein) 2. Secretin (acid) 3. GIP (carbohydrate)
29
Where does migrating motility complex occur?
In between meals (fasting state) approx. every 90 minutes
30
What is MMC intervals of?
Strong populsive contractions
30
What does MMC sweep?
Stomach and small intestine of indigestible material until meal is ingested
31
MMC is ______ to ENS and involves hormone _________
Intrinsic; motilin
32
What is the cell type, source, and function of HCl?
Exocrine Parietal cell Activation of pepsinogen, sterilization of meal
33
What is the cell type, source, and function of intrinsic factor?
Exocrine Parietal cell Vit B12 absorption
34
What is the cell type, source, and function of pepsinogen?
Exocrine Chief cell Protein digestion
35
What is the cell type, source, and function of mucous, HCO3?
Exocrine Surface mucous cells Gastroprotection
36
What is the cell type, source, and function of trefoil factors?
Exocrine Surface mucous cells Gastroprotection
37
What is the cell type, source, and function of histamine?
Paracrine ECL cells Regulation of gastric secretion
38
What is the cell type, source, and function of gastrin?
Endocrine G cells Regulation of gastric secretion
39
What is the cell type, source, and function of gastrin-releasing peptide?
NS nerces Regulation of gastric secretion
40
What is the cell type, source, and function of Ach?
NS Nerces Regulation of gastric secretion
41
What is the cell type, source, and function of somatostatin?
Paracrine D cells Regulation of gastric secretion
42
What is the cell type, source, and function of ghrelin?
Endocrine Gr cells Stimulate hunger
43
What gland is found in the fundus/body?
Oxyntic gland (corpus)
44
What does the oxyntic gland have abundant amounts of?
Parietal and chief cells
45
What does the pyloric gland have?
Abundant mucus secreting cells Hormones that regulate gastric functions
46
What is alkaline tide?
pH of blood rises due to acid into lumen and abosrbtion of base into blood
47
What is alkaline tide neutralized by?
Acid thats secreted by pancreas
48
What are oxyntic cells activated by?
Gastrin, histamine, acetylcholine
49
What are oxyntic cells inhibited by?
Somatostatin
50
What do cells secrete?
Up to 2L/day of HCl Intrinsic factor (IF)
51
Where are protein pumps inserted?
Apical membrane
52
What is synergism?
Combination of factors creates a greater level of acid secretion than just additive
53
Pharmacologically, inhibiting the activity of any one factors greatly _______ acid secretion
Reduces
54
What does Ach do with the oxyntic gland?
Stimulates it to release acid
55
What does GRP (gastrin releasing peptide) do with the oxyntic gland?
Stimulates gastrin secretion from G cells into blood
56
What are neurotransmitters involved in oxyntic cells?
1. ACh 2. GRP (gastrin releasing peptide)
57
What is the stimulus for the oxyntic gland?
Stretch of the gastric wall
58
What does the stretch of the gastric wall cause?
Short and long reflexes to be initiated
59
What does the short and long reflexes stimulate?
Oxyntic glands to secrete acid and intrinsic factor
60
What does somatostatin inhibit?
Parietal cells
61
What are the three phases of GI activation?
Cephalic phase Gastric phase Intestinal phase
62
What are stimulants of the cephalic phase?
Outside GI tract- Sight of food Smell of food Taste of food thoughts of food
63
What is the cephalic phase mediated by?
PNS - vagus nerve
64
What is the gastric phase mediated by?
Signals from lumen Food in stomach
65
What happens during the gastric phase when food is in the stomach?
Buffers acid which increases pH to prevent stimulation of somatostatin secretion
66
When does the intestinal phase occur?
When there is content in the small intestine - Increased H+, distension, osmolarity, fats in duodenum
67
What do the intestinal stimuli in the intestinal phase cause the release of?
Enterogastrones
68
What are examples of enterogastrones?
CCK Secretin GLP-1 GIP
69
What happens with a rise of the enterogastrones?
Inhibit gastrin secretion inhibit PNS function inhibit parietal, ECL, and G cells decrease acid secretion
70
What levels is acid secreted?
Low levels
71
What does a lack of buffer (no food) cause?
Low pH in stomach (3)
72
What are basal secretions stimulated by?
Histamine and Ach
73
Why is gastrin low?
Due to low pH in gastric lumen
74
What are the functions of acid in the stomach?
1. Facilitates digestion of proteins 2. Protects against some pathogens 3. Increases absorption of B12, iron, calcium
75
What are PPIs?
Proton pump inhibitor
76
What do PPIs bind to and inhibit?
H-K pump **may be side effects due to functions of acids
77
What is intrinsic factor?
Glycoprotein secreted by oxyntic cells Exocytosis - secretion activated by same secretagogues that activate HCl secretion
78
What is the mechanism for secretion of intrinsic factor?
Unknown but different than acid secretion (inhibitors or proton pump do not inhibit intrinsic factor secretion, but does reduce its function)
79
What is intrinsic factor required for?
Vitamin B12 absorption Red cell production
80
What does a deficiency in intrinsic factor cause?
Pernicious anemia
81
What do chief cells secrete?
Pepsinogen to initiate digestion of protein Exocytosis
82
When is pepsinogfen activated?
To pepsin by low pH (inactivated by pH >5)
83
What are chief cells mainly activated by?
Local and vagal reflexes that release ACh
84
What is ghrelin produced by?
Endocrine cells located in oxyntic glands
85
What is ghrelin known as?
Appetite stimulant
86
What does ghrelin stimulate?
Hypothalamic NT neuropeptide Y
87
What does grehlin account for in patients following gastric resection?
Anorexia and weight loss
88
What is the flow chart of grehlin?
89
Why doesn't the stomach digest itself?
Two hydrophilic layers separated by hydrophobic barrier
90
What is mucus secreted by in gastric mucosal barrier?
Mucous cells onto surface of epithelium
91
What does the gastric mucosal barrier contain long chains of?
Oligosaccharides that expand and retain water
92
What coats the surface of gastric epithelial cells?
Viscoelastic substances
93
What is viscous fingering?
Limit diffusion of acid through the plane of the gel
94
What is mucus secretion stimulated by?
Prostaglandins (NSAIDs)
95
What do trefoil proteins help with?
Stabilizing barrier
96
Where can ulcers be located?
Gastric Duodenal Esophagus
97
No acid =
No ulcer
98
What are causes of ulcers?
Helicobacter pylori-bacterial infection that destroys the gastric diffusion barrier Zollinger-ellison syndrome-G cell tumor
99
What is mucosal destruction?
"gastritis", mostly oxyntic gland mucosa damage
100
What are examples of emptying?
Obstruction Gastroparesis Dumping

D1 Spring - Physiology Exam 6 (6 decks)

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