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GI 2 Flashcards

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1
Q

skipped

Gastric (Stomach) Function (6)

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 (Chemical Digestion)
 Produce Specialized Secretions

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2
Q

Produce Specialized Secretions (5)

A
  • HCl acid
  • Pepsinogen
  • Intrinsic factor
  • Mucus
  • Hormones/Paracrines
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3
Q
  1. Receptive relaxation (2)
A

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

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4
Q
  1. Peristalsis (trituration/homogenization) (2)
A

 Chyme production

 Trituration

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5
Q

Trituration:

A

Mix ingested nutrients with gastric secretions,

breakdown large particles and increase SA for digestion

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6
Q
  1. Emptying (pyloric sphincter) (2)
A

 ≈ 200 kcal/hr released into small intestine

 Important not to overload Small Intestine

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7
Q
  1. Migrating Motility Complex (MMC) (3)
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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8
Q
  1. Gastric Receptive Relaxation

 Initiated by: (2)

A
  • stretch of gastric or duodenal
    wall
  • protein or fat in duodenum
    (CCK)
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9
Q
  1. Gastric Receptive Relaxation
    reflexes:
    caused by:
A

 ENS (short) and Vago-vagal (long)
reflexes
 Caused by inhibitory signals (NO,
VIP) from ENS.

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10
Q
  1. Gastric Receptive Relaxation

function

A

Accommodates increased

volume of food and slows emptying.

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11
Q
  1. Gastric Peristalsis/Trituration

 Generated by

A

pacemaker cells

(Interstitial Cells of Cajal) located in GI smooth muscle

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12
Q 
2. Gastric Peristalsis/Trituration
Smooth muscle cells undergo 
spontaneous phases of 
depolarizations and 
repolarizations =
A

slow waves
or Basic Electrical Rhythm
(BER) of stomach

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13
Q
  1. Gastric Peristalsis/Trituration

Frequency =

A

3/minute

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14
Q
  1. Gastric Peristalsis/Trituration (cont.)

Functions: (4)

A 
 Acts to mix and break down 
(triturate) gastric contents 
(Retropulsion)
 Regulate Gastric emptying
 Peristaltic wave forces 
chyme through pyloric 
sphincter
 Causes pyloric sphincter to 
contract reducing volume 
released to Small Intestine.
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15
Q 
3. Rate of Gastric Emptying
Influenced by (3)
A

 Solid vs. Liquid
 Nutrient content
 Force of gastric contractions

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16
Q
  1. Rate of Gastric Emptying

On average: (4)

A

 50% of stomach contents emptied 2.5 to 3 hours
 Total emptying of the stomach 4 to 5 hours
 Total emptying of the small intestine 3 to 5 hours
 Transit through the colon 8 to 15 hours

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17
Q

Factors that increase force of antral contractions that increase Gastric emptying (2)

A

 Gastrin (Gastric hormone)

 Distension of stomach

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18
Q

Factors that decrease force of antral contractions which decrease Gastric emptying

A

 Contents of Duodenum

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19
Q

Enterogastrones =

A

hormones secreted by
duodenum in response
to nutrients and acid in
chyme.

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20
Q

Enterogastrones EX (3)

A
  1. CCK (Fat, Protein)
  2. Secretin (Acid)
  3. GIP (Carbohydrate)
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21
Q
  1. Migrating Motility Complex (MMC)
     Occurs in between meals
    (fasting state)
    approximately every
A

90

minutes

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22
Q
  1. Migrating Motility Complex (MMC)

Intervals of

A

strong

propulsive contractions

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23
Q
  1. Migrating Motility Complex (MMC)
    Sweep stomach and small
    intestine of
A

indigestible

material

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24
Q
  1. Migrating Motility Complex (MMC)
    Intrinsic to — and
    involves hormone —
25
4. Migrating Motility Complex (MMC) | Continue until
meal | ingested
26
Exocrine Gland  Produce  Variety of cell types and secretions
gastric juice
27
Oxyntic Gland (Corpus)
 Abundant Parietal and | Chief cells
28
Pyloric Gland (Antral) (2)
 Abundant Mucus-secreting cells  Hormones that regulate gastric function
29
Oxyntic cells: - activated by (3) - Inhibited by (1)
gastrin, histamine, acetylcholine | somatostatin
30
Oxyntic cells: | Cells secrete: (2)
- up to 2L/day of HCl | - Intrinsic Factor (IF)
31
Oxyntic cells: | Proton pumps inserted into --- membrane
apical
32
Synergism –
combination of factors creates a greater level of | acid secretion than just additive
33
Pharmacologically, inhibiting the activity of any one factor greatly reduces
acid secretion
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Neural Control of Oxyntic Cell Function | Stimulus =
Stretch of | Gastric wall
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Neural Control of Oxyntic Cell Function | Both (2) reflexes initiated
short and long
36
Neurotransmitters (2)
1. Ach 2. GRP (Gastrin Releasing Peptide)
37
Cephalic Phase of Acid Secretion | Stimulants: (4)
Sight of food Smell of food Taste of food Thoughts of food
38
``` Regulation of Acid Secretion – Interdigestive Period (3) ```  Basal secretions stimulated by (2)  Function:  Basal Secretion Rate =  Stimulated Secretion Rate =
 Acid is secreted at low levels  Lack of buffer (no food) causes low pH in stomach (3)  Gastrin low due to low pH in gastric lumen Histamine and Ach  Possibly to sterilize gastric lumen  0-11 mEq/hr  10-63 mEq/hr
39
Why Acid? | Functions (3)
```  Facilitates digestion of proteins.  Protects against some pathogens.  Increases absorption of B12, iron, calcium. ```
40
Why Acid? | PPIs – the Purple Pill (4)
```  Proton pump inhibitor – PPI  Binds to and inhibits H+ - K+ pump  Produces nearly 100% inhibition.  May have side effects related to functions of acid. ```
41
Intrinsic Factor
 Glycoprotein secreted by oxyntic cells
42
Intrinsic Factor | Exocytosis
• Secretion activated by same secretagogues that activate HCl secretion
43
Intrinsic Factor | Mechanisms for secretion unknown but
different than acid secretion (inhibitors of proton pump do not inhibit intrinsic factor secretion, but does reduce its function)
44
Intrinsic Factor | Required for --- absorption
Vitamin B12
45
Vitamin B12 important in
red cell production; deficiency causes | “pernicious anemia.”
46
Chief Cell Function (3)
```  Secretes pepsinogen to initiate digestion of protein.  Exocytosis  Protein digestion (not significant) ```
47
Pepsinogen activated to
pepsin by low pH | inactivated by pH > 5
48
Chief Cell | Main activation through
local and vagal reflexes that | release Ach.
49
Ghrelin | Produced by
endocrine cells located | in oxyntic glands
50
Only known appetite stimulant
Ghrelin
51
Individuals given Ghrelin eat --% | more than placebo control
30
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Ghrelin | Stimulates hypothalamic NT
Neuropeptide Y
53
Ghrelin | May partly account for the
anorexia and weight loss seen in some patients following gastric resection
54
Why Doesn’t the Stomach Digest Itself?
Gastric Mucosal Barrier
55
skipped | Gastric Mucosal Barrier (8)
 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-  Mucus secretion stimulated by Prostaglandins (NSAIDS)  Trefoil proteins help stabilize barrier
56
Disorders of Gastric Function (3)
 Ulcers  Mucosal destruction  Emptying
57
Ulcers – (2) * Helicobacter pylori- * Zollinger-Ellison Syndrome-
gastric, duodenal – “No acid, no ulcer” bacterial infection destroys the gastric diffusion barrier G Cell tumor
58
Mucosal destruction –
“gastritis,” mostly oxyntic gland | mucosa
59
Emptying –(3)
obstruction, gastroparesis, dumping
Physiology
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