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Physiology > GI 2 > Flashcards

GI 2 Flashcards

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 —
A

ENS

Motilin

25
Q
  1. Migrating Motility Complex (MMC)

Continue until

A

meal

ingested

26
Q

Exocrine Gland
 Produce
 Variety of cell types and secretions

A

gastric juice

27
Q

Oxyntic Gland (Corpus)

A

 Abundant Parietal and

Chief cells

28
Q

Pyloric Gland (Antral) (2)

A

 Abundant Mucus-secreting cells
 Hormones that regulate gastric
function

29
Q

Oxyntic cells:

  • activated by (3)
  • Inhibited by (1)
A

gastrin, histamine, acetylcholine

somatostatin

30
Q

Oxyntic cells:

Cells secrete: (2)

A
  • up to 2L/day of HCl

- Intrinsic Factor (IF)

31
Q

Oxyntic cells:

Proton pumps inserted into — membrane

A

apical

32
Q

Synergism –

A

combination of factors creates a greater level of

acid secretion than just additive

33
Q

Pharmacologically, inhibiting the activity of any one factor
greatly reduces

A

acid secretion

34
Q

Neural Control of Oxyntic Cell Function

Stimulus =

A

Stretch of

Gastric wall

35
Q

Neural Control of Oxyntic Cell Function

Both (2) reflexes initiated

A

short and long

36
Q

Neurotransmitters (2)

A
  1. Ach
  2. GRP (Gastrin
    Releasing Peptide)
37
Q

Cephalic Phase of Acid Secretion

Stimulants: (4)

A

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

38
Q 
Regulation of Acid Secretion – 
Interdigestive Period (3)

 Basal secretions stimulated by (2)

 Function:
 Basal Secretion Rate =
 Stimulated Secretion Rate =

A

 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
Q

Why Acid?

Functions (3)

A 
 Facilitates digestion of 
proteins.
 Protects against some 
pathogens.
 Increases absorption of B12, 
iron, calcium.
40
Q

Why Acid?

PPIs – the Purple Pill (4)

A 
 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
Q

Intrinsic Factor

A

 Glycoprotein secreted by oxyntic cells

42
Q

Intrinsic Factor

Exocytosis

A

• Secretion activated by same secretagogues that activate HCl
secretion

43
Q

Intrinsic Factor

Mechanisms for secretion unknown but

A

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

44
Q

Intrinsic Factor

Required for — absorption

A

Vitamin B12

45
Q

Vitamin B12 important in

A

red cell production; deficiency causes

“pernicious anemia.”

46
Q

Chief Cell Function (3)

A 
 Secretes pepsinogen to 
initiate digestion of protein.
 Exocytosis
 Protein digestion (not 
significant)
47
Q

Pepsinogen activated to

A

pepsin by low pH

inactivated by pH > 5

48
Q

Chief Cell

Main activation through

A

local and vagal reflexes that

release Ach.

49
Q

Ghrelin

Produced by

A

endocrine cells located

in oxyntic glands

50
Q

Only known appetite stimulant

A

Ghrelin

51
Q

Individuals given Ghrelin eat –%

more than placebo control

A

30

52
Q

Ghrelin

Stimulates hypothalamic NT

A

Neuropeptide Y

53
Q

Ghrelin

May partly account for the

A

anorexia
and weight loss seen in some
patients following gastric resection

54
Q

Why Doesn’t the Stomach Digest Itself?

A

Gastric Mucosal Barrier

55
Q

skipped

Gastric Mucosal Barrier (8)

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-
 Mucus secretion stimulated by Prostaglandins (NSAIDS)
 Trefoil proteins help stabilize barrier

56
Q

Disorders of Gastric Function (3)

A

 Ulcers
 Mucosal destruction
 Emptying

57
Q

Ulcers – (2)

  • Helicobacter pylori-
  • Zollinger-Ellison Syndrome-
A

gastric, duodenal
– “No acid, no ulcer”
bacterial infection destroys the gastric diffusion barrier
G Cell tumor

58
Q

Mucosal destruction –

A

“gastritis,” mostly oxyntic gland

mucosa

59
Q

Emptying –(3)

A

obstruction, gastroparesis, dumping

Physiology (53 decks)

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