Stomach 1 Flashcards

1
Q

name the two functional regions of the stomach (and their main parts)

A

proximal- fundus and proximal body

distal- distal body and antrum (pylorus)

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2
Q

the proximal region (orad stomach) is responsible for what?

A

receiving ingested meal

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3
Q

the distal region (caudad stomach) is responsible for what

A

contractions that mix food and propel it into duodenum

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4
Q

what are the three functions of the stomach?

A

storage
mixing
emptying

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5
Q

what occurs in the stomach during food storage

A

proximal stomach relaxes to accommodate ingested meal- via receptive relaxation
pressure slowly returns to basal level
stomach can hold up to 1.5 L w/ little change in pressure

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6
Q

receptive relaxation (what is it, what mediates it, how is it abolished)

A

process by which the proximal stomach relaxes to accommodate ingested meal
mediated by vagovagal reflex
abolished by vagotomy

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7
Q

the vagovagal reflex is initiated by what?

A

distention of the stomach

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8
Q

what occurs in the stomach during mixing

A

presence of food causes distal stomach to increase contractions
this mixes food with gastric sections and reduces size of particles
food mixed into pasty consistency (chyme)

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9
Q

what is chyme?

A

semifluid mass of partly digested food passed from the stomach to small intestine (made during mixing in stomach)

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10
Q

what occurs in stomach during emptying

A

distal stomach contracts to propel food into duodenum

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11
Q

peristaltic contractions originate where and proceed how?

A

originate in pacemaker region (midstomach)

proceed distally

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12
Q

a peristaltic contractions move distally toward pylorus what happens to velocity and force of the contractions?

A

they both increase

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13
Q

retropulsion (what is it)

A

process by which most of chime is propelled back into the stomach to be mixed
due to wave on contractions closing distal antrum and pyloric sphincter before chyme reaches there

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14
Q

the wave of peristaltic contractions does what to distal antrum and pyloric sphincter

A

closes them before the chyme can reach there

causes retropulsion

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15
Q

what occurs during fasting (contractions wise and how often)

A

contractions called migrating myoelectric complexes occur at 90 minute intervals

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16
Q

migrating myoelectric complexes (what do they do)

A

occur every 90 minutes during fasting
clear the stomach of any residual food
cause hunger contractions if stomach has been empty for about 2 hours

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17
Q

how are migrating myoelectric complexes abolished

A

eating

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18
Q

hunger pangs (when do they start and how long do they last)

A

start 12-24 hours after last meal

continue for about 3-4 days before subsiding

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19
Q

emptying of the stomach occurs when?

A

chyme decomposed into small enough pieces to fit through pyloric sphincter

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20
Q

following a normal mixed meal emptying of the stomach may take about how long, and is dependent on what?

A

about 3 hours

depends on type of food ingested

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21
Q

place the following in order of fastest to slowest in terms of emptying from the stomach:
protein-rich food
carbohydrate-rich food
fat-rich food

A

carbohydrate-rich food (fastest of these three) > protein-rich food > fat-rich food (slowest of these three)

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22
Q

between liquids and solids which empty from the stomach fastest

A

liquids

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23
Q

the rate of emptying has what type of relationship with the pressure in the proximal stomach (which increases slowing during digestive period)

A

inversely proportional

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24
Q

gastric emptying is controlled mostly by what?

A

signals from duodenum

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25
Q

gastric emptying is inhibited by what stimuli?

A
high [H+]
fat or protein digestion products
non-isotonic solutions
increases distention of proximal stomach
increase pressure in proximal small intestine
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26
Q

gastric emptying prevents what? (in terms of the flow of chyme)

A

prevents flow of chyme from exceeding ability of intestine to handle it

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27
Q

Gastroparesis (what is it, what does it produce, what causes it

A

impaired/ delayed emptying
produces symptoms of fullness, loss of appetite, nausea, vomiting
most common cause is diabetes

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28
Q

increased gastric emptying can cause what?

A
diarrhea (b/c increased osmotic load in small intestine)
duodenal ulcers (b/c stomach acid damages duodenum)
29
Q

dumping syndrome (what is it, when is it common)

A

occurs when lower end of small intestine fills too quickly with undigested food from the stomach
common after surgery

30
Q

dumping syndrome (what are the phases, when do they occur, and what are the symptoms)

A

early phase- occurs either during/right after meal (nausea, vomiting, diarrhea)
late phase- occurs 1-3 hours after meal (sweating, weakness, dizziness)

31
Q

the symptoms of dumping syndrome are due to what?

A

too much fluid in intestine and hypoglycemia

32
Q

based on secretory function what are the two regions of the stomach

A

oxyntic gland mucosa (located in proximal stomach)

pyloric gland mucosa (located in distal stomach)

33
Q

oxyntic gland mucosa (located where and secretes what)

A
located in proximal stomach
secretes:
acid
pepsinogen
intrinsic factor
mucus
34
Q

pyloric gland mucosa (located where and secretes what)

A
located in distal stomach
secretes:
mostly gastrin
some mucus
some pepsinogen
35
Q

in the oxyntic gland the surface mucous cells extend into what?

A

duct opening

36
Q

in the oxyntic gland the mucous neck cells (what do they secrete and what do they serve as)

A

secrete mucus

serve as stem cells

37
Q

in the oxyntic gland the stem cells proliferate and differentiate into what?

A

surface mucous cells
parietal cells
chief cells
endocrine cells

38
Q

in the oxyntic gland the parietal cells secrete what?

A

acid

intrinsic factor

39
Q

in the oxyntic gland the endocrine cells secrete what?

A

products that regulate gastric function

40
Q

in the oxyntic gland the chief (peptic) cells secrete what?

A

pepsinogen

41
Q

what are the 4 components of gastric juice that have physiological function

A

HCl
Pepsin
Mucus
Intrinsic Factor

42
Q

what begins digestion of dietary protein?

A

HCl

43
Q

lack of or reduction in acid production leads to what? (in terms of the stomach and upper small intestine)

A

infections of the stomach and small intestine

44
Q

what kills most bacteria that enter the stomach

A

HCl

45
Q

pepsin is stored and secreted as what?

A

inactive precursor pepsinogen

46
Q

pepsinogen is converted to pepsin by what?

A
gastric acid (HCl)
pepsin
47
Q

what begins digestion of proteins by splitting interior peptide bonds in proteins

A

pepsin

48
Q

what causes greatest increase in secretion of pepsin

A

vagal stimulation

49
Q

the mucus of the stomach serves what purpose?

A

serves as a protective coating for stomach and lubricant and barrier between cells and ingested material
two forms: soluble and insoluble

50
Q

the soluble for of mucus in the stomach is secreted from where, does what, and is present when?

A

secreted from mucus neck cells after stimulation by vagus nerve
mixes with other secretions of glands and lubricates chyme
not present in resting stomach

51
Q

the insoluble/visible form of mucus in the stomach is secreted from where, as what, and what does it do?

A

secreted by surface mucus/goblet cells
secreted as gel forming unstirred layer over mucosa
traps dead cells from mucosa and forms protective coat

52
Q

insoluble/visible form of mucus is secreted when?

A

by resting stomach

in response to chemical or physical irritation

53
Q

what maintains the pH at the surface of the stomach nearly neutral

A

HCO3- trapped in the insoluble layer

54
Q

what happens to insoluble mucus on contact with acid?

A

precipitates into clumps and passes into duodenum with chyme

55
Q

insoluble mucus with alkaline secretions make up part of what barrier?

A

gastric mucosal barrier that prevents damage to mucosa by gastric contents

56
Q

intrinsic factor (what is it, what secretes it, what does it do)

A

glycoprotien
secreted by parietal cells of gastric mucosa
binds vitamin B12

57
Q

where is vitamin B12 absorbed and what is required of the absorption to occur?

A

absorption occurs in ileum

intrinsic factor is required of the absorption

58
Q

the absence of intrinsic factor results in what?

A

pernicious anemia

59
Q

total gastrectomy patients require what?

A

injections of vitamin B12

60
Q

parietal cells secrete what into the lumen of the stomach and what into the bloodstream

A

HCl into lumen of stomach

HCO3- into the bloodstream

61
Q

the H+ secrete into the lumen across the cell membrane is in exchange for what and by what?

A

K+ in a 1:1 ratio by H+/K+ ATPase

62
Q

where does the bicarbonate in the parietal cells come from?

A

CO2 generated by cell metabolism and then carbonic anhydrase

63
Q

Cl- enters the parietal cell how and is secreted into the lumen how?

A

enters cell in exchange for HCO3-

secreted in to lumen through channel

64
Q

alkaline tide (what creates it, where does it occur, and when)

A

HCO3- creates it in venous blood of actively secreting stomach by raising pH

65
Q

chronic vomiting can lead to what?

A

hypokalemia

66
Q

K+ concentration is what in the gastric juice compared to the plasma

A

always zΩhigher concentration in gastric juice than plasma

67
Q

ionic composition of gastric juice changes with what?

A

rate of secretion

68
Q

at low (basal) rates of secretion what is the ionic composition of gastric juice

A

primarily NaCl from nonparietal secretions

69
Q

at high (stimulated) rates of secretion what is the ionic composition of gastric juice

A

primarily HCl from parietal secretion