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HOS Unit 4 > 16 Esophagus and Stomach > Flashcards

16 Esophagus and Stomach Flashcards

1
Q

Is the buccal phase of swallowing voluntary or involuntary?

A

Voluntary– begins with opening mouth, chewing, tongue movement to push food up and back

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2
Q

Is the pharyngeal phase of swallowing voluntary or involuntary?

A

involuntary

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3
Q

Is the epiglottis pulled down when swallowing?

A

No–the larynx is pulled upward and the food pushes the epiglottis down to full close the hole

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4
Q

What relaxes is the pharyngeal phase of swallowing?

A

upper esophageal sphincter relaxes

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5
Q

What nerves are mediating the pharyngeal phase of swallowing?

A

V, IX, X, and XII

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6
Q

T-F respiration continues in the act of swallowing?

A

false

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7
Q

What type of peristalsis is initiated by swallowing?

A

primary peristalsis

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8
Q

What type of peristalsis occurs in response to stretching of the esophagus?

A

secondary peristalsis [usually by retained food or refluxed gastric fluid not accompanied by a swallow]

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9
Q

As the upper esophageal sphincter closes what happens to the lower esophageal sphincter?

A

it opens and peristalsis begins

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10
Q

When does the LES finally close?

A

after the contraction wave reaches the stomach—this prevents a reflux of gastric contents into the esophagus

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11
Q

Control of the esophageal peristalsis occurs via what nerve?

A

vagus nerve and intrinsic plexuses in the wall of the esophagus

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12
Q

What are the 3 major stomach divisions?

A

cardia, body, antrum

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13
Q

The body of the stomach contains which of the gastric gland cell types?

A

parietal
mucus
chief
enterochromaffin-like

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14
Q

In the antrum, what gastric gland cell types are there?

A 
mucus
chief
enterochromaffin-like
G cells
[NO PARIETAL CELLS]
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15
Q

The foveolar epithelial cells in the stomach largely secrete what?

A

bicarb and mucus [contain multiple mucin-containing granules in the apical region]

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16
Q

What are the 4 major functions of the stomach?

A

food accommodation
mechanical breakdown
secretion
digestion

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17
Q

Where does the majority of accommodation occur?

A

in the fundus

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18
Q

The resulting food mixture of mechanical breakdown in the stomach is called?

A

chyme

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19
Q

What are the major things secreted by the stomach?

A

acid, fluid, electrolytes, bicarb

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20
Q

How much fluid do the gastrin glands produce in a given day?

A

around 2 liters

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21
Q

What is the primary cation in the stomach when acid secretion is not induced?

A

Na

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22
Q

What is the primary cation in the stomach when acid secretion is increased?

A

H [Na become remarkably low]

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23
Q

When do gastric pepsin function best?

A

low pH

24
Q

What are the 3 major functions for acid production in the stomach?

A
  • optimum pepsin function
  • bactericide
  • physical breakdown of food
25
Q

T-F—stomach acid is essential for digestion?

A

false

26
Q

During resting state, where are the H-K ATPase molecules found in the parietal cell?

A

contained within intracellular tubulovesicles

27
Q

What part of the parietal cell do the proton pumps fuse with upon activation of parietal cells?

A

canalicular membrane

28
Q

What other channels are inserted into canalicular membrane upon parietal cell activation?

A

K and Cl

29
Q

H-K ATPase is a heterodimer of what units?

A

alpha [catalytic] and beta [delivery to apical membrane]

30
Q

What drug covalently binds to the proton pump on the lumenal side and inhibits it?

A

PPI

31
Q

T-F–water passively follows HCL into lumen

A

True

32
Q

Protons in stomach acid are produced by what?

A

carbonic anhydrase

33
Q

How is HCO3 created in the parietal cell secreted?

A

Cl- HCO3- exchanger on basolateral side

34
Q

What are the 3 secretagogues?

A

gastrin, Ach, and histamine

35
Q

What is the strongest direct stimulator of parietal cells? what does it act on? what is it produced by?

A

Histamine–H2 receptor of parietal cells—produced by ECL cells

36
Q

Is the principal action of gastrin and Ach direct or indirect?

A

indirect via stimulation of histamine release from ECL cells

37
Q

Do H2 blockers strongly block acid production even with gastrin or ACh stimulation?

A

yes [this is the evidence that ACh and gastrin act in an indirect manner]

38
Q

What is gastrin produced by? where are they located? what are the 2 major forms?

A

G cells, in the antrum and duodenum, little and big gastrin

39
Q

What are the 3 major effects of gastrin on the GI tract?

A
  • indirect acid stimulation by histamine release by ECL cells
  • direct stimulation on parietal cells
  • epithelial cell proliferation in stomach, small intestine, colon
40
Q

What stimulates gastrin secretion by G cells into the blood to circulate to ECL and parietal cells?

A

dissension of stomach and stimulation by nutrients [peptides and amino acids]

41
Q

What is the main inhibitor of acid secretion? produced where?

A

somatostatin produced in pyloris by D cells [can act directly and indirectly]

42
Q

What is the most potent inhibitor of acid secretion pertaining to food in the duodenum?

A

fat [acid and hyperosmolarity are the other 2]

43
Q

What is the major hormone involved in feedback inhibition of acid production? what does it do [3 things]?

A

secretin– decreases gastrin release,promotes somatostatin release, and directly inhibits acid release

[others are CCK, vasoactive intestinal peptide, gastric inhibitory peptide, neurotensin, peptide YY]

44
Q

When is acid secretion lowest?

A

basal state- in the morning before awakening

45
Q

What what phase of acid secretion is described by the following–thinking, seeing, smelling, tasting food? what percentage of acid secretion does it produce? What nerve mediates?

A

cephalic phase
30%
vagus nerve

46
Q

The cephalic phase has 4 effects on cells, what are they?

A

parietal cell stimulation
ECL stimulation
G cell stimulation
inhibition of somatostatin secretion

47
Q

The gastric phase entry of food has two major effects that stimulate acid secretion and produce 50-60 % of the acid secretion levels, what are they?

A
  1. stomach wall stretching–>vagus and local ENS nerves

2. protein fragments stimulate G cells

48
Q

What is the major mediator of gastric phase acid secretion?

A

gastrin

49
Q

What is activated in very low pH conditions in the stomach?

A

D cells—> somatostatin secretion

50
Q

What are the 2 types of pepsinogen? what are they secreted by? which one is more dominant?

A

Type I–chief cells–dominant

Type II–chief and mucous neck cells

51
Q

What activates secretion of pepsinogen by chief cells?

A

ACh [secretin may have role too]

52
Q

What is pepsinogen activated by

A

pH less than 5

53
Q

What are the 3 components of the gastric diffusion barrier?

A

tight junctions
mucous gel layer
bicarb rich secretions under mucous

54
Q

what is a glycoprotein secreted by numerous mucous cells in the stomach and located on surface epithelium?

A

Mucin–when hydrated it forms mucus

55
Q

Why does the mucus gel layer need to be constantly renewed?

A

damaged by food,

56
Q

What is release of bicarb and mucin by stomach epithelial cells stimulated by?

A

ACh

57
Q

What doe bicarb also protect cell from besides stomach acid?

A

pepsin—inactivates it

HOS Unit 4 (18 decks)

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