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Physiology II > GI Physiology: Secretion & Motility > Flashcards

GI Physiology: Secretion & Motility Flashcards

1
Q

What are the three major parts of the stomach in order from superior to inferior

A

Fundus, Body, Pyloric Antrum

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2
Q

What are the three muscular layers of the stomach from superficial to deep?

A

longitudinal, circular, oblique

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3
Q

Distension of the lower esophagus relaxes what two structures? What type of relaxation is this?

A

relaxes LES and orad (superior) stomach

called receptive relaxation

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4
Q

Afferent and efferent nerve impulses are carried to the stomach by the…

A

vagus nerve

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5
Q

The vagovagal reflex occurs when the vagus stimulates the release of what substance, leading to what action on the stomach?

A

VIP induced relaxation of stomach

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6
Q

Which cells of the stomach wall have the following characteristics?

Location: Body
Secretes: HCl and Intrinsic Factor

A

Parietal Cells

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7
Q

Which cells of the stomach wall have the following characteristics?

Location: body
Secretes: Pepsinogen

A

Chief Cells

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8
Q

Which cells of the stomach are located in the antrum?

A

G Cells, Mucous Neck Cells

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9
Q

Which cells of the stomach are located in the stomach body?

A

Parietal Cells, Chief Cells

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10
Q

Which cells secrete gastrin?

A

G cells

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11
Q

which cells secrete mucous and pepsinogen?

A

mucous neck cells in antrum pyloric glands

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12
Q

These structures are located in the antrum of the stomach. They contain G-Cells and Mucous Neck Cells

A

Pyloric Glands

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13
Q

These structures are located in the body of the stomach. They are also called oxyntic glands.

A

gastric pits

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14
Q

What are the 4 major components of gastric juice?

A

HCl, pepsinogen, mucus, intrinsic factor

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15
Q

Which gastric secretion has the following characteristics?

necessary for illeal absorption of vitamin B12

A

intrinsic factor

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16
Q

Which gastric secretion has the following characteristics?

protects gastric mucosa from HCl

A

Mucous

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17
Q

Which gastric secretion has the following characteristics?

used in the digestion of proteins

A

pepsinogen/pepsin

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18
Q

Which gastric secretion has the following characteristics?

activates pepsin, aids in protein digestion, kills bacteria

A

HCl

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19
Q

What is the mechanism of HCl secretion?

A
  1. H+ + HCO3- produced via carbonic anhydrase in parietal cell
  2. H+ to lumen in exchange for K+ via K+ ATPase , Cl- enters lumen passively
  3. HCl formed
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20
Q

How does Cl- enter the parietal cell on the basolateral membrane?

A

exchange for bicarb via alkaline tide

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21
Q

Which gastric secretion has the following function?

stimulates acid and pepsinogen secretion

stimulates growth of gastric/intestinal mucosa

stimulates antral/intestinal motility

A

Gastrin (secretion, trophic, motility)

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22
Q

What three things inhibit gastrin?

A

pH < 3, somatostatin, PGE2

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23
Q

Gastrin is released from antral G cells when stimulated by what three things?

A

stomach distension

small peptides and amino acids

vagal stimulation

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24
Q

This cell type is an important pathway by which gastrin can stimulate parietal cells…

A

enterochromaffin-like cells (ECL)

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25
Q

gastrin stimulates ECL cells to release what substances?

A

histamine

26
Q

Gastrin stimulates parietal cells via what two ways?

A
  1. ECL histamine release
  2. direct CCKb receptor binding

(both activate protein kinases)

27
Q

Where does histamine bind on parietal cells?

A

H2 receptor

28
Q

HCl secretion by parietal cells are stimulated by gastrin and what other mechanism?

A

ACh via vagus

29
Q

The cephalic phase is responsible for ___% of total HCl release…

A

30% of HCl release

30
Q

The vagus stimulates what two cells, leading to what two effects?

A

parietal cells, HCl secretion

G cells, Gastrin secretion via GRP

31
Q

What effect does circulating gastrin have on parietal cells?

A

stimulation

32
Q

What three stimuli are responsible for 60% of HCl release from parietal cells?

A

amino acids (G cell mediated), peptides (G cell mediated), distension of stomach

33
Q

By what mechanism does distension of the stomach stimulate HCl secretion?

A

via vagovagal reflex arcs

34
Q

Histamine stimulates HCl secretion via the H2 receptors. What blocks this?

A

cimetidine

35
Q

Pepsinogen is converted to pepsin in a _____ fashion and in the presence of what substance?

A

autocatalytic, presence of acid

36
Q

What is the optimum pH of pepsinogen? When is it denatured?

A

1.5-2

denatured at 7

37
Q

pepsin is responsible for digesting _____ % of protein in a typical meal by breaking what bonds?

A

10-20% by breaking aromatic bonds

38
Q

The _____ phase is the most important regulatory phase of secretion for pepsinogen. It is released when chief cells are stimulated by…

A

cephalic phase

released via vagal stimulation

39
Q

Mucus is secreted by which cell types? (2)

A

neck cells and surface epithelium

40
Q

Gastric Mucus contains what two important substances?

A

mucins (glycoproteins) and bicarb

41
Q

What 3 stimuli promote the secretion of gastric mucus and bicarb?

A

vagus, distension, PGs

42
Q

Gastric mucus forms a gel on the epithelial surface called the…

A

gastric mucosal barrier

43
Q

The gastric mucosal barrier has a pH of ___ at the epithelial cell surface and ___ in gastric juice

A

7 at cell surface, 2 in gastric juice

44
Q

The following have what effect on the gastric mucosal barrier?

PGs
Blood flow
Growth factors

A

protective

45
Q

The following have what effect on the gastric mucosal barrier?

NSAIDs
Smoking
EtOH
H. Pylori

A

damaging

46
Q

What are the three components of gastric motility?

A

receptive relaxation of orad stomach

mixing motions

propulsion of chyme to duodenum

47
Q

What four factors increase gastric mixing and emptying?

A

Vagus, distension, gastrin, motilin

48
Q

secretin, CCK, GIP and SNS stimulation have what effect on gastric mixing and emptying?

A

Decrease

49
Q

What effect do H+, lipid products, protein products in duodenum, enterogastric reflexes have on gastric mixing and emptying?

A

Decrease

50
Q

_______ waves drive bolus of food towards the pyloric valve…

A

antral peristaltic waves

51
Q

What size particles can pass through the pyloric valve? Why?

A

small particles, valve is largely closed

52
Q

What happens to large particles that cannot pass through the pyloric valve?

A

reflected back to antrum via retropropulsion

53
Q

At the beginning of the vomit reflex, what happens to the diaphragm and glottis?

A

diaphragm lowered to inspiratory position

glottis close

54
Q

contraction of abdominal wall muscles during the vomiting process has what effect?

A

increase intra-abdominal pressure

55
Q

After the stomach contracts in the vomit reflex, what happens to the stomach and LES?

A

relax, stomach squeezed between diaphragm and viscera

56
Q

What structure relaxes to allow vomitus to be projected into the mouth?

A

UES

57
Q

This occurs due to excess acid secretion and/or damage to the mucosal barrier

A

peptic ulcer disease

58
Q

by what mechanism in peptic ulcer disease does mucosal damage occur?

A

mucosal damage –> histamine release –> acid secretion

59
Q

What drugs are a common cause of peptic ulcer disease? why?

A

NSAIDs via COX inhibition (decreased PGs)

60
Q

What bacteria is implicated in many peptic ulcer cases?

A

H. pylori

61
Q

tx for h. pylori…

A

abx (clarithro, amox)

62
Q

What three non abx drug classes can treat peptic ulcer disease?

A

h2 blockers (cimetidine, ranitidine)

PPIs (omeprazole, lansoprazole)

Colloidal bismuth (pepto)

Physiology II (28 decks)

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