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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
gastrin stimulates ECL cells to release what substances?
histamine
26
Gastrin stimulates parietal cells via what two ways?
1. ECL histamine release 2. direct CCKb receptor binding (both activate protein kinases)
27
Where does histamine bind on parietal cells?
H2 receptor
28
HCl secretion by parietal cells are stimulated by gastrin and what other mechanism?
ACh via vagus
29
The cephalic phase is responsible for ___% of total HCl release...
30% of HCl release
30
The vagus stimulates what two cells, leading to what two effects?
parietal cells, HCl secretion G cells, Gastrin secretion via GRP
31
What effect does circulating gastrin have on parietal cells?
stimulation
32
What three stimuli are responsible for 60% of HCl release from parietal cells?
amino acids (G cell mediated), peptides (G cell mediated), distension of stomach
33
By what mechanism does distension of the stomach stimulate HCl secretion?
via vagovagal reflex arcs
34
Histamine stimulates HCl secretion via the H2 receptors. What blocks this?
cimetidine
35
Pepsinogen is converted to pepsin in a _____ fashion and in the presence of what substance?
autocatalytic, presence of acid
36
What is the optimum pH of pepsinogen? When is it denatured?
1.5-2 denatured at 7
37
pepsin is responsible for digesting _____ % of protein in a typical meal by breaking what bonds?
10-20% by breaking aromatic bonds
38
The _____ phase is the most important regulatory phase of secretion for pepsinogen. It is released when chief cells are stimulated by...
cephalic phase released via vagal stimulation
39
Mucus is secreted by which cell types? (2)
neck cells and surface epithelium
40
Gastric Mucus contains what two important substances?
mucins (glycoproteins) and bicarb
41
What 3 stimuli promote the secretion of gastric mucus and bicarb?
vagus, distension, PGs
42
Gastric mucus forms a gel on the epithelial surface called the...
gastric mucosal barrier
43
The gastric mucosal barrier has a pH of ___ at the epithelial cell surface and ___ in gastric juice
7 at cell surface, 2 in gastric juice
44
The following have what effect on the gastric mucosal barrier? PGs Blood flow Growth factors
protective
45
The following have what effect on the gastric mucosal barrier? NSAIDs Smoking EtOH H. Pylori
damaging
46
What are the three components of gastric motility?
receptive relaxation of orad stomach mixing motions propulsion of chyme to duodenum
47
What four factors increase gastric mixing and emptying?
Vagus, distension, gastrin, motilin
48
secretin, CCK, GIP and SNS stimulation have what effect on gastric mixing and emptying?
Decrease
49
What effect do H+, lipid products, protein products in duodenum, enterogastric reflexes have on gastric mixing and emptying?
Decrease
50
_______ waves drive bolus of food towards the pyloric valve...
antral peristaltic waves
51
What size particles can pass through the pyloric valve? Why?
small particles, valve is largely closed
52
What happens to large particles that cannot pass through the pyloric valve?
reflected back to antrum via retropropulsion
53
At the beginning of the vomit reflex, what happens to the diaphragm and glottis?
diaphragm lowered to inspiratory position glottis close
54
contraction of abdominal wall muscles during the vomiting process has what effect?
increase intra-abdominal pressure
55
After the stomach contracts in the vomit reflex, what happens to the stomach and LES?
relax, stomach squeezed between diaphragm and viscera
56
What structure relaxes to allow vomitus to be projected into the mouth?
UES
57
This occurs due to excess acid secretion and/or damage to the mucosal barrier
peptic ulcer disease
58
by what mechanism in peptic ulcer disease does mucosal damage occur?
mucosal damage --> histamine release --> acid secretion
59
What drugs are a common cause of peptic ulcer disease? why?
NSAIDs via COX inhibition (decreased PGs)
60
What bacteria is implicated in many peptic ulcer cases?
H. pylori
61
tx for h. pylori...
abx (clarithro, amox)
62
What three non abx drug classes can treat peptic ulcer disease?
h2 blockers (cimetidine, ranitidine) PPIs (omeprazole, lansoprazole) Colloidal bismuth (pepto)

Physiology II (28 decks)

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