Secretions of the GI tract and pancreas Flashcards

1
Q

Where is saliva produced

A

salivary glands

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2
Q

Function of saliva

A

initial digestion of starches and lipis

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3
Q

3 major salivary glands

A

parotid, submaxillary, sublingual

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4
Q

Which is the largest salivary structure

A

parotid gland

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5
Q

Parotid gland secretions

A

serous cells

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6
Q

What percent of daily output of saliva is from parotid gland

A

25%

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7
Q

Secretions from sublingual and submandibular

A

mixed- serous and mucous cells

75% daily output of saliva

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8
Q

Blood supply to salivary glands

A

external carotid artery

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9
Q

4 parts of the structure of salivary glands

A

acinus, myoepithelial cells, intercalated duct, and striated duct

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10
Q

Acinus function

A

secrete initial saliva

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11
Q

Myoepithelial cell function

A

contain actinomycin and contract to eject saliva into the mouth

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12
Q

Intercalated duct function

A

contains myoepithelial cells and has ionic saliva

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13
Q

Striated duct function

A

modify initial saliva to produce final saliva and contain columnar epithelial cells

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14
Q

Composition of final saliva product

A

hypotonic (compared to plasma), increased K+ and HCO3 concentrations, decreased Na and Cl concentrations

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15
Q

What are the components of saliva

A

H20, electrolytes, a-amylase, lingual lipase, kallikrein, and mucus

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16
Q

A-amylase functon

A

begins initial digestion of carbohydrates

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17
Q

Lingual lipase function

A

begins initial digestion of lipids

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18
Q

Kallikrein function

A

protease involved in production of bradykinin

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19
Q

Bradykinin function

A

vasodilator

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20
Q

2 main steps in formation of saliva

A
  1. Form isotonic and plasma like solution by acinar cells

2. Modification of isotonic solution by the ductal cells fvg

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21
Q

3 transport mechanisms for salivary secretion on luminal side

A

1.Na/H+ exchange, 2. Cl-/HCO3- exchange, 3. H+/K+ exchange

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22
Q

2 transport mechanisms for salivary secretion on basolateral (blood) side

A

1.Na+/K+ ATPase, 2. Cl- channels

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23
Q

Net result of salivary secretion mechanism

A

absorption of Na/Cl, secretion of K/HCO3, net absorption of solute (more NaCl absorbed)

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24
Q

2 options on how HCO3 can leave the cell

A

1.through cAMP-activated CFTR (cystic fibrosis transmembrane regulator) Cl- channel, 2. Cl-/HCO3 exchanger

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25
Q

Cystic fibrosis patients

A

lack Cl- transporter (CTFR)

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26
Q

What is elevated in patients with cystic fibrosis

A

Ca+, Na+ and protein

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27
Q

T/F Ductal cells are permeable to H2O

A

F- ductal cells are impermeable to water which helps make saliva hypotonic

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28
Q

What does ionic composition depend on?

A

rate of secretion

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29
Q

An increase flow rate….

A
  • saliva resembles plasma and initial saliva

- less time for ductal cells to be in contact with saliva

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30
Q

A decreased flow rate…

A
  • final saliva has lower concentrations of Na+ and Cl-, and higher concentration of K+
  • more time for ductal cells to modify the saliva
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31
Q

“Contact-time” dependent mechanism

A

amount of time ductal cell is in contact with saliva determines ionic composition
DOES NOT APPLY TO HCO3

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32
Q

HCO3 secretion

A

selectively stimulated when saliva production is stimulated

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33
Q

Innervation to salivary glands

A

ANS

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34
Q

Presynpatic nerves origin for parasympathetic innervation to salivary glands

A

facial and glossopharyngeal nerves

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35
Q

Postsynpatic nerves origin for parasympathetic innervation to salivary glands

A

autonomic ganglia innervate individual glands

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36
Q

What ganglion and nerves is the facial nerve associated with?

A

Submandibular ganglion for sublingual and submandibular glands

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37
Q

What ganglion and nerves is the glossopharyngeal nerve associated with

A

Otic ganglion to the auriculotemporal branch of trigeminal nerve to the parotid gland

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38
Q

Preganglionic nerve origin for sympathetic innervation of salivary glands

A

cervical ganglion

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39
Q

Postganglionic fibers for sympathetic innervation of salivary glands

A

glands in the periarterial spaces to thoracic spinal nerves

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40
Q

What can up regulate the parasympathetic innervation to salivary glands

A

conditioning (?), food, nausea, smell

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41
Q

What can down regulate paraysympathetic innervation to salivary glands

A

fatigue, dehydration, fear, sleep

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42
Q

Neurotransmitter associated with parasymp salivary innervation

A

Ach

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43
Q

Neurotransmitter associated with sympath salivary innervation

A

NE

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44
Q

Receptor on acinar or ductal for parasympath innervation of salivary glands

A

mAchR

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45
Q

Receptor on acinar or ductal for sympath innervation of salivary glands

A

Beta- AR

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46
Q

Stimulation of salivary cells results in…

A

increase saliva production, increase HCO3 and enzyme secretions and contraction of myoepithelial cells

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47
Q

Vasopressin and aldosterone effect on saliva

A

decrease Na+ concentration and increase K+ concentration

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48
Q

T/F Salivary secretion is increased by only parasympathetic nervous system

A

F- salivary secretion is increased by both parasymp and sympath stimulation

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49
Q

What do cells of gastric mucosa secrete

A

gastric juice

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50
Q

5 main components of gastric juice

A

HCl, pepsinogen, mucus, instrinsic factor, H2O

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51
Q

HCl function in gastric juice

A

initiate protein digestion, converts pepsinogen to pepsin, and kill bacteria in stomach

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52
Q

Pepsinogen function in gastric juice

A

inactivates precursor to pepsin

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53
Q

Mucus function in gastric juice

A

protect stomach from damage, lubrication, with HCO3 it neutralizes acid

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54
Q

Intrinsic factor function in gastric juice

A

required for absorption of B12 in ileum, and is indispensable (absolutely necessary)

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55
Q

H2O function in gastric juice

A

solubilized much of ingested material

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56
Q

Location of oxyntic gland

A

proximal 80% of stomach

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57
Q

Function of oxyntic gland

A

secretes acid

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58
Q

Location of pyloric gland

A

distal 20% if the stomach

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59
Q

Function of pyloric gland

A

synthesized and releases gastrin

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60
Q

Cells in oxynotic gland

A

parietal cell, mucous neck cell, enterochromaffin like cells, D cells, chief cells

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61
Q

Cells of pyloric gland

A

mucous neck cells, G cells, D cells

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62
Q

Cells in body of the stomach

A

parietal cells (intrinsic factor and HCl), Chief cells (pepsinogen)

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63
Q

Cells in antrum of the stomach

A

G cells (gastrin into circulation ), Mucus cells (mucus, HCO3, and pepsinogen)

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64
Q

What does the number of parietal cells determine

A

secretory rate

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65
Q

How many L of gastric juices does the stomach secrete everyday

A

1-2 L/day

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66
Q

Function of low gastric pH

A

convert pepsinogen to pepsin

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67
Q

Where is HCl formed

A

villus-like membranes of canaliculi which is continuous with the lumen

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68
Q

Function of Omeprazole

A

inhibit the H+/K+ ATPase making H+ more concetrated in lumen and Cl- follows H+ so HCl is secreted

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69
Q

“Alkaline tide”

A

HCO3 is pumped into the blood because Cl- is being pushed out due to the inhibition of the H+/K+ ATPase

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70
Q

Net result of Omeprazole (inhibition of H+/K+ ATPase)

A

HCl- secretion and HCO3 absorption

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71
Q

Histamine function for HCl secretion

A

stimulates HCl secretion

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72
Q

What cells secrete histamine

A

enterochromaffin-like cells

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73
Q

What stimulates histamine release

A

gastrin and Ach

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74
Q

What receptors does histamine bind to?

A

H2 receptors on parietal cells

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75
Q

What can block H2 receptors on parietal cells

A

Cimetidine

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76
Q

End result of histamine

A

activates cAMP cascade and secretes H+ through the H+/K+ ATPase

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77
Q

Ach function for HCl

A

stimulates HCl secretion

78
Q

Where is Ach released from

A

vagus nerve innervating gastric mucosa

79
Q

What receptor does Ach bind to

A

mAchR on parietal cells

80
Q

Function of Atropine

A

block the mAchR receptors so Ach can’t bind

81
Q

End result of Ach

A

activates IP3 and Ca2+ and secretes H+ through H+/K+ ATPase

82
Q

Indirect effect of Ach on HCl

A

stimulates ECL cells (enterochromaffin-like cells) which release histamine

83
Q

Gastrin function for HCl

A

stimulates HCl secretion

84
Q

What secretes gastrin

A

G cells in antrum of the stomach

85
Q

What receptor does gastrin bind to?

A

CCKB receptor on parietal cells

86
Q

CCKB

A

has equal binding affinity for gastrin and CCK

87
Q

CCKA

A

receptor specific for CCk

88
Q

End result of gastrin

A

activates IP3/Ca2+ and secretes H+ through H+/K+ ATPase

89
Q

Stimuli for gastrin secretion

A

gastric distention, small peptides and amino acids, stimulation of vagus nerve

90
Q

Indirect effect of gastrin for HCl

A

stimulates ECL cells which release histamine

91
Q

Atropine on gastrin

A

DOES NOT block vagal stimulation of the G cells

92
Q

Somatostatin function on HCl

A

inhibits HCl secretion

93
Q

What cells release somatostatin

A

D cells in antrum

94
Q

What receptor does somatostain bind to?

A

somatostatin receptors on parietal cells

95
Q

End result of somatostatin on HCl

A

inhibits adenylate cyclase and inhibits secretion of H+

96
Q

Indirect effect of somatostatin on HCl

A

inhibits histamine release from ECL cells and gastrin release from G cells

97
Q

Potentiation

A

combined response to two stimulants exceeds the sum of their individual responses
requires 2 specific receptors

98
Q

Histamine potentiates with…

A

Ach and gastrin

99
Q

Ach potentiates with…

A

histamine and hastrin

100
Q

Cimetidine potentiation phenomena

A

antagonist of H2 receptors block direct action of histamine and Ach and gastrin

101
Q

Atropine potentiation phenomena

A

antagonist of mAchRs block direct action of Ach and Ach-potentiated actions of histamine and gastrin

102
Q

2 pathways of vagus nerve stimulation

A
  1. Direct pathway

2. Indirect pathway

103
Q

Which pathway does atropine block?

A

direct pathway

104
Q

3 phases of gastric HCl secretion

A

1.Cephalic phase, 2. Gastric phase, 3. Intestinal phase

105
Q

Cephalic phase

A

1.vagus nerve –> parietal cells, 2. vagus nerve –> gastrin –> parietal cells

106
Q

Gastric phase

A

local nervous secretory reflexes, vagal reflexes, gastrin-histamine stimualtion

107
Q

Intestinal phase

A

nervous mechanism and hormonal mechanism

108
Q

Stimuli of cephalic phase

A

smelling, tasting, chewing, swallowing, and conditioned reflexes

109
Q

Direct pathway for cephalic phase

A

1.innervation releasing Ach to parietal cells, 2. Ach stimulates secretion of HCl from parietal cells

110
Q

Indirect pathway for cephalic phase

A

1.Innervation releasing gastrin-releasing peptide to G cells, 2. G cells release gastrin into circulation, 3. Gastrin is delivered back to stomach to stimulate HCl secretion from parietal cells

111
Q

What happens if a vagotomy occurs….

A

abolishes cephalic phase

112
Q

Stimuli for gastric phase

A

distention of the stomach, presence of breakdown of proteins, amino acids and small peptides

113
Q

4 mechanisms of gastric phase

A

1.Direct distention, 2. Indirect distention, 3. Distention of antrum, 4. Amino acids and small peptides

114
Q

Direct distention in gastric phase

A

vagus nerve–> Ach –> parietal cell –> HCl

115
Q

Indirect distention in gastric phase

A

vagus nerve–>gastrin releasing hormone –> G cells –> gastrin in circulation –> gastrin delivered back to stomach –> parietal cells –> HCl

116
Q

Distention of antrum in gastric phase

A

local reflex –> pyloropyloric reflex –> gastrin –> parietal cell

117
Q

Amino acids and small peptides in gastric phase

A

gastrin –> parietal cell –> HCl

118
Q

Coffee effect on HCl

A

stimulates gastric HCl secretion

119
Q

2 intestinal phase mechanisms

A

1.Distention of small intestine 2. Digested protein (amino acids)

120
Q

Distention of small intestine in intestinal phase

A

stimulates acid secretion

121
Q

Digestion of protein in intestinal phase

A

stimulate acid secretion via direct parietal cell activation–> gastrin (intestinal G cells) –> parietal cell

122
Q

What does gastric juice composition depend on..

A

secretion rate

123
Q

Low secretion rate ….

A

final juice is NaCl solution

124
Q

Higher secretion rate …

A

final juice decrease Na concentration and increase in H+ concentration

125
Q

At peak secretion rate …

A

final juice is primarily HCl

126
Q

T/F gastric juice and plasma are isotonic, regardless of secretion rate

A

T

127
Q

2 types of gastric juice mixtures

A

1.Nonparietal 2. Parietal

128
Q

Nonparietal mixture

A

alkaline secretion and low volume

129
Q

Primary components of nonparietal mixture

A

Na+, Cl-, K+ in same concentration

130
Q

Parietal mixture

A

slightly hyperosmotic

131
Q

Only anion present in parietal mixture is …

A

Cl-

132
Q

When is composition of gastric juice knowledge helpful

A

treatment for patient suffering from vomiting or maintained IV

133
Q

GRP function

A

gastrin release

134
Q

Vagal activation on gastrin release

A

releasing GRP and inhibiting release of somatostatin

135
Q

Gastrin association with somatostatin

A

negative feedback and increase somatostatin

136
Q

H+ in the lumen association with somatostatin

A

stimulate release of somatostain

137
Q

When is pepsinogen secreted

A

when gastric pH is acidic enough to be converted to pepsin

138
Q

2 cells that secrete pepsinogen

A

chief cells and mucus cells in oxyntic glands

139
Q

Most important stimulus for pepsinogen secretion

A

vagus nerve stimulation

140
Q

Pepsin positive feedback on pepsinogen

A

pepsin converts more pepsinogen to pepsin

141
Q

What is intrinsic factor

A

mucoprotein secreted by parietal cells

142
Q

Failure to secrete intrinsic factor can lead to..

A

pernicious anemia

143
Q

What can cause pernicious anemia/failure to secrete intrinsic factor

A

destruction of gastric parietal cells

144
Q

Where is vitamin B12 stored

A

liver

145
Q

What is secreted by gastric epithelium

A

HCO3 and mucus to make gel-like mucosal barrier

146
Q

What do mucus neck cells secrete

A

mucus

147
Q

What do gastric epithelial cells secrete

A

HCO3

148
Q

Function of mucosal barrier

A

protects gastric mucosal epithelium against HCl and pepsin

149
Q

What components can protect gastric mucosa

A

HCO3, mucus, prostaglandins, mucosal blood flow, and growth factors

150
Q

What components can damage gastric mucosa

A

Acid, pepsin, NSAID, H. pylori, aspirin, alcohol, bile, and stress

151
Q

S/S of Gastrinoma

A

diarrhea, vomitting, peptic ulcer, increase resting gastrin, weight loss, GERD, epigastric pain

152
Q

What syndrome are gastrinoma tumors associated with

A

ZOllinger-Ellison syndrome

153
Q

How can a peptic ulcer form

A

loss of protective mucosal layer, excessive H+ and pepsin

154
Q

Two types of peptic ulcers

A

Gastric ulcers and duodenal ulcers

155
Q

What can cause a gastric ulcer

A

defective mucosal barrier and/or H pylori

156
Q

H. pylori function on gastric ulcer

A

release cytotoxins that bkdown mucosal barrier, contain urease that allow bacteria to colonize and convert urea to NH3 which makes basic environment

157
Q

Diagnostic test for gastric ulcer

A

urease activity

158
Q

How can duodenal ulcer form

A

H+ secretory rate are higher than normal

159
Q

H. pylori function on duodenal ulcer

A

indirect effect- inhibits somatostatin from D cells (inhibit inhibition) and gastric H. pylori speads to duodenum and inhibits duodenal HCO3 secretion

160
Q

Excessive H+ in duodenum

A

overwhelms buffer of HCO3 in pancreatic juice

161
Q

Zollinger-Ellison syndrome

A

tumor, usually pancreas secretes large amt gastrin

162
Q

Low duodenal pH inactivates..

A

pancreatic lipases, resulting in steatorrhea

163
Q

Treatment options for duodenal ulcers

A

cimetidine, omeprazole, surgical removal of tumor

164
Q

Components of pancreatic juice

A
  • HCO3 for neutralization

- enzymes to secrete carbs, proteins, lipids

165
Q

Two main components of exocrine pancreas

A

1.aqueous solution containing HCO3, 2. Enzymatic secretion

166
Q

Acinus of exocrine pancreas

A

lined by acinar cells that secrete enzymatic portion

167
Q

Ducts of exocrine pancreas

A

lined by ductal cells that extend into acinus containing centroacinar cells

168
Q

What do ductal and centroacinar cells secrete

A

aqueous solution containing HCO3

169
Q

Parasympathetic innervation of exocrine pancreas

A

vagus nerve

170
Q

Preganglionic fibers of exocrine pancreas for parasym

A

ENS

171
Q

Postganglionic fibers of exocrine pancreas for sympath

A

synapse ON exocrine pancreas

172
Q

Sympathetic innervation of exocrine pancreas

A

Postganglionis nerves from celiac and superior mesenteric plexus

173
Q

Difference btwn innervation of salivary gland and exocrine pancreas

A

in exocrine pancrease- parasymp stimulates pancreatic secretion and sympath activity inhibits pancreatic secretion

174
Q

Two components of pancreatic secretion

A
  • enzymatic secretion of acinar cells

- aqueous secretion by centroacinar and ductal cells

175
Q

Enzymatic section by acinar cells

A

enzymes that digest carbs, proteins, lipids

pancreatic amylase and lipase

176
Q

Where are pancreatic proteases converted to active form

A

in the lumen of duodenum

177
Q

What cells produce initial isotonic solution

A

centroacinar and ductal cells

178
Q

Where does modification of initial pancreatic section occur

A

ductal cells

179
Q

Net result of pancreatic modification

A

secretion of HCO3 into pancreatic juice and net absorption of H+

180
Q

Ionic composition of pancreatic juice depends on…

A

rate of secretion

181
Q

Increased flow rate on pancreatic juices

A

HCO3 is highest and Cl- is lowest

182
Q

Decreased flow rate on pancreatic juices

A

HCO3 is lowest and Cl- is highest

183
Q

How is relationship between HCO3 and Cl- concentrations maintained in pancreatic juice

A

HCO3-/Cl- exchanger in apical membrane of ductal cells

184
Q

3 phases of pancreatic secretion

A

1.Cephalic, 2. Gastric, 3. Intesitnal

185
Q

Cephalic phase of pancreatic secretion

A

produces mainly enzymatic secretion, mediated by vagus nerve

186
Q

Gastric phase of pancreatic secretion

A

produces mainly enzymatic secretion, mediated by vagus nerve

187
Q

Intestinal phase of pancreatic secretion

A

!! most importan phase! - 80% of pancreatic secretion

- both enzymatic and aqueous secretion stimulated

188
Q

Upregulators of pancreatic secretion in intestinal phase for I cells

A

phenylalanine, methionine, tryptophan, small peptides, fatty acids

189
Q

Upregulators of pancreatic secretion in intestinal phase for IScells

A

H+

190
Q

How does acute pancreatitis occur?

A

pancreatic enzymes are activation in pancreas and autodigest the pancreas