Secretions of the GI tract and pancreas Flashcards
1
Q
Where is saliva produced
A
salivary glands
2
Q
Function of saliva
A
initial digestion of starches and lipis
3
Q
3 major salivary glands
A
parotid, submaxillary, sublingual
4
Q
Which is the largest salivary structure
A
parotid gland
5
Q
Parotid gland secretions
A
serous cells
6
Q
What percent of daily output of saliva is from parotid gland
A
25%
7
Q
Secretions from sublingual and submandibular
A
mixed- serous and mucous cells
75% daily output of saliva
8
Q
Blood supply to salivary glands
A
external carotid artery
9
Q
4 parts of the structure of salivary glands
A
acinus, myoepithelial cells, intercalated duct, and striated duct
10
Q
Acinus function
A
secrete initial saliva
11
Q
Myoepithelial cell function
A
contain actinomycin and contract to eject saliva into the mouth
12
Q
Intercalated duct function
A
contains myoepithelial cells and has ionic saliva
13
Q
Striated duct function
A
modify initial saliva to produce final saliva and contain columnar epithelial cells
14
Q
Composition of final saliva product
A
hypotonic (compared to plasma), increased K+ and HCO3 concentrations, decreased Na and Cl concentrations
15
Q
What are the components of saliva
A
H20, electrolytes, a-amylase, lingual lipase, kallikrein, and mucus
16
Q
A-amylase functon
A
begins initial digestion of carbohydrates
17
Q
Lingual lipase function
A
begins initial digestion of lipids
18
Q
Kallikrein function
A
protease involved in production of bradykinin
19
Q
Bradykinin function
A
vasodilator
20
Q
2 main steps in formation of saliva
A
- Form isotonic and plasma like solution by acinar cells
2. Modification of isotonic solution by the ductal cells fvg
21
Q
3 transport mechanisms for salivary secretion on luminal side
A
1.Na/H+ exchange, 2. Cl-/HCO3- exchange, 3. H+/K+ exchange
22
Q
2 transport mechanisms for salivary secretion on basolateral (blood) side
A
1.Na+/K+ ATPase, 2. Cl- channels
23
Q
Net result of salivary secretion mechanism
A
absorption of Na/Cl, secretion of K/HCO3, net absorption of solute (more NaCl absorbed)
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
25
Cystic fibrosis patients
lack Cl- transporter (CTFR)
26
What is elevated in patients with cystic fibrosis
Ca+, Na+ and protein
27
T/F Ductal cells are permeable to H2O
F- ductal cells are impermeable to water which helps make saliva hypotonic
28
What does ionic composition depend on?
rate of secretion
29
An increase flow rate....
- saliva resembles plasma and initial saliva
| - less time for ductal cells to be in contact with saliva
30
A decreased flow rate...
- final saliva has lower concentrations of Na+ and Cl-, and higher concentration of K+
- more time for ductal cells to modify the saliva
31
"Contact-time" dependent mechanism
amount of time ductal cell is in contact with saliva determines ionic composition
DOES NOT APPLY TO HCO3
32
HCO3 secretion
selectively stimulated when saliva production is stimulated
33
Innervation to salivary glands
ANS
34
Presynpatic nerves origin for parasympathetic innervation to salivary glands
facial and glossopharyngeal nerves
35
Postsynpatic nerves origin for parasympathetic innervation to salivary glands
autonomic ganglia innervate individual glands
36
What ganglion and nerves is the facial nerve associated with?
Submandibular ganglion for sublingual and submandibular glands
37
What ganglion and nerves is the glossopharyngeal nerve associated with
Otic ganglion to the auriculotemporal branch of trigeminal nerve to the parotid gland
38
Preganglionic nerve origin for sympathetic innervation of salivary glands
cervical ganglion
39
Postganglionic fibers for sympathetic innervation of salivary glands
glands in the periarterial spaces to thoracic spinal nerves
40
What can up regulate the parasympathetic innervation to salivary glands
conditioning (?), food, nausea, smell
41
What can down regulate paraysympathetic innervation to salivary glands
fatigue, dehydration, fear, sleep
42
Neurotransmitter associated with parasymp salivary innervation
Ach
43
Neurotransmitter associated with sympath salivary innervation
NE
44
Receptor on acinar or ductal for parasympath innervation of salivary glands
mAchR
45
Receptor on acinar or ductal for sympath innervation of salivary glands
Beta- AR
46
Stimulation of salivary cells results in...
increase saliva production, increase HCO3 and enzyme secretions and contraction of myoepithelial cells
47
Vasopressin and aldosterone effect on saliva
decrease Na+ concentration and increase K+ concentration
48
T/F Salivary secretion is increased by only parasympathetic nervous system
F- salivary secretion is increased by both parasymp and sympath stimulation
49
What do cells of gastric mucosa secrete
gastric juice
50
5 main components of gastric juice
HCl, pepsinogen, mucus, instrinsic factor, H2O
51
HCl function in gastric juice
initiate protein digestion, converts pepsinogen to pepsin, and kill bacteria in stomach
52
Pepsinogen function in gastric juice
inactivates precursor to pepsin
53
Mucus function in gastric juice
protect stomach from damage, lubrication, with HCO3 it neutralizes acid
54
Intrinsic factor function in gastric juice
required for absorption of B12 in ileum, and is indispensable (absolutely necessary)
55
H2O function in gastric juice
solubilized much of ingested material
56
Location of oxyntic gland
proximal 80% of stomach
57
Function of oxyntic gland
secretes acid
58
Location of pyloric gland
distal 20% if the stomach
59
Function of pyloric gland
synthesized and releases gastrin
60
Cells in oxynotic gland
parietal cell, mucous neck cell, enterochromaffin like cells, D cells, chief cells
61
Cells of pyloric gland
mucous neck cells, G cells, D cells
62
Cells in body of the stomach
parietal cells (intrinsic factor and HCl), Chief cells (pepsinogen)
63
Cells in antrum of the stomach
G cells (gastrin into circulation ), Mucus cells (mucus, HCO3, and pepsinogen)
64
What does the number of parietal cells determine
secretory rate
65
How many L of gastric juices does the stomach secrete everyday
1-2 L/day
66
Function of low gastric pH
convert pepsinogen to pepsin
67
Where is HCl formed
villus-like membranes of canaliculi which is continuous with the lumen
68
Function of Omeprazole
inhibit the H+/K+ ATPase making H+ more concetrated in lumen and Cl- follows H+ so HCl is secreted
69
"Alkaline tide"
HCO3 is pumped into the blood because Cl- is being pushed out due to the inhibition of the H+/K+ ATPase
70
Net result of Omeprazole (inhibition of H+/K+ ATPase)
HCl- secretion and HCO3 absorption
71
Histamine function for HCl secretion
stimulates HCl secretion
72
What cells secrete histamine
enterochromaffin-like cells
73
What stimulates histamine release
gastrin and Ach
74
What receptors does histamine bind to?
H2 receptors on parietal cells
75
What can block H2 receptors on parietal cells
Cimetidine
76
End result of histamine
activates cAMP cascade and secretes H+ through the H+/K+ ATPase
77
Ach function for HCl
stimulates HCl secretion
78
Where is Ach released from
vagus nerve innervating gastric mucosa
79
What receptor does Ach bind to
mAchR on parietal cells
80
Function of Atropine
block the mAchR receptors so Ach can't bind
81
End result of Ach
activates IP3 and Ca2+ and secretes H+ through H+/K+ ATPase
82
Indirect effect of Ach on HCl
stimulates ECL cells (enterochromaffin-like cells) which release histamine
83
Gastrin function for HCl
stimulates HCl secretion
84
What secretes gastrin
G cells in antrum of the stomach
85
What receptor does gastrin bind to?
CCKB receptor on parietal cells
86
CCKB
has equal binding affinity for gastrin and CCK
87
CCKA
receptor specific for CCk
88
End result of gastrin
activates IP3/Ca2+ and secretes H+ through H+/K+ ATPase
89
Stimuli for gastrin secretion
gastric distention, small peptides and amino acids, stimulation of vagus nerve
90
Indirect effect of gastrin for HCl
stimulates ECL cells which release histamine
91
Atropine on gastrin
DOES NOT block vagal stimulation of the G cells
92
Somatostatin function on HCl
inhibits HCl secretion
93
What cells release somatostatin
D cells in antrum
94
What receptor does somatostain bind to?
somatostatin receptors on parietal cells
95
End result of somatostatin on HCl
inhibits adenylate cyclase and inhibits secretion of H+
96
Indirect effect of somatostatin on HCl
inhibits histamine release from ECL cells and gastrin release from G cells
97
Potentiation
combined response to two stimulants exceeds the sum of their individual responses
*requires 2 specific receptors*
98
Histamine potentiates with...
Ach and gastrin
99
Ach potentiates with...
histamine and hastrin
100
Cimetidine potentiation phenomena
antagonist of H2 receptors block direct action of histamine and Ach and gastrin
101
Atropine potentiation phenomena
antagonist of mAchRs block direct action of Ach and Ach-potentiated actions of histamine and gastrin
102
2 pathways of vagus nerve stimulation
1. Direct pathway
| 2. Indirect pathway
103
Which pathway does atropine block?
direct pathway
104
3 phases of gastric HCl secretion
1.Cephalic phase, 2. Gastric phase, 3. Intestinal phase
105
Cephalic phase
1.vagus nerve --> parietal cells, 2. vagus nerve --> gastrin --> parietal cells
106
Gastric phase
local nervous secretory reflexes, vagal reflexes, gastrin-histamine stimualtion
107
Intestinal phase
nervous mechanism and hormonal mechanism
108
Stimuli of cephalic phase
smelling, tasting, chewing, swallowing, and conditioned reflexes
109
Direct pathway for cephalic phase
1.innervation releasing Ach to parietal cells, 2. Ach stimulates secretion of HCl from parietal cells
110
Indirect pathway for cephalic phase
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
What happens if a vagotomy occurs....
abolishes cephalic phase
112
Stimuli for gastric phase
distention of the stomach, presence of breakdown of proteins, amino acids and small peptides
113
4 mechanisms of gastric phase
1.Direct distention, 2. Indirect distention, 3. Distention of antrum, 4. Amino acids and small peptides
114
Direct distention in gastric phase
vagus nerve--> Ach --> parietal cell --> HCl
115
Indirect distention in gastric phase
vagus nerve-->gastrin releasing hormone --> G cells --> gastrin in circulation --> gastrin delivered back to stomach --> parietal cells --> HCl
116
Distention of antrum in gastric phase
local reflex --> pyloropyloric reflex --> gastrin --> parietal cell
117
Amino acids and small peptides in gastric phase
gastrin --> parietal cell --> HCl
118
Coffee effect on HCl
stimulates gastric HCl secretion
119
2 intestinal phase mechanisms
1.Distention of small intestine 2. Digested protein (amino acids)
120
Distention of small intestine in intestinal phase
stimulates acid secretion
121
Digestion of protein in intestinal phase
stimulate acid secretion via direct parietal cell activation--> gastrin (intestinal G cells) --> parietal cell
122
What does gastric juice composition depend on..
secretion rate
123
Low secretion rate ....
final juice is NaCl solution
124
Higher secretion rate ...
final juice decrease Na concentration and increase in H+ concentration
125
At peak secretion rate ...
final juice is primarily HCl
126
T/F gastric juice and plasma are isotonic, regardless of secretion rate
T
127
2 types of gastric juice mixtures
1.Nonparietal 2. Parietal
128
Nonparietal mixture
alkaline secretion and low volume
129
Primary components of nonparietal mixture
Na+, Cl-, K+ in same concentration
130
Parietal mixture
slightly hyperosmotic
131
Only anion present in parietal mixture is ...
Cl-
132
When is composition of gastric juice knowledge helpful
treatment for patient suffering from vomiting or maintained IV
133
GRP function
gastrin release
134
Vagal activation on gastrin release
releasing GRP and inhibiting release of somatostatin
135
Gastrin association with somatostatin
negative feedback and increase somatostatin
136
H+ in the lumen association with somatostatin
stimulate release of somatostain
137
When is pepsinogen secreted
when gastric pH is acidic enough to be converted to pepsin
138
2 cells that secrete pepsinogen
chief cells and mucus cells in oxyntic glands
139
Most important stimulus for pepsinogen secretion
vagus nerve stimulation
140
Pepsin positive feedback on pepsinogen
pepsin converts more pepsinogen to pepsin
141
What is intrinsic factor
mucoprotein secreted by parietal cells
142
Failure to secrete intrinsic factor can lead to..
pernicious anemia
143
What can cause pernicious anemia/failure to secrete intrinsic factor
destruction of gastric parietal cells
144
Where is vitamin B12 stored
liver
145
What is secreted by gastric epithelium
HCO3 and mucus to make gel-like mucosal barrier
146
What do mucus neck cells secrete
mucus
147
What do gastric epithelial cells secrete
HCO3
148
Function of mucosal barrier
protects gastric mucosal epithelium against HCl and pepsin
149
What components can protect gastric mucosa
HCO3, mucus, prostaglandins, mucosal blood flow, and growth factors
150
What components can damage gastric mucosa
Acid, pepsin, NSAID, H. pylori, aspirin, alcohol, bile, and stress
151
S/S of Gastrinoma
diarrhea, vomitting, peptic ulcer, increase resting gastrin, weight loss, GERD, epigastric pain
152
What syndrome are gastrinoma tumors associated with
ZOllinger-Ellison syndrome
153
How can a peptic ulcer form
loss of protective mucosal layer, excessive H+ and pepsin
154
Two types of peptic ulcers
Gastric ulcers and duodenal ulcers
155
What can cause a gastric ulcer
defective mucosal barrier and/or H pylori
156
H. pylori function on gastric ulcer
release cytotoxins that bkdown mucosal barrier, contain urease that allow bacteria to colonize and convert urea to NH3 which makes basic environment
157
Diagnostic test for gastric ulcer
urease activity
158
How can duodenal ulcer form
H+ secretory rate are higher than normal
159
H. pylori function on duodenal ulcer
indirect effect- inhibits somatostatin from D cells (inhibit inhibition) and gastric H. pylori speads to duodenum and inhibits duodenal HCO3 secretion
160
Excessive H+ in duodenum
overwhelms buffer of HCO3 in pancreatic juice
161
Zollinger-Ellison syndrome
tumor, usually pancreas secretes large amt gastrin
162
Low duodenal pH inactivates..
pancreatic lipases, resulting in steatorrhea
163
Treatment options for duodenal ulcers
cimetidine, omeprazole, surgical removal of tumor
164
Components of pancreatic juice
- HCO3 for neutralization
| - enzymes to secrete carbs, proteins, lipids
165
Two main components of exocrine pancreas
1.aqueous solution containing HCO3, 2. Enzymatic secretion
166
Acinus of exocrine pancreas
lined by acinar cells that secrete enzymatic portion
167
Ducts of exocrine pancreas
lined by ductal cells that extend into acinus containing centroacinar cells
168
What do ductal and centroacinar cells secrete
aqueous solution containing HCO3
169
Parasympathetic innervation of exocrine pancreas
vagus nerve
170
Preganglionic fibers of exocrine pancreas for parasym
ENS
171
Postganglionic fibers of exocrine pancreas for sympath
synapse ON exocrine pancreas
172
Sympathetic innervation of exocrine pancreas
Postganglionis nerves from celiac and superior mesenteric plexus
173
Difference btwn innervation of salivary gland and exocrine pancreas
in exocrine pancrease- parasymp stimulates pancreatic secretion and sympath activity inhibits pancreatic secretion
174
Two components of pancreatic secretion
- enzymatic secretion of acinar cells
| - aqueous secretion by centroacinar and ductal cells
175
Enzymatic section by acinar cells
enzymes that digest carbs, proteins, lipids
| pancreatic amylase and lipase
176
Where are pancreatic proteases converted to active form
in the lumen of duodenum
177
What cells produce initial isotonic solution
centroacinar and ductal cells
178
Where does modification of initial pancreatic section occur
ductal cells
179
Net result of pancreatic modification
secretion of HCO3 into pancreatic juice and net absorption of H+
180
Ionic composition of pancreatic juice depends on...
rate of secretion
181
Increased flow rate on pancreatic juices
HCO3 is highest and Cl- is lowest
182
Decreased flow rate on pancreatic juices
HCO3 is lowest and Cl- is highest
183
How is relationship between HCO3 and Cl- concentrations maintained in pancreatic juice
HCO3-/Cl- exchanger in apical membrane of ductal cells
184
3 phases of pancreatic secretion
1.Cephalic, 2. Gastric, 3. Intesitnal
185
Cephalic phase of pancreatic secretion
produces mainly enzymatic secretion, mediated by vagus nerve
186
Gastric phase of pancreatic secretion
produces mainly enzymatic secretion, mediated by vagus nerve
187
Intestinal phase of pancreatic secretion
!! most importan phase! - 80% of pancreatic secretion
| - both enzymatic and aqueous secretion stimulated
188
Upregulators of pancreatic secretion in intestinal phase for I cells
phenylalanine, methionine, tryptophan, small peptides, fatty acids
189
Upregulators of pancreatic secretion in intestinal phase for IScells
H+
190
How does acute pancreatitis occur?
pancreatic enzymes are activation in pancreas and autodigest the pancreas
