Gastric, Pancreatic, & Bile Secretions Flashcards
Trace the direct path of vagal stimulation for HCl secretion. (2 pathways)
vagus nerve —> Ach —> parietal cells —> HCl
vagus nerve —> GRP —> G cells (first part)
Trace the indirect path of vagal stimulation for HCl secretion.
gastrin from G cells —> systemic circulation —> HCl from parietal cells (rest of pathway)
Why won’t atropine block HCl secretion completely?
you have GRP in the G cell path
T/F: The cephalic phase is the primary phase of HCl secretion at 60%
FALSE - only 30%
What are the stimuli for the cephalic phase in HCl secretion?
smelling, tasting, chewing, swallowing, conditioned reflexes
What are 2 mechanisms in the cephalic phase that promote HCl secretion?
- direct stimulation by vagus n - Ach
- indirect via gastrin
What are the stimuli for the gastric phase in HCl secretion?
distention of stomach and presence of aa and peptides (PROTEIN)
What are the 4 mechanisms in the gastric phase that promote HCl secretion?
- distention - vagal stimulation
- indirect via gastrin
- distention of antrum - local reflexes of gastrin
- amino acids and peptides - gastrin
What are the phases in HCl secretion?
cephalic
gastric
intestinal
What is the stimuli for the intestinal phase?
products of protein digestion
What inhibits HCl secretion?
decreased pH of gastric contents
somatostatin - directly and indirectly
prostaglandins
How does somatostatin DIRECTLY inhibit HCl secretion?
binds parietal cells
antagonizes histamine pathway by decreasing cAMP
How does somatostatin INDIRECTLY inhibit HCl secretion?
inhibits both histamine and gastrin release
What helps prohibit acid and pepsin damage to gastric mucosa?
bicarbonate
mucus
How does HCO3 help inhibit gastric mucosa damage?
gastric epithelial cells and neck cells that secrete HCO3- get trapped in mucus
acid is then neutralized
pepsin deactivated
What is peptic ulcer disease caused by?
loss of mucus
excessive H+ and pepsin secretion
combination of both factors
Peptic ulcer disease is classified as either
gastric or duodenal ulcers
Why do gastric ulcers occur?
mucosal barrier is defective - H+ ions and pepsin digest mucosa
What is one cause of gastric ulcers? (Hint: colonizes)
H. pylori colonizes gastric mucus and attaches to epithelial cells
releases cytotoxins
Why does H. pylori survive in acidic environments?
converts urea to ammonia which increases pH of local environment
binds cells inside of being shed
Why do duodenal ulcers occur?
when H+ secretory rate is higher than normal
overwhelming buffering capacity
What is Zollinger-Ellison syndrome?
high rates of H+ secretion due to high gastrin
delivery of H+ to duodenum
causes steatorrhea
Why does steatorrhea occur in Zollinger-Ellison syndrome?
low pH in the small intestine inactivates lipases, so there is no fat digestion
T/F: The exocrine pancreas comprises 90% of the pancreas
TRUE
The exocrine pancreas has ______ and _______ components
aqueous
enzymatic
There is a high amount of _____ to neutralize acid in the pancreas
HCO3-
The enzymatic components of the exocrine pancreas digest what
digest carbohydrates, proteins, and fat
What is the structure of exocrine glands in the pancreas?
acinus lines with acinar cells
ducts lined with ductal cells
centroacinar cells
What do centroacinar cells of the exocrine pancreas do?
secrete the aqueous portion
The exocrine pancreas has ________ innervation
PSNS
SNS
Pancreatic secretions are [hypertonic/hypotonic/isotonic] to the blood
isotonic
Fill in the blanks.
- acinar cells
- ductal cells
- Cl-
- HCO3-
- Na+
- K+
- H+
- Na+
The innervation of the exocrine pancreas involves the SNS which has _________ plexuses. It is [stimulatory/inhibitory].
celiac and superior mesenteric (celiacomesenteric?)
inhibitory
The innervation of the exocrine pancreas involves the PSNS which has _________ nerve. It is [stimulatory/inhibitory].
vagus
stimulatory
Where are the enzymes of the enzymatic component of the pancreas?
on the rough ER facing cells
After synthesis (enzymatic component of pancreas), everything is transferred to the ______ and stored as ________
golgi
zymogens (inactive form of enzyme)
_______ are secreted in inactive form
proteases
The juice in the aqueous component of the pancreas is [hypertonic/hypotonic/isotonic] and contains which ions?
isotonic
Na+
Cl-
HCO3-
K+
The centroacinar and ductal cells of the aqueous component make the ______ secretion, then modified by _________
initial
transport processes in ductal cells
What is on the luminal membrane for the aqueous component of the pancreatic secretions?
HCO3-/Cl- exchanger
What is on the basolateral (blood) membrane for the aqueous component of the pancreatic secretions?
Na+/K+ ATPase
Na+/H+ exchanger
Regarding pancreatic secretions, ______ goes into the lumen, and ______ goes into the blood.
HCO3-
H+
What ion concentrations are constant regarding pancreatic secretions?
Na+
K+
At high juice flow rates, HCO3- is [high/low] and Cl- is [high/low]
HCO3-: high
Cl-: low
At low flow rates, solution contains mostly _____, ______, and ______
Na+
Cl-
water
At high flow rates, solution contains mostly _____, ______, and ______
Na+
HCO3-
water
T/F: Aqueous and enzymatic portions are regulated separately
TRUE
Regulation of aqueous portion in the pancreas is stimulated by ______
H+ in duodenum
Regulation of enzymatic portion is stimulated by ______
products of digestion
What are the three phases regulating pancreatic secretion?
cephalic
gastric
intestinal
The cephalic phase regarding pancreatic secretions is initiated by _______. What nerve?
smell
taste
conditioning
vagus nerve
The gastric phase regarding pancreatic secretions is initiated by _______. What nerve?
distention of stomach
vagus nerveE
What is the most important phase regulating pancreatic secretions?
intestinal phase (80% secretions)
Acinar cells in the pancreas is [enzymatic/aqueous] and has receptors for
enzymatic
CCKA receptors, muscarinic
In regulating enzymatic section of pancreatic secretions, there is a _____ stimulus from amino acids, peptides, and fatty acids
CCK
What potentiates an action of CCK for acinar cells in the pancreas?
Ach
Ductal cells in the pancreas is [enzymatic/aqueous] and has receptors for
aqueous
CCK, Ach, secretin
How is secretin important with ductal cells and regulating aqueous pancreatic secretions?
stimulate aqueous HCO3- from pancreas
The actions of secretin is potentiated by _____ and _____
CCK
Ach
Bile secretion is needed for
digestion and absorption of lipids
______ synthesize components of bile, flow out of bile ducts into gallbladder
hepatocytes
CCK in the gallbladder does what?
stimulates contraction of gallbladder
relaxes sphincter of Oddi
The liver conjugates bile acids with aa to form bile salts. Which amino acids primarily?
glycine
taurine
What is bilirubin?
product of hemoglobin degradation
The epithelial cells of the gallbladder do what?
absorb ions and water
Bile is ejected ______ after a meal is ingested. It is ejected [continuously/in spurts]
30 minutes
in spurts
Most bile salts return to the liver via _______ circulation
enterohepatic
Bile salts are transported from the small intestine lumen into portal blood by ________
Na+/bile salt co-transporters
Do bile salts get absorbed?
not normally
