3/30: Accessory GI Organs Flashcards
Is the pancreas exocrine or endocrine?
More than 90% is exocrine
What do acinar cells synthesize and secrete?
Hydrolases for digestion
What do duct cells secrete?
Bicarbonate and water
What does the pancreas have luminal digestion of?
Carbohydrate, protein, fat
What does impaired digestion function of the pancreas cause?
Maldigestion and malabsorption
What does the pancreas neutralize?
Gastric H+: secretes HCO3- into duodenum up to 145 mEq/l
How are proteolytic enzymes synthesized, stored, and secreted as?
Inactive precursors
Where are proteolytic enzymes activated in/
Intestinal lumen
1. Enterokinase
2. Trypsin
What is trypsin inhibitor synthesized, stored, and secreted with/
Precursors
What is the function of acinar cells?
Digestive enzyme secretion
What are the two stimuli for acini cell enzyme secretion?
- CCK
- ACh/GRP (Vagovagal reflex)
What are CCKs function in the gallbladder?
Contraction
What do CCKs do in the pancreas?
Acinar secretion
What do CCKs do in the stomach?
Stimulates receptive relaxation
Reduce emptying
Reduce HCl secretion
What do CCK do in the sphincter of Oddi?
Relaxation
What cells secrete CCK?
I cells
What two substances stimulate I cells to secrete CCK?
Monitor peptide
CCK-RP
What does CCK-RP need to function?
Fatty acids
Amino acids
What are the two stimuli for ductal cell secretion of H2O and HCO3?
- Secretin (secretin receptor)
- ACh (M3 receptor)
What does secretin induce when bound?
cAMP
Phosphorylation of CFTR
Increase Cl conductance
Increase HCO3- secretion
What is HCO3 bicarbonate output used as an index of?
Secretin release
What pH is secretin released at?
pH <4.5
At what pH is secretin release maximal in segment of duodenum?
Below pH of 3
What does further release of secretin depend upon?
Area of small intestine affected
When is pH rarely <3.5 or 4?
During a meal
Compare the rate of pancreatic secretion of CCK and secretin
HCl-
- increases levels of Water and HCO3 because HCl stimulates secretin which stimulates ductal cells to secrete water and NaHCO3
Soap-
- fatty acids
Acids secrete secretin
Fats secrete CCK
Peptone-
- increases levels of enzymes because peptides stimulate CCK which stimulates acinar cells to secrete enzymes
What are cephalic and gastric phases mediated by?
Vagovagal reflex
What kind of secretion is vagovagal secretion?
Low volume, high enzyme (Ach/GRP)
What does acid in the intestine stimulate?
Secretin -> HCO3-/H2O
What do fats/proteins stimulate in the intestine?
CCK -> Enzymes
(indirectly via CCK-RP and monitor peptide)