L28: Gastric, Pancreatic, and Intestinal Secretions Flashcards
What is the stimulus for conversion of pepsinogen to pepsin?
H+
____ is an inactive proenzyme secreted from chief cells of gastric mucosa
Pepsinogen
At which pH is pepsin most active in?
A. Acidic
B. Basic
C. Neutral
A. Acidic
True or False: Pepsin is active at pH of 7
False
Pepsin digests 10-20% of the total ___ in a meal
A. Protein
B. Fiber
C. Carbohydrates
A. Protein
True or False: Most protein enters the duodenum intact
True
True or False: Gastric lipase is an enzyme secreted from chief cells of gastric mucosa in its inactive form
False - while gastric lipase is secreted from chief cells of gastric mucosa, it is secreted in its ACTIVE form
What is the function of Gastric Lipase?
A. Digest dietary carbohydrates
B. Digest dietary protein
C. Digest dietary triglycerides
C. Digest dietary triglycerides
(into FFA)
What pH ranges is Gastric Lipase active at?
pH of 4-5; pH of 2
Gastric lipase secretion is stimulated by _____
Ach
____, secreted by Parietal Cels, binds Vit B12 in the duodenal lumen, protecting it from enzymatic degradation and transporting it to the ileum where it is absorbed
Intrinsic Factor
Where it Vit B 12 absorbed?
Ileum
True or False: The same substances that stimulate HCl secretion from parietal cells also stimulate IF secretion
True
The gastric mucosal barrieris made of both ___ and ____
mucins; bicarbonate
Three functions of the gastric mucosal barrier?
1) Prevent mixing of gastric luminal contents with enterocytes
2) Protect underlying mucosa from digestion by pepsin and damage by H+
3) Buffer any luminal H+ that enters barrier with secreted HCO3
What are the two mechanisms by which enterocytes secrete mucins?
1) Exocytosis - continuos secretion of mucin
2) Cell exfoliation
Which three molecules increase the production of mucin and secretion?
Ach, gastrin, and prostaglandins
What is the pH of the gastric lumen? pH of the enterocyte surface?
gastric lumen = less than 3.0
enterocyte surface = 7.0
All gastric enterocytes secrete ___ and ___ to form gastric mucosal barrier
mucins; HCO3
How do enterocytes secrete HCO3?
HCO3-Cl antiporter in apical membrane
Which two molecules stimulate HCO3 secretion in the enterocyte?
Prostaglandins and Ach
___ are important in maintaining health and integrity of the gastric mucosal barrier. It is said to have “cytoprotection.”
Prostaglandins
What are the four benefits of prostaglandins?
1) Decrease HCl secretion
2) Increased mucin secretion
3) Increase HCO3 secretion
4) Increase mucosal blood flow
How can NSAID use affect the gastric mucosal barrier?
NSAID’s decrease PG synthesis, thereby decreasing the thickness and integrity of the GMB