APMLE Part 1 GI Physiology Questions With Complete
Solutions
What cells secrete CCK?
I cells of the duodenum
What stimulates CCK release?
small peptides, amino acids and fatty acids in the duodenum
What is the action of CCK?
it acts on acinar cells to increase enzyme secretion (amylase,
lipases, and proteases)
What effect does CCK potentiate?
the effect of secretin on the S cells
What is the effect of ACh vasovagal reflex on the pancreas?
It increases ezyme secretion by acinar cells
It potetiates Secretin on S cells
What is cystic fibrosis?
a disosrder of PANCREATIC secretion that is caused by a
mutation in the CFTR gene CHLORIDE CHANNEL
Results in malabsorption and steatorrhea
What is the composition of bile?
,AMPIPHATIC phospholipids, cholesterol and bile pigments
(bilirubin)
What is the purpose of bile salts?
Aids in intestinal digestion by emulsifying and solubilizing in
micelles
When do micelles form?
when bile salts are above a critical micellar concetration
Where are bile salts positioned on the micelle?
On the outside with their hydrophilic portions partially dissolved
Whats present on the inside of a micelle?
Free fatty acids, monoglycerides are present in the inside of the
micelle
Where is bile formed?
produced continuously by hepatocytes
From the liver where does bile drain into?
drains from hepatocytes into the HEPATIC DUCTs and is
stored in the gall bladder for release
What fat is a precursor to bile?
Primary bile salts are synthesized from cholesterol by
hepatocytes
In the intestine how is primary bile converted into secondary
bile?
,By bacteria in the intestine bile is converted to secondary bile
(deoxycholic, lithocholic)
What is bile conjugated with to form bile salts?
Glycine and Taurine
During what times does the gall bladder fill?
During interdigestive periods the sphincter of Oddi closes and
bile fills
What two stimuli cause contraction of the gall bladder?
1) CCK released in response to fatty acids and small peptide
causes bile to emulsify and contraction of gallbladder and
relaxation of sphincter of oddi
2) ACh causes contraction
How is bile recycled to the liver?
in the TERMINAL ILEUM Na+-Bile acid cotransporter
recirculates the bile acids
bile acids is available for maximal absorption in the upper SI
After ileal resection what happens to bile recirculation?
It is not recirculated but excreted ad the bile acid pool is
depleted resulting in STEATORHEA
Where are carbs, proteins and fat absorbed and digested?
Small intestine along the brush border
What is the only type of carb that is absorbed?
, MONOSACHARRIDES only= glucose, galatose and fructose
What is the action of alpha amylase?
hydrolyze 1,4 glycosidic bonds in starch, yielding maltose,
maltotriose and alpha limit dextrins
How are maltose, maltotriose and alpha limit dextrins absorbed?
via maltase, dextrinase, sucrase, in the brush border of the small
intestine
What receptor transports the intestinal lumen into the cells?
Na+Dependent cotransporter (SGLT-1) in the luminal
membrane
How is fructose transported into cells?
facilitate diffusion and cannot be absorbed against a gradient
How does lactose intolerance result?
absence of LACTASE in the brush border thus the inability to
hydrolyze lactose to glucose and galactose for absorption
Non absorbed lactose and water remain in the lumen of the GI
and cause osmotic diarrhea
What is the difference between endopeptidases and
exopeptidases?
Endopeptidases degrade protein by hydrolyzing interior peptide
bones
Solutions
What cells secrete CCK?
I cells of the duodenum
What stimulates CCK release?
small peptides, amino acids and fatty acids in the duodenum
What is the action of CCK?
it acts on acinar cells to increase enzyme secretion (amylase,
lipases, and proteases)
What effect does CCK potentiate?
the effect of secretin on the S cells
What is the effect of ACh vasovagal reflex on the pancreas?
It increases ezyme secretion by acinar cells
It potetiates Secretin on S cells
What is cystic fibrosis?
a disosrder of PANCREATIC secretion that is caused by a
mutation in the CFTR gene CHLORIDE CHANNEL
Results in malabsorption and steatorrhea
What is the composition of bile?
,AMPIPHATIC phospholipids, cholesterol and bile pigments
(bilirubin)
What is the purpose of bile salts?
Aids in intestinal digestion by emulsifying and solubilizing in
micelles
When do micelles form?
when bile salts are above a critical micellar concetration
Where are bile salts positioned on the micelle?
On the outside with their hydrophilic portions partially dissolved
Whats present on the inside of a micelle?
Free fatty acids, monoglycerides are present in the inside of the
micelle
Where is bile formed?
produced continuously by hepatocytes
From the liver where does bile drain into?
drains from hepatocytes into the HEPATIC DUCTs and is
stored in the gall bladder for release
What fat is a precursor to bile?
Primary bile salts are synthesized from cholesterol by
hepatocytes
In the intestine how is primary bile converted into secondary
bile?
,By bacteria in the intestine bile is converted to secondary bile
(deoxycholic, lithocholic)
What is bile conjugated with to form bile salts?
Glycine and Taurine
During what times does the gall bladder fill?
During interdigestive periods the sphincter of Oddi closes and
bile fills
What two stimuli cause contraction of the gall bladder?
1) CCK released in response to fatty acids and small peptide
causes bile to emulsify and contraction of gallbladder and
relaxation of sphincter of oddi
2) ACh causes contraction
How is bile recycled to the liver?
in the TERMINAL ILEUM Na+-Bile acid cotransporter
recirculates the bile acids
bile acids is available for maximal absorption in the upper SI
After ileal resection what happens to bile recirculation?
It is not recirculated but excreted ad the bile acid pool is
depleted resulting in STEATORHEA
Where are carbs, proteins and fat absorbed and digested?
Small intestine along the brush border
What is the only type of carb that is absorbed?
, MONOSACHARRIDES only= glucose, galatose and fructose
What is the action of alpha amylase?
hydrolyze 1,4 glycosidic bonds in starch, yielding maltose,
maltotriose and alpha limit dextrins
How are maltose, maltotriose and alpha limit dextrins absorbed?
via maltase, dextrinase, sucrase, in the brush border of the small
intestine
What receptor transports the intestinal lumen into the cells?
Na+Dependent cotransporter (SGLT-1) in the luminal
membrane
How is fructose transported into cells?
facilitate diffusion and cannot be absorbed against a gradient
How does lactose intolerance result?
absence of LACTASE in the brush border thus the inability to
hydrolyze lactose to glucose and galactose for absorption
Non absorbed lactose and water remain in the lumen of the GI
and cause osmotic diarrhea
What is the difference between endopeptidases and
exopeptidases?
Endopeptidases degrade protein by hydrolyzing interior peptide
bones
