GI Hormones and Physiology Flashcards
Gastric parietal cells secrete
HCl
Intrinsic Factor
GI chief cells secrete
PEPsinogen
GI mucous neck cells secrete
HC03 mucus
What is pepsin?
Proteolytic enzyme that hydrolyzes peptide bonds
What is Intrinsic Factor?
Protein secreted by the parietal cells that combines with vitamin B12 and enables absorption in the terminal ileum
Name the 3 receptors on the parietal cell that stimulate HCl realease.
HAG: Histamine, Ach, Gastrin
What is the enterohepatic circulation
circulation of bile acids from the liver to the gut and back to the liver via the portal vein
Where are most of the bile acids absrobed?
Terminal ileum
How many times is the entire bile acid pool circulated during a typical meal?
Twice
What are the stimulators of gallbladder emptying?
Cholecystokinin, vagal input
What are the inhibitors of gallbladder emptying?
Somatostatin
Sympathetics (it is impossible to flee and digest food at the same time…haha!),
vasoactive intestinal peptide (VIP)
What is the source of Cholecytokinin (ccK)
Duodenal mucosal cells
What stimulates the release of ccK?
Fat
Protein
Amino acids
HCL
What inhibits the release of ccK?
Trypsin and chymotrypsin
What are its actions?
Empties Gallbladder
Opens Gallbladder ampulla
Slows GI emptying
Stimulates pancreatic acinar cell growth and release of exocrine products
What is the source of Secretin?
Duodenal cells
What stimulates the release of secretin?
pH <4.5 (acid)
fat in duodenum
What inhibits secreten release?
high pH in the duodenum
What are its actions?
Release pancreatic bicarbonate/enzymes/H20
Releases bile/bicarbonate
Decreases LES tone
Decreases release of Gastric Acid
What is the source of Gastrin?
Gastric antrum G cells
What stimulates Gastrin release?
Stomach peptides/amino acids
Vagal input
Calcium
What inhibits Gastrin release?
ph<3.0
Somatostatin
What are the actions of Gastrin?
Release of HCl from parietal cells
Trophic effect on mucosa of the stomach and small intestine
What is the source of Somatostatin?
Pacreatic Dcells
What stimulates Somatostatin release?
Food
What are the actions of Somatostatin?
Globally inhibits GI function
What is the purpose of the colon?
Reabsorption of H20 and storage of stool
What is the main small bowel nutrition source?
glutamine
what is the main nutritional source of the colon?
Butyrate (short chain fatty acid)
Where is calcium absorbed?
Duodenum
Where is calcium absorbed?
Duodenum, actively
Jejunum, passively
Where is iron absorbed?
Duodenum
Where is vitamin B12 absorbed?
Terminal ileum
Which hormone primarily controls gallbladder contraction?
ccK
What supplement does a patient need after removal of the terminal ileum or stomach?
Vitamin B12
Nam the main constituents of bile
Water Phospholipids lecithins bile acids cholesterol bilirubin
what are most of gallstones made of?
Cholesterol
How do opiates affect the bowel?
By stimulating Na absorption and inhibiting secretion in the ileum as well as decreasing GI motility by incoordinated peristalsis (Therefor, place patients on stool softeners when dispensing pain medication)
Which type of muscle fibers, smooth or striated, does the esophagus contain?
Both:
U/3 - striated muscle control of nerves
M/3 - mixed
L/3 - smooth muscle, primarily under control of vagal motor fibers
Which electrolytes does the colon actively absorb?
Na, Cl
Which electrolyte does the colon actively SECRETE?
HC03
Which electrolyte does the colon passively secrete?
K
What is the gastrocolic reflex?
Increased secretory and motor functions of the stomach result in increased colonic motility
What is the blood supply to the liver?
75% portal vein, rich in products of digestion
25% from hepatic artery, rich in O2
but each provide 50% of oxygen
Nodules of lymphoid tissue with B and T lymphocytes in the small intestine that selectively sample lumenal Ag found in the terminal ileum
Peyer Patches
