General Surgery - GI Hormones & Physiology Flashcards
Define the products of the following cells:
Gastric parietal cells
HCl
Intrinsic Factor
Product of Chief Cells?
Pepsinogen
PEPpy Chief
Product of G Cells?
Gastrin
G cells are found in the antrum
G = Gastrin
Mucous Neck Cell Products?
Bicarbonate mucus
What is pepsin?
Proteolytic enzyme that hydrolyzes peptide bonds
What is Intrinsic Factor?
Protein secreted by parietal cells that combines with vitamin B12 and enables absorption in the terminal ileum
Name three receptors on the parietal cell that stimulates HCl release
Think HAG:
Histamine
Acetylcholine
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 absorbed?
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’s impossible to flee and digest food at the same time!)
vasoactive intestinal polypeptide (VIP)
Source of cholecystokinin (CCK)?
duodenal mucosal cells
what stimulates release of cck?
fat
protein
amino acids
HCl
What inhibits release of CCK?
trypsin
chymotrypsin
Actions of CCK?
Empties gallbladder
opens ampulla of Vater
slows gastric emptying
stimulates pancreatic acinar cell growth & release of exocrine products
Source of secretin?
Duodenal cells
SPECIFICALLY: argyrophilic S cells
Whats stimuates release of secretin?
pH <4.5 (acidity)
fat in the duodenum
What inhibits release of secretin?
High pH in duodenum
What are secretin actions?
Releases pancreatic bicarbonate, enzymes, H2O
Releases bile, bicarbonate
Decreases Lower Esophageal Sphincter (LES) tone
Decreases release of gastric acid
Source of gastrin?
Gastric antrum G cells
What stimulates release of gastrin?
stomach peptides/amino acids
vagal input
calcium
What inhibits gastrin release?
pH <3.0
Somatostatin
Actions of gastrin?
Release of HCl from parietal cells
Trophic effect on mucosa of the stomach and small intestine
Source of somatostatin?
pancreatic D cells
What stimulates somatostatin release?
FOOD
Actions of somatostatin?
Globally inhibiting GI function
Purpose of the colon?
Reabsorption of H2O, storage of stool
Main small bowel nutritional source?
Glutamine
What is the main nutritional source of the colon?
Butyrate (short chain fatty acid)
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
Main constituents of bile?
Water
phospholipids (lecithins)
bile acids
cholesterol
bilirubin
What are most gallstones made of?
Cholesterol
How do opiates affect the bowel?
By stimulating sodium absorption & inhibiting secretion in the ileum as well as decreasing GI motility by incoordinated peristalsis
Therefore, place patients on stool softeners when dispensing pain medication
Which type of muscle fibers, smooth or striated, does the esophagus contain?
BOTH
upper third: striated muscle control of motor nerves
middle third: mixed
lower third: 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?
HCO3-
plays a role in diarrhea causing the patient to have a normal anion gap acidosis
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% from the portal vein, rich in products of digestion
25% from the hepatic artery, rich in O2 (but each provide for 50% of oxygen!)
What are Peyer patches?
Nodules of lymphoid tissue with B & T lymphocytes in the small intestine that selectively sample lumenal antigens found in the terminal ileum