3/4 GI Flashcards
Where is gastrin made and where is it sent?
- made by G cells in gastric antrum.
- sent to blood, its a hormone.
Who does gastrin act on?
- gastrin stimulates ECL cells to make histamine.
- histamine acts on parietal cells to make acid.
*gastrin also directly stimulates parietal cells as well. But majority of its effect on parietal cells is indirectly thru histamine.
What are parietal cells stimulated by?
-gastrin, histamine, ACh.
Whats the most important mechanism for stimulating parietal cells?
-ECL cells & histamine
Where is the highest pH you’ll find in a healthy body?
- veins leaving stomach b/c of all the bicarb that gets pumped into there for all the acid thats pumped into lumen.
- you make up for it by all the bicarb secretions that are pumped into intestines later.
Which receptors do the stimulatory factors for parietal cells act on?
- gastrin =
- ACh =
- histamine =
- gastrin = CCKb = Gq
- ACh = M3 = Gq
- histamine = H2 = Gs
*they all inc. cAMP which inc. activity of H/K ATPase.
Hypertrophy of brunners glands
- seen in what disease?
- seen where?
- Peptic ulcer disease
- duodenal submucosa
Pancreatic secretions
- Isotonic fluid;
- low flow =
- high flow =
- low flow= high Cl-
- high flow=high HCO3-
- -think of the CFTR channel that pumps Cl (& Na & H2O) into secretions.
- the lower the flow, the more time it has to pump this in.
What are the monosaccs?
-glucose, galactose, fructose.
- enterocytes take up glucose via?
- pump it into blood via?
- SGLT1 (Na+ dependent).
- thats why gatorade has sugar and sodium in it.
- Transported to blood by GLUT-2.
enterocytes take up galactose via?
-pump it into blood via?
SGLT1 (Na+ dependent)
-Transported to blood by GLUT-2.
enterocytes take up fructose via?
-pump it into blood via?
- GLUT-5 (facilitated diffusion, doesn’t need Na).
- Transported to blood by GLUT-2.
D-xylose absorption test:
- distinguishes GI mucosal damage from other causes of malabsorption.
- D-xylose = monosacc that can be absorbed directly w/o action of any enzymes (salivary, pancreatic, etc.) b/c its already a monosacc.
- -Its absorption requires an intact mucosa only.
Peyers patches
- encapsulated?
- where is it found?
- which layers?
- what are its specialized cells called?
- which bug invades through here?
- Unencapsulated lymphoid tissue found in lamina propria and submucosa of ileum.
- M cells.
- shigella.
How do you turn bile acids into bile salts?
-what do you use to conjugate it?
-bile acids conjugated to glycine or taurine, making them water soluble.
Whats the rate limiting enzyme in bile synthesis?
Cholesterol 7α-hydroxylase.
How is bilirubin removed from blood?
Bilirubin is removed from blood by liver, conjugated with
glucuronate, and excreted in bile.
- hepatocyte uptake of unconj. bili = active or passive?
- hepatocyte secretion of conj. bili = active or passive?
- hepatocyte uptake of unconj. bili = passive process
- hepatocyte secretion of conj. bili = active process.
Direct & indirect bilirubin
-are they water soluble?
- Direct bilirubin—conjugated with glucuronic acid; water soluble.
- Indirect bilirubin—unconjugated; water insoluble.
- Can indirect bilirubin be peed out?
- what gives pee its yellow color?
-No, its not water soluble. Its not filtered by glomerulus.
-Excreted in urine as urobilin, which gives yellow color of
urine.
- What enzyme conjugates bilirubin?
- Where is it found?
- UDP-glucuronosyl-transferase
- hepatocytes
What happens to conjugated bilirubin once its in the gut?
- Gut bacteria convert it to urobilinogen.
- 80% is oxidized to stercobilin & pooped out.
- 20% is divided:
- -90% recycled in terminal ileum.
- -10% excreted in urine as urobilin.
What gives urine yellow color?
-Urobilinogen is colorless. Once it hits the air in the kidneys, turns into urobilin which is yellow.
biphasic tumor
-any tumor involving both stromal and epithelial
tissue.