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.
Pleomorphic adenoma (benign mixed tumor)
-most common salivary gland tumor.
-Presents as a painless, mobile mass.
-Composed of chondromyxoid stroma and epithelium
and recurs if incompletely excised.
*has irregular borders, hard to excise completely.
-if you get signs of facial nerve damage, the tumor has
transformed into a carcinoma (malignant).
Warthin tumor
- benign salivary gland tumor
- Papillary cystadenoma lymphomatosum.
- Benign cystic tumor in lymphoid tissue (with germinal centers).
Mucoepidermoid carcinoma
- Most common malignant salivary gland tumor.
- Mucinous and squamous components.
- It typically presents as a painless, slow-growing mass.
- facial n. often affected.
What does chalasia mean?
-chalasia = relaxation.
Achalasia
-inc. risk of which cancer?
esophageal SCC.
Esophageal strictures are associated w/ingestion of what?
- Lye & acid reflux.
- 70-80% due to GERD.
- esophagus venous drainage?
- Where do you find esophageal varices?
- Most drained via esophageal veins to azygos to SVC.
- Some drained from left gastric vein to the portal vein. In portal HTN there will be backup.
-Varices found in lower 1/3 of esophagus.
Adult onset asthma
-associated w/what common esophageal problem?
GERD
Obesity
-risk factor for squamous or adeno carcinoma of esophagus?
-adeno
Classic locations of esophageal cancer:
- squamous vs adenocarcinoma
- also, which is more common in the US?
- Squamous cell—upper 2 ⁄ 3 .
- Adenocarcinoma—lower 1 ⁄ 3 .
*Worldwide, squamous cell is more common.
*In the United States, adenocarcinoma is more
common.
Esophageal web
-inc risk for squamous or adeno carcinoma of esophagus?
-squamous
Cushing ulcer:
- acute gastritis
- inc. ICP = inc. vagal stim = inc. H production
How does achlorhydria cause G-cell hyperplasia?
-low levels of gastric acid in the stomach. Will result in increased gastrin b/c you’ve lost the negative feedback. (leads to G-cell hyperplasia).
Type A chronic gastritis
- pernicious anemia
- type 4 HSR.
Ménétrier disease
- Gastric hypertrophy with protein loss, parietal cell atrophy, and inc. mucous cells.
- Precancerous.
- Rugae of stomach are so hypertrophied that they look like brain gyri.
Sister Mary Joseph nodule
-subcutaneous periumbilical metastasis.
Ruptured gastric ulcer on the lesser curvature of the stomach.
-which artery will bleed?
-Bleeding from left gastric artery.
Ruptured ulcer on the posterior wall of the duodenum.
-which artery will bleed?
-Bleeding from gastroduodenal artery.
Ulcer complications -ant or post -which one more likely to 1-hemorrhage 2-perforate
- posterior = hemorrhage
- anterior = perforate
Perforated duodenal ulcer
-what can you see? pain where?
May see free air under the diaphragm with referred pain to the shoulder.
Tropical sprue vs Celiac
- response to Abx?
- location affected?
- tropical sprue does respond to Abx
- tropical sprue affects jejunum and ileum rather than duodenum like celiac disease.
Is mucus release inc or decreased in inflammatory states?
-increased
Paneth cell
- pathocytic & secretory functions.
- occur at base of intestinal crypts.
- first line of immune defense against intestinal microbes.
- secrete lysozyme and defensins.
Liver failure after surgery think what?
-halothane anesthetic is very hepatotoxic.
Liver failure after surgery think what?
- halothane anesthetic is very hepatotoxic.
- can not be histologically distinguished from acute viral hepatitis.
If you have acute liver failure, why do you get inc. PT time but your albumin level is fine? If liver cell is failing to make coag factors isn’t it also failing to make albumin?
-yes it is but albumin has a long half life (20 days), compared with some coag factors. Factor 7 has a half life of 3-6 hours.
How to Dx celiac sprue?
-test for which Abs?
-IgA anti-endomysial & anti-tissue transglutaminase Abs.