Flashcards in GI and Nutrition UWorld Deck (51)
Retroperitoneal abdominal structures
S: Suprarenal (adrenals)
A: Aorta + IVC
D: Duodenum parts 2-4
P: Pancreas, except for its tail
C: Colon, descending + ascending parts
E: Esophagus, thoracic part
Ligaments that make up the lesser omentum
Hepatoduodenal ligament and hepatogastric ligament
Chemotactic factors for neutrophils
How does secretory IgA differ from serum IgA
It has a J chain that holds two IgA molecules together and a secretory component that allows it to enter the G.I. lumen
Why is the rectum always involved in hirschsprung's disease?
The neural crest cells migrate caudally during embryogenesis and the rectum is narrow because it cannot relax due to the absence of Auerbach and Meissner plexuses
What cells are present in the different layers of the stomach mucosa?
The uppermost layer is composed of simple columnar epithelial cells that secrete mucus.
The next layer is the upper glandular layer and it contains oxyntic (pink) parietal cells that secrete gastric acid and intrinsic factor.
The next layer down is the deep aspect of the gastric glands. It contains basophilic chief cells that secrete pepsinogen.
The next layer down is the muscularis mucosa, separating the lamina propria from the submucosa.
Why does shigella cause bloody diarrhea
It first infects M-cells in the Peyer's patches of the ileum and spreads laterally to other M-cells and secretes its toxin. This causes all of the superficial mucosa to slough off and present with bloody mucus-containing stool
First line defense cell in the intestine
Paneth cells. They are found in small groups at the base of intestinal crypts and secrete lysozyme and defensins that help protect against infection.
Genetic mutations associated with Lynch Syndrome
MSH2 and MLH1 that code for MutS (mismatch repair enzyme that detects mismatches and recruits MutL). MutL and MutS form a complex that recruits exonuclease I to cut out the mismatched DNA. DNA polymerase delta refills the degraded daughter strand and DNA ligase seals the correction.
How does nucleotide base excision repair occur?
Glycosylases detect the abnormal base, remove it and leave an empty sugar phosphate in its place. Endonuclease cleaves the 5' end and lyase cleaves the 3' end. The normal base is then placed there by DNA polymerase and it is sealed by ligase.
Coarse pigmented granules found within hepatocytes of a patient with jaundice
Dubin-Johnson. This is due to AR mutation in a canalicular membrane transport protein that prevents excretion of conjugated bilirubin into bile canliculi. The granules are black due to accumulation of epinephrine metabolites in lysosomes.
What drugs are most effective for motion sickness and why?
Motion sickness occurs when there is incongruent stimulus occurring between the visual, vestibular and somatosensory systems. Integration of these sensory pathways occurs at the vestibular nuclei via M1 and H1 receptors. Consequently scopolamine (anti-muscarinic) and anti-histamines (diphenhydramine, meclizine and promethazine) are first line for motion sickness.
Why does the urease breath test work for diagnosis of H. pylori infection?
H. pylori has urease, which converts urea to CO2 and NH3. You can give a patient radiolabeled 13C and measure the amount of labeled CO2 expired for diagnosis.
Like the Lac operon, multiple proteins are synthesized from the single mRNA (rare in eukaryotes, common in prokaryotes)
What happens to pancreatic fluid content as flow increases and there is increased release of secretin?
HCO3- increases and Cl- decreases
Frequent source of retroperitoneal bleeding after blunt abdominal trauma
Common etiology for true esophageal diverticula
Traction diverticula from mediastinal masses
Toxin produced by E. coli that do not ferment sorbitol on MacConkey's agar or produce glucuronidase
E. coli O157:H7 produces shiga-like toxin that has a B binding domain for M-cells and an A toxin that inhibits the 60S ribosomal subunit by deleting an adenosine residue and preventing tRNA linkage to the 60S subunit.
Bacteria that produce toxins capable of activating adenylyl cyclase
Anthrax (edema factor)
Pertussis (pertussis toxin)
ETEC (heat labile toxin)
Bacteria that produce toxins capable of activating guanylyl cyclase
ETEC (heat stable toxin)
Bacteria that produce toxins capable of inactivating EF-2
Pseudomonas (exotoxin A)
C. difficile toxin
Toxin A is enterotoxic and causes inflammation and fluid secretion
Toxin B inactivates Rho-regulatory proteins, resulting in depolymerization of actin and causes cell death via membrane disruption
Site of secretion and action:
Gastrin - G cells - increases HCl release
Somatostatin - pancreatic D cells - decreases secretion of most GI hormones
CCK - I cells - increases pancreatic enzyme and HCO3- secretion
Secretin - S cells - increases HCO3- secretion and decreases HCl release
GIP - K cells - decrease HCl and increase insulin release
Motilin - M cells - increase GI motility
VIP - pancreas - increases HCO3- secretion, stimulates intestinal water secretion and counteracts gastrin in the stomach
Pathophysiology of ulcers that develop second to H. pylori infection
H. pylori destroys somatostatin-secreting D cells, disinhibiting gastrin release from G cells
Function of apolipoproteins:
E3 & E4
A-I: activates LCAT, which esterifies cholesterol (deficiency results in low HDL cholesterol and increased circulating free cholesterol)
B-48: chylomicron assembly and intestinal secretion
B-100: LDL uptake by extra hepatic cells
C-II: lipoprotein lipase activation (deficiency results in type 1 hyperlipoproteinemia with hyperchylomicronemia)
E3 & E4: VLDL and chylomicron remnant uptake by hepatocytes
Mechanism of action of medications you give for hepatic encephalopathy
Rifamixin: non-absorbable antibiotic that reduces bacteria in the gut that generate NH3
Lactulose: catabolized to short-chain fatty acid in gut by bacteria, lowers gut pH and generates non-absorbable NH4+ from NH3
Colon cancer that may present as high volume, mucus-containing diarrhea
Origin of the round acidophilic Councilman bodies seen on biopsy of patients with hepatitis
These are apoptotic hepatocytes
2 main watershed areas of the colon
Splenic flexure (SMA -> IMA)
Distal sigmoid colon (IMA -> hypogastric arteries)