USMLE - GI Flashcards Part 6

Anatomy and Physiology25 CardsCreated 18 days ago

This deck covers key concepts related to gastrointestinal physiology and pathology, focusing on digestion, absorption, and related disorders.

Salivary Amylase Role MoA Yields

Starts digestion | Hydrolyzes α(1-4) linkages to yield disaccharides (maltose and α-limited dextrins)
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Key Terms

Term
Definition
Salivary Amylase Role MoA Yields
Starts digestion | Hydrolyzes α(1-4) linkages to yield disaccharides (maltose and α-limited dextrins)
Pancreatic Amylase Concentrated in MoA
Highest concentration in duodenal lumen | Hydrolyzes starch to oligosaccharides and disaccharides
Oligosaccharide Hydrolase Location Role MoA
At brush border of intestines Rate limiting step in carbohydrate digestion Produces monosaccharides from oligo- and disaccharides
Carbohydrate absorption What kind of carbs? By what cells? What enzymes remove them from lumen? What enzymes transport them to the blood?
Only monosaccharides (glucose, galactose, and fructose are absorbed by enterocytes Glucose and Galactose are taken up by SGLT1 (Na dependent) Frucose ...
How to distinguish GI mucosal damage from other causes of malabsorption?
D-xylose absorption test
Iron absorption Ionic state? Location
As Fe2+ in duodenum

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TermDefinition
Salivary Amylase Role MoA Yields
Starts digestion | Hydrolyzes α(1-4) linkages to yield disaccharides (maltose and α-limited dextrins)
Pancreatic Amylase Concentrated in MoA
Highest concentration in duodenal lumen | Hydrolyzes starch to oligosaccharides and disaccharides
Oligosaccharide Hydrolase Location Role MoA
At brush border of intestines Rate limiting step in carbohydrate digestion Produces monosaccharides from oligo- and disaccharides
Carbohydrate absorption What kind of carbs? By what cells? What enzymes remove them from lumen? What enzymes transport them to the blood?
Only monosaccharides (glucose, galactose, and fructose are absorbed by enterocytes Glucose and Galactose are taken up by SGLT1 (Na dependent) Frucose taken up by facilitated diffusion through GLUT5 All sugars enter blood via GLUT2
How to distinguish GI mucosal damage from other causes of malabsorption?
D-xylose absorption test
Iron absorption Ionic state? Location
As Fe2+ in duodenum
Folate absorption | Location
Jejunum
Peyer's Patches What are they? Where are they? Contain what kind of specialized cells?
Unencapsulated lymphoid tissue in LP and submucosa of ileum | Contains specialized M cells that take up antigen
Peyer's Patches | What happens in germinal centers? Where do cells from germinal centers go? What do they do?
In germinal centers, B cells are stimulated to differentiate into IgA secreting plasma cells IgA cells migrate to LP IgA receives protective secretory component and is then transported across the epithelium to the gut to deal with intraluminal antigen
Antibody in the gut?
Secretory IgA | "Intra Gut Antibody"
Composition of Bile
Bild salts (bile acids conjugated to glycine and taurine to be made water soluble), Phospholipids, Cholesterol, Bilirubin, Water, Ions
Rate limiting step in bile production
Cholesterol 7α hydroxylase
Functions of Bile
Digestion and absorption of lipids and fat soluble vitamins Cholesterol excretion (the body's only means) Antimicrobial activity (via membrane disruption)
Bilirubin Product of Removed from blood by Conjugated with Excreted in
Product of heme metabolism Removed from blood by liver Conjugated with glucuronate Excreted in bile
Direct Bilirubin
Conjugated with glucuronic acid | Water soluble
Indirect Bilirubin
Unconjugated | Water insoluble
How is unconjugated bilirubin transported in the blood
Bound to albumin
What enzyme conjugates bilirubin
UDP glucuronsyl transferase
What happens to conjugated bilirubin in the gut?
Gut bacterial break it down into urobilinogen 80% of excreted in feces as stercobilin to give stool its brown color 20% is reabsorbed
What happens to the reabsorbed urobilinogen?
10% goes to kidneys and excreted in urine as urobilin (gives urine yellow color) 90% enters enterohepatic circulation
Salivary Gland Tumor Dangerous? Common Location?
Generally benign and occurs in the parotid gland
Salivary Gland Pleomorphic Adenoma Dangerous? Kind of tumor? Composition? Frequency? Presentation Recurrence?
Benign Mixed tumor of cartilage and epithelium Most common salivary gland tumor Painless and mobile mass Frequently recurs
Warthin's Tumor Kind of tumor? Descriptive name? Dangerous? Description
Salivary Gland Tumor Papillary Cystadenoma Lymphomatosum Benign Cystic tumor with germinal centers
Achalasia What is it? Presentation Diagnosis Increased Risk of...
Failure of the lower esophageal sphincter to relax due to loss of myenteric plexus Progressive dysphagia to solids and liquids Barium swallow shows dilated esophagus with area of distal stenosis (Birds Beak) Increased risk of squamous cell carcinoma
Secondary Achalasia may arise from…
Chagas disease