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Lec6 Flashcards

1
Q

Where are most minerals absorbed?

A

duodenum

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2
Q

Where are bile acids absorbed?

A

ileum

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3
Q

Where is cobalamin [B12] absorbed?

A

ileum

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4
Q

Where is iron absorbed?

A

duodenum

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5
Q

What are gross folds of the small bowel vs the large bowel called?

A 
small = plicae circulares
large = haustrae
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6
Q

How is digestion initiated in the small intestine?

A
  • acid in duodenum –> duodenal S cells secrete secretin –> cause pancreas to secrete bicarb
  • fatty acids and amino acids in duodenum –> duodenal I cells secrete CCK –> cause pancreas to secrete enzymes, gallbladder to empty
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7
Q

What is ratio of starch to sucrose to lactose of ingested carbs?

A

starch 50%
sucrose 30%
lactose 10%

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8
Q

How is starch digested?

A
  • amylase from pancreas/saliva converts to maltose

- maltase on intestinal BBM to glucose

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9
Q

How is sucrose digested?

A

sucrase-isomaltase on intestinal BBM to glucose and fructose

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10
Q

How is lactose digested?

A

lactase on intestinal BBM to glucose and galactose

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11
Q

How are carbs absorbed?

A

glucose/galactose active transported into cell then diffuse into portal vein

fructose facilitated diffusion

unabsorbed carbs converted to short chain fatty acids in colon

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12
Q

What are the components of starch?

A

maltoses each made of glucose

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13
Q

What are the components of sucrose?

A

glucose and fructose

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14
Q

What are the components of lactose?

A

glucose and galactose

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15
Q

How are proteins digested?

A

in stomach: denatured by acid; pepsin hydrolyzes into polypeptides

in duodenum: digested by pancreatic proteases; duodenal brush border membrane enterokinase activates trypsin which then activated the other pancreatic pro-enzymes

BBM oligopeptidases then hydrolyze into smaller oligopeptides and amino acids

final digestion inside enterocytes by intracellular peptidases that convert everything to amino acids

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16
Q

How are proteins absorbed?

A

as amino acids and oligopeptides

intracellular pepitdases in enterocytes finish digestion into AAs

AAs absorbed and transported to capillaries into portal vein

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17
Q

What is role of brush border membrane enterokinase in protein digestion?

A

activates trypsin which in turn activates other pancreatic pro-enzymes

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18
Q

How are lipids digested?

A

in stomach: churn fats into unstable emulsion

in duodenum/small intestine: emulsion stabilized by phospholipids and bile salts

CCK released in response to dietary fat in duodenum causes bile salt and lipase [panc.] release

pancreatic lipase and co-lipase convert TG–> MG + FFA

mixed micelles form with MGs and FFAs inside; bile salts outside

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19
Q

What is necessary for pancreatic lipase to work?

A
  • CCK causes its release from pancreas in response to fatty acids in duodenum
  • requires neutral pH in duodenum to work
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20
Q

How are lipids absorbed ?

A

passive diffusion across BBM into cell

intracellular resynthesized as cylomicrons and VLDL –> exported into lymphatics

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21
Q

What is exception to the rule that lipids are absorbed into the lymph system?

A

medium chain TGs are absorbed into the portal vein

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22
Q

What is role of B lipoprotein in fat absorption?

A

important role in repackaging of fats into chylomicrons inside enterocytes for absorption into lymphatics

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23
Q

How is vit B12 absorbed [steps]?

A
  • dietary B12 complexes with salivary R protein in stomach
  • in duodenum trypsin cleaves R-B12 complex
  • IF from gastric parietal cells binds B12
  • IF-B12 complex absorbed in terminal ileum
  • B12 transported into portal circulation
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24
Q

Which vitamins are fat soluble?

A

ADEK

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25
What happens to B12 with bacterial overgrowth?
luminal bacteria compete for B12; with bacterial overgrowth --> have low serum B12
26
What are some causes of B12 deficiency
- not enough dietary B12 [rare] - not enough R - not enough IF [autoimmune gastritis] - pancreatic insufficiency [can't dissociate B12-R] - ileal disease [can't absorb]
27
What happens to folate level if bacterial overgrowth?
high serum folate
28
How is Ca absorbed?
active transport in duodenum; calbindin in cell delivers Ca to ATPase for export into circulation vit D stimulates calbindin synthesis and helps Ca entry into enterocytes
29
What is major symptom of protein malabsorption?
edema
30
What major symptoms of fat malabsorption?
steatorrhea | weight loss
31
What major symptoms of carb malabsorption?
- diarrhea - bloat - gas from bacteria in colon
32
What major symptoms of vit A malabsorption?
nigh blindness (nyctalopia) dry scaly skin (zerosis, cutis) alopecia
33
What major symptoms of vit D/Ca malabsorption?
``` tetany = cramping of fingers/toes osteomalacia = thinning of bones ```
34
What major symptoms of Vit E malabsorption?
neuropathy | muscle weakness
35
What major symptoms of Vit K malabsorption?
ecchymoses = non raised discoloration | bruising
36
What major symptoms of Vit B12 malabsorption?
macrocytic megaloblastic anemia glossitis neuropathy; parasthesias
37
What major symptoms of folate malabsorption?
macrocytic, megaloblastic anemia | glossitis
38
What major symptoms of iron malabsorption?
microcytic anemia dyspnea fatigue glossitis
39
When does lactase deficiency present?
lactase almost always present at birth; symptoms occur in adulthood
40
What is pathogenesis of lactase deficiency?
- lactose osmotically active in lumen --> get diarrhea, gas, bloating, borborygmi [stomach gurgling]
41
What are symptoms of lactase deficiency?
diarrhea, gas, bloating, borborygmi [stomach gurgling]
42
Who gets primary lactase deficiency?
asian, african, mediterranean descent
43
What causes secondary lactase deficiency?
after loss of enterocytes from infection, resection, radiation
44
How do you diagnose lactase deficiency?
hydrogen breath test | lactose intolerance test
45
What is treatment for lactase deficiency?
avoid dairy | use exogenous lactase or lactose-free products
46
What is pathogenesis of pancreatic exocrine insufficiency?
- need to lose > 90-95% of pancreatic function to get this
47
What are some underlying diseases associated with pancreatic exocrine insufficiency?
cystic fibrosis [in kids] chronic pancreatitis pancreatic resection
48
How does pancreatic exocrine insufficiency present?
maldigestion of fat, protein, carbohydrates
49
What is treatment for pancreatic exocrine insufficiency?
oral pancreatic enzyme replaement
50
How does bile salt deficiency present?
maldigestion of fats and fat soluble vitamins
51
What are some causes of bile salt deficiency?
- severe cholestasis - distal ileal resection or disease [Crohns] - bacterial overgrowth
52
What is treatment for bile salt deficiency?
treat underlying conditions and give medium chain TGs
53
What is bacterial count in small intestine vs large instestine?
way lower in small intestine; but flourishes if stasis
54
What are some underlying cause of bacterial overgrowth?
- motility disorder: ileus, pseudo-obstruction | - anatomical disorder: blind loop, fistulae, diverticula
55
What are consequences of bacterial overgrowth?
- fat malabsorption: bacteria deconjugate bile acids | - vitamin B12 deficiency: bacteria consume vit B12
56
How do you diagnose bacterial overgrowth?
schilling test | breath tests for bacterial counts
57
What is short bowel syndrome? effect?
removal of terminal ileum due to crohns, infarct, or cancer, etc effects: B12 and bile acid malabsorption, rapid transit, cholesterol gallstones due to bile acid depletion; oxalate kidney stones
58
Why do you get oxalate kidney stones in patient with short bowel?
normally oxalate precipitated by Ca and excreted in stool; but if fat malabsorption --> long chain free fatty acids bind Ca leaving free oxalate to be absorbed by colon and excreted in kidney
59
What is D-lactic acidosis?
rare syndrome of metabolic acidosis with neurologic symptoms; due to colonic bacteria occurs in short bowel syndrome
60
What is treatment for short bowel syndrome?
enteral feeding; total parenteral nutrition; small intestine transplant
61
What is peptide YY action? from where?
slows gastric emptying | secreted from ileum
62
What is pathogenesis of celiac?
inappropriate immune response to gliadin causes malabsorption and villous atrophy primarily duodenum/jejunum not ileum
63
What do you see histologically with celiac?
- villous atrophy - crypt hyperplasia - intra-epithelial lymphocytes
64
What HLA types in celiac?
HLA-DQ2 | HLA-DQ8
65
What immune abnormalities associated with celiac?
- selective IgA deficiency - diabetes - autoantibodies to tissue transglutaminase, endomysial, and gliadin
66
What other complications with celiac?
- dermatitis herpetiformis - T cell lymphoma collagenous sprue
67
What are is tropical sprue?
acquired malabsorption syndrome in central america, caribbean, southeast asia cause unknownl responds to antibiotics
68
What is treatment for tropical sprue?
replace folate + vitamin B12 | antibiotics
69
What is distribution of tropical sprue vs celiac?
celiac = proximal small intestine | tropical sprue = throughout small intestine
70
What is clinical picture of tropical sprue?
steatorrhea following diarrhea
71
What is radiation enteritis?
loss of replicating epithelial cells --> villous atrophy but not hyperplastic crypts heals over wks to mos
72
What is abetaliporpoteinemia?
genetic; epithelial cells cannot assemble chylomicrons so lipid accumulates in cell have fat malabsorption
73
What is inheritence of abatalipoproteinemia?
autosomal recessive
74
What is treatment for abetaliporpoteinemia?
- dietary fat restriction
75
What does CBC tells you?
if microcytic anemia --> iron deficiency if macrocytic anemia --> B12 or folate deficiency
76
What does prolonged thrombin time tell you?
vit K deficiency
77
What does low albumin tell you?
problem absorbing protein
78
What does low Ca tell you?
vitamin D deficient
79
What does low cholesterol tell you?
fat malabsorption
80
What is D-Xylose test of malabsorption?
- drink D xylose [monosaccharide] | 50% absorbed --> liver --> circ --> kidney --> at least 25% secreted in urine
81
What is whipples disease?
rare systemic disease due to tropheryma whippelii causing malabsorption
82
What do you see in histology of whipple's?
macrophages with pas positive bacteria in intestinal lamina propria lymphatic obstruction "foamy macrophages"
83
What is pseudo-whipples?
seen in AIDS patients --> macrophages filled with acid fast mycobacteria
84
What is treatment for whipples?
antibiotics [sulfonamides] | watch for relapse
85
What are symptoms of whipples?
cardiac symptoms arthralgias/joint pain neurologic symptoms malabsorption symptoms

GI/Liver (36 decks)

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