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31 Cards in this Set
- Front
- Back
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villi are composed of
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absorptive cells (enterocytes)
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secretion of mucous by goblet cells is stimulated by
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ACh
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stem cells are located in the
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base of the crypt
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undifferentiated cells of the crypt secrete
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NaCl (and water follows)
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jejunal enterocytes absorb
ileal enterocytes absorb |
NaHCO3
NaCl |
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Transcellular vs. Paracellular Pathway:
*passive diffusion *bulk flow *electrodiffusion *carrier-mediated transport *active transport |
*passive diffusion: both (diffusion into the lumen is mostly via paracellular pathway)
*bulk flow: paracellular *electrodiffusion: paracellular *carrier-mediated transport: transcellular *active transport: transcellular |
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solutes and nutrients absorbed by the jejunum (5)
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monosaccharides
proteins fats water-solube vitamins fat-soluble vitamins |
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solutes and nutrients absorbed by the distal ileum (2)
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vitamin B12 (complexed with intrinsic factor)
bile salts |
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ability to adapt
ileum can take over for jejunm? jejunum can take over for ileum? |
ileum can take over for jejunm? Yes
jejunum can take over for ileum? No |
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jejunal enterocyte absorbs (4)
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Na (Na/H exchanger or Na/glucose co-transporter)
HCO3 (HCO3/Cl exchanger) glucose (Na/glucose co-transporter) amino acids (Na/amino acid co-transporter) |
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ways in which Na enters the apical membrane of the jejunal enterocyte (2)
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Na/glucose or Na/amino acid co-transporter
Na/H exchanger |
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Na leaves the jejunal enterocyte via
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Na/K ATPase pump (located at the basolateral membrane)
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membrane potential on the serosal side of the jejunal enterocyte:
*before a meal *after a meal |
*before a meal: +5 mV
*after a meal: +15 mV (due to electrogenicity of Na/K ATPase pump) |
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ileal enterocyte absorbs (1)
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NaCl
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way in which NaCl enters the ileal enterocyte
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Na/H exchanger (apical membrane)
HCO3/Cl exchanger (apical membrane) |
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NaCl absorption by the ileum is inhibited by
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increased levels of cAMP
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cAMP production is stimulated by (4)
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ACh
VIP (when vipomas are present) E.coli Vibriocholera toxin |
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inhibition of NaCl absorption leads to
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diarrhea (water follows NaCl into ileal lumen)
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NaCl enters the lumen of the jejunum, ileum, and colon via:
*cell type *transporters (2) |
crypt cells
CFTR Cl channel (apical membrane) Na/K/2Cl sympoter (basolateral membrane) |
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conductane of the CFTR Cl channel is increased by
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increasing levels of cAMP
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conductane of K channel is increased by
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increased intracellular Ca (due to ACh)
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endogenous secretory stimuli (8)
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ACh
histamine CCK secretin gastrin GIP motilin VIP |
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exogenous secretory stimuli (6)
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Vibriocholera toxin
E.coli Salmonella bile salts fatty acids laxatives |
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endogenous absorptive stimuli (5)
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alpha adrenergic agonists (Epi, NE)
dopamine enkephalins somatostatin glucocorticoids |
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exogenous absorptive stimuli (1)
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nutrients (glucose, amino acids)
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transferrin carries Fe++ to (2)
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bone marrow
liver |
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jejunal enterocytes absorb Ca via
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Ca+CaBP ATPase
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Ca ATPase is activated by
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calmodulin
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calcium binding protein (CABP) synthesis in the intestine is stimulated by
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1,25(OH)2D3 (vitamin D3)
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vitamin D synthesis pathway
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7-dehydrocholesterol (skin) + UV light --> vitamin D3/cholecalciferol (liver) --> 25(OH)D3 (kidney) --> 1,25-dihydroxycholecalciferol (1,25(OH)2D3)
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increased plasma [Ca] results in (4)
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decreased secretion of PTH
inhibition of 1,25(OH)2D3 formation decreased synthesis of CABP decreased absorption of Ca |
