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31 Cards in this Set

  • Front
  • Back
villi are composed of
absorptive cells (enterocytes)
secretion of mucous by goblet cells is stimulated by
ACh
stem cells are located in the
base of the crypt
undifferentiated cells of the crypt secrete
NaCl (and water follows)
jejunal enterocytes absorb

ileal enterocytes absorb
NaHCO3

NaCl
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
solutes and nutrients absorbed by the jejunum (5)
monosaccharides

proteins

fats

water-solube vitamins

fat-soluble vitamins
solutes and nutrients absorbed by the distal ileum (2)
vitamin B12 (complexed with intrinsic factor)

bile salts
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
jejunal enterocyte absorbs (4)
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)
ways in which Na enters the apical membrane of the jejunal enterocyte (2)
Na/glucose or Na/amino acid co-transporter

Na/H exchanger
Na leaves the jejunal enterocyte via
Na/K ATPase pump (located at the basolateral membrane)
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)
ileal enterocyte absorbs (1)
NaCl
way in which NaCl enters the ileal enterocyte
Na/H exchanger (apical membrane)

HCO3/Cl exchanger (apical membrane)
NaCl absorption by the ileum is inhibited by
increased levels of cAMP
cAMP production is stimulated by (4)
ACh

VIP (when vipomas are present)

E.coli

Vibriocholera toxin
inhibition of NaCl absorption leads to
diarrhea (water follows NaCl into ileal lumen)
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)
conductane of the CFTR Cl channel is increased by
increasing levels of cAMP
conductane of K channel is increased by
increased intracellular Ca (due to ACh)
endogenous secretory stimuli (8)
ACh
histamine
CCK
secretin
gastrin
GIP
motilin
VIP
exogenous secretory stimuli (6)
Vibriocholera toxin
E.coli
Salmonella
bile salts
fatty acids
laxatives
endogenous absorptive stimuli (5)
alpha adrenergic agonists (Epi, NE)
dopamine
enkephalins
somatostatin
glucocorticoids
exogenous absorptive stimuli (1)
nutrients (glucose, amino acids)
transferrin carries Fe++ to (2)
bone marrow

liver
jejunal enterocytes absorb Ca via
Ca+CaBP ATPase
Ca ATPase is activated by
calmodulin
calcium binding protein (CABP) synthesis in the intestine is stimulated by
1,25(OH)2D3 (vitamin D3)
vitamin D synthesis pathway
7-dehydrocholesterol (skin) + UV light --> vitamin D3/cholecalciferol (liver) --> 25(OH)D3 (kidney) --> 1,25-dihydroxycholecalciferol (1,25(OH)2D3)
increased plasma [Ca] results in (4)
decreased secretion of PTH

inhibition of 1,25(OH)2D3 formation

decreased synthesis of CABP

decreased absorption of Ca