fluid absorption and cholera Flashcards
how many litres of water do we get a day from food and drink
2L
how much water is absorbed in the small intestine compared to the large intestine
400ml per day in the large intestine
8500 ml per day in the small intestine
how much water do we loose a day in excretion
about 100ml
what follows ion uptake in the intestines
water via osmosis following the gradient
how do ions pass into the interstitium in the duodenum and the jejunum
paracellular routes
how do ions pass through the ileum
transcellularly
what two ways are ions absorbed in the ileum of the small intestine
na cl symporter from the lumen into the cell
co transporters, hco3 with cl
na with H
describe the mechanism of a symporter
symporter on apical membrane transfers cl and na into the cell
K/Na active transport on basolateral surface - k into the cell and na out into ECF
k leaks out cell into ECF and so does Cl
describe the antitrasnporter system of the colon and the ileum
in the cell: water and co2 make HCO3 and H+
apical membrane: HCO3 out and Cl in
Na in and H out into lumen
basolateral membrane: na into ecf and K into cell via active transport
k leaks out
cl leaks out
what transport system occurs only in the colon
Na passively in on apical
k leaks out on apical
na out k in active transport on basolateral
k leak out on basolateral
why is ORS good in cholera
SGLT absorbs glucose and na quickly so water travels with them out the lumen
in what forms do calcium travel in the blood
bound to proteins or as inorganic ca2+w
where does calcium absorption normally occur
in the duodenum and jejunum
what increases the amount of ca absorption
vitamin D3 which gets transformed in the liver then the kidney to calcitrol which causing increase in number of ca binding proteins available on the lumen of the cells
also parathyroid increases metabolism of vitamins d3 to calcitrol to increase ca absorption
describe the process of ca absorption
ca binds to ca binding protein on the apical membrane - ca then either sequesters in the er or bind to proteins in the cell
ca moves out the basolateral side via ca atpase or by na ca antitransporter
where do we get absorbed iron from
meat and pants in diet and absorption of heme
what must happen to iron to be absorbed
reduced from iron 3 to iron 2 as iron 3 is insoluble
what reduces iron 3 to iron 2
low ph in the stomach favours the reduction
reductase enzyme present on the apical surface
what are the two ways iron is absorbed
via endocytosis of heme - heme is then broken down by heme oxygenase - this produce biliverdin which is removed by bile salts - also produces CO and fe 3+ which is reduces in the cell to fe2+
fe 2+ is absorbed with H+ co transporter into the cell
how do iron leave the basolateral membrane
fe2+ binds to mobilferrin which binds to the surface to release fe2+ across where it binds to plasma transferrin
what happens if we have to high a conc of iron in our system
causes production of ROS and therefore dan damage
why do we need to eat vitamins
they are not made in the body
what are the two types of vitamins
fat soluble and water soluble
what are the fat soluble vitamins
A, D, E, K - follow absorption with micelles and chylomicrons
what are the water soluble vitamins
vit b 12
1, 2, 6
folic acid
vit c
how is vitamins b absorbed
in food b12 is bound to proteins
in the stomach the proteins are broken down and b12 binds to r protein
it then travels to the small intestine where proteases break down R protein and it binds to intrinsic factor
endocytosis occurs in the small intestine
it is carried in the plasma by transcobalamin 2
