Case 3 - H2O absorption Flashcards
how does H20 move on the osmotic gradient
moves down the osmotic gradient
what is the osmotic gradient created by
mainly by absorption of nutrients
how much H20 is absorbed in total per day
8.4 litres
how much is absorbed by the small intestine
6.5 litres
how much is absorbed by the colon
1.9 litres
what is the route for H20
via junctional complexes between cells
via SGLT1 and a.a transporters
what is absorption not by of H20
aquaporins
how much water does saliva secrete a day
1.5 litres
how much water is in gastric secretion a day
2 lites per day
how much water is in pancreatic secretion a day
1.5 litres
how much water is in bile secretion a day
0.5 lires
how much water is in the small intestine secretion a day
1 litre a day
in total, how much is the inflow a day
8.5 litres
what is the total outflow a day
8.4 litres
what is the net loss in faeces
100mls
where are the Na/glucose and Na/amino acid cotransporters found
found in jejunum and ileum
where is the Na-H exchanger found
the duodenum and jejunum
where are the parallel Na-H and Cl-HCO3 exchangers found
the ileum and proximal colon
where is the epithelial Na+ channel found
distal colon
what happens to K+ in the small intestine
paracellular diffusion in ileum
what happens to K+ in the large intestine
predominantly secretion
what is the normal K+ concentration in faeces
90mM
HCO3 absorption in the SI or LI
there is no active absorption in these places
what does severe or chronic diarrhoea lead to
hypokalaemia and metabolic acidosis
what does increased osmotic load in colon lead to
increased ldiid in faeces
what does lack of enzymes or transporters lead to
congenital (neonate) = ‘watery’
Glucose-galactose malabsorption (SGLT1)
Lactase deficiency
what infections can lead to damage to the mucosa
Bacteria (shigella and campylobacter) lead to destruction of intestinal wall which decreases surface area and leads to blood in faeces (dysentery)
Bacteria (salmonella) leads to inflammation
Protozoa (giardia, entamoeba)
what are toxins produced by and what do they do
they are produced by bacteria which normally hi jacks normal cellular processes
what cells normally secrete h20
intestinal cells and about 1 litre a day
what does secretion exceed a day in cholera
secretion exceeds 20 litres per day
what may toxins also do
may also inhibit Na+ absorption BUT not SGLT1
what Is this the basis of
oral rehydration therapy
