renal 5 - water Flashcards
what is insenstible water loss
when you cant see the water you lose, like skin and airways
what are aquaporins
water channels that allow the diffusion of water
where is most of water reabsorbed
in the proximal tubules
where are aquaporins always open
in the proximal tubules
what does water reabsorption depend on?
Na+ reabsorption
the osmotic gradient acts as the driving force
what is another name for vasopressin
antidiuretic hormone
what is another name for antidiuretic hormone
vasopressin
how are cortical and medullary collecting duct controlled
physiologically by hormones
what do ADH/vasopressin regulate
specific aquaporins
where do ADH/vasopressin regulate
in the cells of the collecting duct
what is the main role of ADH/vasopressin
regulate blood pressure and try to prevent water loss
are there aquaporins in the distal tubule
no
are there aquaporins in the proximal tubule
yes, the most
do hormones regulate water permeability in the proximal tubule
no
do hormones regulate water permeability in the distal tubule
no
do hormones regulate water permeability in the loop of henle
no
do hormones regulate water permeability in the large distal tube and collecting duct
yes
how is water reabsorbed in the proximal tubule
passively
AQP-1
how is water reabsorbed in the loop of henle
only in the descending limb
passively
AQP-1
how is water reabsorbed in the distal tubule
no water reabsorption
how is water reabsorbed in the large distal tubule and collecting duct
passive (AQP-2,3,4)
vasopression/ADH works on AQP-2
which aquaporin does vasopressin work on
AQP-2
does the descending limb of the loop of henle reabsorb water
yes
does the ascending limb of the loop of henle reabsorb water
no
what is osmolarity of fluid inside the tube between prox and loop of henle
very close to plasma
how does water flow in the proximal tubule
follows sodium, bulk flow
how does water reabsorb in the descending loop of henle
passively through AQP-1
how does water reabsorb in the thin ascending loop of henle
no water reabsorption
how does sodium reabsorb in the thick ascending loop of henle
NKCC allows Na K and Cl in
then Na and K exchange out into peritubular capillaries
how is urine concentrated
juxtamedullary nephrons use loop of henle to concentrate the urine
made by the countercurrent
where is Na reabsorbed in the loop of henle
in the ascending limb
what is the most critical characteristic of the loop of henle that allows for salt reabsorption
the different transport capabilities on each side of the tubules (H2O descending, salt ascending)
how is NaCl transported and where
actively in the ascending limb
what is the osmolarity of the descending limb
300mOsm/L
what is the gradient difference between the interstitial space and ascending limb
200 mOsm
what kind of osmolarity do you want the adrenal medulla to be
hyperosmolar
what is the counter current multiplier
multiplication of the gradient down the length of the loop of henle, always a 200mOsm difference
would beavers have a longer or shorter loop of henle
shorter because they dont have a big need to conserve water
would camels have a longer or shorter loop of henle
longer because they have a big need to conserve water
what is the osmolatiry of the distal convoluted tubule (start)
100mOsm/L
very dilute
what does ADH do to the cortical collecting duct
it causes the tubule to become isoosmotic with the interstitial space (300mOsm/L)
what happens in the medullary collecting duct
water leaves as it descends to maintain the same osmolarity of the interstitial space
what does the concentration in the medullary collecting duct cause
highly concentrated urine by the end of it bc water always leaving
can the vasa recta absorb water
yes
can the vasa recta absorb salt
yes
which direction does the vasa recta flow
opposite to the flow of urine
why do we need the counter current exchange
so that the gradient is not washed away
how does vasa recta help the counter current exchange
maintains na and cl gradient, absorbs water from descending loop
how does the vasa recta create the medullary hyperosmolarity
it doesnt
but it prevents it from being washed out
maintains it, not create
what is blood flow like in the medulla and how does this help with counter current
low and sluggish blood flow which prevents solute loss
is the vasa recta permeable to urea
yes
where does water enter the vasa recta
ascending limb (opposite direction of flow as the loop of henle)
where does Na Cl enter the vasa recta
descending limb (opposite direction of flow as the loop of henle)
where is urea filtered/secreted/reabsorbed in proximal
50%reabsorbed in proximal tubule
where does ADH regulate water reabsorption
in the collecting ducts
what are the critical features that initiate the gradient
reabsorption of NaCl in ascending limb and impermeability to water in ascending limb
where is urea filtered/secreted/reabsorbed in loop of henle
50%secreted back into loop of henle from the inner medulla collecting duct
where is urea filtered/secreted/reabsorbed in collecting duct
30%reabsorbed into interstitial space
55% reabsorbed (to be secreted back into loop of henle and 5% into vasa recta)
what % of urea moves into the vasa recta
5%
what % of urea is excreted
15%
what % of urea is filtered
100%
how does urea help contribute to the concentration gradient
it is trapped in the medulla
formula for amount of urea excreted
filtered+secreted-reabsorbed
