Renal: Tubules Flashcards
describe the structures of the nephrons in order
bowmans capsule, proximal tubule, descending limb of loop of henle, loop of henle, asc limb of loop of henle, distal tubule, collecting duct
what does the glomerulus do
filters a large vol of plasma water and solutes
where does filtered fluid go
goes into the tubules
what are the tubules responsible for
reabsorbing parts of the filtrate back into the blood, or secreting solutes to maintain proper composition and volume
what is a normal gfr?
150L per day
what is a normal urine volume
l per day0.5 - 2
how much water gets reabsorbed by the tubules
99% of the water entering bowmans space gets reabsorbed by the tubules into the blood, letting kidney secrete waste but also conserve water
explain the path of fluid from cardiac output to the bladder
output from heart, 20% goes to the kidneys, half of that to each kidney, 100% of this goes into the AA, 20% of that filters through into bowmans, 19% of this is reabsorbed into the peritubular cap, 1% gets excreted into environment
how much sodium is filtered vs excreted in a day
22500 mmol filtered, only 150 mml excreted, therefore most of it is reabsorbed into the blood
how much sodium must get reabsorbed in a day
more than 99%
how does the fact that kidney cells are polarized help them reabsorb sodium?
they have different transport proteins on the luminal and basolateral (blood) membrane: so, each transporter only allows for transport in the direction that we want the sodium to go
where is na k atpase localized
basolateral: makes sense this lets more sodium leave, and go back into the blood
what do sodium hydrogen exchangers do
its an antiporter that moves sodium in from the lumen, and moves hydrogen out. once sodium is in the cell, since the nakatpase is maintaining a low intercell sodium conc, sodium now has no choice but to go through the basolateral transporter out into the interstit fluid
what kind of transport protein is NHE
antiporter
what is SGLT and its role
sodium co transporter. also in the lumenal membrane, moves in sodium with another molecule (glucose, phosphate, amino acids)
what is NaP and its role
another sodium co transporter found on the lumenal side of PT cell, moves in sodium and phosphate into the PT cell
what is ENac and its role
moves sodium in from high na conc lumen, water follows the sodium. its a CHANNEL not a transporter
what is the importance of the na k atpase
maintains the low intercellular sodioum conc that NaP, SGLT and NHE depend upon
describe the pathway of sodium in and out of the cell and how it may be impacted by dif transporters
sodium moves into the cell by way of the nhe (antiporter), sglt, nap (cotransporter), or enca (channel). it moves out of the cell through the basolateral nakatpase
what are ways in which nephron segments differ
transport proteins, leakiness, tight junctions, aq channels, hormone receptors
what happens in the proximal tubule
most na, cl, water, k , and bicarb reabsotion
which transporter is found in the prox tubule
nhe, enac, sglt
why is the prox tub leaky
so stuff can be reabsorbed
what happens in the thick ascending limb of the loop of henle
about 20-30% of the soium gets reabsorbed, using the na k 2cl transporter.
which tranport protein is found in the TAL? what does it do?
na k 2cl - moves sodium out of tal cells into medullary interstitium
describe the fluid conc inside the TAL
fluid leaving the tal will be very hypotonic
why does salt need to be added to medullary interstitium
it concentrates this area, which is necessary for tgetting the right urine concentration
what happens in the distal convoluted tubule
5-10 % of filtered sodium and water gets reabsorbed.
which transporter is found in the distal convoluted tubule
ncc (sodoium chloride co transporter)
contrast function of thiazide vs furosemide
thiazides inhibit nccs, furoseminde inhibits na k cls
thiazides are less potent bc they deal with less sodium reabsorption than furosemide target
what does the collecting duct do
reabsorbs 1-3% of the filtered sodium
what transport protein is in the collecting duct
enac
where are aldosterone receps found? role?
in the ccd, there increase the number of enacs, when we want to reabsorb more sodium back in (this would happen when you dont have enough sodium so you need to conserve!)
where are vasopressin receps found? role?
also in the CCD, the increase the water reabsorption
t/f: collecting duct cant make conc gradients
true
contrast filtration vs reabsorption vs secretion
filtration is filtering from blood into tubule, reabs is from tubule back into blood, secretion is from blood/interstit (after secretion) back into the tubules
what happens to glucose filtration as plasma glucose increases
flitration never saturates, higher plasma conc, higher filtration
what point does glucose stop getting reabsorbed
once it hits the transport maximum, at which point it cant get reabsorbed back into the blood
when does glucose start getting excreted
once you reach the transport maximum
should there normally be glucose in the urine
no!
how many na glucose transporters do we have? whats the dif?
na glucose symporter, which brings glucose into cell against gradient (two of these: one proximal, low affinity, high capacity and one distal: high affinity, low capacity)
glut transporter which transfers glucose out into ecf by diffusion
how does glucose and na get in vs out of the cell
glucose: in with glucose na symporter, out with glut
na; in with sympoter, out with nakatpase
