tubular function Flashcards
(17 cards)
how much is reabsorbed in the renal corpuscle?
99%
describe sodium handling
na transport facilitates reabsorption of nutrients, water and ions
65% reabsorbed in PCT
25% reabsorbed in ascending loop of henle
8% in DCT- depending on rn
98% reabsorbed
what is passive diffusion?
movement of molecules from high to low concentration until equilibrium is reached
in what direction is the concentration gradient between the PCT and peritubular capillaries
high -> low
tubules lumen -> tubule wall -> interstitial space -> peritubular capillary
how does water move?
aquaporins
how do glucose and aa move across the apical surface?
sodium co-transporters
describe how the proximal tubule reabsorbs 2/3 of filtrate
Na+K+ pump on basolateral membrane facilitates 65% reabsorption, everything else follows Na+ eg. water follows by osmosis, chroride follows electrical gradient
what does Na+ active transport facilitate?
100% nutrient reabsorption 65% water reabsorption 65% neg ions follow electrical gradient no effect on waste removal remaining filtrate continues through loop of henle
what are the 3 parts of the loop of henle?
thin descending limb
thin ascending limb
thick ascending limb
what are the loop rules?
thin descending contains aquaporins-freely permeable to water
both ascending do not contain aquaporins-impermeable to water
thick ascending - site of active sodium reabsorption
how does sodium reabsorption occur?
via NKCC2 on apical membrane
what is countercurrent multiplication?
mechanism for reabsorbing water from tubular fluid
energy used to create osmotic gradient-produce concentrated urine
why does the vasa recta employ counter current exchange?
to maintain concentration gradient of the medulla
what is the function of the distal convoluted tubule?
fine-tuning - site of fluid volume and electrolyte regulation
Na & water reabsorption hormonally reg.
ADH- increases reabsorption
aldosterone- increases Na+ reabsorption
AND- promotes Na+ secretion
how does ADH affect urine production?
acts on distal and collecting tubules
insertion of aquaporins allows water to be reabsorbed from the filtrate
small vol. cons. urine prod.
how does aldosterone affect urine production?
acts on distal and collecting tubules
upregulates activity and insertion of Na+K+ pumps and channels
small vol. conc. unrine prod.
how does ANH affect urine production?
acts on distal and collecting tubules
inhibits action of ADH and aldosterone
large vol. dilute urine prod.
