Lecture 2 Renal Flashcards
(52 cards)
two modes of transport across tubular epithelial cells in a nephron are
transcellular and paracellular, what are these two?
transcellular- transport THROUGH tubular cells
paracellular- transport BETWEEN tubular cells
Osmosis results in solvent drag, what is solvent drag
solvent drag results from solutes being carried by water in paracellular transport
how can osmosis (rate of water diffusion) be regulated
by aquaporins
3 types of transported proteins and their definition
uniporter- 1 molecule moves
symporter (cotransport)- 2 molecules moved same direction
antiporter - 2 molecules moved in opposite directions (against concentration gradient)
endocytosis is what?
exocytosis is what?
endocytosis is transport into a cell
exocytosis is transport out of cell
BOTH BY Vesicles!
where is the ONLY spot in the nephron where Na is NOT reabsorbed?
Na NOT reabsorbed in the Thin Descending Limb of LoH
Na reabsorption %s in PCT? Thin ascending limb? thick ascending limb? DCT? Collecting duct
PCT-65% Thin AL: 7% Thick AL: 20% DCT: 5% Collecting duct: 2-3% SO KIDNEYS Excrete VERY LITTLE Na
The PCT reabsorbs several things
name them and how they are reabsorbed
Glucose, AAs= Na symporters
Active transport on basal side keeps Intracellular Na low
Water and solutes via paracellular transport
Na reabsorption in conjunction with Bicarbonate using Na/H antiporter
How is Na reabsorption done in PCT?
in conjunction with bicarbonate reabsorption using Na/ H antiporter
BUT reabsorption not direct H is secreted and HCO3 is absorbed
what rxn facilitates the absorption of bicarbonate
Carbonic Anhydrase produces H and HCO3 in tubule cells allowing HCO3 to be moved to blood and H is transported back into tubule so it recombines with filtered HCO3
LEADING To NET EFFECT of bicarbonate REABSORPTION
End of PCT what happens
2/3 of Na, Cl, and water reabsorbed and small proteins
K and divalent cations reabsorbed by solvent drag
AAs and glucose reabsorbed
Bicarbonate reabsorbed due to Na/ H antiporter
secretion of organic ions (IE organic drugs)
how much of filtered NaCl and water are reabsorbed in the LoH
NaCl= 25% reabsorbed Water= 15% reabsorbed
what is the permeability of salt and water in the the THIN Descending Limb
Thin DL= impermeable to SALT, Permeable to water
Bc it has aquaporins
permeability of salt and water in THIN ASCENDING LIMB
THIN ASCENDING LIMB
PERMEABLE to SALT (passive reabsorption)
IMpermeable to water
the ascending THICK limb has what to dilute fluid
Na K 2CL symporter in apical membrane
NaK ATPase in basolateral membrane
Paracellular transport of monovalent and divalents NOT DUE to Solvent Drag in THICK ascending limb
TRUE or FALSE
why?
TRUE! due to voltage gradient!!
Tubular fluid becomes positive due to Cl reabsorption so cations diffuse along an electrical gradient
fluid leaving LoH is hyposmotic then how do we get the formation of hyperosmotic urine?
renal countercurrent mechanism establishing an osmotic gradient allowing water to be reabsorbed in the collecting ducts by the actions of ADH (vasopressin)
In the absence of ADH what happens
no water reabsorption in collecting ducts so urine stays hyposmotic
how does the osmolarity of the blood leaving the kidneys to veins stay the same (normal)
bc peritubular capillaries are permeable to NaCL and water so plasma osmolarity changes as the capillaries follow the loop but returns to normal by the end
how does the DCT reabsorb about 8% of the filtered NaCl ?
VIA a Na Cy symporter in the apical membrane and a Na K ATPase in the basolateral membrane
describe reabsorption of K, H , and water in DCT
variable!
What 2 types of cells are in the latter DCT and the collecting duct?
Principal cells and Intercalated cells
what are principal cells in the late DCT and collecting duct for
Principal cells have ENaC channels that reabsorb Na and secrete K
Na reabsorption drives paracellular Cl absorption
K secreted due to Na K ATPase activity in basal membrane
What are intercalated cells involved in
Intercalated cells involved in acid base balance and help REABSORB K!
