Renal Phys ML: 6 Flashcards
What are the two routes water can take to be reabsorbed?
paracellular and transcellular
What is the main water route in proximal tubule
paracellular
What is the main water route in the collecting ducts
transcellular
Which route requires aquaporins
transecullar because it has to go through the cell
How are aquaporins regulated
by ADH
Diuresis
loss of fluid via urine
What secretes adh
posterior pituitary
What does ADH do
secretes more aquaporins and it reduces amount of water in urine by increasing reabsorption
Where is AQP2 located
on the apical membrane
Where are AGP3 and 4 located
on the basolateral membrane
Proximal Tubule:
Na+ reabsorption is high and constant (non regulated)
H20 permeability is high and constant (not regulated)
Reabsorption of Na+ and H20 are coupled
Descending Loop of Henle
H20 reabsorption is high and constant (not regulated); No Na+ reabsorption
Ascending Loop of Henle
Na+ reabsorption is high and constant ( not regulated); No H20 reabsorption
Collecting duct
Na+ reabsorption is variable, is regulated by aldosterone and is NOT directly couple to water reabsorption
Water permeability is variable is regulated by ADH and requires the renal medullary gradient
What creates and maintains the renal medullary gradient?
juxtamedullary nephrons with long loops of henle
What relies on the gradient?
all nephrons flow through it and rely on it for water reabsorption
As you go deeper into the medulla what happens
osmolarity increases
What two mechanisms create the gradient
countercurrent multiplier system
urea recycling
What is the mechanism that maintains this gradient
vasa recta circualtion
What is the highest possible concentration at the bottom of the medulla
1400 mOsm
How does the vasa recta maintain the gradient
it returns reabsorbed water and solutes to the circulation, without washing out the gradient
What is happening in the vasa recta circulation
solutes keep getting exchanged between ascending and descending vasa recta and are trapped in the medulla
