Loop of henle Flashcards
Site of major reabsorption of NaCl, water
Proximal tubule
What protein gets filtered out and what happens to it
Albumin
Completely reabsorbed by a Tm(subscript) carrier mechanism in the proximal tubule
Why are drugs and pollutants hard to get rid of
Many are non-polar so very lipid soluble
So the removal of water in the proximal tubule establishes concentration gradients for their reabsorption.
How do we get rid of drugs and pollutants
The liver metabolizes them to polar compounds thus reducing their permeability and facilitating their excretion.
Where are the proximal and distal tubules of the nephrons
In the cortex
What is responsible for water balance
Loops of henle in juxtamedullary nephrons
What do loops of henle in juxtamedullary nephrons allow us to do
Produce concentrated urine in times of water deficit
Minimum obligatory loss of water in urine per day
500ml
What do loops of henle in juxtamedullary nephrons act as
counter-current multipliers.
What does counter-current mean
Fluid flows down descending limb and up ascending limb
What makes the loops counter-current multipliers
The ascending limb, which is impermeable to water, actively co-transports Na+ and Cl- ions out of the tubule into the interstitium.
The descending limb is freely permeable to H2O but relatively impermeable to NaCl.
What value is isosmotic with plasma
300mOsm/l
What happens to NaCl in the ascending limb and when does it stop
It is pumped out until a gradient of 200mOsm/l is achieved
What happens to the osmolarity of the ascending limb and to the interstitium
Ascending limb = decreases
Interstitium = increases
What happens to the descending limb and why
Water moves into interstitium
Because the descending limb is exposed to a greater osmolarity so water moves to equate the osmolarity
What happens to the water after it leaves the descending limb
It moves into the vasa recta
What is the change in the vertical gradient of the interstitium
300-1200 mOsm/l
What is the key step in creating the concentration gradient and what drug can impair it
The active transport of NaCl
Furosemide (loop diuretic)
How does fluid in the distal tubule compare to plasma concentration wise
It is more dilute than plasma
Fluid enters the counter-current multipliers at what concentration and leaves at what concentration
Enters = 300 mOsm/l
Leaves at 100mOsm/l
What is the juxtamedullary nephron all about
concentrating the medullary interstitium
And delivering hypotonic fluid to the distal tubule.
Three functions of the vasa recta
Provide O2 for medulla
In providing O2 MUST NOT DISTURB GRADIENT
Removes volume from the interstitium
What’s the flow rate like in the vasa recta and why
Very low
Allows plenty of time equilibration to occur in the interstitium
Site of water regulation and by what hormone is it controlled by
The collecting Duct
ADH (controls permeability of collecting duct)
