Loop Of Henle Flashcards
Where is the Loop of Henle located
Located in the medulla
The proximal and distal tubules are located in the cortex
What is the only function of the Loop of Henel
Reabsorbs 15-20% of NaCl and H20 (up to 36L)
What is the concentration of fluid entering the loop of henle from the proximal tubule
300mmoles/L = isosomatic
Why is the fluid entering the loop of henle isosmotic
Because all the solutes movements in the proximal tubule was accompanied by the equivalent H2O, so the osmotic equilibrium is maintained
What is the Loop of Henle specifically adapted for
The mechanisms of the loop of henle allows you to deal with conditions of H2O deficit and excess H2O
What is the minimum obligatory H2O loss a day
500mls
What is the importance of Obligatory H2O loss a day
Allows the excretion of metabolic waste ions (Urea, sulphate, phosphate) and other non waste ions, (Na+ and K+) that amounts to 600Osmoles to be excreted
How can you “urinate to death”
As long as your kidneys are functioning the volume needed to excrete will be excreted even if there is no H2O intake, can cause major dehydration in the body as fail to conserve water
In times of H2O deficit, what is the maximum concentration of urine produced
maximum concentration of urine that can be produced by the kidney = 1200-1400mOsmoles (4X more concentrated then plasma
In times of H2O excess, what is the maximum dilution of urine produces
Minimum urine concentration produced in a man is 30-50mosmoles
How does the urine concentration become so diluted/concentrated
Diluted - H2O excreted in excess of solum
Concentrated -Solutes excreted in excess over water
How is the Loops of Henel specifically adapted to H2O defects, H2O excess
Is able to produce urine of varying concentrations because the loops of henle juxtameduallry nephron act as counter -current multipliers creating an concentration gradient in interstium
What is the characteristic if the loop of Henle’s ascending limb
actively co-transports Na+ and CL- ions
Impermebale to H2O
What is the characteristic of the loop of Henle’s descending limb
Freely permeable to H2O
relatively impermeable to NaCl
What does characteristics of the ascending limb and descending limbs as a counter current system achieve
Achieve a concentration gradient in the medulla
How is the concentration gradient in the medulla achieved by the counter current sysyem
Na+ is actively pumped out the ascending limb,
This increases the osmolarity of the interstrium to increase, creating an established gradient of 200mOsm between interstium and ascending limb
H2O now moves out the descending limb to equate the osmolarity in the interstium, but is then reabsorbed by high osmotic pressure into the vasa recta
So the interstium remains concentrated
This process continues to happen and the fluid in the tubule is then progressively concentrated as it moved down descending limb and progressively diluted as it moved up the ascending limb
and as more concentrated fluid is delivered to the ascending limb the interstium becomes more concentrated
showing the counter- current flow multiplies the gradient moving down the interstium at increasing concentration, with this continual horizontal level of 200mOsmol shown between ascending limb and interstium
What is the vertical gradient in the interstitum
300 –> 1200mOsmol
What does the 200mosmol gradient at each step of the interstium and ascending limb represent
The pumping ability of the active NaCl pumps
Why is the active transport of NaCl from the ascending limb the key step in the loop of henel
As without couldn’t set up concentration gradient in the interstium, so the water wouldnt move out and the kidneys would only produce isotonic water
Therefore couldn’t deal with conditions fo H2O deficit or H2O excess
What is the concentration of the fluid at the end of the loop of henel
100mOsmoles
The fluid enters the loop of henel 300mOsmols and leaves 100mOsmols, what has happened to the remainder concentration
Th fluid entering the distal tubule is more dilute then the plasma at 100mOsmoles
as 200mosmol is left behind in the interstium that sets up the gradient
What is the overall function of the loop of henle
Concentrating the medullary interstitial
delivering hypotonic fluid to distal tubule
Removes 15-20% of initial filtrate
What is the vasa recta
A portion of the peritubular capillaries system which enters the medulla
How does the vasa recta participate in the counter current mechanism,
by acting as counter current exchangers
How does the vasa recta act as counter current exchanger
As blood enters descending limb of vasa recta H2O diffuses out and Na+ diffuses in to equilibrate the increasing osmolarity of the medullary interstitial gradient
The Water diffuses out of the descending limb vasa recta and into the ascending limb of vasa recta = hypotonic blood
Hypotonic Blood ascends through the ascending vasa recta, water diffuses in and NaCl diffuses out to equilibrate the descending osmolarity of the medullary interstitial gradient
the solutes diffuse out of ascending limb of vasa recta and into the descending of vasa recta
solutes seem to re-circulate in medulla and water bypass which maintain hypertonicity
Overall removing the volume from the interstium and maintaining the equilibrium gradient
What is the functions of the vasa recta
Remove volume (H2O) from interstium
Provide O2 for the medulla
Special arrangement of hair pin loop, prevent medullary capillaries carry NaCl away, so does not disturb the interstial gradient
Why is the flow rate through the vasa recta very low
so that there is plenty of time for the equilibration to occur with the interstium further ensuring that the medullary gradient is not disturbed
