Lecture 5 Loop of Henle

Question 1

Fluid that leaves the proximal tubule is____

Answer 1

Isosmotic (plasma 300 mOmoles/l. because all the solute movements are accompanied by equivalent H2O movements, so that osmotic equilibrium is maintained

Question 2

What is the maximum concentration of urine that can be produced by the human kidney

Answer 2

1200-1400 mOsmoles/l

Question 3

Excretion of waste products required a minimum obligatory loss of what

Answer 3

H20 loss of 500mls

Question 4

Describe the permeability of the descending loop

Answer 4

Freely permeable to H20 but impermeable to NaCl

Question 5

Describe the permeability of the ascending loop

Answer 5

Freely permeable to NaCl but impermeable to H2O

Question 6

Water absorption occurs in the

Answer 6

Descending loop

Question 7

NaCl reabsorption occurs in the

Answer 7

Ascending loop

Question 8

Describe the counter current multiplier

Answer 8

1. Loop or Henle filled with stationary isosmotic fluid
2. Active removal of NaCL from ascending limb, increases osmolarity in interstitial and decreases osmalrity in tubule
3. This causes H2O t leave the descending limb and enter the interstitium where is it reabsorbed by the high oncotic pressure into the vasa recta
4. Fluid becomes progressively concentrated as it moves down the descending and more diluted as it moves up the ascending

Question 9

At horizontal levels what is the mOsmol gradient between the ascending limb and interstitium

Answer 9

200 mOsmol

Question 10

What is the purpose of the counter-current multiplier

Answer 10

Delivers hypotonic fluid to the distal tubeConcentrates medullary interstitium facilitates the passive movement of water out of the collecting ducts = concentrated urine

Question 11

What drives fluid from the interstitium into the vasa recta

Answer 11

High oncotic pressure and high hydrostatic pressure due to tight renal capsule

Question 12

What is the function of the vasa recta

Answer 12

Provide O2 for medulla

Remove volume from the interstitium (36l/day)