Loop of Henle

Question 1

If albumin gets filtered what happens to it?

Answer 1

completely reabsorbed by Tm mechanism in proximal tubule

Question 2

What does the liver do to drugs and pollutants to prevent reabsorption?

Answer 2

metabolises them from non polar to polar substances

Question 3

Why is the fluid leaving the proximal tubule isosmotic with plasma?

Answer 3

all solute movements are accompanied by equal water movement - osmotic equilibrium maintained

Question 4

What part of the kidney are the proximal and distal tubules found?

Answer 4

cortex

Question 5

What is a juxtamedullary nephron and what do these contain?

Answer 5

deep to the medulla

loops of henle

Question 6

What is the main function of the loops of henle

Answer 6

Allow kidney to produce concentrated urine in time of water deficit which is key to survival without water

Question 7

What is the max urine concentration?

Answer 7

1200-1400mosmoles/l

Question 8

What is the minimum obligatory water loss per day? Why?

Answer 8

500mls

urea, sulphate, waste and non waste products must be excreted to 600mosmoles

Question 9

Min concentration of urine

Answer 9

30-50mOsmoles/l

Question 10

Why can the kidneys produce urine of various concentrations (what does the loop of henle act as?)

Answer 10

counter-current multiplier

Question 11

What does the ascending limb transport?

Answer 11

actively transport NaCl and Cl out of lumen and into interstitium
impermeable to water

Question 12

What does the descending limb allow movement of?

Answer 12

water freely

impermeable to NaCl

Question 13

What happens in the ascending limb to start of the process of the loop of henle?

Answer 13

NaCl pumped out into interstitium which drops the concentration of the lumen but interstitium increases
occurs until limiting gradient

Question 14

What is the limiting gradient of NaCl transport from ascending limb?

Answer 14

200mosmoles/l

Question 15

Due to the ascending limb pumping out NaCl what happens to descending limb?

Answer 15

exposed to greater osmolarity in interstitium and H20 moves out of descending limb to equilibrate

Question 16

What happens to the water which moves out of the descending limb?

Answer 16

high oncotic pressure and tissue P - reabsorbed into the vasa recta

Question 17

Is the fluid in loops of henle progressively concentrated or diluted in the ascending and descending limb?

Answer 17

concentrated - descending

diluted - ascending

Question 18

What happens to the interstitium concentration following the ascending and descending limb?

Answer 18

becomes more concentrated due to addition of salt from ascending limb

Question 19

What is the maximum difference in concentration gradient at any horizontal level between ascending limb and interstitium?

Answer 19

200mOsmol

Question 20

What does the vertical gradient in interstitium range from?

Answer 20

300-1200mOsmol

Question 21

If furesmide (loop diuretic) is used that blocks active transport of NaCl from ascending limb what happens to urine?

Answer 21

isotonic

Question 22

How does the ascending limb re-dilute the fluid in the lumen?

Answer 22

removing NaCl

not by removing water

Question 23

Is fluid entering distal tubule more or less concentrated than plasma?

Answer 23

less –> more dilute (hypotonic)

Question 24

What is the overwhelming significance of the counter-current multiplier achieved?

Answer 24

increasingly concentrated gradient in interstitium

Question 25

What concentration does fluid enter and leave loops of henle?

Answer 25

300mosmol

100mosmol

Question 26

What are the vasa recta?

Answer 26

special arrangement of peritubular capillaries allows them to do countercurrent exchanges

Question 27

Why do vasa recta not interfere with interstitial gradient?

Answer 27

arranged in hairpin loops

slow flow

Question 28

What are vasa recta permeable to and significance of this

Answer 28

water and solutes

equilibrate with medullary interstitial gradient

Question 29

3 main functions of vasa recta

Answer 29

supply oxygen for medulla
in providing oxygen must not disturb gradient
removes volume from interstitium

Question 30

What is the flow rate in vasa recta and significance of this

Answer 30

very slow - plenty time for equilibration with interstitium

ensures medullary gradient not disturbed

Question 31

Where is the site of water regulation?

Answer 31

collecting duct

Question 32

What is the permeability of collecting duct under control of?

Answer 32

ADH