Loop Of Henle

Question 1

Where is the Loop of Henle located

Answer 1

Located in the medulla

The proximal and distal tubules are located in the cortex

Question 2

What is the only function of the Loop of Henel

Answer 2

Reabsorbs 15-20% of NaCl and H20 (up to 36L)

Question 3

What is the concentration of fluid entering the loop of henle from the proximal tubule

Answer 3

300mmoles/L = isosomatic

Question 4

Why is the fluid entering the loop of henle isosmotic

Answer 4

Because all the solutes movements in the proximal tubule was accompanied by the equivalent H2O, so the osmotic equilibrium is maintained

Question 5

What is the Loop of Henle specifically adapted for

Answer 5

The mechanisms of the loop of henle allows you to deal with conditions of H2O deficit and excess H2O

Question 6

What is the minimum obligatory H2O loss a day

Answer 6

500mls

Question 7

What is the importance of Obligatory H2O loss a day

Answer 7

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

Question 8

How can you “urinate to death”

Answer 8

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

Question 9

In times of H2O deficit, what is the maximum concentration of urine produced

Answer 9

maximum concentration of urine that can be produced by the kidney = 1200-1400mOsmoles (4X more concentrated then plasma

Question 10

In times of H2O excess, what is the maximum dilution of urine produces

Answer 10

Minimum urine concentration produced in a man is 30-50mosmoles

Question 11

How does the urine concentration become so diluted/concentrated

Answer 11

Diluted - H2O excreted in excess of solum

Concentrated -Solutes excreted in excess over water

Question 12

How is the Loops of Henel specifically adapted to H2O defects, H2O excess

Answer 12

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

Question 13

What is the characteristic if the loop of Henle’s ascending limb

Answer 13

actively co-transports Na+ and CL- ions

Impermebale to H2O

Question 14

What is the characteristic of the loop of Henle’s descending limb

Answer 14

Freely permeable to H2O

relatively impermeable to NaCl

Question 15

What does characteristics of the ascending limb and descending limbs as a counter current system achieve

Answer 15

Achieve a concentration gradient in the medulla

Question 16

How is the concentration gradient in the medulla achieved by the counter current sysyem

Answer 16

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

Question 17

What is the vertical gradient in the interstitum

Answer 17

300 –> 1200mOsmol

Question 18

What does the 200mosmol gradient at each step of the interstium and ascending limb represent

Answer 18

The pumping ability of the active NaCl pumps

Question 19

Why is the active transport of NaCl from the ascending limb the key step in the loop of henel

Answer 19

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

Question 20

What is the concentration of the fluid at the end of the loop of henel

Answer 20

100mOsmoles

Question 21

The fluid enters the loop of henel 300mOsmols and leaves 100mOsmols, what has happened to the remainder concentration

Answer 21

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

Question 22

What is the overall function of the loop of henle

Answer 22

Concentrating the medullary interstitial

delivering hypotonic fluid to distal tubule

Removes 15-20% of initial filtrate

Question 23

What is the vasa recta

Answer 23

A portion of the peritubular capillaries system which enters the medulla

Question 24

How does the vasa recta participate in the counter current mechanism,

Answer 24

by acting as counter current exchangers

Question 25

How does the vasa recta act as counter current exchanger

Answer 25

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

Question 26

What is the functions of the vasa recta

Answer 26

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

Question 27

Why is the flow rate through the vasa recta very low

Answer 27

so that there is plenty of time for the equilibration to occur with the interstium further ensuring that the medullary gradient is not disturbed