Loop of Henle

Question 1

What happens to the concentration of drugs when water is removed?

Answer 1

Concentration increases

Question 2

Some protein does get through reabsorption, which type in particular?

Answer 2

Albumin

Question 3

Most drugs are highly lipid soluble and non-polar. The removal of water establishes their concentration gradients so they would never be removed…so how are drugs removed from the body?

Answer 3

Liver metabolises them to polar compounds reducing their permeability meaning they can be excreted.

Question 4

Osmolality does not change when solutes are moved, why is this?

Answer 4

All solute movements are accompanied by equivalent water movements

Question 5

What is the loop of Henle important for?

Answer 5

Water balance

Question 6

What is the maximum concentration human urine can achieve?

Answer 6

1200-1400 mOsmoles/L

Question 7

What are some of the waste products removed through the urine?

Answer 7

Urea, sulphate, phosphate

Question 8

Waste products must be removed everyday, this amounts to 600mOsmoles per day. How much water loss occurs for this amount?

Answer 8

500mls

Question 9

What happens to urine if we don’t drink?

Answer 9

As long as the kidneys are functioning, this volume will always be excreted, even if no water intake.
Can urinate to death
Water needs to be consumed for water balance

Question 10

In conditions of excess water intake, how much is the minimum urine concentration?

Answer 10

30-60mOsmoles/L

->has been diluted

Question 11

What is the role of the loop of Henle?

Answer 11

Concentrates urine

Question 12

What format does the Loop of Henle have which allows for the concentration of urine?

Answer 12

The juxtamedullary nephrons act as counter-current multipliers

Question 13

What happens to fluid in a counter-current set up?

Answer 13

Fluid flows down the descending limb and up the ascending limb

Question 14

There are critical characteristics of loops which make them counter-current multipliers.
What is the characteristic of the ascending loop of Henle?

Answer 14

Ascending loop actively co-transports sodium and chloride ions out the tubule lumen into the interstitium.

Question 15

Is the ascending limb permeable or impermeable to water?

Answer 15

Impermeable

Question 16

There are critical characteristics of loops which make them counter-current multipliers.
What is the characteristic of the descending loop of Henle?

Answer 16

Freely permeable to water but relatively impermeable to NaCl

Question 17

Therefore, what is removed in the ascending limb?

Answer 17

NaCl

Question 18

What happens to the osmolality in the
1. tubule
2. interstitium
when NaCl is removed from the ascending limb?

Answer 18

1. Osmolarity in tubule decreases
2. Osmolarity in interstitium increase

Question 19

What happens to compensate for the increased osmolality in the nterstitium?

Answer 19

Descending limb is exposed to greater osmolality so water moves out the equate the osmolarity

Question 20

When does the fluid in the tubule progressively concentrated?

Answer 20

When it moves down the descending limb as water is removed

Question 21

When does the fluid in the tubule progressively diluted?

Answer 21

When the fluid moves up the ascending limb as more NaCl added

Question 22

What happens to the intersitium when there is increased delivery of concentrated fluid to the ascending limb?

Answer 22

Interstitium becomes increasingly concentrated

Question 23

At any horizontal level in the loop of the Henle, how much, in mOsmoles is the gradient between the ascending limb and the interstitium?

Answer 23

200mOsmoles

->small gradient but overall is a bit gradient as vertical gradient in the interstitium goes from 300->1200mOsmol

Question 24

The active transport of NaCl out of the ascending limb is a key step. Use of which drugs disrupts this?

Answer 24

Diuretic frusemide

Question 25

Therefore, what is the mechanism of diuretic frusemides?

Answer 25

Inhibit the transport of NaCl in the ascending loop of Henle

Question 26

What would happen to the horizontal osmolarity gradient in someone on diuretic frusemides?

Answer 26

No horizontal osmolarity gradient can be established.

->kidney can then only produce isotonic urine

Question 27

Just to recap, what happens as fluid goes down and up the loop of Henle?

Answer 27

Concentrates fluid going down descending limb, dilutes fluid going up ascending limb

Question 28

What is the concentration of the fluid in the proximal tubule?

Answer 28

100mOsmols

Question 29

Vasa Recta?

Answer 29

Specialised arrangement of the peritubular capillaries of the juxtamedullary nephrons

->acts as counter current exchangers

Question 30

What are the functions of the Vasa Recta?

Answer 30

1. Provide oxygen for the medulla, whilst not disturbing the gradient
2. Removes water from the interstitium

Question 31

How much water can the Vasa Recta remove from the interstitium each day?

Answer 31

36 litres

Question 32

Where is the site of water reulation?

Answer 32

Collecting duct

Question 33

What is the collecting duct’s permeability under the control of?

Answer 33

ADH- anti-diuretic hormone

Question 34

What can ADH also be known as?

Answer 34

Vasopressin

Question 35

Where is ADH released from?

Answer 35

Posterior pituitary

Question 36

Therefore, whether or not the dilute urine is delivered to the distal tubule is concentrated depends of the presence of what?

Answer 36

Anti-diuretic hormone aka ADH aka vasopressin