Loop of Henle Flashcards
What happens to the concentration of drugs when water is removed?
Concentration increases
Some protein does get through reabsorption, which type in particular?
Albumin
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?
Liver metabolises them to polar compounds reducing their permeability meaning they can be excreted.
Osmolality does not change when solutes are moved, why is this?
All solute movements are accompanied by equivalent water movements
What is the loop of Henle important for?
Water balance
What is the maximum concentration human urine can achieve?
1200-1400 mOsmoles/L
What are some of the waste products removed through the urine?
Urea, sulphate, phosphate
Waste products must be removed everyday, this amounts to 600mOsmoles per day. How much water loss occurs for this amount?
500mls
What happens to urine if we don’t drink?
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
In conditions of excess water intake, how much is the minimum urine concentration?
30-60mOsmoles/L
->has been diluted
What is the role of the loop of Henle?
Concentrates urine
What format does the Loop of Henle have which allows for the concentration of urine?
The juxtamedullary nephrons act as counter-current multipliers
What happens to fluid in a counter-current set up?
Fluid flows down the descending limb and up the ascending limb
There are critical characteristics of loops which make them counter-current multipliers.
What is the characteristic of the ascending loop of Henle?
Ascending loop actively co-transports sodium and chloride ions out the tubule lumen into the interstitium.
Is the ascending limb permeable or impermeable to water?
Impermeable
There are critical characteristics of loops which make them counter-current multipliers.
What is the characteristic of the descending loop of Henle?
Freely permeable to water but relatively impermeable to NaCl
Therefore, what is removed in the ascending limb?
NaCl
What happens to the osmolality in the
1. tubule
2. interstitium
when NaCl is removed from the ascending limb?
- Osmolarity in tubule decreases
- Osmolarity in interstitium increase
What happens to compensate for the increased osmolality in the nterstitium?
Descending limb is exposed to greater osmolality so water moves out the equate the osmolarity
When does the fluid in the tubule progressively concentrated?
When it moves down the descending limb as water is removed
When does the fluid in the tubule progressively diluted?
When the fluid moves up the ascending limb as more NaCl added
What happens to the intersitium when there is increased delivery of concentrated fluid to the ascending limb?
Interstitium becomes increasingly concentrated
At any horizontal level in the loop of the Henle, how much, in mOsmoles is the gradient between the ascending limb and the interstitium?
200mOsmoles
->small gradient but overall is a bit gradient as vertical gradient in the interstitium goes from 300->1200mOsmol
The active transport of NaCl out of the ascending limb is a key step. Use of which drugs disrupts this?
Diuretic frusemide
Therefore, what is the mechanism of diuretic frusemides?
Inhibit the transport of NaCl in the ascending loop of Henle
What would happen to the horizontal osmolarity gradient in someone on diuretic frusemides?
No horizontal osmolarity gradient can be established.
->kidney can then only produce isotonic urine
Just to recap, what happens as fluid goes down and up the loop of Henle?
Concentrates fluid going down descending limb, dilutes fluid going up ascending limb
What is the concentration of the fluid in the proximal tubule?
100mOsmols
Vasa Recta?
Specialised arrangement of the peritubular capillaries of the juxtamedullary nephrons
->acts as counter current exchangers
What are the functions of the Vasa Recta?
- Provide oxygen for the medulla, whilst not disturbing the gradient
- Removes water from the interstitium
How much water can the Vasa Recta remove from the interstitium each day?
36 litres
Where is the site of water reulation?
Collecting duct
What is the collecting duct’s permeability under the control of?
ADH- anti-diuretic hormone
What can ADH also be known as?
Vasopressin
Where is ADH released from?
Posterior pituitary
Therefore, whether or not the dilute urine is delivered to the distal tubule is concentrated depends of the presence of what?
Anti-diuretic hormone aka ADH aka vasopressin
