loop of Henle Flashcards
What is the importance of H2O conservation in humans compared to other animals?
- Convoluted/twisted to make the tube longer and to create a stronger ion gradient between the interstitial and the tubules so more water reabsorption cam take place
- Ensures that water is reabsorbed as we do not know when the next water availability would be
- Allow humans to adapt from the straight nephron so we can live on land
- Animals who have a straight nephron live in the water
- The longer the animals nephron the less water availably is in their habitat
What is the role of the Loop of Henle in creating the cortico-medullary hyperosmotic interstitial gradient?
- Loop of Henle will set the stage for the concertation by the collecting ducts, without them we couldn’t concentrate our urine as much
- The only part of the nephron that can vary the amount of reabsorption is the collecting duct. This is because of the loop of Henle
- Surroundings of ducts have a very high solute osmolarity- as you go from the outer renal cortex to the inner renal medulla the concertation of ions progressively increases
- Filtrate in the descending limb is surrounded by the hyperosmotic medulla
- Not obligatory H2O is reabsorbed at the PCT where H2O is directly linked the Na+ reabsorbing so filtrate becomes hyperosmotic
This slide is in the exam
* This is done by:
1. When filtrate enters the loop of Henle for the first time the intestinal fluid and the filate are isosmotic
2. In the ascending limb of the loop of Henle the ions are removed by active transport to create a difference between the interstitial fluid and filtrate of 200mOsm/L so the ions are pumped out to decrease the osmolality of the filtrate
3. The descending limb ions need to equilibrate with the interatrial fluid so water will move by osmosis out of the descending limb of the loop of Henle (equilibration doesn’t change the osmolarity of the interstitial fluid)
4. Filtrate will move along the nephron causing new filtrate to arrive in the descending limb of the loop of Henle
5. The filtrate in the loop of Henle is pushed further along is means that the filtrate bow in the accenting limb of the loop of Henle doesn’t have a difference of 200mOsm/L with the interstitial
6. More ions will be pumped out of the ascending limb to reach this difference but not the same amount of ions will be pumped out at all parts
7. Filate in the descending limb will equilibrate
8. This process will produce a ion gradient/cortico-medullary hyperosmotic interstitial gradient
9. This will continue until a 1203mOsm/L concertation maximum is reached in the medulla/interstitum (dessert animals will have a longer lop of Henle so will have a higher maximum)
10. H2O which has entered the medulla will be picked up by the vasa recta
* This can occur because
○ The descending limb is permeable to water but not ions
○ The ascending limb is impermeable to water but is permeable to ions
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This slide is in the exam
* Na+/2 Cl-/K+ channel protein helps reabsorb the Na+ , Cl- and K+ from the filtrate (cotransporter)
* It does this by actively transporting Na+ out of the cell using a Na+/K+ ATPase
○ Diuretic drugs e.g. the Drug furosemide will inhibit the Na+/2 Cl-/K+ channel
○ This stops/reduced the ions being reabsorbed so no creation of the ion gradient in the medulla
○ This means there is no osmotic pull of the water out of the collecting duct
○ These drugs will decrease the blood pressure will be given to patients will hypertension
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Role of urea in contributing to hyperosmotic medullary interstitum?
- Last bit of the collecting duct may put urea into medulla to increase water absorption
- Urea in the medulla will increase the concentration of solutes in the interstitium and cause more water to be reabsorbed
What is the importance of the cortico-medullary hyperosmotic interstitial gradient?
- Provides the necessary osmotic garment to pull water out of the filtrate into the renal medulla so more water can be reabsorbed
