Flashcards in F214:02:06 Water Reabsorption Deck (38):
What is a hairpin countercurrent multiplier?
The arrangement of a tubule in a sharp hairpin so that one part of the tubule passes close to another part of the tubule with the fluid flowing in the opposite directions.
What does the hairpin countercurrent allow to happen?
The exchange between the contents of each tube and it can be used to create a very high concentration of solutes
What is osmoregulation?
The control and regulation of the water potential of the blood and body fluids
Where is the water potential of blood controlled in humans?
How much fluid is filtered out of the blood and enters the nephron tubules per minute?
How much fluid is there left in the nephron after selective reabsorption on the proximal convoluted tube?
What is the role of the loop of Henle?
to create a low water potential in the tissue fluid of the medulla to ensure that even more water is reabsorbed from the fluid in the collecting duct
What does the loop of Henle consist of?
a descending limb that goes into the medulla
an ascending limb that raises back into the cortex
How does the arrangement loop of Henle help the with its function?
As it allows salts to be transferred from the ascending limb to the descending limb
What is the overall effect of the loop of Henle?
the increase the concentration of salts in the tubule fluid making sure they diffuse out of the asc. limb into the surrounding medulla tube
by building up the salt concentrations in the surrounding tissue fluid
Why is the ascending limb wall really thin?
To make the flow of tubule fluid easier
What happens to the fluid in the tubule as it descends deeper into the medulla?
its water potential becomes lower
Why does the water potential become lower in the descending tubule as it gets lower?
- there is loss of water by osmosis to the surrounding tissue fluid
- diffusion of sodium and chloride ions into the tubule from the surrounding tissue fluid/
What happens to the fluid as it it ascends back up to the cortex?
its water potential gets higher again
Why does the water potential get higher as the fluid ascends back up the loop of Henle towards the cortex?
- at the base of the tubule, Sod + Chl ions diffuse out into the tissue fluid
- higher up, Sod + Chl are actively transported out into the tissue fluid
- Walls of the ascending limb are impermeable to water, so it cant leave the tubule
- fluid loses salts but not water as it moves up the ascending limb
What is the role of the hump of a camel?
to store fat which can be metabolised to release energy and water
What is different about the loop of Henle in a camel compared to a human?
It is longer than most so ensure that there is a longer counter current mechanism to increase the salt concentration in the medulla
Explain why it is beneficial to mammals living in arid conditions to be able to have higher salt concentrations in their medullas
Higher concentrations in the medulla means that a higher water potential gradient can be achieved between the urine in the collecting ducts and the medulla
This means that more water can be reabsorbed from the collecting ducts and then pass into the blood capillaries and the urine is more concentrated.
So there will be less water lost.
What effect does it have to remove ions from the ascending limb on the urine?
it ensures the urine is very dilute, so that water can be reabsorbed in the distal tubes and collecting ducts
What effects the amount of water reabsorbed in the nephrons?
The needs of the body
The permeability of the walls in the collecting ducts
Where does omosis take place in the loop of Henle?
In the descending limb
Where does diffusion take place in the loop of Henle?
Descending limb: sodium and chloride ions in
lower part of asc: sodium and chloride ions diffuse out
Where does active transport take place in the loop of Henle?
The ascending limb of sodium and chloride
What happens to the concentration in the medulla as you descend deeper?
It increases (from 600-1200)
Which tuber is thicker, the asc or desc lib?
What is the distal convoluted tube?
The coiled portion of the nephron between the loop of Henle and the collecting duct
By the time the tubule fluid reaches the collecting duct, what condition is its water potential in?
What happens as the tubule fluid passes down the collecting duct?
Water moves out by osmosis, decreasing the water potential and creating a very highly concentration urine by the time the solution reaches the bladder
How much liquid (fluid) reaches the pelvis each day?
What condition is the urine in in terms of water potential by the time it reaches the pelvis?
How does the concentration of salts etc in the urine compare with that of the blood plasma by the time it has reached the pelvis?
Its higher than the blood plasma (more concentration)
What is the concentration in the medulla measured in?
Milliosmoles per Kilogram (mOsm kg-1)
What are the Milliosmoles per Kilogram (mOsm kg-1)?
the units of concentration, the thousandths of a mole of molecules, ions or both per 1kg of solution
How much does 1 kg weigh roughly in terms of dm3?
Suggest an arrangement of blood vessels that could create blood plasma with an even lower water potential than the tissue fluid
The blood vessels running down into the medulla are looped in a similar fashion to the loop of Henle. This allows the exchange of solutes between the ascending vessel and the descending vessel.
Why must the collecting duct pass back through a region of lower water potential?
This arrangement allows the water to be reabsorbed from the collecting ducts back into the tissue fluid of the medulla, which concentrates the urine
Why is it important for terrestrial mammals to reabsorb as much water as possible?
Terrestrial mammals gain water by eating and drinking
They lose it through sweat, inhaling, exhaling, excretion and egestion.
So it is important not to lose more water than necessary as it may not be readily available.