loop of henel

Question 1

what is the process ?

Answer 1

• Salt (Na⁺) is pumped out of the ascending limb into the medulla (by active transport).
• The ascending limb doesn’t let water out, so water stays inside.
• This makes the medulla very salty (low water potential).
• The descending limb lets water out, so water moves out by osmosis into the salty medulla.
• This makes the fluid in the tubule more concentrated as it moves down.
• The water in the medulla is reabsorbed into the blood.
• In the collecting duct, more water leaves by osmosis (due to the salty medulla).
• This water is also reabsorbed into the blood, so less water is lost in urine.

Question 2

quizlet flashcard version

Answer 2

Near to the top of ascending limb, Na+ are pumped out into the medulla by active transport.
- Since the ascending limb is impermeable to water, so water stays inside the tubule.
- This has creates a low water potential in the medulla, because there’s a high concentration of ions.
- Because of low water potential in the medulla than in the descending limb (which is permeable to water) into the medulla by osmosis.
- This makes the filtrate more concentrated (the ions cannot able to diffuse out: the descending limb is not permeable to them). The water in the medulla is reabsorbed into the blood through the capillary network.
- The ascending limb is impermeable to water, so it stays in the tubule.
- Water moves out of the DCT by osmosis and is reabsorbed into the blood.
- The stages above massively increase the ion concentration in the medulla, which lowers the water potential.
- This causes water to move out of the collecting duct by osmosis.
- As before, the water in the medulla is reabsorbed into the blood through the capillary network.