the loop of Henle and the collecting duct

Question 1

what are the two limbs called which make up the loop of Henle

Answer 1

1) descending limb

2) ascending limb

Question 2

what does the loop of Henle do

Answer 2

1) reabsorption of water in the descending limb

2) reabsorption of NaCl in the ascending limb

Question 3

outline reabsorption in the ascending limb

Answer 3

1) it is impermeable to water and permeable to NaCl
2) Na+ and Cl- are actively pumped out the ascending limb causing the solute potential of the medulla tissue to increase and the water potential to decrease
3) has filtrate climbs to the top of the loop it contains far fewer ions so water potential increases

Question 4

outline reabsorption in the descending limb

Answer 4

1) the descending limb is permeable to water and relatively permeable to ions
2) water moves out the descending limb by osmosis as the water potential is higher inside the loop than the medulla tissue due to the transport of Na+ and Cl- from the ascending limb
3) the medulla tissue does not become diluted as the water molecules move directly into the blood of the vasa recta
4) as fluid moves down the descending limb it becomes more concentrated with Na+ and Cl-

Question 5

what is the relationship between the length of the loop of Henle and the environment of the organism?

Answer 5

1) the LOH is longer in drier environments as more water needs to reabsorbed into the body due to low water availability therefore more needs to be conserved ie in a Kangaroo rat
2) the LOH is shorter in wetter environments as less water needs to be conserved as it is in high availability ie in a beaver

Question 6

why is the loop of Henle referred to as a counter-current multiplier

Answer 6

flow in the two limbs moves in opposite directions and the concentration of solutes is increased

Question 7

what is the functions of the collecting duct

Answer 7

the transportation of urine and absorption of water

Question 8

outline the processes which occur in the collecting duct

Answer 8

1) filtrate from the loop of Henle is passed into the collecting duct which travels back down into the medulla passing through the low water potential region
2) this causes any water still in the filtrate to diffuse out the collecting duct by osmosis down the water potential gradients into the medulla
3) the water is absorbed by the vasa recta
4) the filtrate becomes more concentrated than the blood by the time it reaches the base of the collecting duct as urine