5.2.6 function of kidney 2

Question 1

what does the loop of Henle consist of

Answer 1

descending limb (descends into medulla) & ascending limb (ascends back out to cortex)

Question 2

water potential of descending limb

Answer 2

• mineral ions enter descending limb = concentration of fluid increases
• water potential decreases (more negative)
• increasingly negative the deeper into medulla

Question 3

water potential of ascending limb

Answer 3

• fluid rises up = mineral ions leave fluid
• base of ascending limb = via diffusion
• higher up the ascending limb = active transport used to move mineral ions out of the
• upper portion of ascending limb impermeable to water

Question 4

effect of ionic movements in ascending/descending limb

Answer 4

• create high water potential in fluid of ascending limb
• decreases water potential in tissue fluid of medulla
• water potential of tissue fluid becomes lower towards bottom of loop of Henle

Question 5

water reabsorption in collecting duct

Answer 5

• as fluid passes down = passes through tissues with constantly decreasing water potential
• always water potential gradient between fluid in collecting duct & tissues
• allows water to move out of collecting duct into tissue fluid by osmosis

Question 6

name for shape of loop of Henle

Answer 6

hairpin countercurrent multiplier system

Question 7

effect of hairpin countercurrent multiplier system

Answer 7

increase efficiency of transfer of mineral ions from ascending limb to descending limb = create water potential gradient seen in medulla

Question 8

reabsorption in distal convoluted tubule

Answer 8

active transport used to adjust concentrations of various mineral ions

Question 9

summary of water reabsorption in ascending limb

Answer 9

• active removal of sodium/chloride ions
• diffuse out of lower part of ascending limb

Question 10

summary of water reabsorption in descending limb

Answer 10

• diffusion of sodium & chloride ions into
• water moves out by osmosis & enters capillaries

Question 11

summary of water reabsorption in collecting duct

Answer 11

• water moves out by osmosis & enters capillaries
• urine passes down to pelvis

Question 12

describe the 4 steps of concentration changes in tubule fluid from the PCT to the collecting duct
- sodium ions
- potassium ions
- urea
- glucose

Answer 12

1. glucose decreases in concentration as selectively reabsorbed from PCT
2. sodium ions
   - diffuse into descending limb = concentration rises
   - pumped out of ascending limb = concentration falls
3. urea
   - rises as water withdrawn from tubule
   - actively moved into tubule
4. sodium/potassium ions
   - sodium ions: removed from tubule but concentration rises as water removed
   - potassium ions: increase in concentration as water removed & actively transported into tubule to be removed from urine