Water Reabsorption

Question 1

What is the role of the Loop of Henle?

Answer 1

create a low (very negative) water potential in the tissue of the medulla, ensures more water can be reabsorbed from the fluid in the collecting duct

Question 2

How are the limbs of the Loop of Henle arranged?

Answer 2

descending limb (into medulla) and ascending limb (into cortex), allows salts (sodium and chloride ions) to be transferred from ascending to descending limb

Question 3

What is the overall effect of the movement of salts in the LoH?

Answer 3

increase the concentration of salts in the tubule fluid, then diffuse out of thin-walled ascending limb into medulla tissue = very low water potential

Question 4

As fluid ascends back to the cortex, how does its water potential become higher?

Answer 4

base of tubule: salts diffuse out of tubule into tissue fluid, higher up: salts actively transported into tissue fluid, wall of limb (esp. near top) = impermeable to water so none lost

Question 5

What is a hairpin counter current multiplier?

Answer 5

arrangement of tubule in sharp hairpin so one part of tubule is close to another but with fluid in different directions, allows exchange and creation of high concentration of solutes

Question 6

What is osmoregulation?

Answer 6

control and regulation of water potential of blood and body fluids, in humans this is done by the kidneys

Question 7

What happens to the water potential of the medulla the deeper you go in?

Answer 7

increasingly negative when deeper in medulla

Question 8

How does the removal of ions from ascending limb affect the urine?

Answer 8

At top of limb: very dilute, water may be reabsorbed from urine in distal tubules and collecting ducts, amount of water reabsorbed depends on needs of body

Question 9

What happens to the tubule fluid in the distal convoluted tubule?

Answer 9

active transport used to adjust concentrations of various salts

Question 10

Where does the collecting duct carry the tissue fluid?

Answer 10

back down through medulla to the pelvis

Question 11

What happens to the tubule fluid as it is carried down he collecting duct?

Answer 11

water moves by osmosis from tubule fluid into surrounding tissue, enters blood capillaries by osmosis

Question 12

How much urine reaches the pelvis per day? What is the water potential of the urine like at this point?

Answer 12

1.5-2dm3, very low water potential, concentration of salts and urea is higher than that of blood plasma