Renal Lec 5

Question 1

sources of water gain (input)

Answer 1

• ingested liquid

- water from oxidation of food

Question 2

sources of water loss (output) (6)

Answer 2

• skin
• respiratory airways
• sweat
• GI tract
• urinary tract
• menstrual flow

Question 3

water moves via diffusion across water channels called

Answer 3

aquaporins

Question 4

percentage of water reabsorbed in proximal tubules

Answer 4

67%

Question 5

aquaporins in proximal tubule cells are

Answer 5

always open

Question 6

water reabsorption is dependent on

Answer 6

Na+ reabsorption

Question 7

the driving force for water reabsorption is

Answer 7

the osmotic gradient set up by Na+

Question 8

cortical collecting duct

Answer 8

collecting duct in the cortex

Question 9

medullary collecting duct

Answer 9

collecting duct in the medulla

Question 10

cells in cortical and medullary collecting ducts are

Answer 10

under physiological control

Question 11

hormone that controls water reabsorption (2 names)

Answer 11

-vasopressin/ antidiuretic hormone (ADH)

Question 12

vasopressin/ADH regulate

Answer 12

a specific type of aquaporin

Question 13

vasopressin/ADH act on (location)

Answer 13

cells of the collecting cuts

Question 14

percentage of water reabsorbed in loop of henle

Answer 14

15%

Question 15

percentage of water reabsorbed in distal tubule

Answer 15

0%

Question 16

percentage of water reabsorbed in large distal tubule and collecting duct

Answer 16

8 to 17%

Question 17

mechanism of water reabsorption in proximal tubule (via)

Answer 17

passive via AQP-1

Question 18

mechanism of water reabsorption in loop of henle- descending thin limb only (via)

Answer 18

passive via AQP-1

Question 19

mechanism of water reabsorption in large distal tubule and collecting duct (via)

Answer 19

passive via AQP-2, AQP-3, AQP-4

Question 20

water reabsorption in PCT (summary)

Answer 20

• Na+ movement from tubular lumen to epithelial cells then into interstitial fluid via Na+/K+ ATPase
• local osmolarity of tubular lemn decrease
• local osmolarity of interstitial fluid increase
• water enters interstitial fluid through gap junctions and through epithelial cells via osmosis
• bulk flow of water into peritubular capillaries

Question 21

ascending limb of loop of henle is impermeable to

Answer 21

water

Question 22

water reabsorption in loop of henle (on which limb?)

Answer 22

descending thin limb

Question 23

salt reabsorption in loop of henle (on which limb?)

Answer 23

ascending thick limb

Question 24

loop of henle structure

Answer 24

• single tubule
• two sides closely juxtaposed
• fluid streams in opposite direction
• different transport capabilities on each side of tubule

Question 25

structure-function relationship

Answer 25

a relationship between the structure of a biological entity and the functions (and sometimes the mechanisms) carried out by that entity

Question 26

countercurrent mechanism system is a mechanism

Answer 26

that expends energy to create a concentration gradient.

Question 27

loop of henle descending limb (osmolarity of interstitial fluid)

Answer 27

isotonic to tubule

Question 28

loop of henle descending limb (osmolarity of tubule lumen increases as...because...)

Answer 28

loop descends because tubule is permeable to water and water diffuses out into the interstitial fluid

Question 29

loop of henle ascending limb (osmolarity of interstitial fluid)

Answer 29

hypertonic to tubule

Question 30

loop of henle ascending limb (osmolarity of tubule lumen decreases as...because...)

Answer 30

loop ascendes because tubule is impermeable to water and salt is actively transported into interstitial fluid/out of tubule

Question 31

gradient difference between interstitial space and ascending limb is

Answer 31

200 mOsm

Question 32

counter current multiplier

Answer 32

multiplication of gradient down the length of the loop of Henle

Question 33

long loop of henle =

Answer 33

high osmotic gradient= better water retention

Question 34

osmolarity in distal tubule is ... because

Answer 34

low (80 mOSm) because permeable only to salt so salt moves out to the interstitial fluid

Question 35

cortical collecting duct becomes

Answer 35

isosmotic with interstitial fluid (300 mOsm/L)

Question 36

cortical collecting duct is permeable to both.. so

Answer 36

salt and water so salt and water are reabsorbed

Question 37

ADH works on cortcial collecting duct to

Answer 37

reabsorb more water

Question 38

the osmolarity gradient created by loop of henle

Answer 38

helps draw water out into interstitial space from medullary collecting tubule

Question 39

in medullary collecting duct, osmolarity is

Answer 39

increasing (1400 mOsm/L)

Question 40

fluid flow in vasa recta is

Answer 40

opposite to the flow in the loop of henle

Question 41

vasa recta is permeable to

Answer 41

both water and salt, ions,urea

Question 42

descending vasa recta picks up

Answer 42

salt and osmolarity increases

Question 43

ascending vasa recta picks up

Answer 43

water and osmolarity decreases

Question 44

vasa recta prevents

Answer 44

salt from being carried away and therefor maintains the gradient

Question 45

blood flow in vasa recta serve as

Answer 45

counter-current exchnager

Question 46

blood flow in medulla is ... so

Answer 46

low so it prevents solute loss

Question 47

vasa recta does not create

Answer 47

medullary hyperosmolarity

Question 48

urea in the tubule (summary)

Answer 48

-100% filtrated -50% reabsorbed in the proximal tubule -50% secreted back -100% enters the distal tubule -30% enters reabsorbed from cortical collecting duct -55% reabsorbed from inner medullary collecting duct (due to ADH action) -Only 5% diffuses out to vasa recta and another 50% secreted back into tubule - 15% of the original amount is excreted (much less than the filtered amount)

Question 49

minimal uptake of urea by vasa recta and recycling urea in the interstitial space

Answer 49

helps in maintaining high osmolarity in the medulla

Question 50

Why is there a need for concentrated urine?

Answer 50

-kidneys save water by producing hyperosmotic urine

Question 51

Mechanisms used to maintain the hyperosmotic environment of the medulla:

Answer 51

1. Counter-current anatomy and opposing fluid flow through the Loop of Henle of the juxta medullary nephrons 2. reabsorption of NaCl in ascending limb 3. impermeability of ascending limb to water 4. trapping of urea in medulla 5. hairpin loops of vasa recta maintains the hyperosmotic interstitium in medulla