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Flashcards in Physiology 3 Deck (43):
1

What is the osmolarity in the cortex?

Same as the rest of the body 300

2

What happens to the concentration as we move deeper into the medulla?

It increases - eventually gets to 1200

3

What is the basis of healthy kidney function?

The ability to form a cortico-medullary concentration gradient

4

What is the innermost part of the medulla called?

The papilla

5

How thick is the boundary around the tubule?

1 epithelial cell thick

6

what is the concentration of the fluid entering into the thick descending loop?

It is iso-osmotic

7

What is the fluid percentage remaining after the proximal tubule?

1/3 of original

8

Two membranes:

Luminal
Basolateral

9

What happens in the thin descending loop?

It increases

10

Why is the descending loop thin?

The cells do not contain much (i.e. mitochondria etc)

11

What are the properties of thin descending loop?

It is permeable to water
It is impermeable to almost everything else

12

Why are lipids hard to get rid of?

They can diffuse across membranes very easily

13

Does the descending loop have aquaporins?

Yes

14

What is the relationship between depth and concentration?

The deeper you go the higher the concentration

15

Why does water leave the lumen?

It is drawn out osmotically (because of the high osmolarity of interstitial fluid)

16

What happens to the concentrations of sodium and chloride at the bottom of the loop?

It is 4x normal

17

What makes up the high osmolar concentration in the deep medulla?

Urea - it is trapped allowing for the movement of water

18

What happens in the thin ascending limb to sodium and water permeability?

It is high but the water permeability is low

19

What happens in the ascending limb?

There is an enormous passive movement of sodium into the interstitium
i.e. sodium is reabsorbed

20

How much sodium is reabsorbed in the thick ascending limb?

25%

21

How much water is reabsorbed by the descending limb?

10-15%

22

What would be expected of the urine at the macula densa?

It should be dilute

23

What is specific about the distal tubule?

It responds to circumstances
Specifically regulates sodium balance

24

What is the sodium concentration in the urine

50mOsM

25

What does the collecting duct primarily regulate?

The water concentration

26

What regulates the expression of aquaporins and water reabsorbtion?

Adh
It regualtes aquaporin expression and binding

27

What is seen in the urine of someone with kidney failure?

It has the same specific gravity of plasma

28

What drives the majority of tubular reabsorption?

Active transport of Na

29

What does the Na/kATPase do?

It maintains the the intracellular concentration inside the cells

30

What occurs at the basolateral membrane?

Always the same mechanism (sodium/potassium ATPase)

31

What occurs at the luminal membrane?

A series of different transporters including co-transporters.
It is made up of a variety of co-transporters

32

What type of co-transporters are there?

Lots - glucose etc etc

33

How do co-transporters act?

They do not use energy, but rather use the concentration gradient

34

How many amino acid co-transporters are there?

About 5-6 (transport more than one amino acid)

35

Where is the sodium phosphate transporter?

It is in the proximal tubule

36

how much sodium phosphate transporter is there?

No that much and as such not all phosphate is reabsorbed (unlike glucose which is there in high concentration)

37

How is chloride reabsorbed?

The sodium is absorbed and causes a electrochemical gradient.
Sodium is absorbed trans-cellularly
the sodium and the water which are dragged behind take the para-cellular route.

The occurs for a number of other molecules in the proximal tubule. As water moves across there is a growing concentration gradient which allows movement via bulk flow.

38

Where is the sodium hydrogen exchanger?

Luminal membrane

39

Why doesn't sodium flow back into the lumen?

It does - as the concentration is higher in the interstium

40

Where are potassium channels?

They are present at the basolateral membrane and not at the apical membrane.
The potassium diffuses out back into the interstitium and not

41

How much oxygen in used by the kidney for active transport?

80%

42

What is reabsorbed via the movement of sodium?

Water, chloride, glucose, amino acids, urea

43

Where does sodium diffuse back into the lumen through?

Tight junctions between cells