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Kidneys > Physiology 3 > Flashcards

Physiology 3 Flashcards

1
Q

What is the osmolarity in the cortex?

A

Same as the rest of the body 300

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2
Q

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

A

It increases - eventually gets to 1200

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3
Q

What is the basis of healthy kidney function?

A

The ability to form a cortico-medullary concentration gradient

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4
Q

What is the innermost part of the medulla called?

A

The papilla

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5
Q

How thick is the boundary around the tubule?

A

1 epithelial cell thick

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6
Q

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

A

It is iso-osmotic

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7
Q

What is the fluid percentage remaining after the proximal tubule?

A

1/3 of original

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8
Q

Two membranes:

A

Luminal

Basolateral

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9
Q

What happens in the thin descending loop?

A

It increases

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10
Q

Why is the descending loop thin?

A

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

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11
Q

What are the properties of thin descending loop?

A

It is permeable to water

It is impermeable to almost everything else

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12
Q

Why are lipids hard to get rid of?

A

They can diffuse across membranes very easily

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13
Q

Does the descending loop have aquaporins?

A

Yes

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14
Q

What is the relationship between depth and concentration?

A

The deeper you go the higher the concentration

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15
Q

Why does water leave the lumen?

A

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

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16
Q

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

A

It is 4x normal

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17
Q

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

A

Urea - it is trapped allowing for the movement of water

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18
Q

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

A

It is high but the water permeability is low

19
Q

What happens in the ascending limb?

A

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

20
Q

How much sodium is reabsorbed in the thick ascending limb?

A

25%

21
Q

How much water is reabsorbed by the descending limb?

A

10-15%

22
Q

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

A

It should be dilute

23
Q

What is specific about the distal tubule?

A

It responds to circumstances

Specifically regulates sodium balance

24
Q

What is the sodium concentration in the urine

A

50mOsM

25
Q

What does the collecting duct primarily regulate?

A

The water concentration

26
Q

What regulates the expression of aquaporins and water reabsorbtion?

A

Adh

It regualtes aquaporin expression and binding

27
Q

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

A

It has the same specific gravity of plasma

28
Q

What drives the majority of tubular reabsorption?

A

Active transport of Na

29
Q

What does the Na/kATPase do?

A

It maintains the the intracellular concentration inside the cells

30
Q

What occurs at the basolateral membrane?

A

Always the same mechanism (sodium/potassium ATPase)

31
Q

What occurs at the luminal membrane?

A

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

32
Q

What type of co-transporters are there?

A

Lots - glucose etc etc

33
Q

How do co-transporters act?

A

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

34
Q

How many amino acid co-transporters are there?

A

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

35
Q

Where is the sodium phosphate transporter?

A

It is in the proximal tubule

36
Q

how much sodium phosphate transporter is there?

A

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

37
Q

How is chloride reabsorbed?

A

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
Q

Where is the sodium hydrogen exchanger?

A

Luminal membrane

39
Q

Why doesn’t sodium flow back into the lumen?

A

It does - as the concentration is higher in the interstium

40
Q

Where are potassium channels?

A

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

41
Q

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

A

80%

42
Q

What is reabsorbed via the movement of sodium?

A

Water, chloride, glucose, amino acids, urea

43
Q

Where does sodium diffuse back into the lumen through?

A

Tight junctions between cells

Kidneys (15 decks)

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