Physiology 3

Question 1

What is the osmolarity in the cortex?

Answer 1

Same as the rest of the body 300

Question 2

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

Answer 2

It increases - eventually gets to 1200

Question 3

What is the basis of healthy kidney function?

Answer 3

The ability to form a cortico-medullary concentration gradient

Question 4

What is the innermost part of the medulla called?

Answer 4

The papilla

Question 5

How thick is the boundary around the tubule?

Answer 5

1 epithelial cell thick

Question 6

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

Answer 6

It is iso-osmotic

Question 7

What is the fluid percentage remaining after the proximal tubule?

Answer 7

1/3 of original

Question 8

Two membranes:

Answer 8

Luminal

Basolateral

Question 9

What happens in the thin descending loop?

Answer 9

It increases

Question 10

Why is the descending loop thin?

Answer 10

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

Question 11

What are the properties of thin descending loop?

Answer 11

It is permeable to water

It is impermeable to almost everything else

Question 12

Why are lipids hard to get rid of?

Answer 12

They can diffuse across membranes very easily

Question 13

Does the descending loop have aquaporins?

Answer 13

Yes

Question 14

What is the relationship between depth and concentration?

Answer 14

The deeper you go the higher the concentration

Question 15

Why does water leave the lumen?

Answer 15

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

Question 16

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

Answer 16

It is 4x normal

Question 17

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

Answer 17

Urea - it is trapped allowing for the movement of water

Question 18

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

Answer 18

It is high but the water permeability is low

Question 19

What happens in the ascending limb?

Answer 19

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

Question 20

How much sodium is reabsorbed in the thick ascending limb?

Answer 20

25%

Question 21

How much water is reabsorbed by the descending limb?

Answer 21

10-15%

Question 22

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

Answer 22

It should be dilute

Question 23

What is specific about the distal tubule?

Answer 23

It responds to circumstances

Specifically regulates sodium balance

Question 24

What is the sodium concentration in the urine

Answer 24

50mOsM

Question 25

What does the collecting duct primarily regulate?

Answer 25

The water concentration

Question 26

What regulates the expression of aquaporins and water reabsorbtion?

Answer 26

Adh | It regualtes aquaporin expression and binding

Question 27

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

Answer 27

It has the same specific gravity of plasma

Question 28

What drives the majority of tubular reabsorption?

Answer 28

Active transport of Na

Question 29

What does the Na/kATPase do?

Answer 29

It maintains the the intracellular concentration inside the cells

Question 30

What occurs at the basolateral membrane?

Answer 30

Always the same mechanism (sodium/potassium ATPase)

Question 31

What occurs at the luminal membrane?

Answer 31

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

Question 32

What type of co-transporters are there?

Answer 32

Lots - glucose etc etc

Question 33

How do co-transporters act?

Answer 33

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

Question 34

How many amino acid co-transporters are there?

Answer 34

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

Question 35

Where is the sodium phosphate transporter?

Answer 35

It is in the proximal tubule

Question 36

how much sodium phosphate transporter is there?

Answer 36

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

Question 37

How is chloride reabsorbed?

Answer 37

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.

Question 38

Where is the sodium hydrogen exchanger?

Answer 38

Luminal membrane

Question 39

Why doesn't sodium flow back into the lumen?

Answer 39

It does - as the concentration is higher in the interstium

Question 40

Where are potassium channels?

Answer 40

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

Question 41

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

Answer 41

80%

Question 42

What is reabsorbed via the movement of sodium?

Answer 42

Water, chloride, glucose, amino acids, urea

Question 43

Where does sodium diffuse back into the lumen through?

Answer 43

Tight junctions between cells