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Human Epithelial Biology > Proximal Tubule and Loop of Henle > Flashcards

Proximal Tubule and Loop of Henle Flashcards

1
Q

What do the kidneys reabsorb?

A

99% fluid and salt
100% glucose and amino acids
50% urea
0% creatinine

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2
Q

What amount of filtered fluid is reabsorbed in the proximal tubule?

A

80 ml/min

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3
Q

What is iso-osmotic with filtrate?

A

fluid reabsorbed in the proximal tubule

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4
Q

What is secreted in the proximal tubule?

A 
H
Hippurates
NTs
Bile pigments
Uric acid
Drugs
Toxins
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5
Q

What is reabsorbed in the pT?

A 
sugars
amino acids
phosphate
sulphate
lactate
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6
Q

What are the steps involved with tubular reabsorption?

A

transcellular

paracellular

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7
Q

What are the types of carrier mediated transport?

A

primary active transport
secondary active transport
facilitated diffusion

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8
Q

What diffuses through lipid bilayer?

A

O2 and CO2

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9
Q

What diffuses through channels?

A

Na

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10
Q

What is facilitative diffusion molecule?

A

glucose

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11
Q

What is reabsorbed through primary active transport?

A

K and Na through Na-K ATPase - essential for Na reasborption

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12
Q

What is reabsorbed through secondary active transport?

A

Na and Glucose

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13
Q

What is the iso-osmotic fluid reabsorption across leaky PT due to?

A

standing osmotic gradient

oncotic pressure gradient

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14
Q

How is glucose absorbed into the tubular epithelial cell?

A

SGLT

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15
Q

How is water reabsorbed?

A

through the NaCl osmotic gradient

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16
Q

What is the transport maximum for glucose?

A

2mmol/min

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17
Q

What is the renal threshold for glucose?

A

10-12mmol/l

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18
Q

What happens when Tm is reached?

A

clearance of reabsorbed or secreted substances is not constant

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19
Q

What is Na reabsorption driven by?

A

Na-K ATPase

20
Q

What is the osmolarity of the tubular fluid?

A

300mosmol/l

21
Q

What is the function of the loop of henle?

A

generates a cortico-medullary solute concentration gradient

22
Q

WHat does the solute concentration gradient allow?

A

the formation of hypertonic urine

23
Q

How does the loop function?

A

as a countercurrent multiplier

24
Q

What is the function of the ascending limb?

A

Na and Cl reabsorbed in thick ascending limb

impermeable to water

25
Q

What is the function of the descending limb?

A

does not reabsorbed NaCl

highly permeable to water

26
Q

What ensures that NaCl is absorbed into the interstitial fluid?

A

K recycling

27
Q

What allows K recycling and Na, Cl reabsorption?

A

NKCC channel

28
Q

What blocks the NKCC channel?

A

loop diuretics

29
Q

What is the effect of solute being removed in the ascending limb?

A

tubular fluid is diluted and osmolality of interstitial fluid is raised

30
Q

How is the osmolality maintained?

A

interstitial solute cannot enter the descending limb

31
Q

What does the high osmolality allow?

A

water to leave descending limb by osmosis

32
Q

What type of fluid moves into the distal tubule?

A

200mOsmol/l

33
Q

What is the osmolarity at the renal pelvis?

A

1200mosmol/l

34
Q

What contributes to approx half of the medullary osmolality?

A

the urea cycle

35
Q

Where is urea impermeable?

A

the distal tubule

36
Q

Where is 50% of urea absorbed?

A

the collecting duct

37
Q

Where does urea diffuse passively?

A

into the loop of henle

38
Q

What is the purpose of countercurrent multiplication?

A

to concentrate the medullary interstitial fluid

39
Q

Why is counter current multiplication important?

A

to enable the kidney to produce urine of different volume and concentration according to the amounts of circulating ADH

40
Q

What is the Vu on normal fluid intake?

A

around 1ml/min

41
Q

what is the counter current exchanger?

A

the vasa recta run alongside the long loop of henle of the juxtamedullary nephrons

42
Q

Where does blood osmolality rise?

A

as it dips into the medulla - water loss and solute gained

43
Q

Where does blood osmolality fall?

A

as it rises back to the cortex - water gained and solute lost

44
Q

How does the countercurrent system solve the problem of NaCl being washed away by essential blood flow?

A

vasa recta capillaries follow hairpin loops
vasa recta capillaries freely permeable to NaCl and water
Blood flow to vasa recta is low

45
Q

What is the function of the countercurrent exchange?

A

ensures that solute is not washed away

Human Epithelial Biology (20 decks)

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