Tubular function Flashcards

1
Q

What are the two parts to the proximal tubule?

A

First 60% is the proximal convoluted tubule

The remainder is the proximal straight tubule

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2
Q

What is present on the apical surface of proximal tubule cells?

A

Microvilli

forming a brush border

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3
Q

Through which pathways do ions move in the proximal convoluted tubule?

A

Paracellular

Transcellular

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4
Q

How much water has been reabsorbed by the end of the proximal convoluted tubule?

A

70%

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5
Q

What ion moves in the proximal convoluted tubule?

A

Na+ down its electrochemical gradient

NaKATPase on basolateral membrane to maintain gradient

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6
Q

What moves into proximal convoluted tubules as a result of Na+ movement?

A

Glucose

Amino acids

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7
Q

How does water move transcellularly in the proximal convoluted tubule?

A

Aquaporin 1 (AQP 1)

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8
Q

Why does water move paracellularly in the proximal convoluted tubule?

A

Hydrostatic and osmotic force

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9
Q

Is inulin absorbed in the proximal tubule?

A

No

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10
Q

Is urea absorbed in the proximal tubule?

A

Weakly

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11
Q

Is chloride absorbed in the proximal tubule?

A

Weakly

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12
Q

Is Na+, K+ absorbed in the proximal tubule?

A

Yes

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13
Q

Is HCO3- absorbed in the proximal tubule?

A

Yes

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14
Q

Are amino acids absorbed in the proximal tubule?

A

Strongly

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15
Q

Is glucose absorbed in the proximal tubule?

A

Strongly

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16
Q

What transports glucose?

A

90% by SGLT2

10% by SGLT1

17
Q

What transports glucose at the basolateral membrane?

A

Glut2 and Glut1

Primarily Glut2

18
Q

How can we use the transport of glucose to treat diabetes?

A

SGLT2 inhibitors

19
Q

How are amino acids taken up in the proximal tubule?

A

Variety of amino acids means a variety of transporters

Most are sodium cotransporters

20
Q

How is HCO3- removed from the proximal tubule?

A

Reaction with H+
H+ from Na/H exchanger
Increased rate by carbonic anhydrase
Water and CO2 can then move into the cell

21
Q

How does Cl- move in the proximal tubule?

A

Passively

Actively

22
Q

Where is most Cl- absorbed?

A

The later stages of the proximal tubule

23
Q

What would happen to any albumin in the proximal tubule?

A

Very little albumin enters the filtrate
Binds to the plasma membrane
Endocytosed and catabolised into amino acids for recycling

24
Q

What is actively secreted in the proximal tubule?

A

Organic anions

25
Q

What are thiazides?

A

Block the Na+/Cl- cotransporter

Act as a diuretic