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Kidney > Proximal tubule- reabsorption > Flashcards

Proximal tubule- reabsorption Flashcards

1
Q

Label?

A
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2
Q

Label

A
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3
Q

What epithelial cells present in proximal tubule?

A

Simple cuboidal

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4
Q

What does proximal tubule recieve filtrate from?

A

Bowmans space

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5
Q

What is blood supply of proximal tubule?

A

Efferent arteriole

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6
Q

State function of proximal tubule? (2)
What involved?

A

1) Reabsorption of: Na, Cl, H2O, Glucose, Amino acids,
HCO3-, Phosphate
2) Secretion organic ions

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7
Q

State 3 things reabsorbed at proximal tubule?

A

Na, HcO3-, Glucose

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8
Q

What facilitates reabsorption Na+?
Location?

A

Na/K ATPase on basolateral membrane

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9
Q

How are substrate reabsorbed in proximal tubule? (4)

A

1) Na+- Na/K ATPase on basolateral membrane
2) Secondary active transport
3) Tight junctions
4) Passive diffusion

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10
Q

How is proximal tubule adapted?

A

1) Lots mitochondria
2) Good vascular supply- Na/K ATPase
3) High permeability H2O- osmosis

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11
Q

Where are Cl- ions usually absorbed?

A

Proximal tubule
Latter

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12
Q

Through what channel is water absorbed?
Where?

A

Aquaporin 1
Apical and basolateral membrane
Osmosis

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13
Q

Name two ways water passes through?

A

1) Aquaporin 1 (AQP1) channels on apical and basolateral
membranes
2) Tight junctions leaky to water- paracellularly

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14
Q

How is glucose reabsorbed in proximal tubule?

A

SGLT1 (carrier protein) 2Na+ and 1 glucose
Latter parts proximal tubule
High affinity for glucose as low concentration

SGLT2 (carrier protein) 1Na+ and 1 glucose
Earlier parts tubule

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15
Q

How does glucose cross basolateral membrane?

A

Passively
GLUT

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16
Q

What should glucose content be in urine?

A

0 (almost)

17
Q

What function SGLT1/2

A

Reabsorb glucose

18
Q

How is sodium reabsorbed?

A

1) Na+ actively transported out of proximal CT epithelial cell
Via Na/K ATPase pump (3Na+ out, 2 K+ in) on basolateral membrane
Into the interstitial fluid
2) Lowers conc Na+ intracellularly
3) Na+ move from the tubular lumen into the cell
4) Na+ transported into cell: in exchange for H+ or
co-transported (glucose or phosphate)
5) Once in cell pumped into the interstitium with Na/K ATPase or co-
transported with HCO3-
6) Water follows Na+ passively through osmosis
7) Differences water concentration between lumen and interstitial fluid results in net diffusion of water from lumen across the cell membrane and tight junctions

19
Q

What percentage of Na+ is reabsorbed for protons?

A

80%

20
Q

What pump used for reabsorption Na?

A

Na/K ATPase pump

21
Q

What 2 ways N+ moves into cell?

A

1) Exchange for H+
2) Co-transported e.g. with glucose or phosphate- secondary active transport

22
Q

When in cell how is Na+ pumped into interstitium?

A

1) Na/K ATPase
2) co-transported with HCO3-

23
Q

What follows Na+?

A

Water

23
Q

What follows Na+?

A

Water

24
Q

How is bicarbonate reabsorbed?

A

1) Tubular secretion of H+ in exchange Na+
2) H+ combines with HCO3– to produce H2CO3 (carbonic acid)
3) H2CO3 dissociates into H2O and CO2
4) CO2 diffuses through the cell wall as it small and non-polar
5) H2O is reabsorbed through osmosis through AQP1 channels
6) Inside cell H2O and CO2 join together to form H2CO3
7) Dissociates into HCO3– and H+
8) H+ is recycled through this sequence again

2 methods of HCO3– transport across the basolateral membrane:
1) HCO3- (bicarbonate) is co-transported with Na+ into the interstitium
and then into the blood; 1Na+ with 3HCO3-
2) Pumped passively in exchange for an anion

25
Q

What are two methods of transporting HCO3- across basolateral membrane?

A

1) HCO3- (bicarbonate) is co-transported with Na+ into the interstitium
and then into the blood; 1Na+ with 3HCO3-
2) Pumped passively in exchange for an anion

26
Q

What does the combination of HCO3- and H+ form?
What does it require?

A

H2CO3
Carbonc anhydrase

27
Q

What does CO2 and H20 form?
What is needed?

A

H2C03
Carbonic anhydrase

28
Q

Write important equation needed move bicarbonate?

A
29
Q

How is chloride reabsorbed?
How transported on basolateral membrane?

A

Paracellularly (between cells)
Exchanged base on apical membrane (formate)

Transported in NKCC2 channel on the basolateral membrane into blood

30
Q
A
31
Q

What base is exchanged with chloride on apical membrane?

A

Formate
Becomes formic acid- diffuse- reused

32
Q

Give 2 ways amino acids transported?
Flow past basolateral membrane?

A

1) Amino acid transporters
2) Co-transported Na+

Can flow out passively on the basolateral membrane through their own channels

33
Q

Should protein be present in proximal tubule?

A

No

34
Q

If proteins manages get in what occurs?

A

1) Microvilli specialised sensors- bind any protein
2) Endocytosis occurs in endosomes
3) Protein degraded by lysosomes to produce amino acids

Kidney (11 decks)

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