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BRS UROLOGY & RENAL > Renal Tubules Transport Mechanisms > Flashcards

Renal Tubules Transport Mechanisms Flashcards

1
Q

What are the three methods of passive transport that occurs in the kidneys?

A

Diffusion
Osmosis
Electrochemical gradients

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2
Q

What are the two types of active transport which occurs in the Kidneys?

A

Primary Active Transport and Secondary Active Transport

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3
Q

How is endocytosis used in the renal tubules?

A

Small proteins are reabsorbed in the proximal convoluted tubules

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4
Q

What is an example of a symporter?

A

The Na+ / Glucose Symporter

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5
Q

How do symporters and antiporters provide methods of secondary active transport?

A

Involves the coupled transport of two or more ions, one moves down electrochemical gradient which provides energy for the movement of another up the electrochemical gradient

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6
Q

Describe how Na+ / K+ ATPase Pumps work?

A

one molecule of ATP is used to Pump 3 x Na+ out the cell, into the blood and 2 x K into the cell from the blood

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7
Q

How does the presence of Na + / K+ ATPase Pumps on the basolateral membrane help the transportation of other substances?

A

The movement of 3 x Na+ out the cell into the blood creates a low concentration of Na+ within the cell

Therefore, on the apical side, Na+ moves into the Cell, down the electrochemical gradient through a syn/antiporter which therefore transports another molecule up their concentration gradient

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8
Q

Describe the reabsorption of sodium in the Early Proximal Convoluted Tubule?

A
  1. Na+ / K+ ATPase Pump creates low Na+ inside cell
  2. Na+ moves through Na+ / H+ Anti Porter on Apical Side, as H+ moves into tubular fluid - this H+ is generated through the breakdown of Water and carbon Dioxide by carbonic Anhydrase
  3. Then Na+ moves through Na+ / HCO3- Symporter on Basolateral side into blood
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9
Q

Describe the reabsoprtion of HCO3- in the early proximal convoluted tubule

A
  1. Na+ / K+ ATPase Pump creates low Na+ inside cell
  2. Carbonic Anhydrase converts water and co2 into H+ and HCO3-
  3. Na+ moves through Na+ / H+ Anti Porter on Apical Side into the cell, as H+ moves into tubular fluid
  4. Then Na+ and HCO3- move through Na+ / HCO3- Symporter on Basolateral side into blood
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10
Q

How does Angiotensin II regulate Na+ reabsorption in the Early Proximal Convoluted tubule?

A

By Increasing the number of Na+ / H+ Antiporters

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11
Q

What happens to sodium, bicarbonate and glucose in the Early Proximal CT?

A

Sodium - Reabsorbed
Bicarbonate - Reabsorbed
Glucose - Reabsorbed

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12
Q

Describe the reabsorption of glucose into the Blood in the Early Proximal Convoluted Tubule?

A
    1. Na+ / K+ ATPase Pump creates low Na+ inside cell
  2. Na+ and glucose from tubular fluid moves through Na+ / Glucose Symporter on Apical Side
  3. Then glucose moves through GLUT2 transporter on the basolateral side into the blood
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13
Q

What is the name of the Na+ / H+ Antiporter found on the apical side of the Early Proximal Convoluted Tubule?

A

NHE3

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14
Q

What is the name of the Na+ / Glucose Symporter found on the apical side of the Early Proximal Convoluted Tubule?

A

SGLT2

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15
Q

What percentage of glucose is reabsorbed in the Early Proximal Convoluted tubule

A

100%

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16
Q

What percentage of Water, Na+ and Cl- are reabsorbed in the Early Proximal Convoluted Tubule?

A

67% Water
67% Na+
67% Cl-

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17
Q

What percentage of amino acids are reabsorbed in the early Proximal Convoluted tubule?

A

100%

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18
Q

What percentage of bicarbonate is reabsorbed in the Early Proximal Convoluted Tubule?

A

80%

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19
Q

What substances are secreted in the Early Proximal Convoluted Tubule?

A

Drugs, Ammonia, Bile Salts, Prostaglandins, Vitamins

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20
Q

What is the osmolarity of the fluid entering the LOH?

A

Isosmotic

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21
Q

Is Na+ Cl+ reabsorbed in the descending LOH?

A

No

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22
Q

What is passively reabsorbed in the descending LOH?

A

Water

23
Q

Where is Na+ and Cl- passively reabsorbed?

A

Thin ascending LOH

24
Q

Where is Na+ Cl- actively reabsorbed?

A

Thick ascending LOH

25
Q

Is Water reabsorbed in the ascending LOH?

A

No

26
Q

Why does water get passively reabsorbed in the descending LOH?

A

In the Ascending LOH, a lot of Na + and Cl - is being reabsorbed into medullary interstitium, creating low H20 in interstitium.

Therefore, by simple osmosis which is passive transport H2O can move from Descending LOH into the hyperosmotic medullary interstitium

27
Q

What is the osmolarity of the medullary interstitium?

A

Hyperosmotic

28
Q

What is the osmolarity of the tubular fluid after passing down the descending limb?

A

Hyperosmotic (Little water)

29
Q

What is the osmolarity of the tubular fluid after passing up the ascending limb of the LOH?

A

Hypoosmotic (A lot of water)

30
Q

What substances are reabsorbed in the LOH?

A

25% Na+, 25% Cl- and 15% H2O

31
Q

What is the symporter found on the apical side of the LOH?

A

Na+ - K+ - 2Cl- Symporter - Moves all these ions into the cell

32
Q

What is the symporter found in the basolateral side of the LOH?

A

K+ Cl- Symporter

33
Q

Which cations are reabsorbed paracellularly in the LOH?

A

Na+, Ca2+, K+ and Mg2+

34
Q

Describe how Na+ and Cl- is actively reabsorbed in the Thick Ascending limb of the LOH?

A
  1. Na+ / K+ ATPase Pumps Na+ out and K+ in
  2. Creates Gradient for the Na+ K+ 2Cl- Symporter to pump these ions into the cell on the apical side
  3. Then, K+ Cl- Symporter on Basolateral side transports both ions into the Blood - K+ moving down conc gradient, Cl- moving against
35
Q

What three substances are reabsorbed in the early DISTAL convoluted tubule?

A

Na+ Cl- and Active Ca2+ reabsorption

36
Q

Are aquaporin molecules found in the early distal CT?

A

No - they are absent

37
Q

What is a key ion that is absorbed in the Early Distal CT?

A

Ca2+

38
Q

By what two transporters is Ca2+ reabsorbed in the Early Distal CT?

A

Na+ Ca2+ Antiporter

Ca2+ ATPase Pump

39
Q

How does Ca2+ enter into the cell from the tubular fluid?

A

Via Ca2+ channels

40
Q

How is Na+ and Cl- reabsorbed in the Early Distal Convoluted Tubule?

A

Na+ K+ ATPase Pump brings Na+ out cell, creating low conc within
and K+ into cell, creating high conc within
Na+ Cl- Symporter brings Na+ and Cl- into the cell
K+ Cl- Symporter brings both into the blood

41
Q

What are the two cell types are found in the late distal CT and Collecting Duct?

A

Principal Cells and Intercalated Cells

42
Q

What is the primary role of the principal cells?

A

Na+ reabsorption and K+ Secretion

43
Q

In what situation does the role of the principal cells become very important?

A

In Hyperkalaemia - where there is too much K+ in the body, so it is secreted out the blood into the tubule and out the body as urine

44
Q

In the Late Distal CT and CD, where are aquaporin molecules always found?

A

Basolateral side

45
Q

How does Aldosterone regulate Na+ reabsorption in the LDCT and CD?

A
  1. Increases Apical Na+ channels
  2. Increases basolateral Na+ K+ ATPase pumps
46
Q

How does ADH regulate water reabsoprtion in the LDCT and CD?

A

Increases apical Aquaporin molecules

47
Q

What is the role of the intercalated cell?

A

Maintaining acid-base balance

48
Q

What happens in the alpha Intercalated cells?

A

HCO3- Reabsorption into blood

H+ Secretion into fluid

49
Q

What happens in the beta intercalated cells?

A

HCO3- secretion into fluid

H+ reabsorption into blood

50
Q

Which intercalated cells are active during alkalosis and why?

A

Alkalosis = blood is too alkaline, therefore beta intercalated cells are used as H+ into blood reabsorption occurs there

51
Q

Where is the H+ ATPase pump located in the alpha Intercalated cells in the LDCT and CD?

A

Apical Side

52
Q

Where is the H+ ATPase pump located in the beta Intercalated cells in the LDCT and CD?

A

Basolateral side

53
Q

Where is the Cl- HCO3- Anti-porter located in alpha and beta intercalated cells?

A

Alpha = basolateral side
Beta = Apical Side

54
Q

Describe how principal cells facilitate the reabsorption of Na+ and secretion of K+

A
  1. Na+ / K+ pumps on basolateral side pump three Na+ out into blood for every K+ pumped into the cell
  2. This creates as low concentration of Na+ inside the cell
  3. Na+ moves from the tubular fluid through Na+ channels in the apical side
  4. Water is reabsorbed through Aquaporin molecule - normally found on the basolateral side, but number on apical side is increased by ADH

BRS UROLOGY & RENAL (11 decks)

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