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CRRAB II Week 2 KT > Muster: Loop of Henle, Distal Tubule, Collecting Duct > Flashcards

Muster: Loop of Henle, Distal Tubule, Collecting Duct Flashcards

1
Q

The loop of Henle dives into what part of the kidney?

A

Medulla

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2
Q

The loop of Henle reabsorbs what % of filtered sodium?

A

25 %

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3
Q

Is more sodium or water reabsorbed in the Loop of Henle?

A

Sodium is absorbed in excess of water! Allows for excretion of urine with osmolality that is different from the plasma (so more H2O stays in the Loop!) Part of the loop is not permeable to water.

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4
Q

What is the descending limb permeable to?

A

ONLY water! Solute cannot leave!

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5
Q

What is the osmolarity of fluid that enters the descending limb?

A

300 mOsms

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6
Q

Which part of the loop of Henle is not permeable to water? why?

A

Thick ascending limb.

It is composed of huge, fat, cuboidal cells

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7
Q

What special pump is found in the Thick Ascending Limb of the Loop of Henle?

A

NKCC pump

Na+ K+ Cl- Cl-

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8
Q

What is the osmolarity of the fluid in the bottom of the loop that is in the deep medullary space?

A

1400 mOsms

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9
Q

What is the osmolarity of the fluid in the thick ascending limb?

A

100 mOsms

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10
Q

What does fluid enter after it leaves the thick ascending limb?

A

Macula Densa (part of the early distal tubule)

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11
Q

Where does the fluid go after the macula densa?

A

Distal convoluted tubule and then the collecting duct

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12
Q

The NKCC pump uses secondary transport dependent on which ion?

A

Sodium

sodium is going down its gradient while K+ and Cl- are going up their gradients

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13
Q

What channels ARE NOT present in the thick ascending limb?

A

Aquaporins

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14
Q

What % of the filtered load of sodium does the NKCC pump reabsorb?

A

20 %

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15
Q

What is the rate limiting ion in the NKCC pump?

A

Choride

The affinity for Na+ and K+ is very high!

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16
Q

What ions get transported paracellularly in the thick ascending limb?

A

Na+
Ca2+
Mg+

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17
Q

What disease is caused by genetic mutations in any of the transporters in the Thick Ascending Limb?

A

Bartter Syndrome

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18
Q

What is the fate of Chloride after the NKCC pump?

A

It is reabsorbed into the peritubular capillary

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19
Q

What is the fate of Potassium after the NKCC pump?

A

Some is reabsorbed into the peritubular capillary and some is filtered back out into the lumen.

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20
Q

Describe Bartter Syndrome.

A

Genetic mutation in any transporter in thick ascending limb.
Can be seen early or later in life.
Growth retardation and mental retardation.
Volume depletion w/ low BP.
Hypokalemia.
Metabolic Acidosis.
Normal or elevated urinary calcium excretion.

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21
Q

What drug blocks the NKCC pump?

In what conditions would you use it?

A

Furosemide

CHF, Hypertension, Hypernatremia etc.

22
Q

Are there aquaporins in the distal tubule?

A

NO. So it contributes to urinary dilution!

23
Q

What % of filtered sodium is reabsorbed in the distal tubule?

A

5 %

24
Q

What transported can be mutated in the distal tubule to cause disease?
What is the disease?

A

NaCl symporter.

Gitleman Syndrome

25
Q

Describe the key features of Gitleman Syndrome.

A 
Normal BP
Metabolic Alkalosis
Hypocalciuria
Hypomagnesemia
Hypokalemia
26
Q

What drug works in the distal tubule to block the NaCl transporter?

A

Hydrochlorothiazide

27
Q

What is the sodium reabsorption in the collection duct?

Explain.

A

Variable! 0-5 %
The first area that is directly controlled to determine urinary electrolyte concentration.
Variable permeability to water too!

28
Q

What are the 2 primary cell types in the collecting duct?

A

Principal cell

Intercalated cell

29
Q

What is the role of the Principal cell?

A

Salt, Chloride, and Potassium reabsorption/excretion

30
Q

Which channel is present on the principal cell to bring in Sodium?

A

ENaC (epithelial Na+ channel)

31
Q

What channel is present on the principal cell to remove K+?

A

ROMK (renal outer medullar K+ channels)

32
Q

What are the %’s of sodium reabsorption for the proximal tubule, Loop of Henle, Distal tubule, and collecting duct respectively?

A

65 % Proximal
20 % loop
5 % distal
0-4.9 % collecting duct

33
Q

What is the filtered load in mM/day?

A

25,000

34
Q

If we reabsorb 99.9 %, what amount is excreted?

A

.1 % = 25 mM

35
Q

What is the primary mechanism of controlling salt reabsorption in the collecting duct?

A

Aldosterone

36
Q

What cells release Renin?

A

Juxtaglomerular cells

37
Q

What do sympathetic nerve fibers attach to?

A

Afferent arteriole

38
Q

What 3 things stimulate renin release?

A

Sympathetics (NE)
Decreased stretch in afferent arteriole
Decreased chloride delivery to macula densa

39
Q

What are the primary actions of Angiotensin II?

A

Stimulates aldosterone
Systemic vasoconstrictor
Stimulates proximal tubule reabsorption of Na+
Increases sympathetic activity

40
Q

What does aldosterone bind to (its receptor)?

A

Steroid response element (SRE)

41
Q

What is the result Aldosterone binding SRE?

A

Increase transcription, translation, and insertion of the 3 channels on the principal cell (Na+/K+ ATPase, ENaC, ROMK)

42
Q

What property of aldosterone allows it to cross freely through the cell?

A

Lipophilic

43
Q

What are the stimuli for aldosterone release? What does this cause?

A

Stimuli: Low sodium, High potassium
Causes: Increased sodium reabsorption, potassium secretion

44
Q

What is Little’s Syndrome?

A

Increase in ENaC channels that can’t shut off!

45
Q

What is Type 1 pseudo-hypo aldosteronism?

A

Decrease in ENaC function

46
Q

What is the equation for fractional excretion of sodium?

A

Excreted Na/Amount Filtered x 100

47
Q

What is the Equation for Clearance of Na+?

A

Excretion rate/[plasma]

48
Q

In what state is aldosterone stimulated?

A

low salt state

49
Q

Why would a genetic mutation in the distal tubule suck less than a genetic mutation in the thick ascending limb?

A

Distal tubule only reabsorbs 5 % of sodium whereas the thick ascending limb reabsorbs 20 % of it.

50
Q

Equation for Filtered Na load:

A

GFR x Serum sodium

51
Q

Equation for Na excretion rate:

A

Urine sodium x Total urine output

CRRAB II Week 2 KT (12 decks)

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