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Cardio I > Exam 3- Urine Concentration and Dilution in the Kidneys - Knaak > Flashcards

Exam 3- Urine Concentration and Dilution in the Kidneys - Knaak Flashcards

1
Q

What is responsible for the yellow color of urine?

A

Urochrome (a product of hemoglobin) billirubin or urobillin)

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2
Q

What does darker urine an indication of?

A

Your body trying to conserve water.

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3
Q

What is most/least concentrated your urine can be?

A

30 mOsm/L to 1200 mOsm/L (Osmolarity)

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4
Q

How much intake do we take in on average per day?

What is the least amount that we must excrete per day?

A

2500 mOsm/L.

600 mOsm/L.- if not toxicities will occur

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5
Q

What makes up the least/ most source of OUTPUT?

A

Feces (least at 4 percent)

Urine (most at 60 percent)

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6
Q

What makes up the least/most INPUT?

A

Metabolism (least at 10 percent)

Beverages (most at 60 percent)

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7
Q

Dehydration Equation- Obligatory Urine Volume

A

600 mOsm/day divided by 1200 mOsm/L = 0.5 L/day

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8
Q

Over Hydration Equation - Obligatory Urine Volume

A

600 mOsm/day divided by 30 mOsm/L = 20 L/day

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9
Q

Why can’t we drink salt water?

A

It has 2000 mOsm.

2000 mOsm + 600 mOsm divided by 1200 mOsm= 2.2 L/day

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10
Q

What is happening to the following components as water is being ingested?

  • Osmolarity
  • Urine Flow Rate
  • Urine Solute Excretion
  • plasma
A
  • Osmolarity: decreasing (urine beind diluted)
  • Urine Flow Rate: increasing and getting rid of solutes
  • Urine Solute Excretion: isn’t changing much???
  • plasma: stays the same
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11
Q

What is the osmolarity trend in the kidney?

A

Osmolarity increases from the cortex to the medulla.

downward through the renal pyramid towards the calyces.

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12
Q

What is the mOsm of the CORTEX?

A

300 mOsm

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13
Q

What creates the osmolarity gradient in the kidneys?

A

The nephron loops and the vasculature

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14
Q

Where is ADH located in the nephron and what is it’s function?

A

It is located in the collecting duct where it allows for the reabsorption of water via aquaporins in times of dehydration. Final osmolarity= 30 mOsm (dilute urine)

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15
Q

As we go through the nephron, what happens to mOsm?

  • descending tubule
  • ascending tubule
  • collecting duct
A
  • descending tubule: losing water ONLY = increase in osmolarity (mOsm)
  • ascending tubule: losing solutes ONLY= decreasing osmolarity (mOsm)
  • collecting duct: losing more solutes -ADH is present = decreasing osmolarity (mOsm) even more.
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16
Q

What would happen if ADH was not present?

A

Water would not be reabsorbed and urine would go straight out?

17
Q

What is the normal mOsm for blood?

A

300 mOsm

18
Q

What activates ADH?

A

-INCREASED levels of Osmolarity (dehydration)

19
Q

How is ADH activated?

A
  • INCREASED osmolarity = osmoreceptor release of ADH (pituitary gland)
  • ADH= increases permeability in the collecting ducts/tubules and water is absorbed.
  • result= back to homeostasis
20
Q

What mediates ADH (vasopressin) activation? How?

A

V2 (Gq) receptors on principal cells.

  • ADH binds to the V2 receptors
  • this increases exocytosis and decreases endocytosis
  • increase in aquaporin release + decrease in break down. New + old ones are staying present.
21
Q

Where does the counter multiplier and the countercurrent exchanger occur?

A 
counter multiplier (tubules)
countercurrent exchanger (vasa recta)
- juxtamedullary nephrons only
22
Q

What is required to make concentrated urine during dehydration?

A

Vasopressin ADH

23
Q

What forms and maintains the interstitial osmolarity gradient?

A

countercurrent mechanism

24
Q

What is responsible for 40 % of the medullary osmotic gradient?

A

Urea

25
Q

What is the interaction between the flow of filtrate through the ascending and descending limbs of the juxtamedullary nephrons?

A

countercurrent multiplier

26
Q

What happens when urea is secreted and reabsorbed? Where does this happen?

A
  • urea recycling occurs

- between loop of henle and distal tubules

27
Q

What is the end result of urea recycling?

A
  • layers of urea are being built up in the interstitial fluid which is causing a gradient.
  • there is more urea at the bottom of the medulla which helps to increase osmolarity . (K+ is doing this as well)
28
Q

Explain the Vasa recta and its participation in countercurrent EXCHANGE.

A
  • The vasa recta goes in the opposite direction of solutes in the nephron.
  • the vasa recta is picking up the solutes in the collecting ducts and carrying it towards the loop
  • once it passes the loop, water is pulled out
29
Q

What is cloudy urine and indication of ?

A

infection or salt crystals

30
Q

What type of urine odor is linked to bacterial metabolism?

A

ammonia odor

31
Q

T/F?

urine is mostly made up of solutes.

A

False

95% = water

Cardio I (9 decks)

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