bodily fluid control (midterm 3) Flashcards

1
Q

what do the kidneys do

A

maintain bodily fluid volumes and compositions

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2
Q

how much water does a 70 kg person contain

A

42 liters of water (60%) (Vt)

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3
Q

how many liters of water are inside the 75 trillion cells of the body and what are they part of

A

28 liters - intracellular fluid (Vic)

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4
Q

how many liters of water are extracellular

A

14 - 11 are interstitial (Vis), 3 are plasma (Vp)

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5
Q

how many liters of water are blood and how many are plasma

A

5 liters; 3 liters

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6
Q

how do you measure total body water

A

add a bolus of radioactive water and measure concentration after a few hours (Vt)

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7
Q

how do you measure extracellular fluid volume

A

add a bolus of radioactive sodium and measure concentration after a few hours (Vec)

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8
Q

how do you measure intracellular fluid volume

A

equals total body water minus extracellular fluid volume (Vic)

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9
Q

how do you measure plasma volume

A

add a bolus of radioactive serum albumin and measure concentration after a few hours (Vp)

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10
Q

how do you measure interstitial fluid volume

A

equals extracellular fluid volume minus plasma volume (Vis)

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11
Q

how do you measure total blood volume

A

plasma volume / (1 minus hematocrit)
hematocrit = total blood cell volume

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12
Q

what is osmosis

A

the diffusion of water, through a selectively permeable membrane, from a region of low solute concentration to high solute concentration

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13
Q

why does osmosis happen

A

water moves to try to equilibrate solute concentration on either side of the membrane

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14
Q

what is an osmole

A

the total number of particles in solution that are establishing an osmotic gradient
= moles x dissociable particles

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15
Q

what is the normal value for osmoles

A

280 mOsm/L
dominated by Na+, glucose, urea

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16
Q

what is osmosis equilibrium

A

if a cell is placed in a solution with normal osmolarity (280 mOsm/L) the cell will neither shrink or swell - isotonic solution

17
Q

what is a hypotonic solution vs hypertonic solution

A

solution with less osmolarity vs solution with more osmolarity

18
Q

what does a hypotonic solution result in

A

the cell will swell as it tries to dilute its solutes

19
Q

what does a hypertonic solution result in

A

the cell will shrink as it tries to concentrate its solutes

20
Q

what two basic principles guide the discussion of fluid regulation

A
  1. intracellular = extracellular osmolarity due to water transport across membrane
  2. total osmolarity of a system (intracellular + extracellular) is constant unless added or removed
21
Q

if a hypertonic solution is administered to a patient, what happens?

A
  • The osmolarity of the extracellular fluid increases, intracellular decreases
  • Osmosis pushes water out of the cell and into the extracellular space
22
Q

if a hypotonic solution is administered to a patient, what happens?

A
  • The osmolarity of the extracellular fluid decreases, intracellular increases
  • Osmosis pushed water into the cell and out of the extracellular space
23
Q

what is an edema

A

the presence of excess fluid in the body, typically in the extracellular fluid space but sometimes involving the intracellular fluid space

24
Q

what two conditions lead to an intracellular edema and how common are they

A

RARE
- Depression of metabolic systems of the tissues
- Inadequate nutrient delivery to the cell

25
what two conditions lead to an extracellular edema and how common are they
COMMON - Abnormal leakage of fluid from the plasma through the capillary wall and into the interstitial space - failed lymphatic drainage
26
what is the equation that describes capillary filtration and what does each variable stand for
Filtration = Kf x (Pc - Pif - πc + πif) - Kf = capillary filtration coefficient - Pc = capillary hydrostatic pressure - Pif = interstitial fluid hydrostatic pressure - πc = capillary osmotic pressure - πif = interstitial osmotic pressure
27
what increases capillary filtration
increased Kf, increased Pc, decreased πc
28
what results in heart failure
decreased cardiac output, increased capillary pressure leads to increased capillary filtration
29
what results in renal failure
decreased Na+/H2O excretion, increased blood volume, increased arterial pressure, increased Pc leads to increased capillary filtration
30
what three safety factors prevent an edema
- increased interstitial fluid volume will lead to increased interstitial fluid pressure - the ability of the lymph flow to increase 10-50 fold - washdown of interstitial fluid protein