Body Fluids Flashcards

1
Q

functions of the kidney

A

control ECF volume
control ECF osmolarity
excrete some metabolic wastes, toxins and drugs
synthesize hormones directly or indirectly
control ECF concentration of specific ions

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2
Q

Why is control of ECF volume important?

A

it accumulates in the interstitial spaces and causes edema!

- it accumulates in the cardiovascular space and increases myocardial work!

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3
Q

Where is extracellular volume located?

A

in the interstitial and vascular space

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4
Q

Why is osmolarity important?

A

normal osmolarity of ECF is 285 mOsm (can round this up to 300 mOsm)!

  • if ECF osmolarity is too high, water is pulled out of cells, cells shrink!
  • if ECF osmolarity is too low, cells swell!
  • neither state is conducive to normal cell function!
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5
Q

Why do changes in plasma parameters affect the entire ECF?

A

because water and solutes readily exchange between plasma and interstitial fluid

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6
Q

How does the renal system regulate ECF volume?

A

by controlling the amount of NaCl in ECF

if you put salt in, water will follow

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7
Q

how does the renal system regulate ECF osmolarity?

A

by controlling the amount of ingested or synthesized water

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8
Q

What happens to the ECF if you add more water?

A

it becomes more dilute

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9
Q

What happens to the ECF if you remove water?

A

ECF becomes more concentrated

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10
Q

What is filtration?

A

the movement of water due to differences in hydrostatic pressure
important in movement between the vascular and interstitial spaces only
water does not enter or leave cells via filtration

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11
Q

What is osmosis?

A

important in moving water in and out of capillaries!

• the ONLY factor that determines whether water moves into or out of cells

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12
Q

What does tonicity of the surrounding fluid determine?

A

the cell size

tonicity is a function of the non-penetrating solute particles in solution

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13
Q

What do both the plasma and interstitial fluid compartments contain?

A

large levels of Na+ and Cl- and very small levels of K+, Mg2+

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14
Q

What does the intracellular compartment contain?

A

lots of K+, Mg+2, phosphates, and protein!

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15
Q

How do these compartments remain different in composition?

A

cells expend energy to maintain these differences - ATP is used to power active
transport

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16
Q

how might body fluid compartment size and osmolarity respond to very rapid ingestion of water?

A

absorbed into capillaries!
- whatever happens in plasma happens in interstitial fluid, therefore both
compartments increase in size!
- both compartments equilibrate in osmolarity, decreased (more dilute) compared
to control!

17
Q

What occurs during water intoxicaton?

A

ECF is diluted and the cell swells

18
Q

a human RBC placed in a bathing medium with an osmolarity of 400 mOsm that contains 300 mOsm of penetrating solutes and 100mOsm of non-penetrating solutes would be most likely to….

A

SWELL

19
Q

What type of solute determines the tonicity (cell size)?

A

only non-penetrating solutes determine cell size