Body Fluids Flashcards
functions of the kidney
control ECF volume
control ECF osmolarity
excrete some metabolic wastes, toxins and drugs
synthesize hormones directly or indirectly
control ECF concentration of specific ions
Why is control of ECF volume important?
it accumulates in the interstitial spaces and causes edema!
- it accumulates in the cardiovascular space and increases myocardial work!
Where is extracellular volume located?
in the interstitial and vascular space
Why is osmolarity important?
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!
Why do changes in plasma parameters affect the entire ECF?
because water and solutes readily exchange between plasma and interstitial fluid
How does the renal system regulate ECF volume?
by controlling the amount of NaCl in ECF
if you put salt in, water will follow
how does the renal system regulate ECF osmolarity?
by controlling the amount of ingested or synthesized water
What happens to the ECF if you add more water?
it becomes more dilute
What happens to the ECF if you remove water?
ECF becomes more concentrated
What is filtration?
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
What is osmosis?
important in moving water in and out of capillaries!
• the ONLY factor that determines whether water moves into or out of cells
What does tonicity of the surrounding fluid determine?
the cell size
tonicity is a function of the non-penetrating solute particles in solution
What do both the plasma and interstitial fluid compartments contain?
large levels of Na+ and Cl- and very small levels of K+, Mg2+
What does the intracellular compartment contain?
lots of K+, Mg+2, phosphates, and protein!
How do these compartments remain different in composition?
cells expend energy to maintain these differences - ATP is used to power active
transport
