body fluid compartments Flashcards
what is osmosis
diffusion of water form high to low solutes
what is osmolarity
[C} of all particle mosm/L
what is normal body osmolatiry
295 mosm/L
what are 2 types of pressure that can move fluids
- hydrostatic - push
2. osmosis - pulls (sucking)
what is total body water in men and women
men - 60%
women - 50%
how much water in most tissue
75-80%
where is total body water
ECF - 1/3
ICF - 2/3
where is most ECF water
interstitial 3/4 (25% total)
plasma 1/4 (8% total)
what is composition of plasma
93% water, 7% solids
what is sequestered water
unavailable water in the bone and CT - not counted for calclulations
what factors affect water
age - less with age
women - less water
fat - less with fat
what is average blood volume
70cc/kg – 5L in normal male - 3L plasma
what is border between ICF and other
cell membrane
what is border between plasma and ISF
cap walls
how does water get into cells
through aquaporin channels
what happens when add salt to body
water exits cells
what is tonicity
[C] off effective osmoles (usually Na)
what is hypertonic
more solute than normal
what are main ECF and ICF cations
ECF - Na
ICF - K
what maintains differences between Na and K
ATP ase - NA out and K in
what is normal ECF [Na}
140
what percentage of osmolarity is Na
95%
what is size of ICF and ECF compartments dep on?
water - follows the solutes, but solutes don’t pass easily
what is osmolarity forumula
particles/vol
what us ICF volume formula
ICF vol = # ICF particles/ECF osmolarity – ICF volume is inversely proportional to ECF osmolarity
what happens if add 3L of water to ECF
2L to ICF and 1L stays in ECF
what happens to ICF in hyponatremia
ICF up - swollen
what happens to ICF in hypernatremia
ICF down - shrunken
what are 2 exception to hyponatreemia rules
- hyperglycemia - water leaves cells and shrink, yet hyponatremia
- hypertriglyceridemia
what does [Na} tell you about ECF volume
nothing!
what can diffuse through a small cap
only water and small solutes
what is main diff between plasma and ISF consitiuents
plasma has high protein concentrations, solute levels are about the same
what are 2 ways solute move across the membrane
- diffusion
2. solvent drag
what happens to ECF volume if we add Na
volume rises
what happens to ICF if add isotonic fluid
no change - ECF will go up though
physical exam signs of increased ECF
- edema
- JVP
- rapid weight gain
- maybe hypertension
physical exam signs of low ECF
- dry mouth/eyes
- poor skin turgor
- low blood volume signs
