Physiology 1: body fluid compartments Flashcards
what is osmolarity
concentration of osmotically active particles in a solution (osmol/l)
what does high osmolarity mean
lots of ions that drive water osmosis eg a concentrated solution (usually weak salts)
what 2 factors must be known to calculate osmolarity
molar concentration and number of osmotically active particles
what would the osmolarity of 100mM of MgCl2 be
moles = 100mM, active particles = 3: 3x100 = 300mosmol/l
what is the difference between osmolality and osmolarity
osmolality is units /kg of water vs osmolarity is units /l
what is the osmolarity of most body fluids
300mosmol/l
what is tonicity
the effect an osmotic solution has on a cell
what effect does a hypotonic solution have on a a cell
hypotonic = not many active particles eg very dilute - causes water to diffuse into cell to higher concentration and cell to swell/ Burst (lysis)
what effect does a hypertonic solution have on a a cell
hypertonic = lots of active particles eg very concentrated - causes water to diffuse out of cell to higher concentration and cell to shrink
what is an isotonic solution
osmolarity is same inside and outside the cell
what % of males and females are water
males 60% and women 50%
what are the 2 major compartments total body water exists as
intercellular fluid (66%) and extracellular fluid (33%)
what is extracellular fluid made of
interstitial fluid 80% / plasma 20% (liquid component of blood) / negligible lymph and transcellular
what different tracers are used to calculate how much water are in each compartment: TBW, ECF and plasma
TBW: titrated water 3H2O / ECF: inulin / plasma: labelled albumin
how would you use a tracer to figure out total volume of compartment (volume of distribution)
1) add specific dose of tracer eg D=42mg to unknown water volume (V) 2) mix and take a small sample volume eg 5ml 3) measure concentration and scale back eg 0.005mg/5ml = 1mg/l 4) insert into calculation V = D/C eg 42/1 = 42L