Body Fluid Compartments Flashcards
What are the units of osmolarity?
osmol/l
What is required to calculate osmolarity?
2 factors i.e. 150mM NaCl and 100mM MgCl2
What is tonicity?
the effect on cell volume
isotonic - normal
hypotonic - too much water
hypertonic - too little water
What does hypertonicity cause?
cell shrinkage
What does hypotonicity cause?
cell lysis from swelling
What are the units of osmolality?
osmol/kg
What is different between osmolarity and tonicity?
tonicity takes into consideration the ability of a solute to cross the cell membrane
What is the Total Body Water percentage of a male and female?
male 60% of body weight
female 50% of body weight
What does total body water exist as?
2 major compartments of ICF and ECF
What is the concentration of water in ICF and ECF?
ICF 67% TBW
ECF 33% of TBW
What is included in EC fluid?
plasma
interstitial fluid
lymph - negligible
transcellular fluid - negligible
How might you trace TBW?
3H2O
How might you trace ECF?
Inulin
How might you trace plasma?
labelled albumin
What is TBW equivalent to?
ECF+ICF
How do you measure the volume of distribution?
take the tracer and equilibrate it with water
take a small sample and measure the concentration
c=m/v
work out volume of distribution
What is the equation for calculating the volume of distribution?
V (L)=Dose/Sample concentration
What is insensible loss of water?
loss through skin and lungs
What is sensible loss of water?
faeces
urine
sweat
What is the general input and output of water/day?
2500ml
What may increase water loss through sweat?
hot weather and exercise
What may increase water loss through the lungs?
exercise
What decreases the water loss from urine?
hot weather and exercise
What is the general ICF and ECF concentrations of Na?
ICF - 10
ECF -140
What is the general ICF and ECF concentrations of K?
ICF - 140
ECF - 4.5
What is the general ICF and ECF concentrations of Cl?
ICF - 7
ECF - 115
What is the general ICF and ECF concentrations of HCO3?
ICF -10
ECF -28
What is particularly potent in the plasma?
Na, Cl, HCO3, protein anions
What is particularly potent in the interstitial fluid?
Na, HCO3, Cl
What is particularly potent in the IC fluid?
K, PO4, Mg, protein anions, small Na
What is the difference in osmotic concentration of ECF and ICF?
none - they are identical
Why is there no difference in ICF and ECF?
because any change in solute concentration leads to immediate change in water distribution
What is fluid shift?
the movement of water between the ICF and ECF in response to an osmotic gradient
What are some challenges to fluid homeostasis?
gain or loss of water
gain or loss of NaCl
gain or loss of isotonic fluid
What happens when NaCl is gained in the ECF?
ECF increases water volume
ICF decreases water volume
What happens when NaCl is lost in the ECF?
ECF loses water volume
ICF gains water volume
what does a gain or loss of isotonic fluid cause?
change in ECF volume but not fluid osmolarity
What alters the composition and volume of the ECF?
kidney
What is regulation of ECF vital for?
regulation of blood pressure
What is electrolyte balance important for?
can directly affect water balance
the concentrations of electrolytes can affect cell function
What is particularly important about Na and K?
they are major contributors to the osmotic concentrations of ECF and ICF
they directly affect the functioning of all cells
What can result from increasing plasma K?
muscle weakness - paralysis
cardiac irregularities - cardiac arrest
