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Physiology 209 > Body Fluids > Flashcards

Flashcards in Body Fluids Deck (16):

% of Water in various tissues

-Skin 70%
-Muscle 75%
-Heart,Liver, 70-80%
,Brain Kidney

-Bone 25%
-Fat (adipose) 10%


How does water differentiate in proportions of body mass

Normal = 60%
obese/fatter: lower percent = 45%
Skinny = 75%

Amount of water remains constant but percent changes depending on mass


Body Water (as % of body mass)
Percents for age and gender:

Infants = 65%
10-18 yrs = 59%m - 57%f
18-40yrs = 61%m - 51%f
40-60yrs = 55%m - 47%f
>60yrs = 52%m - 46%f

*m= male f= female


How to calculate approximate Body Water

For 70 kg male: %water ~60%

Absolute amount of water
(70x60)/100 = 42 kg = ~42L


Sources for intake of water

Oral fluid - 1.2L
Oral Intake as food - 1.1L
Oxidative water-
from metabolism 0.4L


Sources for Output of water

Lungs - 0.4L )__> Insensible
Skin - 0.5L )

Kidney - 0.5L
Stool (feces) 0.1 L


Obligatory Losses

Account for 1.5 L of water

insensible ~1.0L
Urine + Stool ~0.5L


Facultative Losses

Vary with intake
-kidney(major homeostatic organ)


Insensible perspiration

1. Pure Water
2. Passive Evaporation(affected by ambient temp. and relative humidity)
3. Entire skin surface(present even in individuals lacking sweat glands)
4. Continous



1. Electrolyte solution
2. Active secretion
3. Sweat glands
4. Activated by heavy work or high temperature


Approximate turnover of water in a 24 hr period

3-4% of body weight --- adults
~10% of body weight ---- infant


Compartments of Total body Water

Total body Water =60% of mass

Of this 60% mass
Intracellular Fluid(ICF) = 2/3 or 40% or body mass
Extracellular Fluid(ECF) = 1/3 or 20% of body mass

Of the ECF
5% of body weight is plasma
15% of body weight is ISF

Two subcompartments
Lymph Drainage ~1-2% of ECF


Interstitial Fluid

fluid which percolates between individual cells


Transcellular fluid

aggregate of small fluid volumes secreted by specific cells into a number of body cavities (line by epithelial cells) and having specialized functions


Calculating Total Water Mass + mass of compartments

Equation for find total volume
V= Q/c q=quantity c=conc.

Use Antipyrine, D20, T2O for measuring TOTAL (ICF+ECF)

Use Inulin, sucrose, mannitol to measure TOTAL ECF

Use Evans Blue to measure TOTAL PLASMA volume


Body fluids- ionic composition

ICF - high in K+ (and Mg++)
but low in Na+ and Cl-

ECF - High in Na+, Cl- and low in K+