1. Body Fluids Flashcards
Homeostasis
relative constancy of Milieu Intérieur
Body water percentage (PRI)
60%
Physiological Reference Individual (PRI)
21 yo white male 70kg
Body water varies with
sex, age and body fat
Body water of newborn
75%
Body water after puberty
women = 50%
men = 60%
Body water over 65yo
women = 45%
men = 50%
Calculating absolute body water
(weight(kg) x body water(%))/100
Water balance
input = output
Water input
- oral fluid
- oral intake as food
- oxidative water from metabolism
Water output
- breathing (lungs)
- passive evaporation (skin)
- urine (kidneys)
- stool
- facultative loss
Obligatory loss
will always be lost no matter the input, can be insensible or sensible
Insensible loss
can’t feel it: breathing + passive evaporation loss
Sensible loss
aware: urine + stool
Facultative loss
vary with intake but necessary to maintain balance
Insensible perspiration key points
- pure water
- passive evaporation
- entire skin surface (no sweat glands needed)
- continuous and obligatory
Sweating key points
- electrolyte solution
- active secretion
- involves sweat glands
- activated by heavy work/temp
Negative water balance
water loss greater than water intake
Causes of negative water balance (5)
- reduced intake
- excessive loss from gut
- excessive sweating
- excessive loss in expired air
- excessive loss in urine
Positive water balance (water intoxication)
water loss smaller than water intake
Causes of positive water balance
- excessive intake
- renal system failure
2 major body water compartments and distribution
Intracellular Fluid (ICF) = 2/3, 40%
Extracellular Fluid (ECF) = 1/3, 20%
Components of Extracellular Fluid
- plasma = 5%
- Interstitial Fluid (ISF) = 15%
- lymph
- transcellular fluid
Hematocrit (Ht)
percentage of blood volume occupied by red blood cells
Hematocrit formula
erythrocyte column height/whole blood column height
Hematocrit normal value
45%
Plasma
fluid medium in which blood cells are suspended
Interstitial Fluid (ISF)
fluid which percolates between individual cells
Lymph
lymphatic vessels
Transcellular fluid
aggregate of small fluid volumes secreted by epithelial cells that line in body cavities
Out of 60% body water:
- 40% =
- 20% =
->15% =
-> 5% =
- 40% = ICF
- 20% = ECF
->15% = ISF
-> 5% = Plasma
Indicator Dilution Method
add known quantity of indicator and measure concentration in unit/volume of plasma
Indicator Dilution Method: calculating total body water
indicator must be able to cross capillary wall + cell membrane
Indicator Dilution Method: calculating ECF
indicator can’t cross cell membrane
Indicator Dilution Method: calculating plasma
indicator can’t cross capillary wall
Indicator Dilution Method: calculating ICF
ICF = total body water - ECF
–> need 2 indicators
Indicator Dilution Method: calculating ISF
ISF = ECF - Plasma
–> need 2 indicators
Viability of cells depends on… and requires…
- relative constancy of internal environment
- exchanges within internal and external environment
