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Body Fluid Compartments - Coggle Diagram
Body Fluid Compartments
List the main fluid compartments
TOTAL BODY WATER (TBW)
Intracellular Fluid (ICF)
found
INSIDE all cells
Extracellular Fluid (ECF)
found
surrounding all cells
divided into:
interstitial fluid (ISF) = 3/4
plasma = 1/4
transcellular fluid = 0.5L
total amount of body fluid in weight of a 70kg man
60%
∴ 70kg = 70L
so 60% =
42L
Estimate the volume of the main fluid compartments based on sex & mass
factors affecting TBW
age
gender
percentage body fat
TBW in:
MALES = 60%
FEMALES = 50%
INFANTS = 80%
why difference between male & female?
females higher % of adipose tissue
Compare & contrast the composition of the main body fluid compartments
In EXTRACELLULAR FLUID
higher %
Na+
Cl-
HCO3+
in INTRACELLULAR FLUID
higher %
K+
PO4 3-
protein
similar levels of
Ca 2+
Mg 2+
Explain how body fluid compartments can be measured
volume of compartments measured using technique....
INDICATOR (DYE) DILUTION METHOD
indicator properties:
even distribution through relevant compartments
no leak, loss or metabolism
non-toxic
method
known
amount of indicator =
X
injected into body compartments
unknown
volume of fluid (body compartments) =
V
final concentration =
C
DIFFERENT INDICATORS used to calculate volumes of DIFFERENT COMPARTMENTS
some spaces CANNOT be measured
with markers
must use other values calculated from
other compartments
e.g. ICF = TBW-ECF
ISF = ECF - plasma volume
Explain the mechanisms responsible for fluid exchange between the main compartments
OSMOSIS
requires:
solute conc gradient
semipermeable membrane
D: water moves from LOW solute conc to HIGH solute conc
primary force that drives fluid exchange between different compartments
OSMOLARITY
total no. of particles in solution
mosmol/L
OSMOTIC PRESSURE
opposing pressure required to prevent osmotic movement of H2O across given membrane
kPa or mmHg
TONICITY
osmotic effect of a solution at cell membrane relative to normal extracellular fluid
isotonic, hypertonic, hypotonic
what causes fluid exchange?
difference in hydrostatic & osmotic pressure
hydrostatic pressure
pressure of fluid within compartment
e.g. plasma within capillary exert pressure on capillary wall
osmotic pressure
pressure required to prevent osmosis occurring
process of
fluid exchange
1.
fluid leaves plasma
(at arteriolar end of capillary)
why?
outward force hydrostatic pressure predominates
fluid returns to plasma
(at venular end of capillary)
why?
inward force of colloid osmotic pressure predominates
fluid enters lymph capillaries
why?
hydrostatic pressure in interstitial spaces forces fluid
interstitial fluid now in
EQUILIBRIUM
with transcellular & intracellular fluid
plasma, ISF & ICF have
SAME OSMOLARITY
at equilibrium
278-300 mOsmol/kg H2O
Appreciate that there are mechanisms that regulate body fluid volume and osmolality
to maintain equilibrium in body...
water intake must equal water output
water gain = 2.5L/day
food & drink = 2.2L
metabolism = 0.3L
water loss = 2.5L/day
skin & lungs = 0.9L
urine = 1.5L
faeces = 0.1L
how body increases body water/retains water?
plasma volume more concentrated
(
↑ plasma osmolarity or ↓ blood volume
= dehydrated)
↑ thirst = ↑ water ingestion
or
↑ ADH released = ↓ water excretion
plasma volume returns to normal conc
(
↓ plasma osmolarity or ↑ blood volume
)
NEGATIVE FEEDBACK = decrease ADH & decrease thirst
how can body decrease body water?
increases urine output as decrease in ADH
limits amount of water reabsorbed into blood
sweating (exercise/hot weather)
blood loss
diarrhoea
vomiting
burns (seeps out of body)
alcoholic beverages
excessive intake of water =
water intoxication
hyponatremia
(important electrolytes diluted - leads confusion, headaches, swelling of brain)
excessive loss of water =
dehydration
hypovolaemia
(when body loses fluid - leads to dizziness, dry mouth, fatigue)
Describe the effects of intravenous infusion of solutions of differing osmolality & tonicity
4 different types of intravenous fluids
WATER
exact same effect as hypotonic saline
HYPOTONIC SALINE
ECF volume = increase
ICF volume = increase - water moves in via osmosis
ECF osmolality = decreases
ICF osmolality = decreases
HYPERTONIC SALINE
ECF volume = dramatically increase - water
pulled
out of cells from ICF
ICF volume = decreases
ECF osmolality = increases (because added hypertonic solution w/ lots of solutes)
ICF osmolality = increase
ISOTONIC SALINE
ECF volume = increase
ICF volume = stay same
ECF osmolality = stay same
ICF osmolality = stay same
