body fluids Flashcards
what is the fundamental principle
functional activities are directed at maintaining homeostasis
what is homeostasis
the relative constancy of the milieu interieur (internal environment)
who is claude bernard
father of physiology - created milieu interieur
what are the 2 principles of milieu interieur
environment surrounding individual cells is vastly different from external environment (external can change)
internal environment remains relatively constant under conditions of health (must stay constant)
name the aspects body fluids milieu interieur includes
volume
distribution
characteristics
functions
what is the most abundant single constituent of the body
water
how much of body weight is water
around 45%-75% depends on individual
what happens in body water
medium in which solutes are dissolved and metabolic reactions take place
name functions of body water (8)
regulated body temp
lubricates joints
lessens burden on kidneys and liver (flush out waste)
carries nutrients and O2 to cells
helps dissolve minerals and nutrients
helps prevent constipation
protects body organs and tissues
moistens tissues (mouth, eyes, nose)
why is there a large body water content difference in people
depends on where water is in body
not the same as blood sugar or pH (has a small range of acceptable numbers)
name % of water in various tissues
skin
muscle
heart, liver, brain, kidney
bone
fat
skin = 70%
muscle = 75%
heart, liver, brain, kidney = 70-80%
bone = 25%
fat = 10%
what accounts for the large difference in %body water
adipose tissue
its only 10% water - its very dry
leads to big difference in body water
describe body water and weight trends
the more fat the less % body water
since the fat takes up more space
the more thin the more % body water
if body water content was calculated as a fraction of lean body mass what would happen
differences in % body water would be insignificant
around the same for all
standard values for a physiological reference individual
21 y/o white male 70kg
must adjust for age sex and weight
generally describe how % body water changes from infant–>old (factor in sex)
infants (regardless of sex) = little subcutaneous fat so higher %body water (~75%)
puberty = more fat so percent goes down, but here different for sex
males = ~60%
females = ~50%
as you age = loose muscle mass so % decreases
males = ~50%
females = ~45%
why does female %body water change at puberty (lower than males)
sex hormone estrogen leads to characteristic fat deposit in butt and breasts - this difference continues for rest of life
how to calculate body water
for 70kg male, ~60% water
(70x60)/100 = 42kg ~ 42L
weight x %body water / 100 = kg (approx same amount of litres)
if 70kg female, ~50% water
70x50/100 ~ 35L
why is knowing amount of body water important (+ calculations)
when administering water soluble medication
differs a lot when looking at elderly, infants, very thin people
could lead to a low concentration in body or high one - which isnt good
calculations
L TO mL then use dosage
ex 70kg male - 42L water and dosage = 10mg/7kg
so final concentration in body
100/42,000 = 0.0024mg/mL
T OR F: body water needs to be constant in health
TRUE
its in a dynamic steady state
not static - dynamic equilibrium
exchanges between individual and external environment must be equal
describe intake of body water
oral fluid
oral intake as food
oxidative water from metabolism (cellular respiration produced H20)
what must be equal for body to be in water balance
intake and output total values must be equal
describe output of body water
insensible (stuff you don’t feel)
sensible (stuff you feel)
describe insensible (output)
skin - passive evaporation NOT SWEAT tho
lungs - lose h20 when breathe
depends on how dry air is
describe sensible (output)
kidneys (flush out waste)
stool (feces)
additional facultative losses (by kidneys, to make up difference, urine, creates fluid balance and depends on h2o intake)
describe obligatory losses
just getting rid of waste ~1.5L per day
insensible (lungs and skin)
sensible (urine and stool)
these always happen (this is why you need water and can’t survive long without it)
describe facultative losses
vary with intake
urine (produce more urine if drank more water)
what is the kidney
major homeostatic organ for water balance
what is insensible perspiration (compare to sweat, brief)
through skin not sweating tho very different
sweating is in loss column too but it’s different
describe insensible perspiration (4)
1 - pure water
2 - passive evaporation (affects by ambient temp and humidity) *no energy required
3 - entire skin surface (present even when person doesn’t have sweat glands)
4 - continuous (day and night)
describe sweating (4)
1 - electrolyte solution
2 - active secretion (requires energy)
3 - only sweat glands
4 - activated by heavy work or high temp
describe turnover in adults
around 3-4% body weight over 24 hours
describe turnover in infants
around 10% total body weight in 24 hours
much more sensitive to dehydration and over heating bc no subcutaneous fat (high surface to vol ratio) and kidneys are developed (also why can’t give baby water)
compare water turnover in adults and infants
for adults it’s like they are a sphere - a water molecule must travel radius to get to surface
for infants it’s like they are a tube so water doesn’t have to travel far to get out
what does constant body water help maintain
normal solute concentrations
normal blood volume and pressure
=
allows for adequate supply of O2 to tissues (and for nutrients to get places)
what is a negative water balance
water loss > water intake
name and describe the 5 ways to create negative water balance
1 - reduced intake (if obligatory losses are great and you aren’t drinking water)
2 - excessive loss from gut (diarrhea)
3 - excessive sweating (heavy exercise)
4 - excessive loss in expired air (dry air at high altitudes)
5 - excessive loss in urine (medical issue like diabetes)
what is water intoxication
water intake > water loss
name and describe the 2 ways to create water intoxication
1 - excessive intake (like in a marathon race, overloading by drinking too much water too fast = throws off electrolyte balance, also hyponatremia)
2 - renal system failure (kidneys don’t lose enough water)
is sweat obligatory or facultative
NEITHERRRRR - is an output
what is state of body water
dynamic steady state
how much % of body mass is total body water
60%
how many major compartments is body water in
2
describe subdivisions of one major compartment (ECF)
2 major subcompartments
2 minor subcompartments
what do the major/minor subcompartments differ in
size
volume
composition (electrolyte/protein concentration)
function
T OR F: body water compartments & subcompartments are rigidly isolated chambers
FALSE
they are NOT rigidly isolated chambers
compartments are continuously interacting in a dynamic fashion
water exchanges freely between them
name the 2 main body water compartments and percentages
intracellular fluid = ICF ~ 2/3 body water = 40% of body mass
extracellular fluid = ECF ~ 1/3 = 20% of body mass
what is intracellular fluid
water inside cells of body
aggregate of fluid bound by internal surfaces of all cell membranes
what is extracellular fluid
outside cells and in different parts of body
give litres of body water % and compartments for reference male
total body water = 42L
ICF ~ 28 L
ECF ~ 14L
name subdivisions of ECF
2 major = plasma and ISF (interstitial fluid)
2 minor = lymph and transcellular fluid
what is plasma
fluid medium in which blood is suspended
fluid inside circulatory system surrounding blood cells
what happens when you centrifuge blood
plasma
buffy layer
RBCs
heavy components at bottom
what is the buffy layer
WBCs
platelets
what is hematocrit
Ht
percentage of blood volume that is occupied by rbcs (erythrocytes)
what is normal hematocrit
~45%
what is Ht
Ht = packed cell volume (PCV)
why is hematocrit important
RBCS are important to transport O2
helps to see what is wrong - like if someone is anemic
how to calculate Ht
height of erythrocyte column OVER height of whole blood column
what percent of body weight is plasma
5%
what percent of body weight is ISF
15%
what is ISF
true milieu interieur
fluid which percolates between individual cells
(plasma moves out of capillaries and becomes ISF)
describe interstitial fluid and lymphatic drainage
lymphatic system picks up ISF (becomes lymph)
blind ended tubules
describe lymphatic system (lymph volume)
network of blind ended terminal tubules
coalesce to form larger lymphatic vessels
converge to form large lymphatic ducts
drain into large veins in the chest
lymph vol = ~ 1-2% of ECF
what is transcellular fluid
aggregate or small fluid volumes secreted by specific epithelial cells that line some body cavities
found in different body compartments
fluids have specialized functions
what is volume of transcellular fluid
<1-2% of ECF
describe transcellular fluids (generally)
doesn’t contribute to overall water exchanges - local changes do not affect body fluid balance
locally it plays an important role in function (must have the right amount of fluid)
T or F: total volume remains constant
TRUEEE
T or F: compartments are in a state of static equilibrium
FALSE
dynamic equilibrium- water can move freely between compartments
T or F: relative distribution between compartments remains constant
TRUE
total water = 60%
ICF = 40%
ECF = 20%
ISF = 15%
plasma = 5%
name 2 ways how to determine compartment volumes
direct
indirect
describe direct method of determining compartment volumes
weigh spider then put into desiccator and weigh again - not always used bc spider dies
describe indirect method of determining compartment volumes
indicator dilution method - figure out volume if shape is irregular
take known quantity of solution and add to unknown volume and allow time to mix and then take out known volume and determine concentration to find volume
what info do you need for indicator dilution method
total quantity of test substances introduced
concentration of substance/unit volume of fluid after dispersion
V= Q/c
describe steps of indicator dilution method (5)
1 - introduce known quantity (Q) of indicator into vein
2 - allow time to equilibrate and move between different compartments
3 - remove known volume of blood and centrifuge to get plasma
4 - measure concentration (c) in unit volume of plasma
5 - calculate V=Q/c
describe how to choose indicator for indicator dilution method (4)
must be non toxic
diffuse readily - distribute evenly throughout compartments to be measured - need to know where indicator will go and cross through
cannot induce changes in distribution of water between compartments
must be easy to measure
to determine total body water what indicator to use (indicator dilution method)
antipyrine
D2O
T2O
must be able to cross plasma, capillary wall, ISF and cell membrane into ICF
to determine total ECF volume what indicator to use (indicator dilution method)
inulin
sucrose
mannitol
must make sure it won’t cross cell membrane
to determine total plasma volume what indicator to use (indicator dilution method)
evans blue
radioactive albumin
wont cross capillary wall
how to use indicator dilution method in clinical setting - how to adjust and for what
must correct for any amount that has been removed from body by metabolism or excretion during the time allowed for mixing
how to calculate ICF
total body water - ECF = ICF
how to calculate ISF
ECF - plasma = ISF
what type of fluids are body fluids
aqueous solutions of inorganic ions with variable amounts of proteins
describe ionic composition of ICF
high in K+ (and Mg++)
low in Na+ and Cl-
describe ionic composition of ECF
high in Na+ and Cl-
low in K+
ISF and plasma = slightly different
plasma has more protein than ISF
0.9%NaCl
what are artificial physiological solutions
substitute for plasma/ISF
name 3 artificial physiological solutions
physiological saline (0.9% NaCl)
ringers solution
locke ringer solution
describe physiological saline
9g NaCl and H2O to make 1L
restoring body water - in dehydration and acute blood loss
describe locke ringer solution
has 0.5g dextrose (sugar)
used for energy for fluid movement
