Body Fluids Flashcards
What are organizational, functional activities directed at maintaining
Homeostasis
What is Homeostasis
The relative constancy of the milieu interieur
What are the aspects of body fluids
Volume, distribution, characteristics, functions
What is the most abundant constituent of the body and what is its percentage range
Water 45%-75%
Body water is the medium in which…
All solutes are dissolved
Metabolic reactions take place
What is the relationship between fat and water percentage
The more adipose tissue in body, the smaller the percentage of body water is
If body water content is computed as a fraction of lean body mass (excluding fat) how can we describe the differences between individuals
Insignificant
The standard values for a physiological reference individual is a 21 year old white male with 70 kg weight, what must we adjust for
Age, sex and weight
What are the variations in body water with age and sex
Newborn: 75%, low fat
Adult: 50% women 60% male, puberty and estrogen deposited fat in breasts and butt causes difference
Old: 50% man 45% woman as we age we lose muscle mass
How to calculate amount of water in a person
Percent water * weight / 100
What is necessary to know when administering water-soluble medication
Amount of body water
What kind of state is water in in order to maintain constant for health
Dynamic steady state
What are examples of water intake
Oral fluid, oral intake as food, oxidative water form metabolism (breakdown of glucose)
What are examples of water output
Lungs, skin, kidneys, stool
What is insensible output and what are some examples
Water output we are unable to feel (lungs and skin)
What is sensible output and what are some examples
Water loss that we can feel (kidneys aka pee and stool aka feces)
What are obligatory losses
Insensible (lungs and skin) and sensible (urine and stool) losses we must have very day
What are facultative losses and what is a major homeostatic organ for water balance
Losses that vary with intake (urine)
kidneys
What are the differences between insensible perspiration and sweating
Insensible perspiration ==> not obligatory or facultative sweating
IP: pure water ==> S: electrolyte solution
IP: Passive evaporation affected by ambient temp and relative humidity ==> S: active secretion (energy dependant)
IP: entire skin surface ==> S: sweat glands only
IP: continuous ==> activated by heavy work or high temp
Normally an individual is in what state
Water balance
Difference between 24 hour water turnover in adult vs infant body weight and why
A: 3-4% total body weight
I: 10% total body weight
Reason: high surface to volume ration in baby (very thin, no fat, less for water to travel before leaving body)
What does consistency in water volume under conditions of health maintain
Normal solute concentration, normal volume and pressure ==> adequate supply of O2 to to tissues
What is a negative water balance
Water loss > water intake
What causes a negative water balance
- Reduced water intake
- Excessive loss from gut (vomiting or diarrhea)
- Excessive sweating
- Excessive loss in expired air (dry air)
- Excessive loss in urine
What is water intoxication
Water intake > water loss
What causes water intoxication
- Excessive intake (if fluid around cells become more dilute than concentration inside, water will flow in cells causing cells to inflate)
- Renal system failure
How are the body water compartments organized
2 major compartments ==> one major compartment is subdivided into ==> two major and two minor sub compartments
How do the subcompartments of water differ
Size, volume, composition, function
Are body water compartments and subcompartments rigidly isolated chambers
No
How do the compartments interact with each other
In a continuous dynamic fashion
Does water exchange freely between compartments
Yes
What are the two main components and what percentage of the 60% body mass and body water do they contain
Intracellular fluid (water inside all cells of body): 2/3 total body water, 40% body mass
Extracellular fluid (fluid outside of cell in different parts of body): 1/3 total body water, 20% body mass
What are the two major subcompartments of the ECF component
Plasma and interstitial fluid
What are the two minor subcompartments of the ECF component
Lymph and transcellular fluid
What is hematocrit (Ht)
The percentage of blood volume that is occupied by red blood cells
Formula for Ht
Height of erythrocyte column / height of whole blood column
Normal Ht value
45%
What percentage of body mass does plasma take up
5% (1/4 of ECF)
What is interstitial fluid
True milieu interieur, fluid which percolates between individual cells
How does the movement of interstitial fluid move relative to lymphatic drainage
Some fluid moves into the lymph tubules then further into the lymphatic system
How does the lymphatic system work
Network of blind-ended terminal tubules ==> form larger lymphatic vessels ==> converge to form large lymphatic ducts ==> drain into large veins in the chest
What percentage of ECF is the lymph volume
1-2%
What is trans cellular fluid
Aggregate of small fluid volumes secreted by specific epithelial cells that line some body cavities that have specialized functions
What is the volume of ECF that is trans cellular fluid
< 1-2% does not contribute significantly to overall water exchanges
How does trans cellular fluid affect body fluid balance relative to local changes
TF affects and plays an important role in functions that affect local changes but local changes do not affect body fluid balance
Overall takeaway of body fluid relative to total volume, relative distribution between compartments and the compartments themselves
- Total volume remains constant
- Relative distribution between compartments remains constant
- Compartments are in a state of dynamic equilibrium
What are the methods of determining compartment volumes and which one is used most often
- Direct (literally taking out body water)
- Indirect (used most often)
How does the indicator dilution method work
- Introduce a known quantity (q) for indicator into vein
- Allow time to equilibrate
- Remove known volume of blood and centrifuge to obtain plasma
- Measure concentration (c) in unit of volume of plasma
- Calculate v= Q/c
What does one need to know in order to use the indicator dilution method
- Total quantity of test substance introduced
- Concentration of substance / unit volume of fluid after dispersion
What is the formula for indicator dilution method
V = Q/c
What are the considerations for indicator (Q) choice
- Non-toxic
- Will it diffuse into different compartments and diffuse readily
- Induce no changes in distribution of water between compartments
- Easy to measure
Total body water drug possibilities
Antipyrine, D2O, T2O
ECF compartment measurement indicators
Radioactively labeled INULIN, SUCROSE or MANNITOL
What is a normal ECF value
14L
Indicators for plasma volume measurements
Evan’s Blue or Albumin
Normal plasma volume value
3.5L
What must be corrected when finding a plasma volume measurement
Any amount which has been removed from body by metabolism or excretion during the time allowed for mixing
How to find ICF volume determination
Total body water - ECF
How to find ISF volume determinations
ECF - plasma = ISF
Why is there not a direct calculation or indicator to use when finding ICF or ISF
Water is split into ICF and ECF (ISF + Plasma) anything that goes into ICF will automatically cross the ICF ECF membrane and plasma ISF membrane and thus only give total body water. For ISF, anything put in ISF can cross into plasma from the ISF plasma membrane but not everything put in plasma can cross into ISF and not everything put in ECF can cross into ICF
What are the barriers to transport between ICF and external environment (ECF)
- Cell (plasma) membrane between ICF and ECF
- Capillary wall: barrier between ECF and plasma and between plasma and external environment
