Body fluids Flashcards
What process is responsible for relative constancy of the “Milieu Interieur”?
What is the importance of the “Milieu Interieur”
Homeostasis
*Maintaining health = constant milieu intérieur by homeostasis
- Environment surrounding individual cells is vastly different from external environment
- Internal environment remains relatively constant under conditions of health
*Milieu intérieur = ISF (fluid which percolates between individual cells)
What are the 4 aspects of body fluids?
- Volume
- Distribution
- Characteristics
- Functions
*All impact homeostasis
What is the importance of water in our body?
Most abundant single constituent –> 45% to 75%
- Solutes are dissolved
- Metabolic reactions take place
Also:
- Regulates body temperature
- Lubricates joints
- Moistens tissues
- Protects organs and tissues
- Caries nutrients, O2 to cells
- Helps flushing out wastes
What is responsible for this change of % of water between 45% and 75% from one individual to another?
Change in qty of fat from one person to another
Same qty (#L) for pretty much everyone but if a lot of fat, that qty in a smaller % of the body
Fat contains only 10% water Other tissues = around 75%
If exclude fat in calculus of water content, difference = insignificative
What are the standard values for physiological references?
What parameters can make these values change?
21 y-o, white, male, 70kg weight –> 60% water
Must adjust:
Age, sex, weight, race, ethnicity, lifestyle…
What happens with the % of water as we age?
And what is the difference between men and women?
It goes down
Babies –> 75% (no difference between boys and girls)
Adults –> 50% (women), 60% (men)
Elders –> 45% (women), 50% (men)
Reduces because tissues become dryer, loss of muscle mass (75% water)
Why is the % of water an important information on an individual?
When administrating water-soluble medication –> for good concentration
What is a “Dynamic Steady State”?
Body water remains CONSTANT in health –> total %
changes internally between different compartments
*Amount water that comes in = amount comes out (from external environment)
What are the sources of intake of water?
- Oral fluid
- Oral intake as food
- Oxidative water from metabolism (body itself produces water)
What are the different losses of water ?
2 types
Obligatory:
Whatever comes in, this goes out
- Lungs (insensible)
- Skin (insensible)
- Kidneys (sensible, bare min to flush out wastes)
- Stools (sensible, bare min to flush out wastes)
Facultative:
Depends on intake
- Kidneys –> Urine
Kidney = major homeostatic organ of water balance
Sweat –> not in a category
What is the difference between perspiration (obligatory loss) and sweating?
Insensible Perspiration:
- Pure water
- Passive evaporation (no energy required)
- Entire skin surface (even when lacking sweat glands)
- Continuous
Sweating:
- Electrolyte solution
- Active secretion (requieres energy)
- Sweat glands (some people don’t have them so won’t sweat)
- Activated by heavy work and high temp
What is the normal turnover for water balance for an adult and an infant?
Which is one of them higher?
Adult: 3-4% of body weight
Infant: 10% of body weight –> greater surface to mass ration so molecule of water closer to skin + kidney less mature so more loss electrolytes (don’t give just water)
Why is it important thant the Body water volume stays constant to maintain health conditions?
Helps maintain normal solute concentration
Helps maintain normal blood volume and pressure
–> Aequate supply of O2 to tissues
What can by the causes of a negative water balance?
negative water balance = loose> intake
- Reduced intake
- Excessive loss from gut
- Excessive sweating
- Excessive loss in expired air (dry air at high altitudes)
- Excessive loss in Urine (Kidney problems)
What can be the causes of water “Intoxication”?
Water intake > loss
- Excessive intake
- Renal systme failure –> no way to get rid of excess water
What involves the dynamic steady state?
Exchanges between individual and environment
+
Internally, between different compartments
What are the 2 body water main compartments? (%)
And their sub compartments?
Water = 60% body mass
Intracellular Fluid (2/3): 40% of body mass
(Homogenous for all type cells)
Extracellular Fluid (1/3): 20% or B.M.
2 Major: Plasma (5% B.M) + Interstitial Fluid (15% B.M.)
2 Minor: Lymph + Transcellular (negligeable % but important role)
What is the difference between the capillaries and the lymphatic vessels?
Capillaries are continous, all connected
Lymphatic system has extremities
*ISF which goes into lymphatic system becomes lymph
What is Transcellular fluid?
(minor subcompartment of ECF)
aggregate of small fluid volumes into body cavities (lined by epithelial cells) with specialized functions (important local role)
*Very localized, doesn’t contribute significantly to overall water exchanges, local changes do not affects body water balance!
Volume negligeable in body < 1-2%
examples:
- Intraocular (eye)
- Cochlear (ear)
- Synovial (articulation)
- Cerebro-spinal
- Pleural and pericardial
- Peritoneal
- Fluid in ducts of glands, bladder, etc.
What in implied when we say compartments are in state of DYNAMIC equilibrium of body water?
Total volume = Constant
Relative Distribution = Constant
but water flows freely between them
Which methods are used to determine compartments volumes?
- Direct –> weight with water, take all water out and weight again, caluclate difference
- Indirect –> Indicator Dilution Method
When can’t calulate volume easy bc irregular shape compartment
- Add qty
- Wait for mix
- remove a sample to calulate the concentration of the solution that was fist added
All we need to know:
- total qty of test substance
- concentration of substance/unit volume after dispersion
V = Q/c
How can we know the volume of plasma in the body?
By indicator dilution Procedure:
1. Introduce Quantity (Q) of indicator
2. Wait to equilibrate
3. Remove a certain known volume
4. Cetrifuge to obtain Plasma
5. Measure concentration
6. Calculate V = Q/c
How is the indicator chosen for the indicator dilution procedure?
- Non-toxic
- Diffuse readily
- Induces no changes in DISTRIBUTION of water between compartments
*Does work if because of it, more fluid goes into cells - Easy to measure
ex for total body water: has ot be able to cross the cell membrane and capillary membrane
D2O, T2O, Antipyrine
For ECF, substance can’t cross the cell membrane
What indicators are usually chosen for ECF volume measurement?
What is the normal ECF value?
- Radioactively labeled INULIN
- Sucrose or Mannitol
–> They don’t cross cell membranes
Normal EFC volume = 14L
What can cause error in clinical situation for plasma measurment for example?
What is the normal plasma volume value?
correct for any amount which has been removed from body metabolism or excretion during mixing time
Normal plasma volume value = 3.5L
How is ICF volume water is measured?
How is ISF measure?
ICF = Total body water - ECF
ISF = ECF - Plasma
*much easier to calculate plasma, total body water of ECF volume by indirect method
What are the ionic differences between ICF and plasma?
ICF = high in K+ and Mg++ (low in Na+ and Cl-)
Plasma = high in Na+ and Cl- (low in K+)
0.9% NaCl (physiological saline)
What are the units for :
1. amount (mass) of solute
2. Number of solute molecules
3. # of reactive units
- amount (mass) of solute = g% = g solute/dl (100mL water)
- Number of solute molecules = Mol = mol/L (convert if given in grams)
- # of reactive units = Molarity of Ions * Valency (# charges/unit volume)ex: Ca++ (valency = 2) has 2 equivalents/mol3
On what depends the viability of a cell?
- Constancy of the Milieu Interieur
- Exchanges with internal and (ultimately) external environment
