The Body Fluid Compartments Flashcards
Insensible water loss
Water loss that we are not consciously aware of
Sources by which water is added to the body
- Ingested in the form of liquid or water in food
2. Synthesized in the body by oxidation of Carbohydrates
Amount of water ingested
2100ml/day
Water intake through metabolism
200ml/day
Total amount of daily intake of water
2300ml/day
How is water lost by the body
- Insensible water loss
- Fluid loss in sweat
- Water loss in feces
- Water loss by the kidneys
Ways in which water is lost through Insensible water loss
- Evaporation from respiratory tract
2. Diffusion through the skin
Amount of water lost through Insensible water loss
700ml/day
Amount of water lost through Evaporation from respiratory tract
300-400ml/day, during prolonged heavy exercise 650 ml/day
Amount of water lost by diffusion through the skin
300-400ml/day
How is diffusion through skin minimized
Cholesterol filled cornified layer of skin
How is water lost through respiratory tract
Air enters the respiratory and becomes saturated with moisture to a vapor pressure of 47mmHg before it is expelled. Because the inspired air is below 47mmHg water is continuously lost through respiration.
Why do we get a dry feeling in the respiratory passage during cold weather
Air inspired has a vapor pressure that decreases to nearly 0 causing a great loss of water through the lungs as the temperature decreases
Amount of water lost through sweat
100ml/day, in hot weather or heavy exercise increases to almost 1-2L/hour (5000ml/day)
How is water lost through sweat over come
Activation of the thirst mechanism
Amount of water loss through feces
100ml/day, sometimes increases to liters per day in people with severe diarrhea
Amount of water lost by kidneys
1400ml/day, during prolonged heavy exercise 500ml/day
Total body fluid distributed between two compartments
Extracellular and intracellular fluids
Types of extracellular fluid
- Interstitial fluids
- Blood plasma
- Transcellular fluid
Transcellular fluids
Fluids in enclosed compartments like :fluid in Synovial, peritoneal, pericardial, intra ocular s spaces and cerebrospinal fluid. Specialized fluid and some cases its composition is much different from plasma or Interstitial fluids
Amount of Transcellular fluid present in the body
12L
Total body water of a 70kg adult man
Body water is about 60% of the body weight /about 42L.
Percentage of body water depends on
Agree, gender, and degree of obesity.
As person grows older body fluid decreases
Aging is associated with an increased percentage of body weight being fat which decreases the percentage of water in the body
Women body water percentage
Did to greater percentage of body fat their total body water averages about 50%
Premature and new born babies total body water
70-75%
Amount of intracellular fluid
28L that is about 40%of total body weight
Amount of extracellular fluid
Makes up 20%of the Body weight that is 14L in 70kg man
Amount of Interstitial fluid
11L
Amount of plasma in the body
1/4th of extracellular fluid 3L
Average volume of blood
7%of body weight about 5L. 60% plasma and 40% red blood cells
Hematocrit
Fraction of blood composed of red blood cells determined by centrifuging blood in a “Hematocrit tube” until the cells Brecon tightly packed in the bottom of the tube. 3-4%plasma remains entrapped among the cells therefore true Hematocrit is only 96%of the measured Hematocrit
Plasma and Interstitial fluid separated by
Capillaries membrane
Plasma have higher concentration of_____ than in Interstitial fluid
Protein because of low permeability of capillaries to plasma Proteins
Donnan effect
Plasma protein have have a net negative charge therefore binds to positively charged ions (cation) and since are in greater conc in the plasma give the plasma a higher conc of positively charged ions. Conversely - vely charged Proteins repel - vely charged ions (anions) therefore having a higher conc. In the Interstitial fluid.
Ion content of extracellular fluid
Large amount of Sodium, Chloride, bicarbonate ions and small amounts of calcium, potassium, magnesium, phosphate and organic acid ions
Ionic content of intracellular fluid
Large amounts of potassium, phosphate, magnesium, sulfate ions and proteins and small amount of Sodium, Chloride ions and almost no calcium
Indicator-dilution method
It’s a method of measuring volume of fluid compartments. Indicator sub is placed in the compartment allowing it to disperse evenly throughout them a sample is taken out and analyzed. It uses the conservation of mass principle. If no sub leaks out total mass of the sub of sub in compartment will be equal to total mass of sub injected
What is needed to be know for calculation using indicator-dilution method
- Total amount of sub infected
2. Concentration of fluid in chamber after sub is dispersed
Formula of the indicator - dilution method
Vol B= Vol A x conc A /conc B
Indicator- dilution method used only when
- Dispersed evenly
- Disperse only in the compartment to be measured
- Indicator is not metabolized or excreted before reaching equilibrium
- Indicator easily and accurately measured
- Indicator is non toxic
Measurement of total body water
Use of radioactive water(tritium), heavy water (dueterium) or antipyrine (lipid soluble easily penetrate membrane)
Measurement of extracellular fluid
Subs that are not readily permeable through cell membrane. Radioactive Sodium, radioactive chloride, radioactive iothalamate, thiosulfate ions and insulin. Sometimes radioactive Sodium diffuse into the cells in small amounts therefore measurement is not true
Calculation of intracellular volume
Measured Indirectly
IC vol= total body water - EC Vol
Measurement of plasma volume
Subs that do not readily penetrate capillaries membrane. Serum albumin labeled with radioactive iodine, dyes that bind to plasma Proteins like Evans Blue dye (T-1824)
Calculation of Interstitial fluid
IF vol= EC Vol - plasma volume
Measurement of blood volume
Total blood vol = plasma vol / 1-hematocrit or inject RBCs labeled with radioactive material like radioactive chromium and calculated using indicator-dilution method
