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Body Fluid Compartments and Fluid Balance. Objectives. 1. Differentiate between the terms osmole, osmolarity, osmolality and tonicity. 2. List the typical value and normal range for plasma osmolality. - PowerPoint PPT Presentation
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Body Fluid Compartments
and
Fluid Balance
Objectives 1. Differentiate between the terms osmole, osmolarity,
osmolality and tonicity. 2. List the typical value and normal range for plasma osmolality. 3. Explain osmosis in terms of a differentially permeable
membrane. 4. Understand the concepts of osmosis and osmotic pressure. 5. Define tonicity and be able to use the terms isotonic,
hypertonic, and hypotonic. 6. State the water content of the body, and its physiological
variations with age, fat content and gender 7. Understand the distribution of body water in the various body
fluid compartments. 8. Explain the principles of methods of measurement of body
fluids. 9. List the concentration of some important solutes in
intracellular and extra cellular compartments. 10. Understand the role of osmotic pressure in the distribution of
body water into compartments.
Some useful information One osmole is 1 gram molecular weight of
undissociated solute. Eg. 1 osmole of glucose = 180 grams of glucose , is equal
to 1 osmole of glucose because glucose does not dissociate.
1 gram molecular weight of NaCl (58.5 gm) is equal to 2 osmole because NaCl dissociates into Na+ and Cl- (both are osmotically active).
Osmolality A solution that has 1 osmole of solute dissolved in 1 Kilogram of water
Osmolarity A solution that has 1 osmole of solute dissolved in in 1 liter (1000 ml) of water .
Conventionally: because of low concentration, solute dissolved in mg/litre of water or Kg of H2O milliOsmole (mOsm)
Normal Osmolarity of plasma is about 300 mOsm/L
-1 Mol OF Glucose solution?
- 1 Mol NaCl solution?
In the ECF, max contribution to Osmolalirty is by NaCl
Osmolarity/Osmolality
Is a measure of the total number of dissolved particles in a solution
Ionic composition of the ICF fluid is different from that of ECF
But Osmolarity of ICF is equal to that of ECF.
Concept of osmotic pressure
H2OH2O
Solute
Semi-permeable membrane
Osmosis: Diffusion of H2OAcross semi permeable membrane From high H2O concentration to low H2O concentration. In tissues- via lipid bilayer -Through water channels(acquaporins)
Osmotic pressure is thepressure which is appliedat the membrane to oppose osmosis
Movement of H2O
Osmotic pressure is directly proportionalTo the osmolarity (solute concentration)
Concept of hydrostatic pressure
Pressure = 2 mmHg
Pressure = 30 mmHg
Principle of OsmosisOsmosis is the net movement of water molecules
through a selectively permeable membrane
During osmosis water molecules pass through a selectively permeable membrane in two ways (1) through the lipid bilayer and (2) through
aquaporins (aqua = water) channels.
The osmosis, diffusion, filtration and reabsoption provide for continual exchange of
water and solutes (electrolytes) among different body compartments
Yet, the volume of the fluid in different body compartments remains remarkably stable
Body fluid compartment ECF also includes
lymph, CSF, synovial fluid, aqueous & vitreous humor,
endolymph & perilymph and fuild present in
pleural, pericardial and peritoneal cavities
Constitution of Extra and Intra cellular fluids
Distribution of important ionic and organic constituents