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THREE BODY FLUID COMPARTMENTS FREE

These two compartments are separated by cell membranes, and are very different in their composition (i.e.

Extracellular fluid (ECF) – itself can be divided into:.

Intracellular fluid (ICF) – the fluid within cells which accounts for 65% of total body weight.

Water makes up 50-70% of body mass – approximately 42L in a 70kg person. The osmolality of plasma = 290 mosmol/kg H 2O Body Water Compartments Osmolality is the preferred expression of physiologists because it is independent of temperature and pressure.

Osmolality – osmotic concentration per volume of solution (osmol/kg H 2O).

Osmolarity – osmotic concentration per mass of solvent (osmol/L).

It can be expressed as ‘osmolarity’ or ‘osmolality’: Osmotic potential is determined by the number of osmotically active particles per litre. Fluid at lower osmotic potential is hypotonic.Fluid at higher osmotic potential is hypertonic.Fluid at the same osmotic potential as plasma is hypotonic.The creation of osmotic gradients is the primary method for the movement of water in the body.

THREE BODY FLUID COMPARTMENTS FREE

‘Osmosis is the movement of water across a semi-permeable membrane from regions of low solute concentration to those of higher concentration’.īiological membranes are semi-permeable – they allow the free movement of water but restrict the movement of solutes.