Body Fluid Compartments II

These flashcards are designed to help students review key concepts related to body fluid compartments, osmolality, and the effects of different solutes on fluid movement and balance.

Osmolality

The number of free (dissociated) particles in solution, measured in osm or mosm/kg of H2O.

Osmotic Equilibrium

The state in which the total osmolality between intracellular fluid (ICF) and extracellular fluid (ECF) is equal.

Hypotonic Expansion

A condition where both ECF and ICF volumes expand, resulting from drinking water, causing a fall in osmolality.

Isotonic Expansion

A condition where only ECF expands without a change in osmolality, typically from the infusion of 0.9% NaCl.

Hypertonic Expansion

A condition resulting from ingesting NaCl without water, leading to an increase in ECF osmolality and water moving out of cells.

Reflection Coefficient

A measure of the permeability of a solute across a membrane; a value of 1 indicates impermeability, generating a sustained osmotic effect.

Urea

A permeable substance that diffuses into cells and takes water with it, causing no change in osmolarity.

Osmotic Gradient

A difference in osmolality across a membrane that drives the passive movement of water.

Intracellular Fluid Volume (ICFV)

The volume of fluid within the cells, typically 60% of total body water.

Extracellular Fluid Volume (ECFV)

The fluid volume outside the cells, comprising 40% of total body water and including blood plasma.