Hayley Pearlman
October 11, 2016
PAT 20 Week 5: Fluid and Electrolyte Balance
Total body water (TBW): 60% of the human body is composed of water. The body’s water is
classified into three categories:
-Intracellular fluid (ICF): 67% of TBW
-Interstitial fluid (ISF): 25% of TBW (Outside of blood cells)
-Plasma volume (PV) 8% of TBW (Extracellular but still within blood vessel)
-Plasma: fluid that flows through blood vessels
-TBW describes water in two categories: fluid inside blood vessels (intravascular fluid – IVF) and
fluid outside of blood vessels such as in the lymph system and cerebrospinal fluid (extravascular
fluid –EVF).
-Intravascular: Intracellular fluid
-Extravascular: Interstitial fluid and plasma
-Intracellular (ICF): fluid inside cells
-Extracellular (ECF): Interstitial fluid and plasma
-Large amounts of sodium and chloride
-ECF values are used clinically to analyse electrolytes in the blood.
-Vascular subdivision: Blood
-Interstitial subdivision: Fluids, commonly in gel form, which act to transport
gases, nutrients, wastes, from and to the vascular division.
-Transcellular subdivision: cerebrospinal fluid and fluid contained in various
body spaces (peritoneal, pleural, and pericardial cavities, joint spaces, GI tract,
etc.)
***It is important to note that TBW can be described from a vascular or cellular
perspective.
INTRA: inside blood vessels, INTER: between blood vessels, EXTRA: outside blood vessels.
From the cellular perspective: Extracellular fluid: plasma and ISF
, Hayley Pearlman
October 11, 2016
o -Plasma has a greater protein concentration than ISF
o -Proteins cannot pass through blood vessels into interstitial fluid. This creates a
gradient in which interstitial fluids flow into blood vessels (low solute in
interstitial to high solute in blood vessel) to create an isotonic environment.
The pull of the proteins within blood vessels exert an osmotic pressure which
prevents too much plasma from leaking through the capillaries into the tissues
(without osmotic pressure would we have edema?).
o -Proteins suspended in plasma are in a colloidal state creating colloid oncotic
pressure (COP) of 24mmHg within the blood vessels. The opposing pressure
exerted by ISF is called hydrostatic pressure and is normally 17mmHg.
-Electrolytes are charged molecules which fully dissociate in the body’s fluids.
-Positively charged ions = cations
-Negatively charged ions = anions
Osmosis: The movement of water across a semi-permeable membrane. Water moving along its
gradient creates osmotic pressure whereas the pressure to oppose osmotic pressure is
hydrostatic pressure.
Tonicity: Effect of osmotic pressure on a cell.
-An effective osmole is on that exerts osmotic force and cannot permeate the cell
membrane.
1. Describe the control of cell volume and the effect of isotonic, hypotonic, and hypertonic
solutions on cell size.
-The regulation of cell volume is essential for life because it creates a suitable
environment for all metabolic reactions to occur. Cell volume is kept constant through
intake and excretion.
-Over hydration, or an excess of water, results in the accumulation of water in
interstitial spaces causing edema.
-Death can occur when TBW is equal to 20-25% in comparison to its usual 60%
Hypertonic: Occurs when water loss is greater than sodium loss. This results in a shrunken and
dehydrated call in which fluid in the cell moves into extracellular space.
Hypotonic: The cell swells when solute loss is greater than solvent (water) loss. This is the result
of a high solute concentration inside the cell drawing in water from outside the cell.
October 11, 2016
PAT 20 Week 5: Fluid and Electrolyte Balance
Total body water (TBW): 60% of the human body is composed of water. The body’s water is
classified into three categories:
-Intracellular fluid (ICF): 67% of TBW
-Interstitial fluid (ISF): 25% of TBW (Outside of blood cells)
-Plasma volume (PV) 8% of TBW (Extracellular but still within blood vessel)
-Plasma: fluid that flows through blood vessels
-TBW describes water in two categories: fluid inside blood vessels (intravascular fluid – IVF) and
fluid outside of blood vessels such as in the lymph system and cerebrospinal fluid (extravascular
fluid –EVF).
-Intravascular: Intracellular fluid
-Extravascular: Interstitial fluid and plasma
-Intracellular (ICF): fluid inside cells
-Extracellular (ECF): Interstitial fluid and plasma
-Large amounts of sodium and chloride
-ECF values are used clinically to analyse electrolytes in the blood.
-Vascular subdivision: Blood
-Interstitial subdivision: Fluids, commonly in gel form, which act to transport
gases, nutrients, wastes, from and to the vascular division.
-Transcellular subdivision: cerebrospinal fluid and fluid contained in various
body spaces (peritoneal, pleural, and pericardial cavities, joint spaces, GI tract,
etc.)
***It is important to note that TBW can be described from a vascular or cellular
perspective.
INTRA: inside blood vessels, INTER: between blood vessels, EXTRA: outside blood vessels.
From the cellular perspective: Extracellular fluid: plasma and ISF
, Hayley Pearlman
October 11, 2016
o -Plasma has a greater protein concentration than ISF
o -Proteins cannot pass through blood vessels into interstitial fluid. This creates a
gradient in which interstitial fluids flow into blood vessels (low solute in
interstitial to high solute in blood vessel) to create an isotonic environment.
The pull of the proteins within blood vessels exert an osmotic pressure which
prevents too much plasma from leaking through the capillaries into the tissues
(without osmotic pressure would we have edema?).
o -Proteins suspended in plasma are in a colloidal state creating colloid oncotic
pressure (COP) of 24mmHg within the blood vessels. The opposing pressure
exerted by ISF is called hydrostatic pressure and is normally 17mmHg.
-Electrolytes are charged molecules which fully dissociate in the body’s fluids.
-Positively charged ions = cations
-Negatively charged ions = anions
Osmosis: The movement of water across a semi-permeable membrane. Water moving along its
gradient creates osmotic pressure whereas the pressure to oppose osmotic pressure is
hydrostatic pressure.
Tonicity: Effect of osmotic pressure on a cell.
-An effective osmole is on that exerts osmotic force and cannot permeate the cell
membrane.
1. Describe the control of cell volume and the effect of isotonic, hypotonic, and hypertonic
solutions on cell size.
-The regulation of cell volume is essential for life because it creates a suitable
environment for all metabolic reactions to occur. Cell volume is kept constant through
intake and excretion.
-Over hydration, or an excess of water, results in the accumulation of water in
interstitial spaces causing edema.
-Death can occur when TBW is equal to 20-25% in comparison to its usual 60%
Hypertonic: Occurs when water loss is greater than sodium loss. This results in a shrunken and
dehydrated call in which fluid in the cell moves into extracellular space.
Hypotonic: The cell swells when solute loss is greater than solvent (water) loss. This is the result
of a high solute concentration inside the cell drawing in water from outside the cell.
