FLUID COMPARTMENTS AND FLUID BALANCE Flashcards
In lean adults, body fluids make up between
55 - 60% of total body mass.
Fluids are present in two main “compartments” –
inside cells and outside cells.
About two-thirds of body fluid is
intracellular fluid (ICF) or cytosol, the fluid within cells.
The other third, called extracellular fluid (ECF), is outside cells and includes all other body fluids.
About 80% of the ECF
is interstitial fluid, which occupies the spaces between tissue cells,
and about 20% of the ECF is blood plasma.
Two “barriers” separate intracellular fluid, interstitial fluid, & plasma:
- plasma membrane and
- blood vessel walls
Body Fluid Compartments image
slide 6
means that the various body compartments contain the normal amount of water and solutes.
Fluid balance
Water is the largest single component in the body, is about how much of the total body mass?
45%-50%of total body mass.
Daily water gain and loss are each about
2.5 L/day.
Sources of water gain are ingested liquids, (food and drinks) and water produced by
metabolic reactions.
Water is lost from the body through
urine, evaporation from the skin surface, exhalation by the lungs, and
GI tract (feces, defecation)
An area in the hypothalamus of the brain known as
the thirst center governs the urge to drink.
When water loss is greater than water gain, known as ?
dehydration, a decrease in volume and an increase in osmotic pressure of body fluids—stimulates thirst.
reduces urinary loss of Na+ and Cl– and water, thereby increases the volume of body fluids.
- Aldosterone
(Control of water levels)
promotes natriuresis, elevated excretion of Na+ (and Cl–) and water, which decreases blood volume and blood pressure
- Atrial natriuretic peptide (ANP)
(Control of water levels)
The major hormone that regulates water loss is
Antidiuretic hormone (ADH), also called vasopressin.
An increase in the osmotic pressure of body fluids stimulates ADH, which triggers the kidneys to
to reabsorb water. (RAA System) kicks in when blood pressure drops
Pathways through which Dehydration Stimulates Thirst:Renin - ADH image
Slide 12-13
Summary of Factors that Maintain Body Water Balance
Slide 14
The ions formed when electrolytes break apart serve four general functions in the body:
- Control the movement (osmosis) of water between fluid compartments.
2.Help maintain acid–base balance. (ph)
- Carry electrical current.
- Serve as cofactors for optimal activity of enyzmes.
(Electrolytes in Body Fluids)
are the most abundant extracellular cations.
Sodium ions (Na+)
involved in action potentials, muscle contraction, and fluid and electrolyte balance
(ECF IONS)
Na+ level is controlled by:
chlorine ions (Cl–) are the major extracellular anions.
They play a role in regulating osmotic pressure and forming HCl in gastric juice.
ECF IONS
Cl– level is controlled by processes that
increase or decrease kidney reabsorption of Na+.
ECF IONS
are the most abundant cations in intracellular fluid.
Potassium ions (K+)