Fluid and Electrolyte Balance

functions of water

Transport nutrients

Transport/excrete metabolic waste

Support cell shape and structure

Lubricate surfaces

Sustain normal body temperature

T/F:

maintenance of fluid balance is integrated with maintenance of electrolyte balance

true

can injury or illness affect water balance

yes

what % of our body weight is water

50%

what % of body weight does water make up for infants

75%

why can water be less than 50% of an older persons body weight

due to less lean body mass

is total body water influenced by fat/lean mass

yes it is

what fraction of total body water is composed of intracellular fluid

2/3

interstitial

surrounds cells (2/3 of ECF)

intravascular

within blood

transcellular

found in secretions within organs (GI secretions, cerebrospinal fluid, intraocular fluid)

third spaces

found between the cells or organs

examples of third spaces

ascites

what is the treatment for ascites

paracentesis

what macromolecule is abundant in third space fluid

protein

What kind of tissue has the lowest percentage of water in the body?

fat

osmosis

Movement of fluid across a semipermeable membrane from low concentration to high concentration area

filtration

Fluid moves between compartments

Water and solutes (except for RBC and plasma proteins) move across the membrane b/w compartments

what are the 2 types of pressure control

osmotic and hydrostatic

osmotic pressure control

 Colloid osmotic pressure (oncotic)

 Is the force that “pulls” water through a semi-permeable membrane toward the more concentrated solution

what is hydrostatic pressure control

blood pressure

osmolarity

number of osmols per liter of solution (mOsm/L)

osmolality

number of osmols per kg of solvent (mOsm/kg)

what is the difference between osmolarity and osmolality

osmolality is measured (actual value) and osmolarity is estimated

blood used as “normal” range for body fluids

285-295 mOsm/kg H20

osmotic pressure in the GI tract

300mOsm

are hypertonic conditions associated with swelling or shriveling of the cell

shriveling

are hypotonic solutions associated with swelling or shriveling

swelling

Fluid intake

Anything liquid at room temp.

metabolic water

Contributes little in practical sense

anabolic vs catabolic

anabolic reactions ___ water

release (condensation reactions)

do catabolic reactions release or require water

either

fluid output

 Sensible losses

 Insensible losses

Sensible losses

those that are visible and measurable ex. Urine and feces

Obligatory Urine

minimum urine amount needed to remove waste: 500ml

renal solute load (RSL)

waste in urine

Facultative Urine

excess fluid (that is excreted under normal conditions) consumed over obligatory

total urine output

the sum of obligatory urine and facultative urine

how is the solute concentration in the urine determined

determined by measuring its specific gravity

Insensible losses

usually not seen or measured ex. through respiration or through the skin by evaporation