BODY FLUID COMPARTMENT AND FLUID BALANCE. Body fluid compartment . ECF also includes lymph, CSF, synovial fluid, aqueous & vitreous humor, endolymph & perilymph and fuild present in pleural, pericardial and peritoneal cavities .
ECF also includes lymph, CSF, synovial fluid, aqueous & vitreous humor, endolymph & perilymph and fuild present in pleural, pericardial and peritoneal cavities
The osmosis, diffusion, filtration and reabsoption provide for continual exchange of water and solutes (electrolytes) among different body compartments
Yet, the volume of the fluid in different body compartments remains remarkably stable
Dynamics of capillary exchange (Starling’s Law of capillaries)
Body fluid volume remains constant because water loss is equal to water gain
Rate of formation of metabolic water is not regulated
2% decrease in body mass due to fluid loss causes mild dehydration
Rate of formation of metabolic
water is not regulated to maintain homeostasis
Water gain is regulated mainly
by drinking through thirst
This is mainly done by the kidneys
Osmosis is the net movement of water molecules through a selectively permeable membrane
During osmosis water molecules pass through a selectively permeable membrane in two ways (1) through the lipid bilayer and (2) through aquaporins (aqua = water) channels.
Is a measure of the total number of dissolved particles in a solution
Ionic composition of the ICF fluidisdifferent from that of ECF
But Osmolarity of ICF is equal to that of ECF.
Osmotic equilibrium is maintained rapidly between ICF and ECF
What Causes this?
Accumulation of high levels of osmotically
active solutes (urea in kidney failure)
What happens ?
Water moves into the cells from ECF until osmotic equilibrium is achieved.
Pronounced swelling of neurons leads to brain dysfunction
Swelling of muscle leads to muscle weakness.
Hypertension and edema caused by expansion of plasma volume.
What Causes this?
Over hydration: Renal failure with inability to excrete diluted urine
Excessive drinking (transient)
Increase in ADH secretion
Water intoxication: condition of over hydration, hypotonicity and
cellular swelling from excess water.
Dye-dilution metod (Indicator-dilution)