6. Body Fluid Distribution Flashcards
Body fluid distribution
The balance concept
Fluid loss = fluid intake
Electrolyte loss = electrolyte intake
Fluid intake - regulated by thirst mechanism, drinking habits
Electrolyte intake - controlled by dietary habits
Fluid output- regulated mainly by kidneys
Electrolyte output - regulated mainly by kidneys
Interstitium and interstitial fluid
Space between cells is called sterstitium fluid and space is called interstitial fluid
Two major solid structures in interstitium are collagen fibers and proteoglycan filaments
Almost all fluid in interstitium is in form of fluid proteoglycan mixtures, little free fluid
Determinants of net fluid
Capillary hydrostatics pressure (Pc) - Tends to force fluids outward through the capillary membrane, depends on arterioles resistance and Venus pressure
Increase pressure = increase filtration decrease absorption
Intersititlal fluid (Pif) - opposes filtration
Plasma colloid osmotic pressure ( pie p) - Causing osmosis of water inward through the membrane (where protein goes water goes)
Interstitial fluid colloid pressure (pie if) - Causing osmosis of fluid outward through the membrane
Increase protein in blood = filtration
Arterial end vs venous end
Arterial -Go out to cells (positive is filtration)
Venous - unoxygenated blood back to heart (negative reabsorption)
Filtration vs reabsorption
If capillary BP is treated than capillary osmotic pressure then there will be a net movement of fluid out of the capillary (filtration)
If capillary BP is less than capillary osmotic pressure there will be a net movement of fluid into the capillary (reabsorption)
Net filtration pressure
NFP = (Pc-Pif) - (pie p - pie if)
Hyperemia
Arteriolar dilation leads to increased blood flow
Affected tissues turn red (erythema)
Congestion
Reduced outflow of blood from a tissue
It can be systemic, such as cardiac failure - heart relaxed
Or localized such as isolated venous obstruction - decrease blood flow on venous end
