Question

Starling forces govern the passive exchange of fluid between the capillary beds and the interstitial fluid. For each of the modifications listed below include the following in your answer: a) describe how this change will alter factor(s) of the Starling principle, and b) indicate whether filtration across capillaries into the interstitial fluid will increase or decrease.

i) Increasing blood hematocrit levels.

ii) Increasing release of norepinephrine from the sympathetic nervous system.

iii) Moving from supine (lying horizontally with face and torso upward) to a standing position?

Answer 1

The net movement of fluids occurs by the effect of starling forces. The filteration of fluid depends on:

(Plasma hydrostatic pressure+ tissue oncotic pressure) - (plasma oncotic pressure + tissue hydrostatic pressure).:

i) increasing the blood haematocrit value will increase the viscosity of blood and hence, a) decrease the hydrostatic pressure that will cause b) decrease the filteration across capillaries into interstitial fluid.

ii) increasing release of norepinephrine from the sympathetic nervous system will cause vasoconstriction which in turn a) increases the capillary hydrostatic pressure and hence b) inncrease the filteration across capillaries into interstitial fluid.

iii) Moving from supine to standing position results in the increase in central venous pressure which causes a) increased capillary hydrostatic pressure and hence b) increased filteration across capillaries into interstitial fluid.