Starling Equation - The Equation - Approximated Values

Approximated Values

Following are approximated values for the variables in the equation for both arterioles and venules:

Location Pc (mmHg) Pi (mmHg) σπc (mmHg) σπi (mmHg)
arteriolar end of capillary +35 −2 +28 +0.1
venular end of capillary +15 −2 +28 +3

Some albumin escapes from the capillaries and enters the interstitial fluid where it would produce a flow of water equivalent to that produced by a hydrostatic pressure of +3 mmHg. Thus, the difference in protein concentration would produce a flow of fluid into the vessel at the venous end equivalent to 28 − 3 = 25 mmHg of hydrostatic pressure. The total oncotic pressure present at the venous end could be considered as +25 mmHg.

In the beginning (arteriolar end) of a capillary, there is a net driving force outwards from the capillary of +9 mmHg. In the end (venular end), on the other hand, there is a net driving force of −8 mmHg.

Assumed that the net driving force declines linearly, then there is a mean net driving force outwards from the capillary as a whole, which also results in that more fluid exits a capillary than re-enters it. The lymphatic system drains this excess.

Read more about this topic:  Starling Equation, The Equation

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