Question

In a capillary, the hydrostatic pressure (P) is 30 mm Hg, the osmotic pressure (p) is -2 mm Hg, the hydrostatic pressure in the interstitial space (Pc) is 25 mm Hg, and the osmotic pressure in the interstitial space (pi) is 2 mm Hg. What is the direction of fluid movement and the net driving force?

1) Absorption; 6 mm Hg
2) Absorption; 9 mm Hg
3) Filtration; 6 mm Hg
4) Filtration; 9 mm Hg
5) There is no net fluid movement

Answer 1

The direction of fluid movement is out of the capillary and into the interstitial space, known as filtration. The net driving force for this movement is 9 mm Hg.Thus the correct option is 4.

Step-by-step explanation:

To determine the direction of fluid movement and the net driving force in a capillary, we need to calculate the net filtration pressure (NFP). The NFP is the result of the interplay between the hydrostatic pressures and osmotic pressures within the capillaries and the interstitial space.

Using the provided values, we can calculate the NFP as follows:

NFP = (hydrostatic pressure in the capillary - hydrostatic pressure in the interstitial space) - (osmotic pressure in the capillary - osmotic pressure in the interstitial space)

NFP = (P - Pc) - (π - πc)

NFP = (30 mm Hg - 25 mm Hg) - (-2 mm Hg - 2 mm Hg)

NFP = 5 mm Hg - (-4 mm Hg)

NFP = 5 mm Hg + 4 mm Hg

NFP = 9 mm Hg

Since the NFP is positive, we can conclude that the fluid will move out of the capillary and into the interstitial space, a process known as filtration. The net driving force for this fluid movement is 9 mm Hg.