Colloid osmotic pressure -vs- hydrostatic pressure

For starters. . .hydrostatic pressure is the pressure in the pipes (the veins and arteries); colloidal pressure is the pressure exerted by what is in the tissues of the body. These two pressures work against each other. What results will be fluid balance.

See http://allnurses.com/nursing-student-assistance/could-somebody-please-325965.html - Could somebody please explain hydrostatic and oncotic pressure?

Found this with a search:

http://allnurses.com/nursing-student-assistance/could-somebody-please-325965.html


Basically, oncotic pressure is the "pulling pressure" into a vessel. Depends on the protein concentration in the liquid. A higher protein content sucks more fluid into the vessel.

Hydrostatic pressure is the pressure exerted by fluid at rest ie. pressure "pushing" fluid out of a vessel.

The balance between the two determines how much fluid remains in the vasculature and how much leaks into the interstitium.

My understanding is that hydrostatic pressure is the pushing power of circulating blood and fluid. ie, Fluid pushes itself through the normal "leaks" in the small spaces between the thin cells of the capillary walls. Then the fluid goes into the tissues, cells, etc. outside of the capillaries. This is hydrostatic pressure.

Colloid osmotic pressure is just the opposite, and it is exerted by the protein albumin. Albumin is normally too large to pass through the capillary walls, so it stays inside the capillaries. The structure of albumin is such that it pulls fluid towards itself. (How and why it does this is probably beyond my own ability to understand or explain, but just know that it does this. lol.) This effect of albumin is colloid osmotic pressure. This keeps too much fluid from leaving the capillaries.

The simplified version is that hydrostatic pressure pushes fluid out of the capillaries, while colloid osmotic pressure keeps fluid inside the capillaries.

There's a good visual about this in one of my books. Wish I could show it to you, esp since I had a problem understanding this myself one time.

Anyway, hope this helps!