Tissue fluid

Question 1

How is tissue fluid formed?

Answer 1

• When blood is at the arteriole end of the capillary, the hydrostatic pressure is great enough to push larger molecules out of the capillary.
• Proteins remain in the blood, the increased protein content creates a water potential between the capillary and the tissue fluid > however, overall movement of water is out from the capillaries into the tissue fluid.
• At the venous end of the capillary, less fluid is pushed out of the capillary as pressure within the capillary is reduced.
• The water potential gradient between the capillary and the tissue fluid remains the same as at the arteriole end, so water begins to flow back into the capillary from tissue fluid.
• Overall, more fluid leaves the capillary than returns, leaving tissue fluid behind to bath cells.
• If blood pressure is high (hypertension) then the pressure at the arteriole end is even greater > this pushes more fluid out of the capillary and fluid begins to accumulate around the tissues.