Figure 1 – Physiology of capillary fluid exchange.
Capillary hydrostatic pressure decreases along the capillary path and
becomes lower than oncotic capillary pressure, which remains stable.
Thus, the net filtration pressure (NFP) is positive favorizing
transcapillary fluid filtration (transudation) at the arteriolar side
while it is negative at the capillary outlet responsible for
reabsorption of interstitial fluid into the vascular compartment. For
most tissues, there is an imbalance between filtration and reabsorption
in favor of an excess of fluid in interstitial space which is balanced
by removal of interstitial fluid via the lymphatics according to its
flow rate (Qλ) which finally returns to the bloodstream through the
thoracic duct. |