Interstitial fluid and fluid in body cavities is an ultrafiltrate of plasma. The concentration of small molecules, e.g. electrolytes and glucose, is comparable to that in plasma.
The forces responsible for fluid formation are:
1. Forces in the capillary causing fluid to flow across membranes into the interstitium include: capillary hydrostatic pressure (21 mm Hg) - plasma oncotic pressure (28 mm Hg) = - 7 mm Hg 2. Forces in the interstitium causing fluid to flow back into the capillary include: interstitial hydrostatic pressure (1 mm Hg) - interstitial oncotic pressure (8.5 mm Hg) = - 7.5 mm Hg 3. There is a net positive force (~ 0.5 mm Hg) causing the continued formation of extravascular fluid; the excess influx is drained by the lymphatic system.
Exudates are fluids of inflammatory origin and are characterized by:
|Transudate||Increased||Normal||Absent||Normal||Normal (Increased, if from tumor)|
Most Recent Update on 9/2/2014