The microcirculation and fluid transport in digestive organs.

The microcirculation of digestive organs is responsible for providing the fluid required for salivary, gastric, pancreatic, and biliary secretions and plays a major role in removing fluid from the interstitium of the intestines during absorption. Data from the literature suggest that hydrostatic and oncotic pressures within the interstitium are important in modulating fluid movement between the microcirculation and transporting epithelia in most digestive organs. Changes in capillary hydrostatic pressure appear to play a more important role in some organs, i.e., salivary glands. Alterations in the density of perfused capillaries and capillary permeability also enhance capillary fluid exchange during transport. These factors, coupled to the high capillary hydraulic conductivity, allow the digestive organs to move large amounts of fluid between the blood and transporting epithelia.