Substances move from metabolic microvessels to the tissue channels and back, through the endothelium in their areas of microvasculature. I suggest that this microvascular-tissue complex should be called a "domain of hemo-tissue metabolism". Transport vessels unite the domains into a common system. Domain configuration is determined by the structure of a vascularized area. In the mesentery between two mesothelium layers is a loose connective tissue, veined with a network of different microvessels. A hollow organ can be presented as a sheet rolled in a pipe; muscular layers divide it into membranes with a multi-layer microvasculature, and microcirculatory channels of external layers overlap the transport vessels, going from the inner layers. Formation of folds, villi, crypts, acinuses and lobules leads to an adequate deformation of the domain. They have a network structure: thin fascicles of connective tissue fibers and capillaries form loops of a microvascular-fiber network. Inside the loops, is a dense network of thinner connective tissue fibers and tissue channels. They unite blood and lymphatic microvessels as "functional anastomoses": connective tissue fibers and hydrophilic amorphous substance act as an external cuff, restricting the tissue channels from widening and directing the substance current into the microvessels with a different wall permeability.
The work was submitted to international scientific conference «Medical, social and economic problems of population health preservation», Turkey, May 20-27, 2009. Came to the editorial office on 10.09.2009.