We include in the term “microcirculation” those vessels with lumens (internal diameters) that are some
modest multiple—say 1 to 10—of the major diameter of the unstressed RBC. This definition includes
primarily the arterioles, the capillaries, and the postcapillary venules. The capillaries are of particular
interest because they are generally from 6 to 10 µm in diameter, i.e., about the same size as the RBC.
In the larger vessels, RBC may tumble and interact with one another and move from streamline to
streamline as they course down the vessel. In contrast, in the microcirculation the RBC must travel in
single file through true capillaries (Berman and Fuhro, 1969; Berman et al., 1982). Clearly, any
attempt to adeq