Plasma influences the formation of vortices in blood. In one experiment, the researchers let blood plasma flow through a microfluidic channel such as is found in a constricted blood vessel. They observed vortices at the end of the channel, but also -- as shown in these images -- at the entrance to the channel. These vortices are created because of the viscoelastic properties of blood plasma.
Mathias Brust, Phys. Rev. Lett. 110, 2013, 078305. Copyright (2013) by the American Physical Society