Critical closing pressure or yield shear stress as the cause of disturbed peripheral circulation?

Rheological obstruction is possible on the basis of the known physical properties of blood. The angioarchitectonic arrangement of the mammalian microvasculature makes it especially susceptible to rheological obstruction. This is a price to be paid for the high efficacy and minituarisation which ameliorates the function under physiological conditions. Whenever blood looses its unique fluidity and assumes quasi conventional flow properties of a suspension, obstruction of the microvessels occurs: 1) when the blood perfuses vessels of the appropriate design under pressure insufficient to desaggregate, or deform the cells, or 2) when abnormal interaction between blood cells and cell wall occurs. In these respects, organ-specific differences also have to be taken into consideration; organs in which there are many venules are more susceptible than those with long capillaries: this facts will certainly have to be taken into account when discussing differences between skin and muscle perfusion.