Flow visualization in isolated transparent natural blood vessels.

A novel technique to prepare isolated transparent natural blood vessels was developed and used to study the detailed flow patterns in some regions of the circulation. It was found that paired spiral secondary flows and recirculation zones form downstream of venous valves, at the arterial T-junctions in the dog abdominal aorta, and in the human carotid sinus over a wide range of geometrical and flow conditions, including the time-averaged mean values of the physiological flow rates.