[Flow patterns at the bifurcation and curving portion of the human cerebral artery--in reference to the localization of atherogenesis].

To elucidate the connection between blood flow and the localized genesis and development of atherosclerosis and thrombosis at the bifurcation and curving portion of the human cerebral artery, detailed studies of the flow patterns were carried out by directly observing and photographing the behavior of tracer particles flowing through the isolated transparent segment of the middle cerebral artery, prepared from a human subject post-mortem. It was found that a standing recirculation zone consisting of a pair of complex spiral secondary flow, located on both sides of the common median plane of the bifurcation, was formed in the lateral side of the daughter vessels over wide ranges of inflow Reynolds numbers, Re0, and flow rate ratios, Q1/Q0, The formation and the size of the recirculation zone were largely dependent on Q1/Q0, as well as on Re0. Also a eddy formation was observed in the inner side at the curving portion as well as at the bifurcation of the middle cerebral artery. The results suggest that, under physiological conditions, a standing recirculation zone exists in the bifurcation and bending portion of the middle cerebral artery, thereby affecting local mass transfer and interactions of blood cells with the vessel wall, which may lead to the incidence of atherosclerosis and thrombosis in these region.