SITES OF TRANSITION BETWEEN FUNCTIONAL SYSTEMIC AND CEREBRAL-ARTERIES OF RABBITS OCCUR AT EMBRYOLOGICAL JUNCTIONAL SITES

The vascular smooth muscle of cerebral blood vessels is relatively insensitive to sympathomimetic stimulation compared with muscle from systemic vessels. The transition in the vertebral artery occurs just rostral to the emergence of that artery from the foramen of the lateral process of the atlas and in the internal carotid artery just before it enters the carotid canal. These sites in the adult correspond to embryological junctions between segments of the vertebral and internal carotid arteries derived from the primitive dorsal aortas and their branches with vessels originating locally from the bilateral longitudinal neural arteries. Topographic patterns of vascular properties may in some cases be explained by the different sites of origin of their primordial mesodermal cells. Copyright © 1979 AAAS.