Morphological characteristics and distribution pattern of the arterial vessels in human cerebral cortex: a scanning electron microscope study.

BACKGROUND: The human cerebral cortex is supplied by vessels that arise from the pial arteries. These vessels give rise to a dense vascular network that is highly interconnected. Cortical arteries have been classified in different categories. Both their angioarchitectonic pattern and anatomical structures involved in their regulation are not fully understood.
METHODS: Twelve fresh human brains were studied by scanning electron microscopy of vascular corrosion casts.
RESULTS: Four types of arterial vessels in the cerebral cortex--short, middle, long, and transcortical--were identified. The cortical vascular network was formed by several interconnected clusters of vessels, which were arranged in four vascular layers parallel to the pial surface and characterized by different vascular densities. The greatest vascular density corresponded to the middle and deep vascular layers. Circular constrictions were found at the origin of cortical arteries and at their branching sites, probably related to vascular sphincters. Connections between cortical arteries were observed at their initial course. Plastic strips, occasionally related to constrictions, were observed around both middle and long cortical arteries. Other plastic structures, morphologically similar to pericytes, were found around capillary vessels.
CONCLUSIONS: The blood supply to the human cerebral cortex depends on the short, middle, and long cortical arteries, which give rise to a highly anastomosed capillary network. There exist vascular connections between pial arteries and occasionally between cortical arteries. Blood flow autoregulation is probably mediated by smooth muscle cells at the arteriolar level and by pericytes at the capillary level, through endothelial connections.