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

Abstract

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. Anat. Rec. 251:87-96, 1998.

Evidence for a vascular contribution to diffusion FMRI at high b value

“…Directional diffusion weighting could conceivably attenuate signal from vessels with a component parallel to the direction of weighting while leaving residual signal from vessels perpendicular to the diffusion vector (i.e., vessels with a significant component in the plane that is orthogonal to the weighting). Our data would be consistent with residual, intact signal from vessels with ordered geometry, as occurs in cerebral cortex (29). For our results to be consistent with the cell swelling hypothesis, the swelling would have to be strongly anisotropic, which might be expected in highly structured tissue like white matter (28) but is less likely for the (approximately spherical) cell bodies in gray matter.…”

“…It has been suggested that a directionally selective response to cell swelling might occur in highly oriented tissues (28), but not for the (roughly spherical) cell bodies of gray matter. In contrast, the vascular network within cortex is highly ordered, with different vessel types and vascular layers running either parallel or perpendicular to the cortical surface (29). It may therefore be informative to investigate the dependence of the DFMRI signal on the direction of weighting, although any results must be considered anecdotal and interpreted with caution.…”

Two-Photon Imaging of Cortical Surface Microvessels Reveals a Robust Redistribution in Blood Flow after Vascular Occlusion

“…This failsafe mechanism most likely results from the many short-range loops in this arterial network, which may also play a role in rerouting a fixed supply of blood among different cortical columns during shifts in cortical electrical activity [45]. The highly redundant cortical surface vasculature discussed here for rats is also present in humans [4,46]. In contrast to the present results for the surface vasculature of cortex, the apparent lack of a similar system of anastomoses in the basal ganglia may contribute to its greater vulnerability after a blockage of the MCA [47].…”

An experimental model of lacunar infarction: Embolization of microthrombi

“…3 This finding has been confirmed by microscopic examinations of human brain vascular casts. 30 Furthermore, with aging, arteries of the subcortex are susceptible to coiling of the lumen within the adventitial space. 31 Vessels of the cortex are not affected.…”