Patterns of vascularization in the developing cerebral cortex.

The vascular system of the cerebral cortex can be adapted to changing metabolic requirements which occur during development. Apart from a purely nutritive function the intracerebral vessels influence embryonal gliogenesis and migration of neuroblasts. The internal vascularization of the cerebral cortex starts during embryonic development and continues until the postnatal period. The formation of new penetrating vascular trunks and intracortical capillary branching is terminated before global brain growth reaches a plateau. The information necessary to develop a vascular system designed for functional needs later in development may already be expressed in the basic fetal pattern. The formation of such a system is probably not under direct metabolic control. The cellular composition of the capillary tube changes with the developmental stage and the actual growth rate of the endothelial cells. In the cerebral cortex the maximal growth rate of capillaries proceeds in a regional- and lamina-specific manner according to a defined ontogenetic time-scale. The importance of a local factor in the regulation of vascular growth is strengthened by this observation. The vascular system of the cerebral cortex is evaluated using morphometry and reconstructions of serial sections at different stages of postnatal development. This study aims to provide a morphological basis which may help to define cellular mechanisms associated with vascular patterning during brain development.