Development of the cerebral vasculature
Last reviewed: 23.04.2024
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The circulatory system of the brain is formed from two non-simultaneously developing systems: vertebral-basilar and carotid. About the third month of gestation, they merge and form the Willis polygon, but in some people it remains anatomically open. The vertebral-basilar system at the time of fusion is well developed and has many small branches. In the carotid system, the vessels forming the plexus of the ventricles as well as the branches supplying blood to the thalamus and subcortical nodes are well developed. The major large branches of the middle cerebral and anterior cerebral arteries pass through the brain as a "transit", and the small branches and capillaries begin to develop primarily in the cerebral cortex, leaving the white matter slightly vascularized before the birth of the child. Probably, the expediency of such development of blood supply is explained by the fact that periventricular zones can be fed at the expense of cerebrospinal fluid, and growing neurons of the cortex need a constant inflow of nutrients. The periventricular zones of adjacent circulation (parasagittal, in the region of the posterior horns of the lateral ventricles, etc.) are not particularly sufficient.
The formation of siphons begins with the 8th month of antenatal life and ends after birth. The main purpose of siphons is to "break" the one-stage flow of blood into the systole and ensure its uniform intake regardless of the rhythm of the heart.
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