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[Structural features of the smooth muscle cells in the medial layer of the bifurcation of fetal cerebral arteries].

OBJECTIVE
To study the structural and histogenetic features of the smooth muscle cells (SMCs) in the medial layer of the bifurcation of human cerebral arteries in fetus.


METHOD
Segments of the cerebral arteries from the circle of Willis including the bifurcations of normal human fetuses were sectioned in 1 of the 3 orthogonal planes, wherein the three- dimensional medial layer structure composed of SMCs was observed with light microscope.


RESULT
Microscopic observation identified 1.1 to 9.0 SMC layers in the medial layer of the cerebral arteries from the circle of Willis in the fetuses at different weeks before birth, and 30.3% of the specimens were found to have focal defects of the medial SMC layers at the bifurcation of the developing arteries.


CONCLUSION
The number of SMC layers consisted in the medial layers of the cerebral arteries develops with the fetal growth, and the identification of congenital anomaly of the medial SMCs may help verify the hypothetical pathogenesis for cerebral saccular aneurysms.