6.5-mm human embryo with a single nasal placode: cyclopia or hypotelorism?

Anatomy of the circle of Willis in three cases of human fetal synophthalmic holoprosencephaly

In three human fetuses with synophthalmic holoprosencephaly (8, 14, 23 weeks post conceptionem) the circle of Willis was studied using serial histological sections and computer aided three dimensional reconstruction methods. This structure was abnormal in all cases. In two cases the anterior communicating arteries were absent. In all cases the anterior cerebral arteries could not be found. One case showed an incomplete circle with no posterior communicating artery. The results indicate that the malformation of the circle of Willis reflects the malformation of the brain.

Limb body wall malformation complex: an embryologic etiology?

Four human fetuses with the limb body wall malformation complex, also known as the amniotic band syndrome, were examined. Besides malformations of the body wall and the limb(s), anomalies of the internal organs were found in three fetuses, suggesting a disturbance of normal morphogenesis before the fifth week of development. When analyzing the observed data in relation to their etiology, no support was found for either the amniotic band or the vascular disruption theory. New insights into morphogenesis suggest that the limb body wall malformation complex results from a malfunction in the ectodermal placodes and that it can be considered to be an embryonic dysplasia.