| Abstract: | ![]()
The capillaries within the lateral ventricular choroid plexuses from 14 normal fetal brains and one 5-year-old child were studied with electron microscopy. Endothelial pores and simple tight junctions were not observed until a fetal age of 24 weeks. From 24 weeks through 30 weeks of fetal age, the protein particles of the tight junctions became progressively aligned into a continuous row. Only an intermittent basement-membranelike material was found in the fetal tissues; however, a continuous basement membrane was found in tissues from a 5-year-old child. We suggest fluid in capillary lumina may enter the tissue space through “very leaky” endothelial tight junctions due to the fixed osmotic gradient, while the macromolecular substances pass into the tissue space by pinocytosis of the endothelial cells. The macromolecular substances may in turn be transferred into the ventricular cavities by epithelial cells. Although the pathogeny of fetal interventricular hemorrhage (IVH) is unclear, we suspect that the simple tight junctions found early in development may break down under certain abnormal vascular conditions and allow blood to leak out. Normal deficiencies in the fetal basement membrane and its weak extensibility are also factors which could contribute to fetal IVH. No relationship was demonstrated between the types and numbers of cell organelles present and fetal age. © 1993 Wiley-Liss, Inc. |
